2014年12月31日水曜日

来年は収穫の年にしたい

皆様、

いよいよ2014年も終わろうとしていますね(日本ではもう2015年が明けていると思いますが…)。
今年も大変お世話になりました。
来年もよろしくお願いします。

2014年はカルテクでの研究/生活にも慣れ、良くも悪くもマイペースに過ごした一年でした。

特に研究面では、昨年末に立てた目標:
> 最低でも学会発表、できれば論文アクセプトまで漕ぎ着けたいですね。
> (現実的な目標は「論文投稿」くらいか???)
の予言通り、「論文投稿中」のまま年を越えることになってしまいました(汗)。

来年はぜひとも「第一著者の論文x2」をアクセプトまで持って行きたいですね。
ということで、これを来年の目標にしたいと思います。

プライベートでは、グランドキャニオン、ワシントンDC(出張兼)、ニューヨークと旅行できて満足です。
何より、この一年を健康で無事に過ごせたことに感謝です。

それでは。
世界人類が円高でありますように。

追伸:
共著の論文は出しました。
"Different impressions of other agents obtained through social interaction uniquely modulate dorsal and ventral pathway activities in the social human brain"
Hideyuki Takahashi, Kazunori Terada, Tomoyo Morita, Shinsuke Suzuki, Tomoki Haji, Hideki Kojima, Masahiro Yoshikawa, Yoshio Matsumoto, Takashi Omori, Minoru Asada, Eiichi Naito.
Cortex, Volume 58, September 2014, Pages 289–300.
緩募、引用!

2014年12月7日日曜日

パサデナでの生活(カリフォルニア工科大学周辺の情報)

カリフォルニア州パサデナ市,特にカリフォルニア工科大学周辺,の生活情報を以下のカテゴリに分けて更新/整理しました:
https://sites.google.com/site/shinsukesuzuki0927/life-at-pasadena

・買い物(カルテク徒歩圏内)
・買い物(その他)
・病院
・レストラン(カルテク構内)
・レストラン(カルテク徒歩圏内+オールド・パサデナ)
・レストラン(LA全域)

2014年9月16日火曜日

カリフォルニアでの運転免許更新:ビザが期限切れでもできる?

ぼくの周りに諸説あったので、用事のついでに大学の International Scholar Service で質問してきました。

J1ビザは期限切れだが、滞在許可の期限は切れていない(つまり、有効期間の十分残ったDS2019は手許にある)。
このケースで、カリフォルニア州発行の運転免許を更新できるのか?

答えは、「できる」らしいです。
ただ、「DMVの窓口の人がこのルールを知っているとは限らない。何度も出向いて交渉する必要があることも多い」とも言われました。
毎度御馴染みの”担当者次第…”ですね。

2014年8月27日水曜日

Anterior Insula Activity Reflects the Effects of Intentionality on the Anticipation of Aversive Stimulation

Mimi Liljeholm, Simon Dunne, and John P. O'Doherty
The Journal of Neuroscience, 20 August 2014, 34(34):11339-11348


他人から「意図的」に「嫌がらせ」をされた場合に反応する脳部位は前島皮質。「嫌がらせ」は(お金を奪われるとかじゃなくて)「塩水を飲まされる」のがポイント。たぶん。 http://www.jneurosci.org/content/34/34/11339

If someone causes you harm, your affective reaction to that person might be profoundly influenced by your inferences about the intentionality of their actions. In the present study, we aimed to understand how affective responses to a biologically salient aversive outcome administered by others are modulated by the extent to which a given individual is judged to have deliberately or inadvertently delivered the outcome. Using fMRI, we examined how neural responses to anticipation and receipt of an aversive stimulus are modulated by this fundamental social judgment. We found that affective evaluations about an individual whose actions led to either noxious or neutral consequences for the subject did indeed depend on the perceived intentions of that individual. At the neural level, activity in the anterior insula correlated with the interaction between perceived intentionality and anticipated outcome valence, suggesting that this region reflects the influence of mental state attribution on aversive expectations.

2014年8月12日火曜日

The habenula encodes negative motivational value associated with primary punishment in humans

Rebecca P. Lawson, Ben Seymour, Eleanor Loh, Antoine Lutti, Raymond J. Dolan, Peter Dayan, Nikolaus Weiskopf, and Jonathan P. Roiser
PNAS vol. 111 no. 32, 11858–11863

高解像度fMRIでhabenulaを狙いました、という研究。

Learning what to approach, and what to avoid, involves assigning value to environmental cues that predict positive and negative events. Studies in animals indicate that the lateral habenula encodes the previously learned negative motivational value of stimuli. However, involvement of the habenula in dynamic trial-by-trial aversive learning has not been assessed, and the functional role of this structure in humans remains poorly characterized, in part, due to its small size. Using high-resolution functional neuroimaging and computational modeling of reinforcement learning, we demonstrate positive habenula responses to the dynamically changing values of cues signaling painful electric shocks, which predict behavioral suppression of responses to those cues across individuals. By contrast, negative habenula responses to monetary reward cue values predict behavioral invigoration. Our findings show that the habenula plays a key role in an online aversive learning system and in generating associated motivated behavior in humans.

2014年7月3日木曜日

Context effects produced by question orders reveal quantum nature of human judgments

Zheng Wang, Tyler Solloway, Richard M. Shiffrin, and Jerome R. Busemeyer
PNAS 2014 vol. 111 no. 26, 9431–9436.

「量子」意思決定理論について。
ついに総合誌にも載るようになってきましたね。
(ただし、”PNAS direct submission” ではなくて、NAS会員からの寄稿)

The hypothesis that human reasoning obeys the laws of quantum rather than classical probability has been used in recent years to explain a variety of seemingly “irrational” judgment and decision-making findings. This article provides independent evidence for this hypothesis based on an a priori prediction, called the quantum question (QQ) equality, concerning the effect of asking attitude questions successively in different orders. We empirically evaluated the predicted QQ equality using 70 national representative surveys and two laboratory experiments that manipulated question orders. Each national study contained 651–3,006 participants. The results provided strong support for the predicted QQ equality. These findings suggest that quantum probability theory, initially invented to explain noncommutativity of measurements in physics, provides a simple account for a surprising regularity regarding measurement order effects in social and behavioral science.

2014年7月2日水曜日

The neurobiology of rewards and values in social decision making

Christian C. Ruff & Ernst Fehr
Nature Reviews Neuroscience (2014)

社会的意思決定についての総説論文。
’Decision neuroscience’から見た側面を重視。

How does our brain choose the best course of action? Choices between material goods are thought to be steered by neural value signals that encode the rewarding properties of the choice options. Social decisions, by contrast, are traditionally thought to rely on neural representations of the self and others. However, recent studies show that many types of social decisions may also involve neural value computations. This suggests a unified mechanism for motivational control of behaviour that may incorporate both social and non-social factors. In this Review, we outline a theoretical framework that may help to identify possible overlaps and differences between the neural processes that guide social and non-social decision making.

2014年6月17日火曜日

Role of the Primate Ventral Tegmental Area in Reinforcement and Motivation

John T. Arsenault, Samy Rima, Heiko Stemmann, Wim Vanduffel

サルで微小電気刺激+fMRI。中脳腹側被蓋野(VTA)を刺激すると人為的に強化学習を促進できる。また、その際、線条体や眼窩前頭野など報酬系のfMRI信号が増加する。「VTAの活動」は「強化学習」や「報酬関連脳部位の活動」の原因になっている。

Monkey electrophysiology [1, 2] suggests that the activity of the ventral tegmental area (VTA) helps regulate reinforcement learning and motivated behavior, in part by broadcasting prediction error signals throughout the reward system. However, electrophysiological studies do not allow causal inferences regarding the activity of VTA neurons with respect to these processes because they require artificial manipulation of neuronal firing. Rodent studies fulfilled this requirement by demonstrating that electrical and optogenetic VTA stimulation can induce learning and modulate downstream structures [3–7]. Still, the primate dopamine system has diverged significantly from that of rodents, exhibiting greatly expanded and uniquely distributed cortical and subcortical innervation patterns [8]. Here, we bridge the gap between rodent perturbation studies and monkey electrophysiology using chronic electrical microstimulation of macaque VTA (VTA-EM). VTA-EM was found to reinforce cue selection in an operant task and to motivate future cue selection using a Pavlovian paradigm. Moreover, by combining VTA-EM with concurrent fMRI, we demonstrated that VTA-EM increased fMRI activity throughout most of the dopaminergic reward system. These results establish a causative role for primate VTA in regulating stimulus-specific reinforcement and motivation as well as in modulating activity throughout the reward system.

2014年6月16日月曜日

Decision Making: The Neuroethological Turn

John M. Pearson, Karli K. Watson, Michael L. Platt
Neuron Volume 82, Issue 5, p950–965, 4 June 2014

報酬に基づく意思決定についての総説論文。

Neuroeconomics applies models from economics and psychology to inform neurobiological studies of choice. This approach has revealed neural signatures of concepts like value, risk, and ambiguity, which are known to influence decision making. Such observations have led theorists to hypothesize a single, unified decision process that mediates choice behavior via a common neural currency for outcomes like food, money, or social praise. In parallel, recent neuroethological studies of decision making have focused on natural behaviors like foraging, mate choice, and social interactions. These decisions strongly impact evolutionary fitness and thus are likely to have played a key role in shaping the neural circuits that mediate decision making. This approach has revealed a suite of computational motifs that appear to be shared across a wide variety of organisms. We argue that the existence of deep homologies in the neural circuits mediating choice may have profound implications for understanding human decision making in health and disease.

2014年6月5日木曜日

Value Signals in the Prefrontal Cortex Predict Individual Preferences across Reward Categories

Jörg Gross, Eva Woelbert, Jan Zimmermann, Sanae Okamoto-Barth, Arno
Riedl, and Rainer Goebel
The Journal of Neuroscience, 28 May 2014, 34(22):7580-7586;

「スナック菓子を食べる」vs.「スポーツをする」のような「種類の異なる選択肢間の比較」を行うためには、共通の尺度(効用)が脳内に必要になってくる。
もし共通の尺度があるなら、「種々のスナック菓子の価値に対する脳活動から種々のスポーツをする価値を予測する」ことができるはずだ。
→ 実際、fMRI MVPAを用いて、前頭前野の脳活動でその予測ができた。

Humans can choose between fundamentally different options, such as watching a movie or going out for dinner. According to the utility concept, put forward by utilitarian philosophers and widely used in economics, this may be accomplished by mapping the value of different options onto a common scale, independent of specific option characteristics (Fehr and Rangel, 2011; Levy and Glimcher, 2012). If this is the case, value-related activity patterns in the brain should allow predictions of individual preferences across fundamentally different reward categories. We analyze fMRI data of the prefrontal cortex while subjects imagine the pleasure they would derive from items belonging to two distinct reward categories: engaging activities (like going out for drinks, daydreaming, or doing sports) and snack foods. Support vector machines trained on brain patterns related to one category reliably predict individual preferences of the other category and vice versa. Further, we predict preferences across participants. These findings demonstrate that prefrontal cortex value signals follow a common scale representation of value that is even comparable across individuals and could, in principle, be used to predict choice.

