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.