2013年12月31日火曜日

2013年は仕込みの年

2013年も終わりですね。

皆様、
今年もありがとうございました。
無事に仕事が納まった方も、積み残しがある方も、年末年始も出勤の方も、一年間お疲れ様でした。

というわけで、今年の三大ワースト・ニュースです。

一位:歯科治療で$1500失う(ちなみに保険あり…)
二位:円が対ドルで20%下落(ドルベースで収入が20%減…)
三位:ラスベガスで$300失う(完全に自業自得…)

お金は大事だよ〜♪(←音符とか付けてる場合じゃない)

研究面では、今年は仕込みの年でした。

昨年10月の渡米以来ボスと議論をしていたプロジェクトが始まりました。
また、夏には海外学振に通り、来年度以降もここカルテクで研究を続けられることになりました。

来年はぜひこのプロジェクトを世に出したいですね。
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???)

ということで、来年も元気でがんばって研究していきたいと思います。
それでは皆様、良いお年を!

あ、あと、三月に一本論文出しました。
"Indirect reciprocity is sensitive to costs of information transfer"
Shinsuke Suzuki & Hiromichi Kimura
Scientific Reports 3, Article number: 1435 doi:10.1038/srep01435
緩募、引用!

2013年12月27日金曜日

Effects of Amygdala Lesions on Reward-Value Coding in Orbital and Medial Prefrontal Cortex

Peter H. Rudebeck, Andrew R. Mitz, Ravi V. Chacko, Elisabeth A. Murray
Neuron, Volume 80, Issue 6, 1519-1531, 18 December 2013

サル電気生理/損傷研究。
扁桃体を損傷すると(つまり、扁桃体からの情報が届かなくなる)、前頭皮質での報酬情報の処理がどのように変わるか?
損傷前は眼窩前頭皮質と内側前頭前皮質、両方の領域のニューロンが報酬情報を保持しているが、前者の方が報酬情報を処理しているニューロンの比率が高い。
一方、扁桃体を損傷すると、眼窩前頭皮質で報酬情報を処理しているニューロンが減り、二つの脳領域で比率の差がなくなる。
つまり、報酬情報の処理において扁桃体は、主に「眼窩前頭皮質に報酬情報を送る」という役割を担っていると考えられる。

We examined the contribution of the amygdala to value signals within orbital prefrontal cortex (OFC) and medial prefrontal cortex (MFC). On each trial, monkeys chose between two stimuli that were associated with different quantities of reward. In intact monkeys, as expected, neurons in both OFC and MFC signaled the reward quantity associated with stimuli. Contrasted with MFC, OFC contained a larger proportion of neurons encoding reward quantity and did so with faster response latencies. Removing the amygdala eliminated these differences, mainly by decreasing value coding in OFC. Similar decreases occurred in OFC immediately before and after reward delivery. Although the amygdala projects to both OFC and MFC, we found that it has its greatest influence over reward-value coding in OFC. Notably, amygdala lesions did not abolish value coding in OFC, which shows that OFC’s representations of the value of objects, choices, and outcomes depends, in large part, on other sources.

2013年12月26日木曜日

Causal Evidence of Performance Monitoring by Neurons in Posterior Cingulate Cortex during Learning

Sarah R. Heilbronner, Michael L. Platt
Neuron: Volume 80, Issue 6, 18 December 2013, Pages 1384–1391

サル電気生理+損傷研究。
後部帯状皮質の神経活動は実験課題の成績と逆相関することが知られている。
「成績が悪い→後部帯状皮質が活動」なのか?
「後部帯状皮質が活動→成績が悪い」なのか?
前者っぽい。
つまり、「後部帯状皮質は成績が悪いことを認知して、脳内のリソースを実験課題に集中させる」ことに関与している。

The posterior cingulate cortex (CGp) is a major hub of the default mode network (DMN), a set of cortical areas with high resting activity that declines during task performance. This relationship suggests that DMN activity contributes to mental processes that are antagonistic to performance. Alternatively, DMN may detect conditions under which performance is poor and marshal cognitive resources for improvement. To test this idea, we recorded activity of CGp neurons in monkeys performing a learning task while varying reward size and novelty. We found that CGp neurons responded to errors, and this activity was magnified by small reward and novel stimuli. Inactivating CGp with muscimol impaired new learning when rewards were small but had no effect when rewards were large; inactivation did not affect performance on well-learned associations. Thus, CGp, and by extension the DMN, may support learning, and possibly other cognitive processes, by monitoring performance and motivating exploration.

2013年12月22日日曜日

Keeping up with the Joneses: Interpersonal Prediction Errors and the Correlation of Behavior in a Tandem Sequential Choice Task.

Terry Lohrenz, Meghana Bhatt, Nathan Apple, and P Read Montague
PLoS Comput Biol 9(10): e1003275.