2014年6月4日水曜日

Novelty Enhances Visual Salience Independently of Reward in the Parietal Lobe

Nicholas C. Foley, David C. Jangraw, Christopher Peck, and Jacqueline Gottlieb
The Journal of Neuroscience, 4 June 2014, 34(23):7947-7957;

刺激の「価値(報酬予測)」と「新規性」はどちらもその刺激に対する注意を増加させることが知られている。
価値と新規性は別々に注意に影響を与えているのか?それとも、お互いに関連するのか?
サルの視線とLIPニューロンの活動を調べたところ、前者っぽい。

Novelty modulates sensory and reward processes, but it remains unknown how these effects interact, i.e., how the visual effects of novelty are related to its motivational effects. A widespread hypothesis, based on findings that novelty activates reward-related structures, is that all the effects of novelty are explained in terms of reward. According to this idea, a novel stimulus is by default assigned high reward value and hence high salience, but this salience rapidly decreases if the stimulus signals a negative outcome. Here we show that, contrary to this idea, novelty affects visual salience in the monkey lateral intraparietal area (LIP) in ways that are independent of expected reward. Monkeys viewed peripheral visual cues that were novel or familiar (received few or many exposures) and predicted whether the trial will have a positive or a negative outcome—i.e., end in a reward or a lack of reward. We used a saccade-based assay to detect whether the cues automatically attracted or repelled attention from their visual field location. We show that salience—measured in saccades and LIP responses—was enhanced by both novelty and positive reward associations, but these factors were dissociable and habituated on different timescales. The monkeys rapidly recognized that a novel stimulus signaled a negative outcome (and withheld anticipatory licking within the first few presentations), but the salience of that stimulus remained high for multiple subsequent presentations. Therefore, novelty can provide an intrinsic bonus for attention that extends beyond the first presentation and is independent of physical rewards.

Cognitive Control Functions of Anterior Cingulate Cortex in Macaque Monkeys Performing a Wisconsin Card Sorting Test Analog

Masaru Kuwabara, Farshad A. Mansouri, Mark J. Buckley, and Keiji Tanaka
The Journal of Neuroscience, 28 May 2014, 34(22):7531-7547;

サルの前帯状溝(ACCs)は「実験課題のルールが変わったことによる間違い」と「自分自身のミスによる間違い」の両方をコードしている。

Monkeys were trained to select one of three targets by matching in color or matching in shape to a sample. Because the matching rule frequently changed and there were no cues for the currently relevant rule, monkeys had to maintain the relevant rule in working memory to select the correct target. We found that monkeys' error commission was not limited to the period after the rule change and occasionally occurred even after several consecutive correct trials, indicating that the task was cognitively demanding. In trials immediately after such error trials, monkeys' speed of selecting targets was slower. Additionally, in trials following consecutive correct trials, the monkeys' target selections for erroneous responses were slower than those for correct responses. We further found evidence for the involvement of the cortex in the anterior cingulate sulcus (ACCs) in these error-related behavioral modulations. First, ACCs cell activity differed between after-error and after-correct trials. In another group of ACCs cells, the activity differed depending on whether the monkeys were making a correct or erroneous decision in target selection. Second, bilateral ACCs lesions significantly abolished the response slowing both in after-error trials and in error trials. The error likelihood in after-error trials could be inferred by the error feedback in the previous trial, whereas the likelihood of erroneous responses after consecutive correct trials could be monitored only internally. These results suggest that ACCs represent both context-dependent and internally detected error likelihoods and promote modes of response selections in situations that involve these two types of error likelihood.

2014年5月29日木曜日

Distributed Value Representation in the Medial Prefrontal Cortex during Intertemporal Choices

Qiang Wang, Shan Luo, John Monterosso, Jintao Zhang, Xiaoyi Fang, Qi Dong, and Gui Xue
The Journal of Neuroscience, 28 May 2014, 34(22):7522-7530;

異時点間の意思決定。
「すぐにもらえる(少量の)報酬」と「後でもらえる(多量の)報酬」のどちらを選ぶか?
前者の価値は背内側前頭前野(dmPFC)の後部で、後者の価値は前部で処理されている。
また、「二つの選択肢の価値の差」は腹内側前頭前野(vmPFC)でコードされている。

The ability to resist current temptations in favor of long-term benefits is a critical human capacity. Despite the extensive studies on the neural mechanisms of intertemporal choices, how the subjective value of immediate and delayed rewards is represented and compared in the brain remains to be elucidated. The present fMRI study addressed this question by simultaneously and independently manipulating the magnitude of immediate and delayed rewards in an intertemporal decision task, combined with univariate analysis and multiple voxel pattern analysis. We found that activities in the posterior portion of the dorsal medial prefrontal cortex (DmPFC) were modulated by the value of immediate options, whereas activities in the adjacent anterior DmPFC were modulated by the subjective value of delayed options. Brain signal change in the ventral mPFC was positively correlated with the “relative value” (the absolute difference of subjective value between two intertemporal alternatives). In contrast, the dorsal anterior cingulate cortex activity was negatively correlated with the relative value. These results suggest that immediate and delayed rewards are separately represented in the dorsal mPFC and compared in the ventral mPFC to guide decisions. The functional dissociation of posterior and anterior DmPFC in representing immediate and delayed reward is consistent with the general structural and functional architecture of the prefrontal cortex and may provide a neural basis for human's unique capacity to delayed gratification.

2014年5月28日水曜日

Spatial Generalization in Operant Learning: Lessons from Professional Basketball

Tal Neiman, Yonatan Loewenstein
PLOS Computational Biology
http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003623

オペラント学習における「般化(過去の学習結果を似たような状況に応用する)」の研究。
NBA選手のデータで検証。「成功したので、同じような位置からシュートをしよう」という「地理的な般化」ではなく、「3ptが成功したので、また3ptシュートを打とう」という「ゲームのルールに基づく高度な般化」が見られた。
つまり、般化は(抽象的なゲームのルールの理解のような)高度な認知処理の結果を反映できる。

In operant learning, behaviors are reinforced or inhibited in response to the consequences of similar actions taken in the past. However, because in natural environments the “same” situation never recurs, it is essential for the learner to decide what “similar” is so that he can generalize from experience in one state of the world to future actions in different states of the world. The computational principles underlying this generalization are poorly understood, in particular because natural environments are typically too complex to study quantitatively. In this paper we study the principles underlying generalization in operant learning of professional basketball players. In particular, we utilize detailed information about the spatial organization of shot locations to study how players adapt their attacking strategy in real time according to recent events in the game. To quantify this learning, we study how a make \ miss from one location in the court affects the probabilities of shooting from different locations. We show that generalization is not a spatially-local process, nor is governed by the difficulty of the shot. Rather, to a first approximation, players use a simplified binary representation of the court into 2 pt and 3 pt zones. This result indicates that rather than using low-level features, generalization is determined by high-level cognitive processes that incorporate the abstract rules of the game.

2014年5月27日火曜日

SPMで「パラメトリック・リグレッサーの直交化」を無効にする方法

SPMで「パラメトリック・リグレッサー(Parametric Modulator)」が勝手に直交化(orthogonalization)されるのを防ぐ方法:

spm_get_ons.m と spm_fMRI_design.m を開き、 spm_orth をコメントアウトする。

参考:
http://imaging.mrc-cbu.cam.ac.uk/imaging/ParametricModulations
http://wagerlab.colorado.edu/wiki/doku.php/help/fmri_help/fmri_statistical_models/parametric_modulation

2014年5月26日月曜日

Anterior Cingulate Cortex Instigates Adaptive Switches in Choice by Integrating Immediate and Delayed Components of Value in Ventromedial Prefrontal Cortex

Marcos Economides, Marc Guitart-Masip, Zeb Kurth-Nelson, and Raymond J. Dolan
J. Neurosci. 2014;34 3340-3349

直近の報酬を選ぶべきか?より大きな報酬を待つべきか?
行動が変化する(Switch)する際は、前部帯状皮質(ACC)と前頭前野腹内側部の機能的結合が見られる。

Actions can lead to an immediate reward or punishment and a complex set of delayed outcomes. Adaptive choice necessitates the brain track and integrate both of these potential consequences. Here, we designed a sequential task whereby the decision to exploit or forego an available offer was contingent on comparing immediate value and a state-dependent future cost of expending a limited resource. Crucially, the dynamics of the task demanded frequent switches in policy based on an online computation of changing delayed consequences. We found that human subjects choose on the basis of a near-optimal integration of immediate reward and delayed consequences, with the latter computed in a prefrontal network. Within this network, anterior cingulate cortex (ACC) was dynamically coupled to ventromedial prefrontal cortex (vmPFC) when adaptive switches in choice were required. Our results suggest a choice architecture whereby interactions between ACC and vmPFC underpin an integration of immediate and delayed components of value to support flexible policy switching that accommodates the potential delayed consequences of an action.

2014年5月25日日曜日

Representation of Outcome Risk and Action in the Anterior Caudate Nucleus

Marianna Yanike and Vincent P. Ferrera
J. Neurosci. 2014;34 3279-3290

「線条体尾状核前部(Anterior Caudate Nucleus)はリスクとサッケード方向をコードしている」という話。

The anterior caudate nucleus is essential for goal-directed behavior because it links outcome information to actions. It is well known that caudate neurons provide a variety of reward-related and action signals. However, it is still unclear how the two signals are integrated. We investigated whether and how outcome risk modulates spatial representation. We recorded neural activity in the anterior caudate nucleus while monkeys made saccades to multiple spatial targets, each associated with either fixed (safe) or variable (risky) amount of reward. We report that individual neurons combined the outcome reward signal with spatial information about the direction of saccades. These signals could be reliably read out from the populations of neurons. Moreover, the prospect of a risky outcome improved the quality of spatial information. These results provide direct evidence that global spatial representation in the caudate is modulated by outcome, which can be important for flexible control of behavior, particularly during learning and habit formation, when outcomes vary.

2014年5月22日木曜日

Reward Inference by Primate Prefrontal and Striatal Neurons

Xiaochuan Pan, Hongwei Fan, Kosuke Sawa, Ichiro Tsuda, Minoru Tsukada, and Masamichi Sakagami
J. Neurosci. 2014;34 1380-1396 Open Access

サル電気生理。
線条体と前頭前野背側部はどちらも「報酬予測」に関連している。
直接経験に依る単純な報酬予測だけではなく、線条体は「消去法から導きだされる予測」、前頭前野外側部は「推移律から導きだされる予測」をそれぞれできる。
線条体って思ったより賢い!

The brain contains multiple yet distinct systems involved in reward prediction. To understand the nature of these processes, we recorded single-unit activity from the lateral prefrontal cortex (LPFC) and the striatum in monkeys performing a reward inference task using an asymmetric reward schedule. We found that neurons both in the LPFC and in the striatum predicted reward values for stimuli that had been previously well experienced with set reward quantities in the asymmetric reward task. Importantly, these LPFC neurons could predict the reward value of a stimulus using transitive inference even when the monkeys had not yet learned the stimulus–reward association directly; whereas these striatal neurons did not show such an ability. Nevertheless, because there were two set amounts of reward (large and small), the selected striatal neurons were able to exclusively infer the reward value (e.g., large) of one novel stimulus from a pair after directly experiencing the alternative stimulus with the other reward value (e.g., small). Our results suggest that although neurons that predict reward value for old stimuli in the LPFC could also do so for new stimuli via transitive inference, those in the striatum could only predict reward for new stimuli via exclusive inference. Moreover, the striatum showed more complex functions than was surmised previously for model-free learning.

2014年5月21日水曜日

Performance Monitoring in Monkey Frontal Eye Field

Tobias Teichert, Dian Yu, and Vincent P. Ferrera
J. Neurosci. 2014;34 1657-1671
http://www.jneurosci.org/cgi/content/abstract/34/5/1657?etoc

サル電気生理。
The frontal eye fields (FEF;前頭葉眼球運動野?)の(ほぼ同じ)ニューロンが「自分が犯した間違い(エラー)」と「その課題の難しさ」をコードしている。

The frontal eye fields (FEF) are thought to mediate response selection during oculomotor decision tasks. In addition, many FEF neurons have robust postsaccadic responses, but their role in postchoice evaluative processes (online performance monitoring) is only beginning to become apparent. Here we report error-related neural activity in FEF while monkeys performed a biased speed-categorization task that enticed the animals to make impulsive errors. Twenty-three percent of cells in macaque FEF coded an internally generated error-related signal, and many of the same cells also coded task difficulty. The observed responses are primarily consistent with three related concepts that have been associated with performance monitoring: (1) response conflict; (2) uncertainty; and (3) reward prediction. Overall, our findings suggest a novel role for the FEF as part of the neural network that evaluates the preceding choice to optimize behavior in the future.

2014年5月20日火曜日

Action Monitoring and Medial Frontal Cortex: Leading Role of Supplementary Motor Area

Francesca Bonini, Boris Burle, Catherine Liégeois-Chauvel, Jean Régis, Patrick Chauvel, Franck Vidal
Science 21 February 2014: Vol. 343 no. 6173 pp. 888-891

ヒト電気生理。
「行動の結果を評価する」ことは最適な意思決定/学習に重要な役割を果たす。
補足運動野(SMA)が行動の結果を素早く評価し、その後、前頭前野内側部が行動の結果が悪かった場合(エラー)にのみ反応する。

The capacity to evaluate the outcomes of our actions is fundamental for adapting and optimizing behavior and depends on an action-monitoring system that assesses ongoing actions and detects errors. The neuronal network underlying this executive function, classically attributed to the rostral cingulate zone, is poorly characterized in humans, owing to the limited number of direct neurophysiological data. Using intracerebral recordings, we show that the leading role is played by the supplementary motor area (SMA), which rapidly evaluates successful and erroneous actions. The rostral part of medial prefrontal cortex, driven by the SMA, was activated later and exclusively in the case of errors. This suggests a hierarchical organization of the different frontal regions involved in implementation of action monitoring and error processing.

2014年5月19日月曜日

The problem with value

John P. O’Doherty
Neuroscience & Biobehavioral Reviews, in press

「価値/効用」をコードしていると考えられている神経活動は、本当に「価値をコードしている」と言えるのか?というテーマの総説論文。

Neural correlates of value have been extensively reported in a diverse set of brain regions. However, in many cases it is difficult to determine whether a particular neural response pattern corresponds to a value-signal per se as opposed to an array of alternative non-value related processes, such as outcome-identity coding, informational coding, encoding of autonomic and skeletomotor consequences, alongside previously described “salience” or “attentional” effects. Here, I review a number of experimental manipulations that can be used to test for value, and I identify the challenges in ascertaining whether a particular neural response is or is not a value signal. Finally, I emphasize that some non-value related signals may be especially informative as a means of providing insight into the nature of the decision-making related computations that are being implemented in a particular brain region.

2014年5月18日日曜日

Motivational Salience Signal in the Basal Forebrain Is Coupled with Faster and More Precise Decision Speed

Irene Avila, Shih-Chieh Lin
PLoS Biol 12(3): e1001811.

「Motivational Salience(ある刺激が報酬や罰といった重大な結果をもたらすか否か)」に対する前脳基底部(basal forebrain)の反応は、意思決定の正確さと速さを反映している。

The survival of animals depends critically on prioritizing responses to motivationally salient stimuli. While it is generally believed that motivational salience increases decision speed, the quantitative relationship between motivational salience and decision speed, measured by reaction time (RT), remains unclear. Here we show that the neural correlate of motivational salience in the basal forebrain (BF), defined independently of RT, is coupled with faster and also more precise decision speed. In rats performing a reward-biased simple RT task, motivational salience was encoded by BF bursting response that occurred before RT. We found that faster RTs were tightly coupled with stronger BF motivational salience signals. Furthermore, the fraction of RT variability reflecting the contribution of intrinsic noise in the decision-making process was actively suppressed in faster RT distributions with stronger BF motivational salience signals. Artificially augmenting the BF motivational salience signal via electrical stimulation led to faster and more precise RTs and supports a causal relationship. Together, these results not only describe for the first time, to our knowledge, the quantitative relationship between motivational salience and faster decision speed, they also reveal the quantitative coupling relationship between motivational salience and more precise RT. Our results further establish the existence of an early and previously unrecognized step in the decision-making process that determines both the RT speed and variability of the entire decision-making process and suggest that this novel decision step is dictated largely by the BF motivational salience signal. Finally, our study raises the hypothesis that the dysregulation of decision speed in conditions such as depression, schizophrenia, and cognitive aging may result from the functional impairment of the motivational salience signal encoded by the poorly understood noncholinergic BF neurons.

ロサンゼルス/パサデナ周辺のラーメン屋さん

プライベートネタを増やそう!
ということで、たまには食べ物ネタでも。

今、アメリカは空前のラーメン・ブームらしいです。
もちろん、ロサンゼルス地区にもたくさんのラーメン屋さんがあります。
こんな企画ページ↓もあったりします。
「ジャパラマガジン主催 – ニッポン人が決める第一回ベストラーメン in ロサンゼルス」
http://japa.la/?p=17045

以下は個人的な感想です:

龍の家
http://www.tatsunoyausa.net/

2015年末にオープンした本格派のとんこつラーメン。
LAで一、二を争う人気店になる予感がします。
オールド・パサデナにやっと美味しいラーメン屋ができました!
全パサデナ(在住日本人)が泣いた。


つじ田
http://tsujita-la.com/

LAで二番人気のラーメン屋さん。
とんこつラーメンが美味しくて、我が家では一番人気です。
細麺で正統派の「博多とんこつ」ですね。
つけめんも結構いけます。
ただ、場所はソーテル地区なので、パサデナからはやや遠い(車で40分前後?フリーウェイの渋滞が!)
なお、同じ通りの向かいにある「つじ田アネックス」は同系列店ですが、メニューは違うらしいです。


時代屋
http://www.yelp.com/biz/jidaiya-ramen-dining-gardena

LAで一番人気のラーメン屋さん。
いわゆる「家系」ラーメン。
濃厚な味で美味ですね。
羽根つき餃子が豪快で、面白いです。
こちらはトーランス地区なので、パサデナからは車で40分くらいはかかります。


山頭火
http://santouka.co.jp/shoplist/index.html

日系スーパー最大手「MITSUWA」のフードコートに入っています。
残念ながら、パサデナ最寄りのサンゲーブル店には入っていません…
安定のうまさで、MITSUWAにいく度に毎回訪れてしまいます。


大黒屋
http://www.daikoku-ten.com/

リトルトーキョーの行列のできる老舗ラーメン屋さん。
LAのラーメン屋のパイオニア的存在。
量が多いし,味もなかなかです。


新撰組
http://www.shinsengumigroup.com/

渡米後、初めて行ったラーメン屋さん。
とんこつラーメンです。
豚骨の匂いが強烈なので、個人的にはやや苦手。


Ramen Yukinoya
http://www.yelp.com/biz/ramen-yukino-ya-industry

パサデナからまあまあ近いラーメン屋さん(でも車は必須!15分くらいかな)。
味は普通です。悪くないけど、特筆すべき感じでもない。
売りはとんこつラーメンっぽいです。


べんてんラーメン
http://www.yelp.com/biz/benten-ramen-san-gabriel

パサデナ最寄りの日系スーパー「MITSUWAサンゲーブル店」近くのラーメン屋さん。
あっさり系のとんこつラーメンです。
ここもパサデナから近いので重宝します。


Ramen N.A.O.
http://ramennao.com/

鶏白湯(+醤油)ラーメン。とんこつ全盛のLAにあって珍しい鶏白湯ラーメン。美味しかったです。

2014年5月15日木曜日

Working-memory capacity protects model-based learning from stress

A. Ross Otto, Candace M. Raio, Alice Chiang, Elizabeth A. Phelps, and Nathaniel D. Daw
PNAS December 24, 2013 vol. 110 no. 52 20941-20946

モデル・ベースド強化学習とモデル・フリー強化学習。
ヒトは両方を併用していることが知られているが、被験者にストレスを与えるとモデル・ベースド強化学習を使わなくなる。
また、その効果はワークングメモリー能力の低い被験者に顕著だった。

Accounts of decision-making have long posited the operation of separate, competing valuation systems in the control of choice behavior. Recent theoretical and experimental advances suggest that this classic distinction between habitual and goal-directed (or more generally, automatic and controlled) choice may arise from two computational strategies for reinforcement learning, called model-free and model-based learning. Popular neurocomputational accounts of reward processing emphasize the involvement of the dopaminergic system in model-free learning and prefrontal, central executive–dependent control systems in model-based choice. Here we hypothesized that the hypothalamic-pituitary-adrenal (HPA) axis stress response—believed to have detrimental effects on prefrontal cortex function—should selectively attenuate model-based contributions to behavior. To test this, we paired an acute stressor with a sequential decision-making task that affords distinguishing the relative contributions of the two learning strategies. We assessed baseline working-memory (WM) capacity and used salivary cortisol levels to measure HPA axis stress response. We found that stress response attenuates the contribution of model-based, but not model-free, contributions to behavior. Moreover, stress-induced behavioral changes were modulated by individual WM capacity, such that low-WM-capacity individuals were more susceptible to detrimental stress effects than high-WM-capacity individuals. These results enrich existing accounts of the interplay between acute stress, working memory, and prefrontal function and suggest that executive function may be protective against the deleterious effects of acute stress.

2014年5月14日水曜日

Navigation in human crowds; testing the many-wrongs principle

Jolyon J. Faria, Edward A. Codling, John R.G. Dyer, Fritz Trillmich, Jens Krause
Animal Behaviour. Volume 78, Issue 3, September 2009, Pages 587–591

鳥は群れを形成することで、より正確に移動出来ることが知られている。
ヒトで検証。
「グループが十分に大きい」かつ「個々のメンバーの持つ情報のバラツキが大きい」時に、グループでの移動の方が正確になる。
鳥の移動と同じような実験課題を工夫。

The ‘many-wrongs principle’ predicts that animal group cohesion can cause groups to navigate more accurately than singletons. Recent theoretical work using individual-based simulations and several empirical studies of bird flock behaviour support this principle. However, for real animal groups it remains unclear what key factors are involved and whether group cohesion alone can act to produce the effect. We tested model predictions using human participants in a large circular arena. They were tested alone and in groups of two, three, six and 10, in three trials. For each trial, individuals were instructed to stay together and approach a preset but unmarked target on the arena perimeter. The target instruction included a degree of directional uncertainty of 22.5°, 67.5° or 112.5°. Individual directional uncertainty was equal for each group member within a trial, but differed between trials. As expected, we found that groups comprising individuals with lower directional uncertainty navigated more accurately. Group navigational accuracy increased with group size but only between singletons and groups of 10 and only when individuals had a high directional uncertainty of 112.5°. This study provides evidence in human groups that group cohesion can increase navigational accuracy but that this effect is restricted to larger group sizes and when individual directional uncertainty is high.

Illustrator CS5 が英語環境のMacで起動できない

ずーっと困ってたのですが、ググるとすんなり解決。
参考にしたのは以下のページ。

Macの言語を日本語以外にするとIllustratorが起動しない問題
http://rewish.jp/blog/misc/mac_ai_lang

Illustrator CS5 日本語版を英語環境のMacで起動する
http://blog.livedoor.jp/annotunzdy/archives/1279487.html

2014年5月13日火曜日

Collective Cognition in Humans: Groups Outperform Their Best Members in a Sentence Reconstruction Task

Romain J. G. Clément, Stefan Krause, Nikolaus von Engelhardt, Jolyon J. Faria, Jens Krause, Ralf H. J. M. Kurvers
PLoS ONE 8(10): e77943. doi:10.1371/journal.pone.0077943

グループでの意思決定は個人での意思決定より勝る。
「スピーチを再現する」という実験課題を使用。
ヒトに特徴的な「言語」に注目している点がポイント?

Group-living is widespread among animals and one of the major advantages of group-living is the ability of groups to solve cognitive problems that exceed individual ability. Humans also make use of collective cognition and have simultaneously developed a highly complex language to exchange information. Here we investigated collective cognition of human groups regarding language use in a realistic situation. Individuals listened to a public announcement and had to reconstruct the sentence alone or in groups. This situation is often encountered by humans, for instance at train stations or airports. Using recent developments in machine speech recognition, we analysed how well individuals and groups reconstructed the sentences from a syntactic (i.e., the number of errors) and semantic (i.e., the quality of the retrieved information) perspective. We show that groups perform better both on a syntactic and semantic level than even their best members. Groups made fewer errors and were able to retrieve more information when reconstructing the sentences, outcompeting even their best group members. Our study takes collective cognition studies to the more complex level of language use in humans.

2014年5月12日月曜日

Conflicts of interest and the evolution of decision sharing.

Larissa Conradt and Timothy J Roper
Phil. Trans. R. Soc. B 27 March 2009 vol. 364 no. 1518

集団の構成員間で利害対立がある場合、どのように集団的意思決定を行うのか(どのような意思決定様式が進化するのか)?
利害対立が深刻なケースでは「独裁的な意思決定」が、深刻でないときは「民主的な意思決定」方式が進化する。

Social animals regularly face consensus decisions whereby they choose, collectively, between mutually exclusive actions. Such decisions often involve conflicts of interest between group members with respect to preferred action. Conflicts could, in principle, be resolved, either by sharing decisions between members (‘shared decisions’) or by one ‘dominant’ member making decisions on behalf of the whole group (‘unshared decisions’). Both, shared and unshared decisions, have been observed. However, it is unclear as to what favours the evolution of either decision type. Here, after a brief literature review, we present a novel method, involving a combination of self-organizing system and game theory modelling, of investigating the evolution of shared and unshared decisions. We apply the method to decisions on movement direction. We find that both, shared and unshared, decisions can evolve without individuals having a global overview of the group's behaviour or any knowledge about other members' preferences or intentions. Selection favours unshared over shared decisions when conflicts are high relative to grouping benefits, and vice versa. These results differ from those of group decision models relating to activity timings. We attribute this to fundamental differences between collective decisions about modalities that are disjunct (here, space) or continuous (here, time) with respect to costs/benefits.

2014年5月11日日曜日

Group performance and decision making.

Norbert L Kerr and R Scott Tindale
Annual review of psychology, 2004, 55, 623–655.

心理学の分野における集団的意思決定についての総説論文。

Theory and research on small group performance and decision making is reviewed. Recent trends in group performance research have found that process gains as well as losses are possible, and both are frequently explained by situational and procedural contexts that differentially affect motivation and resource coordination. Research has continued on classic topics (e.g., brainstorming, group goal setting, stress, and group performance) and relatively new areas (e.g., collective induction). Group decision making research has focused on preference combination for continuous response distributions and group information processing. New approaches (e.g., group-level signal detection) and traditional topics (e.g., groupthink) are discussed. New directions, such as nonlinear dynamic systems, evolutionary adaptation, and technological advances, should keep small group research vigorous well into the future.

2014年5月8日木曜日

Neural representation of expected value in the adolescent brain

Emily Barkley-Levenson and Adriana Galván
PNAS. January 28, 2014 vol. 111 no. 4

思春期には、大人に比べ、報酬期待に対する腹側線条体が強く、それがリスク下の意思決定の違いに現れている。

Previous work shows that the adolescent reward system is hyperactive, but this finding may be confounded by differences in how teens value money. To address this, we examined the neural ontogeny of objective value representation. Adolescent and adult participants performed a monetary gambling task in which they chose to accept or reject gambles of varying expected value. Increasing expected value had a stronger influence over gambling choices in adolescents relative to adults, an effect that was paralleled by greater activation in the ventral striatum in adolescents. This unique adolescent ventral striatum response remained even after matching groups on acceptance behavior. These behavioral and neural data suggest that the value of available options has a greater influence in adolescent versus adult choices, even when objective value and subjective choice are held constant. This research provides further evidence that hyperactivation of reward circuitry in adolescence may be a normative ontogenetic shift that is due to greater valuation in the adolescent brain.

2014年5月7日水曜日

Different impressions of other agents obtained through social interaction uniquely modulate dorsal and ventral pathway activities in the social human brain

Hideyuki Takahashi, Kazunori Terada, Tomoyo Morita, Shinsuke Suzuki, Tomoki Haji, Hideki Kojima, Masahiro Yoshikawa, Yoshio Matsumoto, Takashi Omori, Minoru Asada, Eiichi Naito
Cortex (in press)

共著で加わった論文。ヒトは他者やロボットと相互作用する際、相手がどの程度「人間っぽいのか」と「自分の心を読もうとしてくるのか」を別々に評価しており、それらは「社会性関連の脳部位として知られるTPJ」の別々の領域で処理されている。

Internal (neuronal) representations in the brain are modified by our experiences, and this phenomenon is not unique to sensory and motor systems. Here, we show that different impressions obtained through social interaction with a variety of agents uniquely modulate activity of dorsal and ventral pathways of the brain network that mediates human social behavior.

We scanned brain activity with functional magnetic resonance imaging (fMRI) in 16 healthy volunteers when they performed a simple matching-pennies game with a human, human-like android, mechanical robot, interactive robot, and a computer. Before playing this game in the scanner, participants experienced social interactions with each opponent separately and scored their initial impressions using two questionnaires.

We found that the participants perceived opponents in two mental dimensions: one represented “mind-holderness” in which participants attributed anthropomorphic impressions to some of the opponents that had mental functions, while the other dimension represented “mind-readerness” in which participants characterized opponents as intelligent. Interestingly, this “mind-readerness” dimension correlated to participants frequently changing their game tactic to prevent opponents from envisioning their strategy, and this was corroborated by increased entropy during the game. We also found that the two factors separately modulated activity in distinct social brain regions. Specifically, mind-holderness modulated activity in the dorsal aspect of the temporoparietal junction (TPJ) and medial prefrontal and posterior paracingulate cortices, while mind-readerness modulated activity in the ventral aspect of TPJ and the temporal pole.

These results clearly demonstrate that activity in social brain networks is modulated through pre-scanning experiences of social interaction with a variety of agents. Furthermore, our findings elucidated the existence of two distinct functional networks in the social human brain. Social interaction with anthropomorphic or intelligent-looking agents may distinctly shape the internal representation of our social brain, which may in turn determine how we behave for various agents that we encounter in our society.

2014年5月6日火曜日

Social Equality in the Number of Choice Options Is Represented in the Ventromedial Prefrontal Cortex

Ryuta Aoki, Madoka Matsumoto, Yukihito Yomogida, Keise Izuma, Kou Murayama, Ayaka Sugiura, Colin F. Camerer, Ralph Adolphs, and Kenji Matsumoto
The Journal of Neuroscience, 30 April 2014, 34(18):6413-6421

脳・報酬系は(自己の報酬だけではなく)自己と他者の「結果(例:報酬額)の平等」に反応することが知られているが、「機会(例:選択肢の数)の平等」にも反応するのか?前頭前野腹内側部は反応するが、腹側線条体はしない。

現代社会では「結果の平等」より「機会の平等」が重視されているにも関わらず、後者の研究はほとんど行われていない(前者の研究はたくさんあるが)〜というイントロの流れがエレガント。

A distinct aspect of the sense of fairness in humans is that we care not only about equality in material rewards but also about equality in nonmaterial values. One such value is the opportunity to choose freely among many options, often regarded as a fundamental right to economic freedom. In modern developed societies, equal opportunities in work, living, and lifestyle are enforced by antidiscrimination laws. Despite the widespread endorsement of equal opportunity, no studies have explored how people assign value to it. We used functional magnetic resonance imaging to identify the neural substrates for subjective valuation of equality in choice opportunity. Participants performed a two-person choice task in which the number of choices available was varied across trials independently of choice outcomes. By using this procedure, we manipulated the degree of equality in choice opportunity between players and dissociated it from the value of reward outcomes and their equality. We found that activation in the ventromedial prefrontal cortex (vmPFC) tracked the degree to which the number of options between the two players was equal. In contrast, activation in the ventral striatum tracked the number of options available to participants themselves but not the equality between players. Our results demonstrate that the vmPFC, a key brain region previously implicated in the processing of social values, is also involved in valuation of equality in choice opportunity between individuals. These findings may provide valuable insight into the human ability to value equal opportunity, a characteristic long emphasized in politics, economics, and philosophy.

2014年5月5日月曜日

Damage to insula abolishes cognitive distortions during simulated gambling

Luke Clark, Bettina Studer, Joel Bruss, Daniel Tranel, and Antoine Bechara
PNAS 2014(11) 6098–6103

「コイン投げで表が出たら、次は裏が出る可能性が高い」といった種々のギャンブラーの誤りが脳損傷患者で見られるのか?
扁桃体(Amygdala)、前頭前野内腹側部損傷患者(vmPFC)では、健常者と同じく、「ギャンブラーの誤り」が見られた。
一方、島皮質損傷患者では見られなかった。
→ ギャンブルにおける不合理な行動には島皮質が関わっている。

Gambling is a naturalistic example of risky decision-making. During gambling, players typically display an array of cognitive biases that create a distorted expectancy of winning. This study investigated brain regions underpinning gambling-related cognitive distortions, contrasting patients with focal brain lesions to the ventromedial prefrontal cortex (vmPFC), insula, or amygdala (“target patients”) against healthy comparison participants and lesion comparison patients (i.e., with lesions that spare the target regions). A slot machine task was used to deliver near-miss outcomes (i.e., nonwins that fall spatially close to a jackpot), and a roulette game was used to examine the gambler’s fallacy (color decisions following outcome runs). Comparison groups displayed a heightened motivation to play following near misses (compared with full misses), and manifested a classic gambler’s fallacy effect. Both effects were also observed in patients with vmPFC and amygdala damage, but were absent in patients with insula damage. Our findings indicate that the distorted cognitive processing of near-miss outcomes and event sequences may be ordinarily supported by the recruitment of the insula. Interventions to reduce insula reactivity could show promise in the treatment of disordered gambling.

2014年5月1日木曜日

The Brain's Temporal Dynamics from a Collective Decision to Individual Action

Caroline J. Charpentier, Christina Moutsiana, Neil Garrett, and Tali Sharot
The Journal of Neuroscience, 23 April 2014, 34(17):5816-5823;

多数派の選択に同調して自分の意見/選好/選択を変える際の脳活動。
「多数派の選択を観察した」際の眼窩前頭皮質の活動と「その自分の選択を行う」際の活動が似ている人ほど多数派同調を行う。

Social animals constantly make decisions together. What determines if individuals will subsequently adjust their behavior to align with collective choices? Here, using functional magnetic resonance imaging in humans, we characterize a novel temporal model of brain response from the time a collective decision is made to the time an individual action is required. We reveal that whether a behavioral modification will occur is determined not necessarily by the brain's response to the initial social influence, but by how that response (specifically in the orbitofrontal cortex; OFC) is mirrored at a later time when the individual selects their own action. This result suggests that the OFC may reconstitute an initial state of collective influence when individual action is subsequently needed. Importantly, these dynamics vary across individuals as a function of trait conformity and mediate the relationship between this personality characteristic and behavioral adjustment toward the group.

2014年4月30日水曜日

The Anterior Cingulate Gyrus Signals the Net Value of Others' Rewards

Matthew A. J. Apps and Narender Ramnani
The Journal of Neuroscience, 30 April 2014, 34(18):6190-6200

ヒト前帯状皮質(ACC)は「他者のNet Value(ベネフィット−コスト)」を保持しているのか?
前帯状溝(ACCs)はコストを保持しており、前帯状回(ACCg)はNet Valueを保持している。

Evaluating the costs and benefits of our own choices is central to most forms of decision-making and its mechanisms in the brain are becoming increasingly well understood. To interact successfully in social environments, it is also essential to monitor the rewards that others receive. Previous studies in nonhuman primates have found neurons in the anterior cingulate cortex (ACC) that signal the net value (benefit minus cost) of rewards that will be received oneself and also neurons that signal when a reward will be received by someone else. However, little is understood about the way in which the human brain engages in cost–benefit analyses during social interactions. Does the ACC signal the net value (the benefits minus the costs) of rewards that others will receive? Here, using fMRI, we examined activity time locked to cues that signaled the anticipated reward magnitude (benefit) to be gained and the level of effort (cost) to be incurred either by a subject themselves or by a social confederate. We investigated whether activity in the ACC covaries with the net value of rewards that someone else will receive when that person is required to exert effort for the reward. We show that, although activation in the sulcus of the ACC signaled the costs on all trials, gyral ACC (ACCg) activity varied parametrically only with the net value of rewards gained by others. These results suggest that the ACCg plays an important role in signaling cost–benefit information by signaling the value of others' rewards during social interactions.

2014年4月17日木曜日

Oxytocin promotes group-serving dishonesty

Shaul Shalvi and Carsten K. W. De Dreu
PNAS vol. 111 no. 15,  5503–5507

オキシトシンを経鼻投与されると、ヒトは「仲間のために」嘘をつくようになる。一方、自分のためにつく嘘の頻度は変わらない。

To protect and promote the well-being of others, humans may bend the truth and behave unethically. Here we link such tendencies to oxytocin, a neuropeptide known to promote affiliation and cooperation with others. Using a simple coin-toss prediction task in which participants could dishonestly report their performance levels to benefit their group’s outcome, we tested the prediction that oxytocin increases group-serving dishonesty. A double-blind, placebo-controlled experiment allowing individuals to lie privately and anonymously to benefit themselves and fellow group members showed that healthy males (n = 60) receiving intranasal oxytocin, rather than placebo, lied more to benefit their group, and did so faster, yet did not necessarily do so because they expected reciprocal dishonesty from fellow group members. Treatment effects emerged when lying had financial consequences and money could be gained; when losses were at stake, individuals in placebo and oxytocin conditions lied to similar degrees. In a control condition (n = 60) in which dishonesty only benefited participants themselves, but not fellow group members, oxytocin did not influence lying. Together, these findings fit a functional perspective on morality revealing dishonesty to be plastic and rooted in evolved neurobiological circuitries, and align with work showing that oxytocin shifts the decision-maker’s focus from self to group interests. These findings highlight the role of bonding and cooperation in shaping dishonesty, providing insight into when and why collaboration turns into corruption.

2014年4月16日水曜日

Neural Mechanisms of Gain–Loss Asymmetry in Temporal Discounting

Saori C. Tanaka, Katsunori Yamada, Hiroyasu Yoneda, and Fumio Ohtake

The Journal of Neuroscience, 16 April 2014, 34(16):5595-5602;

ヒトは将来の報酬を、損失に比べて、多く割り引くことが知られている(サイン効果)。
サイン効果が見られた被験者と見られなかった被験者の脳活動を比較すると、「報酬/損失の遅延時間に対する線条体の活動」及び「報酬/損失額に対する島皮質の活動」に違いがあることが分かった。

Humans typically discount future gains more than losses. This phenomenon is referred to as the “sign effect” in experimental and behavioral economics. Although recent studies have reported associations between the sign effect and important social problems, such as obesity and incurring multiple debts, the biological basis for this phenomenon remains poorly understood. Here, we hypothesized that enhanced loss-related neural processing in magnitude and/or delay representation are causes of the sign effect. We examined participants performing intertemporal choice tasks involving future gains or losses and compared the brain activity of those who exhibited the sign effect and those who did not. When predicting future losses, significant differences were apparent between the two participant groups in terms of striatal activity representing delay length and in insular activity representing sensitivity to magnitude. Furthermore, participants with the sign effect exhibited a greater insular response to the magnitude of loss than to that of gain, and also a greater striatal response to the delay of loss than to that of gain. These findings may provide a new biological perspective for the development of novel treatments and preventive measures for social problems associated with the sign effect.

2014年4月13日日曜日

Activity of striatal neurons reflects social action and own reward

Raymundo Báez-Mendoza, Christopher J. Harris, and Wolfram Schultz
PNAS October 8, 2013 vol. 110 no. 41 16634-16639

「線条体(報酬の処理に関わっている)」のニューロンは社会的報酬の処理にも関わっているのか?

(1)自分の行為の結果、自分に報酬が来る(通常の報酬関連課題)
(2)自分の行為の結果、他者に報酬が行く
(3)他者の行為の結果、自分に報酬が来る
(4)他者の行為の結果、他者に報酬が来る
の四条件を調べた。

線条体のニューロンは、行為者が自分であろうと他者であろうと関係なく、自分の報酬に反応した。
一方、他者の報酬にはほとんど反応しなかった。
また、「行為者(自分 or 他者)」によって反応が変わるニューロンも見つかった。

Social interactions provide agents with the opportunity to earn higher benefits than when acting alone and contribute to evolutionary stable strategies. A basic requirement for engaging in beneficial social interactions is to recognize the actor whose movement results in reward. Despite the recent interest in the neural basis of social interactions, the neurophysiological mechanisms identifying the actor in social reward situations are unknown. A brain structure well suited for exploring this issue is the striatum, which plays a role in movement, reward, and goal-directed behavior. In humans, the striatum is involved in social processes related to reward inequity, donations to charity, and observational learning. We studied the neurophysiology of social action for reward in rhesus monkeys performing a reward-giving task. The behavioral data showed that the animals distinguished between their own and the conspecific’s reward and knew which individual acted. Striatal neurons coded primarily own reward but rarely other's reward. Importantly, the activations occurred preferentially, and in approximately similar fractions, when either the own or the conspecific's action was followed by own reward. Other striatal neurons showed social action coding without reward. Some of the social action coding disappeared when the conspecific's role was simulated by a computer, confirming a social rather than observational relationship. These findings demonstrate a role of striatal neurons in identifying the social actor and own reward in a social setting. These processes may provide basic building blocks underlying the brain's function in social interactions.

2014年4月11日金曜日

Neural activity associated with enhanced facial attractiveness by cosmetics use

Ueno A, Ito A, Kawasaki I, Kawachi Y, Yoshida K, Murakami Y, Sakai S, Iijima T, Matsue Y, Fujii T.
Neurosci Lett. 2014 Mar 2;566C:142-146.

先日お会いした伊藤さん@京大の東北大時代の仕事かな?

同一人物の「化粧をした顔」と「化粧をしていない顔」。
ヒトは前者の方をより魅力的と感じ、それに対応して(報酬系の脳部位である)眼窩前頭皮質の活動も上昇する。

Previous psychological studies have shown that make-up enhances facial attractiveness. Although neuroimaging evidence indicates that the orbitofrontal cortex (OFC) shows greater activity for faces of attractive people than for those of unattractive people, there is no direct evidence that the OFC also shows greater activity for the face of an individual wearing make-up than for the same face without make-up. Using functional magnetic resonance imaging (fMRI), we investigated neural activity while subjects viewed 144 photographs of the same faces with and without make-up (48 with make-up, 48 without make-up, and 48 scrambled photographs) and assigned these faces an attractiveness rating. The behavioral data showed that the faces with make-up were rated as more attractive than those without make-up. The imaging data revealed that the left OFC and the right hippocampus showed greater activity for faces with make-up than for those without make-up. Furthermore, the activities of the right anterior cingulate cortex, left hippocampus, and left OFC increased with increasing facial attractiveness resulting from cosmetics use. These results provide direct evidence of the neural underpinnings of cosmetically enhanced facial attractiveness.

2014年4月10日木曜日

Multiple Neural Mechanisms of Decision Making and Their Competition under Changing Risk Pressure

Nils Kolling, Marco Wittmann, Matthew F.S. Rushworth
Neuron, Volume 81, Issue 5, 1190-1202, 5 March 2014

ハイリスク・ハイリターンな選択肢を選ぶべきか?
自分の置かれている状況によって異なる。
例えば、莫大な借金がある時は、一か八かでハイリスク・ハイリターンな選択肢を選ぶべき。
その調節はヒトでは背側前帯状皮質(dorsal anterior cingulate cortex: dACC)で行われている。

Sometimes when a choice is made, the outcome is not guaranteed and there is only a probability of its occurrence. Each individual’s attitude to probability, sometimes called risk proneness or aversion, has been assumed to be static. Behavioral ecological studies, however, suggest such attitudes are dynamically modulated by the context an organism finds itself in; in some cases, it may be optimal to pursue actions with a low probability of success but which are associated with potentially large gains. We show that human subjects rapidly adapt their use of probability as a function of current resources, goals, and opportunities for further foraging. We demonstrate that dorsal anterior cingulate cortex (dACC) carries signals indexing the pressure to pursue unlikely choices and signals related to the taking of such choices. We show that dACC exerts this control over behavior when it, rather than ventromedial prefrontal cortex, interacts with posterior cingulate cortex.

2014年4月9日水曜日

Integrative Moral Judgment: Dissociating the Roles of the Amygdala and Ventromedial Prefrontal Cortex

Amitai Shenhav and Joshua D. Greene
J. Neurosci. 2014;34 4741-4749

道徳判断の神経基盤。
判断は、扁桃体が「置かれた状況の感情/自動的な側面」を処理し、その情報が前頭前野内腹側部に送られることで行われる。

A decade's research highlights a critical dissociation between automatic and controlled influences on moral judgment, which is subserved by distinct neural structures. Specifically, negative automatic emotional responses to prototypically harmful actions (e.g., pushing someone off of a footbridge) compete with controlled responses favoring the best consequences (e.g., saving five lives instead of one). It is unknown how such competitions are resolved to yield “all things considered” judgments. Here, we examine such integrative moral judgments. Drawing on insights from research on self-interested, value-based decision-making in humans and animals, we test a theory concerning the respective contributions of the amygdala and ventromedial prefrontal cortex (vmPFC) to moral judgment. Participants undergoing fMRI responded to moral dilemmas, separately evaluating options for their utility (Which does the most good?), emotional aversiveness (Which feels worse?), and overall moral acceptability. Behavioral data indicate that emotional aversiveness and utility jointly predict “all things considered” integrative judgments. Amygdala response tracks the emotional aversiveness of harmful utilitarian actions and overall disapproval of such actions. During such integrative moral judgments, the vmPFC is preferentially engaged relative to utilitarian and emotional assessments. Amygdala-vmPFC connectivity varies with the role played by emotional input in the task, being the lowest for pure utilitarian assessments and the highest for pure emotional assessments. These findings, which parallel those of research on self-interested economic decision-making, support the hypothesis that the amygdala provides an affective assessment of the action in question, whereas the vmPFC integrates that signal with a utilitarian assessment of expected outcomes to yield “all things considered” moral judgments.

2014年4月8日火曜日

Cue-Induced Craving Increases Impulsivity via Changes in Striatal Value Signals in Problem Gamblers

Stephan F. Miedl, Christian Buchel, and Jan Peters
J. Neurosci. 2014;34 4750-4755

ギャンブル中毒者は「ギャンブルを連想させる画像」を見ると、時間割引率が高くなる(衝動的になる=直近の報酬を高く評価する)。
また、その際には、中脳と腹側線条体における「価値」の表現方法が(ギャンブルを連想させない画像を見た際とは)異なっている。

Impulsive behavior such as steep temporal discounting is a hallmark of addiction and is associated with relapse. In pathological gamblers, discounting may be further increased by the presence of gambling-related cues in the environment, but the extent to which the gambling relatedness of task settings affects reward responses in gambling addiction is debated. In the present study, human problem gamblers made choices between immediate rewards and individually tailored larger-but-later rewards while visual gambling-related scenes were presented in the background. N = 17 participants were scanned using fMRI, whereas N = 5 additional participants completed a behavioral version of the task. Postscan craving ratings were acquired for each image, and behavioral and neuroimaging data were analyzed separately for high- and low-craving trials (median split analysis). Discounting was steeper for high versus low craving trials. Neuroimaging revealed a positive correlation with model-based subjective value in midbrain and striatum in low-craving trials that was reversed in high-craving trials. These findings reveal a modulation of striatal reward responses in gamblers by addiction-related cues, and highlight a potentially important mechanism that may contribute to relapse. Cue-induced changes in striatal delayed reward signals may lead to increased discounting of future rewards, which might in turn affect the likelihood of relapse.

2014年4月3日木曜日

Attributing awareness to oneself and to others

Yin T. Kelly, Taylor W. Webb, Jeffrey D. Meier, Michael J. Arcaro, and Michael S. A. Graziano
Proceedings of the National Academy of Sciences 1 April 2014; Vol. 111, No. 13

「他者がある物体を(視覚的に)認識しているか?」を判断する際にはTPJ(側頭頭頂接合部)が活動する。
一方、TMSを用いてTPJの活動を人為的に抑制すると、(被験者自身の)物体の認識がうまくできなくなる。
→「他者の物体認識についての判断」と「自分自身の(視覚的)物体認識」は同じ脳領域で行われている。

This study tested the possible relationship between reported visual awareness (“I see a visual stimulus in front of me”) and the social attribution of awareness to someone else (“That person is aware of an object next to him”). Subjects were tested in two steps. First, in an fMRI experiment, subjects were asked to attribute states of awareness to a cartoon face. Activity associated with this task was found bilaterally within the temporoparietal junction (TPJ) among other areas. Second, the TPJ was transiently disrupted using single-pulse transcranial magnetic stimulation (TMS). When the TMS was targeted to the same cortical sites that had become active during the social attribution task, the subjects showed symptoms of visual neglect in that their detection of visual stimuli was significantly affected. In control trials, when TMS was targeted to nearby cortical sites that had not become active during the social attribution task, no significant effect on visual detection was found. These results suggest that there may be at least some partial overlap in brain mechanisms that participate in the social attribution of sensory awareness to other people and in attributing sensory awareness to oneself.

2014年4月2日水曜日

Disentangling neural representations of value and salience in the human brain

Thorsten Kahnt, Soyoung Q Park, John-Dylan Haynes, and Philippe N. Tobler
Proceedings of the National Academy of Sciences 1 April 2014; Vol. 111, No. 13

脳内での「価値(value)」と「顕著性(salience)」の処理。後部頭頂皮質の中で、上部が価値、下部が顕著性をコードしている。また、眼窩前頭皮質は価値をコードしている. http://www.pnas.org/content/111/13/5000

A large body of evidence has implicated the posterior parietal and orbitofrontal cortex in the processing of value. However, value correlates perfectly with salience when appetitive stimuli are investigated in isolation. Accordingly, considerable uncertainty has remained about the precise nature of the previously identified signals. In particular, recent evidence suggests that neurons in the primate parietal cortex signal salience instead of value. To investigate neural signatures of value and salience, here we apply multivariate (pattern-based) analyses to human functional MRI data acquired during a noninstrumental outcome-prediction task involving appetitive and aversive outcomes. Reaction time data indicated additive and independent effects of value and salience. Critically, we show that multivoxel ensemble activity in the posterior parietal cortex encodes predicted value and salience in superior and inferior compartments, respectively. These findings reinforce the earlier reports of parietal value signals and reconcile them with the recent salience report. Moreover, we find that multivoxel patterns in the orbitofrontal cortex correlate with value. Importantly, the patterns coding for the predicted value of appetitive and aversive outcomes are similar, indicating a common neural scale for appetite and aversive values in the orbitofrontal cortex. Thus orbitofrontal activity patterns satisfy a basic requirement for a neural value signal.

2014年4月1日火曜日

A neural mechanism underlying failure of optimal choice with multiple alternatives

Bolton K H Chau, Nils Kolling, Laurence T Hunt, Mark E Walton & Matthew F S Rushworth
Nature Neuroscience (2014) doi:10.1038/nn.3649

二つの選択肢間の意思決定において,三番目の選択肢が現れたらどうなるのか?
「三番目の選択肢の価値が低い」時の方が,元々の選択が正確にできなくなる.
また,その際には,「二つの選択肢の価値の差」をコードしている前頭前野内腹側部(vmPFC)の活動が低下している.

Despite widespread interest in neural mechanisms of decision-making, most investigations focus on decisions between just two options. Here we adapt a biophysically plausible model of decision-making to predict how a key decision variable, the value difference signal—encoding how much better one choice is than another—changes with the value of a third, but unavailable, alternative. The model predicts a surprising failure of optimal decision-making: greater difficulty choosing between two options in the presence of a third very poor, as opposed to very good, alternative. Both investigation of human decision-making and functional magnetic resonance imaging–based measurements of value difference signals in ventromedial prefrontal cortex (vmPFC) bore out this prediction. The vmPFC signal decreased in the presence of low-value third alternatives, and vmPFC effect sizes predicted individual variation in suboptimal decision-making in the presence of multiple alternatives. The effect contrasts with that of divisive normalization in parietal cortex.

2014年3月31日月曜日

Changing value through cued approach: an automatic mechanism of behavior change

Tom Schonberg, Akram Bakkour, Ashleigh M Hover, Jeanette A Mumford, Lakshya Nagar, Jacob Perez & Russell A Poldrack
Nature Neuroscience 17, 625–630 (2014)

「ある商品を見せられると同時に音が鳴り,素早くボタンを押すことが求められる」という実験課題.
それだけで、その商品に対する主観的価値(評価)が上昇する.
また,価値をコードしている脳部位(vmPFC:前頭前野内腹側部)の活動もそれに対応して変化する.

It is believed that choice behavior reveals the underlying value of goods. The subjective values of stimuli can be changed through reward-based learning mechanisms as well as by modifying the description of the decision problem, but it has yet to be shown that preferences can be manipulated by perturbing intrinsic values of individual items. Here we show that the value of food items can be modulated by the concurrent presentation of an irrelevant auditory cue to which subjects must make a simple motor response (i.e., cue-approach training). Follow-up tests showed that the effects of this pairing on choice lasted at least 2 months after prolonged training. Eye-tracking during choice confirmed that cue-approach training increased attention to the cued items. Neuroimaging revealed the neural signature of a value change in the form of amplified preference-related activity in ventromedial prefrontal cortex.

2014年3月24日月曜日

The Good, the Bad, and the Just: Justice Sensitivity Predicts Neural Response during Moral Evaluation of Actions Performed by Others

Keith J. Yoder and Jean Decety
J. Neurosci. 2014;34 4161-4166

質問紙で測定した「Justice Sensitivity(日本語訳は?)」は、道徳判断課題中の「右・側頭頭頂接合部(rTPJ)、背側前頭前野(dlPFC、dmPFC)」における脳活動と相関する。

Morality is a fundamental component of human cultures and has been defined as prescriptive norms regarding how people should treat one another, including concepts such as justice, fairness, and rights. Using fMRI, the current study examined the extent to which dispositions in justice sensitivity (i.e., how individuals react to experiences of injustice and unfairness) predict behavioral ratings of praise and blame and how they modulate the online neural response and functional connectivity when participants evaluate morally laden (good and bad) everyday actions. Justice sensitivity did not impact the neuro-hemodynamic response in the action-observation network but instead influenced higher-order computational nodes in the right temporoparietal junction (rTPJ), right dorsolateral and dorsomedial prefrontal cortex (rdlPFC, dmPFC) that process mental states understanding and maintain goal representations. Activity in these regions predicted praise and blame ratings. Further, the hemodynamic response in rTPJ showed a differentiation between good and bad actions 2 s before the response in rdlPFC. Evaluation of good actions was specifically associated with enhanced activity in dorsal striatum and increased the functional coupling between the rTPJ and the anterior cingulate cortex. Together, this study provides important knowledge in how individual differences in justice sensitivity impact neural computations that support psychological processes involved in moral judgment and mental-state reasoning.

2014年3月20日木曜日

Dorsal Raphe Neurons Signal Reward through 5-HT and Glutamate

Zhixiang Liu, Jingfeng Zhou, Yi Li, Fei Hu, Yao Lu, Ming Ma, Qiru Feng, Ju-en Zhang, Daqing Wang, Jiawei Zeng, Junhong Bao, Ji-Young Kim, Zhou-Feng Chen, Salah El Mestikawy, Minmin Luo
Neuron, Volume 81, Issue 6, 1360-1374, 19 March 2014

光遺伝学(オプトジェネティクス)。
中脳背側縫線核(midbrain dorsal raphe nucleus)に存在するセロトニン・ニューロンは報酬に反応する。
(従来の理論研究では「セロトニン・ニューロンは(ドーパミンニューロンとは逆に)報酬ではなく罰に反応する」と考えられていた。)

The dorsal raphe nucleus (DRN) in the midbrain is a key center for serotonin (5-hydroxytryptamine; 5-HT)-expressing neurons. Serotonergic neurons in the DRN have been theorized to encode punishment by opposing the reward signaling of dopamine neurons. Here, we show that DRN neurons encode reward, but not punishment, through 5-HT and glutamate. Optogenetic stimulation of DRN Pet-1 neurons reinforces mice to explore the stimulation-coupled spatial region, shifts sucrose preference, drives optical self-stimulation, and directs sensory discrimination learning. DRN Pet-1 neurons increase their firing activity during reward tasks, and this activation can be used to rapidly change neuronal activity patterns in the cortex. Although DRN Pet-1 neurons are often associated with 5-HT, they also release glutamate, and both neurotransmitters contribute to reward signaling. These experiments demonstrate the ability of DRN neurons to organize reward behaviors and might provide insights into the underlying mechanisms of learning facilitation and anhedonia treatment.

2014年2月24日月曜日

Contributions of Orbitofrontal and Lateral Prefrontal Cortices to Economic Choice and the Good-to-Action Transformation

Xinying Cai, and Camillo Padoa-Schioppa
Neuron, 13 February 2014

サル電気生理。
「二種類のモノ(例:リンゴとミカン)のうち、どちらかを得る」という状況では、
(1)まず、「どちらが欲しいのか(例:ミカンが欲しい)」を決め、
(2)その後、「欲しいものを得るための行動(例:右手を伸ばすしてミカンをとる)」を行う、
必要がある。
外側前頭前野は上記二つの過程の両方に関わっている。

Previous work indicates that economic decisions can be made independently of the visuomotor contingencies of the choice task (space of goods). However, the neuronal mechanisms through which the choice outcome (the chosen good) is transformed into a suitable action plan remain poorly understood. Here we show that neurons in lateral prefrontal cortex reflect the early stages of this good-to-action transformation. Monkeys chose between different juices. The experimental design dissociated in space and time the presentation of the offers and the saccade targets associated with them. We recorded from the orbital, ventrolateral, and dorsolateral prefrontal cortices (OFC, LPFCv, and LPFCd, respectively). Prior to target presentation, neurons in both LPFCv and LPFCd encoded the choice outcome in goods space. After target presentation, they gradually came to encode the location of the targets and the upcoming action plan. Consistent with the anatomical connectivity, all spatial and action-related signals emerged in LPFCv before LPFCd.

2014年2月23日日曜日

Dopamine prediction error responses integrate subjective value from different reward dimensions

Armin Lak, William R. Stauffer, and Wolfram Schultz
PNAS vol. 111 no. 6 2343–2348, doi: 10.1073/pnas.1321596111

ドーパミン神経細胞の活動は「様々な種類の刺激/報酬(色々な種類のジュース、不確実性を含んだ選択肢など)」の主観的価値に関する予測誤差をコードしている。

Prediction error signals enable us to learn through experience. These experiences include economic choices between different rewards that vary along multiple dimensions. Therefore, an ideal way to reinforce economic choice is to encode a prediction error that reflects the subjective value integrated across these reward dimensions. Previous studies demonstrated that dopamine prediction error responses reflect the value of singular reward attributes that include magnitude, probability, and delay. Obviously, preferences between rewards that vary along one dimension are completely determined by the manipulated variable. However, it is unknown whether dopamine prediction error responses reflect the subjective value integrated from different reward dimensions. Here, we measured the preferences between rewards that varied along multiple dimensions, and as such could not be ranked according to objective metrics. Monkeys chose between rewards that differed in amount, risk, and type. Because their choices were complete and transitive, the monkeys chose “as if” they integrated different rewards and attributes into a common scale of value. The prediction error responses of single dopamine neurons reflected the integrated subjective value inferred from the choices, rather than the singular reward attributes. Specifically, amount, risk, and reward type modulated dopamine responses exactly to the extent that they influenced economic choices, even when rewards were vastly different, such as liquid and food. This prediction error response could provide a direct updating signal for economic values.

2014年2月20日木曜日

Dopamine dependency for acquisition and performance of Pavlovian conditioned response

Martin Darvas, Amanda M. Wunsch, Jeffrey T. Gibbs, and Richard D. Palmiter
PNAS February 18, 2014 vol. 111 no. 7 2764–2769

古典的条件づけにおける"Goal tracking"行動にも、ドーパミンの活動が不可欠である。

【背景】
刺激・報酬の連合を十分に学習させた後に刺激を呈示すると、「刺激に近付いていく個体」と「報酬(が出現する場所)に近付いていく個体」がいる。
前者は"sign tracking"、後者は"goal tracking"と呼ばれるが、「goal trackingにドーパミンが必要か否か」はよく分かっていなかった。
http://www.nature.com/nature/journal/v469/n7328/abs/nature09588.html

During Pavlovian conditioning, pairing of a neutral conditioned stimulus (CS) with a reward leads to conditioned reward-approach responses (CRs) that are elicited by presentation of the CS. CR behaviors can be sign tracking, in which animals engage the CS, or goal tracking, in which animals go to the reward location. We investigated CR behaviors in mice with only ∼5% of normal dopamine in the striatum using a Pavlovian conditioning paradigm. These mice had severely impaired acquisition of the CR, which was ameliorated by pharmacological restoration of dopamine synthesis with L-dopa. Surprisingly, after they had learned the CR, its expression decayed only gradually in following sessions that were conducted without L-dopa treatment. To assess specific contributions of dopamine signaling in the dorsal or ventral striatum, we performed virus-mediated restoration of dopamine synthesis in completely dopamine-deficient (DD) mice. Mice with dopamine signaling only in the dorsal striatum did not acquire a CR, whereas mice with dopamine signaling only in in the ventral striatum acquired a CR. The CR in mice with dopamine signaling only in the dorsal striatum was restored by subjecting the mice to instrumental training in which they had to interact with the CS to obtain rewards. We conclude that dopamine is essential for learning and performance of CR behavior that is predominantly goal tracking. Furthermore, although dopamine signaling in the ventral striatum is sufficient to support a CR, dopamine signaling only in the dorsal striatum can also support a CR under certain circumstances.

2014年2月19日水曜日

Functional changes of the reward system underlie blunted response to social gaze in cocaine users

Katrin H. Preller, Marcus Herdener, Leonhard Schilbach, Philipp Stämpfli, Lea M. Hulka, Matthias Vonmoos, Nina Ingold, Kai Vogeley, Philippe N. Tobler, Erich Seifritz, and Boris B. Quednow
PNAS February 18, 2014 vol. 111 no. 7 2842–2847

コカイン常習者は社会性に様々な障害があるが、その神経科学的基盤は?
常習者は「社会的刺激に対する内側眼窩前頭野(mOFC)の活動」が弱い。

Social interaction deficits in drug users likely impede treatment, increase the burden of the affected families, and consequently contribute to the high costs for society associated with addiction. Despite its significance, the neural basis of altered social interaction in drug users is currently unknown. Therefore, we investigated basal social gaze behavior in cocaine users by applying behavioral, psychophysiological, and functional brain-imaging methods. In study I, 80 regular cocaine users and 63 healthy controls completed an interactive paradigm in which the participants’ gaze was recorded by an eye-tracking device that controlled the gaze of an anthropomorphic virtual character. Valence ratings of different eye-contact conditions revealed that cocaine users show diminished emotional engagement in social interaction, which was also supported by reduced pupil responses. Study II investigated the neural underpinnings of changes in social reward processing observed in study I. Sixteen cocaine users and 16 controls completed a similar interaction paradigm as used in study I while undergoing functional magnetic resonance imaging. In response to social interaction, cocaine users displayed decreased activation of the medial orbitofrontal cortex, a key region of reward processing. Moreover, blunted activation of the medial orbitofrontal cortex was significantly correlated with a decreased social network size, reflecting problems in real-life social behavior because of reduced social reward. In conclusion, basic social interaction deficits in cocaine users as observed here may arise from altered social reward processing. Consequently, these results point to the importance of reinstatement of social reward in the treatment of stimulant addiction.

2014年2月18日火曜日

Predicting risky choices from brain activity patterns

Sarah M. Helfinstein, Tom Schonberg, Eliza Congdon, Katherine H. Karlsgodt, Jeanette A. Mumford, Fred W. Sabb, Tyrone D. Cannon, Edythe D. London, Robert M. Bilder, and Russell A. Poldrack
PNAS February 18, 2014 vol. 111 no. 7 2470–2475

「認知制御に関わる脳部位の活動(fMRI信号)」から「リスク下の意思決定」を予測出来る。

Previous research has implicated a large network of brain regions in the processing of risk during decision making. However, it has not yet been determined if activity in these regions is predictive of choices on future risky decisions. Here, we examined functional MRI data from a large sample of healthy subjects performing a naturalistic risk-taking task and used a classification analysis approach to predict whether individuals would choose risky or safe options on upcoming trials. We were able to predict choice category successfully in 71.8% of cases. Searchlight analysis revealed a network of brain regions where activity patterns were reliably predictive of subsequent risk-taking behavior, including a number of regions known to play a role in control processes. Searchlights with significant predictive accuracy were primarily located in regions more active when preparing to avoid a risk than when preparing to engage in one, suggesting that risk taking may be due, in part, to a failure of the control systems necessary to initiate a safe choice. Additional analyses revealed that subject choice can be successfully predicted with minimal decrements in accuracy using highly condensed data, suggesting that information relevant for risky choice behavior is encoded in coarse global patterns of activation as well as within highly local activation within searchlights.

2014年2月13日木曜日

Dissociation between Neural Signatures of Stimulus and Choice in Population Activity of Human V1 during Perceptual Decision-Making

Kyoung Whan Choe, Randolph Blake, and Sang-Hun Lee
J. Neurosci. 2014;34 2725-2743 Open Access
http://www.jneurosci.org/cgi/content/abstract/34/7/2725?etoc

知覚的意思決定。
一次視覚野(V1)は「意思決定」に関する情報を保持しているか?
→ 「知覚」とか分離可能な形で保持している.

Primary visual cortex (V1) forms the initial cortical representation of objects and events in our visual environment, and it distributes information about that representation to higher cortical areas within the visual hierarchy. Decades of work have established tight linkages between neural activity occurring in V1 and features comprising the retinal image, but it remains debatable how that activity relates to perceptual decisions. An actively debated question is the extent to which V1 responses determine, on a trial-by-trial basis, perceptual choices made by observers. By inspecting the population activity of V1 from human observers engaged in a difficult visual discrimination task, we tested one essential prediction of the deterministic view: choice-related activity, if it exists in V1, and stimulus-related activity should occur in the same neural ensemble of neurons at the same time. Our findings do not support this prediction: while cortical activity signifying the variability in choice behavior was indeed found in V1, that activity was dissociated from activity representing stimulus differences relevant to the task, being advanced in time and carried by a different neural ensemble. The spatiotemporal dynamics of population responses suggest that short-term priors, perhaps formed in higher cortical areas involved in perceptual inference, act to modulate V1 activity prior to stimulus onset without modifying subsequent activity that actually represents stimulus features within V1.

2014年2月12日水曜日

Cortical Correlates of Human Motion Perception Biases

Brett Vintch and Justin L. Gardner
J. Neurosci. 2014;34 2592-2604
http://www.jneurosci.org/cgi/content/abstract/34/7/2592?etoc

理研時代にものすごくお世話になった Justinの論文.
「動く物体のスピードを知覚する際に存在する偏り」とそれに対応する一次視覚野(V1)の活動。
デコーディング,forward-encoding解析などを使用。

Human sensory perception is not a faithful reproduction of the sensory environment. For example, at low contrast, objects appear to move slower and flicker faster than veridical. Although these biases have been observed robustly, their neural underpinning is unknown, thus suggesting a possible disconnect of the well established link between motion perception and cortical responses. We used functional imaging to examine the encoding of speed in the human cortex at the scale of neuronal populations and asked where and how these biases are encoded. Decoding, voxel population, and forward-encoding analyses revealed biases toward slow speeds and high temporal frequencies at low contrast in the earliest visual cortical regions, matching perception. These findings thus offer a resolution to the disconnect between cortical responses and motion perception in humans. Moreover, biases in speed perception are considered a leading example of Bayesian inference because they can be interpreted as a prior for slow speeds. Therefore, our data suggest that perceptual priors of this sort can be encoded by neural populations in the same early cortical areas that provide sensory evidence.

2014年2月10日月曜日

Neural Computations Underlying Arbitration between Model-Based and Model-free Learning

Sang Wan Lee, Shinsuke Shimojo, John P. O'Doherty
Neuron, Volume 81, Issue 3, 687-699, 5 February 2014

Neuron誌より、同僚のSangWanの論文。「モデル・フリー学習とモデル・ベースド学習、どちらを使うか」をどうやって決めているのか?という話。

There is accumulating neural evidence to support the existence of two distinct systems for guiding action selection, a deliberative “model-based” and a reflexive “model-free” system. However, little is known about how the brain determines which of these systems controls behavior at one moment in time. We provide evidence for an arbitration mechanism that allocates the degree of control over behavior by model-based and model-free systems as a function of the reliability of their respective predictions. We show that the inferior lateral prefrontal and frontopolar cortex encode both reliability signals and the output of a comparison between those signals, implicating these regions in the arbitration process. Moreover, connectivity between these regions and model-free valuation areas is negatively modulated by the degree of model-based control in the arbitrator, suggesting that arbitration may work through modulation of the model-free valuation system when the arbitrator deems that the model-based system should drive behavior.

2014年1月27日月曜日

Individual consistency and flexibility in human social information use.

Toelch U, Bruce MJ, Newson L, Richerson PJ, Reader SM.
Proc Biol Sci. 2013 Dec 18;281(1776):20132864.

ヒトは社会的情報(他者の経験に由来する情報)をどの程度利用するのか?
環境(実験条件)によって柔軟に変えることができる。

Copying others appears to be a cost-effective way of obtaining adaptive information, particularly when flexibly employed. However, adult humans differ considerably in their propensity to use information from others, even when this 'social information' is beneficial, raising the possibility that stable individual differences constrain flexibility in social information use. We used two dissimilar decision-making computer games to investigate whether individuals flexibly adjusted their use of social information to current conditions or whether they valued social information similarly in both games. Participants also completed established personality questionnaires. We found that participants demonstrated considerable flexibility, adjusting social information use to current conditions. In particular, individuals employed a 'copy-when-uncertain' social learning strategy, supporting a core, but untested, assumption of influential theoretical models of cultural transmission. Moreover, participants adjusted the amount invested in their decision based on the perceived reliability of personally gathered information combined with the available social information. However, despite this strategic flexibility, participants also exhibited consistent individual differences in their propensities to use and value social information. Moreover, individuals who favoured social information self-reported as more collectivist than others. We discuss the implications of our results for social information use and cultural transmission.

2014年1月20日月曜日

Similar Roles of Substantia Nigra and Ventral Tegmental Dopamine Neurons in Reward and Aversion

Anton Ilango, Andrew J. Kesner, Kristine L. Keller, Garret D. Stuber, Antonello Bonci, and Satoshi Ikemoto
J. Neurosci. 2014;34 817-822

黒質稠密部(SNc)のドーパミン・ニューロンも、腹側被蓋野(VTA)のドーパミン・ニューロンと同様に、affective functionsに関連している。

Dopamine neurons in the ventral tegmental area (VTA) are implicated in affective functions. However, it is unclear to what extent dopamine neurons in substantia nigra pars compacta (SNc) play such roles. TH-Cre transgenic mice received adeno-associated viral vectors encoding channelrhodopsin2 (ChR2), halorhodopsin (NpHR), or control vector into the VTA or SNc, resulting in selective expression of these opsins in dopamine neurons. Mice with ChR2 learned instrumental responding to deliver photostimulation into the VTA or SNc and also sought for the compartment where they received photostimulation (i.e., operant place preference). Operant place preference scores were highly correlated with self-stimulation responses. In contrast, mice with NpHR avoided the compartment where they received photostimulation into the VTA, SNc, or dorsal striatum, whereas control mice did not. These observations suggest that the excitation and inhibition of SNc dopamine neurons elicit positive and negative affective effects, respectively, similar to those of VTA dopamine neurons.

2014年1月19日日曜日

Neurons in Dorsal Anterior Cingulate Cortex Signal Postdecisional Variables in a Foraging Task

Tommy C. Blanchard and Benjamin Y. Hayden
J. Neurosci. 2014;34 646-655

サル電気生理。
背側前帯状皮質は意思決定「前」の情報(例:各選択肢の価値)を保持しているのか?
意思決定「後」の情報(例:得られたはずの報酬)を保持しているのか?
→ 後者らしい。

The dorsal anterior cingulate cortex (dACC) is a key hub of the brain's executive control system. Although a great deal is known about its role in outcome monitoring and behavioral adjustment, whether and how it contributes to the decision process remain unclear. Some theories suggest that dACC neurons track decision variables (e.g., option values) that feed into choice processes and is thus “predecisional.” Other theories suggest that dACC activity patterns differ qualitatively depending on the choice that is made and is thus “postdecisional.” To compare these hypotheses, we examined responses of 124 dACC neurons in a simple foraging task in which monkeys accepted or rejected offers of delayed rewards. In this task, options that vary in benefit (reward size) and cost (delay) appear for 1 s; accepting the option provides the cued reward after the cued delay. To get at dACC neurons' contributions to decisions, we focused on responses around the time of choice, several seconds before the reward and the end of the trial. We found that dACC neurons signal the foregone value of the rejected option, a postdecisional variable. Neurons also signal the profitability (that is, the relative value) of the offer, but even these signals are qualitatively different on accept and reject decisions, meaning that they are also postdecisional. These results suggest that dACC can be placed late in the decision process and also support models that give it a regulatory role in decision, rather than serving as a site of comparison.

2014年1月17日金曜日

Phasic Dopamine Release in the Rat Nucleus Accumbens Symmetrically Encodes a Reward Prediction Error Term

Andrew S. Hart, Robb B. Rutledge, Paul W. Glimcher, and Paul E. M. Phillips
J. Neurosci. 2014;34 698-704
http://www.jneurosci.org/cgi/content/abstract/34/3/698?etoc

ドーパミンの放出そのものが報酬予測誤差をコードするのか?
負と正の予測誤差の両方を保持するのか?正の予測誤差だけなのか?
よく分かっていなかった。
→ ラットの側坐核における「ドーパミンの放出」は(負と正、両方の)報酬予測誤差と一致する。

Making predictions about the rewards associated with environmental stimuli and updating those predictions through feedback is an essential aspect of adaptive behavior. Theorists have argued that dopamine encodes a reward prediction error (RPE) signal that is used in such a reinforcement learning process. Recent work with fMRI has demonstrated that the BOLD signal in dopaminergic target areas meets both necessary and sufficient conditions of an axiomatic model of the RPE hypothesis. However, there has been no direct evidence that dopamine release itself also meets necessary and sufficient criteria for encoding an RPE signal. Further, the fact that dopamine neurons have low tonic firing rates that yield a limited dynamic range for encoding negative RPEs has led to significant debate about whether positive and negative prediction errors are encoded on a similar scale. To address both of these issues, we used fast-scan cyclic voltammetry to measure reward-evoked dopamine release at carbon fiber electrodes chronically implanted in the nucleus accumbens core of rats trained on a probabilistic decision-making task. We demonstrate that dopamine concentrations transmit a bidirectional RPE signal with symmetrical encoding of positive and negative RPEs. Our findings strengthen the case that changes in dopamine concentration alone are sufficient to encode the full range of RPEs necessary for reinforcement learning.

2014年1月8日水曜日

Solutions to the Public Goods Dilemma in Bacterial Biofilms

Knut Drescher, Carey D. Nadell, Howard A. Stone, Ned S. Wingreen, Bonnie L. Bassler
Current Biology, Volume 24, Issue 1, 50-55, 12 December 2013

バクテリアが公共財のジレンマを解くという研究。

Bacteria frequently live in densely populated surface-bound communities, termed biofilms [1,2,3,4]. Biofilm-dwelling cells rely on secretion of extracellular substances to construct their communities and to capture nutrients from the environment [5]. Some secreted factors behave as cooperative public goods: they can be exploited by nonproducing cells [6,7,8,9,10,11]. The means by which public-good-producing bacteria avert exploitation in biofilm environments are largely unknown. Using experiments with Vibrio cholerae, which secretes extracellular enzymes to digest its primary food source, the solid polymer chitin, we show that the public goods dilemma may be solved by two very different mechanisms: cells can produce thick biofilms that confine the goods to producers, or fluid flow can remove soluble products of chitin digestion, denying access to nonproducers. Both processes are unified by limiting the distance over which enzyme-secreting cells provide benefits to neighbors, resulting in preferential benefit to nearby clonemates and allowing kin selection to favor public good production. Our results demonstrate new mechanisms by which the physical conditions of natural habitats can interact with bacterial physiology to promote the evolution of cooperation.

2014年1月7日火曜日

Optogenetic and Electrical Microstimulation Systematically Bias Visuospatial Choice in Primates

Ji Dai, Daniel I. Brooks, David L. Sheinberg
Current Biology, Volume 24, Issue 1, 63-69, 12 December 2013

サルでオプトジェネティクスができたという研究。
LIPのニューロンを光で刺激することで、(微小電極刺激と同様に)サルの行動を変えることに成功した。

Optogenetics is a recently developed method in which neurons are genetically modified to express membrane proteins sensitive to light, enabling precisely targeted control of neural activity [1,2,3]. The temporal and spatial precision afforded by neural stimulation by light holds promise as a powerful alternative to current methods of neural control, which rely predominantly on electrical and pharmacological methods, in both research and clinical settings [4,5]. Although the optogenetic approach has been widely used in rodent and other small animal models to study neural circuitry [6,7,8], its functional application in primate models has proven more difficult. In contrast to the relatively large literature on the effects of cortical electrical microstimulation in perceptual and decision-making tasks [9,10,11,12,13], previous studies of optogenetic stimulation in primates have not demonstrated its utility in similar paradigms [14,15,16,17,18]. In this study, we directly compare the effects of optogenetic activation and electrical microstimulation in the lateral intraparietal area during a visuospatial discrimination task. We observed significant and predictable biases in visual attention in response to both forms of stimulation that are consistent with the experimental modulation of a visual salience map. Our results demonstrate the power of optogenetics as a viable alternative to electrical microstimulation for the precise dissection of the cortical pathways of high-level processes in the primate brain.

Decision making: from neuroscience to psychiatry.

Lee D.
Neuron. 2013 Apr 24;78(2):233-48. doi: 10.1016/j.neuron.2013.04.008.

意思決定について、経済学や機械学習のモデルと、それらの枠組みを援用した神経科学の最新の知見を紹介した総説。
パーキンソン病、統合失調症、自閉症などとの関連、精神医学への応用についても議論している。

Adaptive behaviors increase the likelihood of survival and reproduction and improve the quality of life. However, it is often difficult to identify optimal behaviors in real life due to the complexity of the decision maker's environment and social dynamics. As a result, although many different brain areas and circuits are involved in decision making, evolutionary and learning solutions adopted by individual decision makers sometimes produce suboptimal outcomes. Although these problems are exacerbated in numerous neurological and psychiatric disorders, their underlying neurobiological causes remain incompletely understood. In this review, theoretical frameworks in economics and machine learning and their applications in recent behavioral and neurobiological studies are summarized. Examples of such applications in clinical domains are also discussed for substance abuse, Parkinson's disease, attention-deficit/hyperactivity disorder, schizophrenia, mood disorders, and autism. Findings from these studies have begun to lay the foundations necessary to improve diagnostics and treatment for various neurological and psychiatric disorders.