ヒトfMRI。
二人の被験者が投資ゲームを行うと、両者の行動(投資額)が相関する。
また、他者の投資額と自分の投資額の差、対人予測誤差、は線条体でコードされている。

In many settings, copying, learning from or assigning value to group behavior is rational because such behavior can often act as a proxy for valuable returns. However, such herd behavior can also be pathologically misleading by coaxing individuals into behaviors that are otherwise irrational and it may be one source of the irrational behaviors underlying market bubbles and crashes. Using a two-person tandem investment game, we sought to examine the neural and behavioral responses of herd instincts in situations stripped of the incentive to be influenced by the choices of one's partner. We show that the investments of the two subjects correlate over time if they are made aware of their partner's choices even though these choices have no impact on either player's earnings. We computed an “interpersonal prediction error”, the difference between the investment decisions of the two subjects after each choice. BOLD responses in the striatum, implicated in valuation and action selection, were highly correlated with this interpersonal prediction error. The revelation of the partner's investment occurred after all useful information about the market had already been revealed. This effect was confirmed in two separate experiments where the impact of the time of revelation of the partner's choice was tested at 2 seconds and 6 seconds after a subject's choice; however, the effect was absent in a control condition with a computer partner. These findings strongly support the existence of mechanisms that drive correlated behavior even in contexts where there is no explicit advantage to do so.

2013年12月20日金曜日

The Behavioral and Neural Mechanisms Underlying the Tracking of Expertise

Erie D. Boorman, John P. O'Doherty, Ralph Adolphs, Antonio Rangel
Neuron, Volume 80, Issue 6, 1558-1571, 18 December 2013

「他者の賢さ(予測の正確さ)」をどうやって学習するか?「他者の予測が正解したか」と「他者の予測が自分の予測と一致したか」の情報をベイズ的に組み合わせて行う。
また、その学習は主に脳内のMentalizingネットワークで行われる。

Evaluating the abilities of others is fundamental for successful economic and social behavior. We investigated the computational and neurobiological basis of ability tracking by designing an fMRI task that required participants to use and update estimates of both people and algorithms’ expertise through observation of their predictions. Behaviorally, we find a model-based algorithm characterized subject predictions better than several alternative models. Notably, when the agent’s prediction was concordant rather than discordant with the subject’s own likely prediction, participants credited people more than algorithms for correct predictions and penalized them less for incorrect predictions. Neurally, many components of the mentalizing network—medial prefrontal cortex, anterior cingulate gyrus, temporoparietal junction, and precuneus—represented or updated expertise beliefs about both people and algorithms. Moreover, activity in lateral orbitofrontal and medial prefrontal cortex reflected behavioral differences in learning about people and algorithms. These findings provide basic insights into the neural basis of social learning.

2013年12月19日木曜日

Do people automatically track others' beliefs? Evidence from a continuous measure

Robrecht P R D van der Wel, Natalie Sebanz, and Guenther Knoblich
Cognition. Volume 130, Issue 1, January 2014, Pages 128–133

ヒト心理実験。
ヒトは他者の考え/信念を自動的に忖度してしまう。

Recent findings suggest that tracking others’ beliefs is not always effortful and slow, but may rely on a fast and implicit system. An untested prediction of the automatic belief tracking account is that own and others’ beliefs should be activated in parallel. We tested this prediction measuring continuous movement trajectories in a task that required deciding between two possible object locations. We independently manipulated whether participants’ belief about the object location was true or false and whether an onlooker’s belief about the object location was true or false. Manipulating whether or not the agent’s belief was ever task relevant allowed us to compare performance in an explicit and implicit version of the same task. Movement parameters revealed an influence of the onlooker’s irrelevant belief in the implicit version of the task. This provides evidence for parallel activation of own and others’ beliefs.

2013年12月18日水曜日

Unintended imitation affects success in a competitive game

Marnix Naber, Maryam Vaziri Pashkam, and Ken Nakayama
PNAS December 10, 2013 vol. 110 no. 50 20046-20050

他人と自分が競争しているような状況でも、ヒトは無意識にその他人の行動を模倣してしてしまう。

Imitation typically occurs in social contexts where people interact and have common goals. Here, we show that people are also highly susceptible to imitate each other in a competitive context. Pairs of players performed a competitive and fast-reaching task (a variant of the arcade whac-a-mole game) in which money could be earned if players hit brief-appearing visual targets on a large touchscreen before their opponents. In three separate experiments, we demonstrate that reaction times and movements were highly correlated within pairs of players. Players affected their success by imitating each other, and imitation depended on the visibility of the opponent’s behavior. Imitation persisted, despite the competitive and demanding nature of the game, even if this resulted in lower scores and payoffs and even when there was no need to counteract the opponent’s actions.

2013年12月17日火曜日

Amazon.comで注文した商品が届かない

寒い日が続いた12月のある日、Amazon.comでハロゲンヒーターを注文しました。

しかし予定日を数日過ぎても品物が届かない。
念のため、Amazonのページでステータスを確認すると、
"delivered"
になってる。

これは困った…
運送会社UPSのページを確認しても"delivered"に。
たぶん配送担当の人が届け先を間違えたのだろうけど、どうしたら良いのだろう?
キャンセルできるのかな?
返金してもらえるのかな?

結論から言うと、Amazonは迅速に対応してくれました。
お金も無事戻ってきました。
「アメリカでの配送トラブル、嫌だな」と思っていたのですが、非常にスムーズに解決しました。
Amazon.comやるな。

さて、具体的な手順ですが、

まず、Amazon.com にサインインし、"Contact US" を選びます。

そうすると、入力フォームが現れて、
[1] What can we help you with?
と聞かれるので、
"An order I placed"で当該商品にチェックを入れます。

次に、
[2] Tell us more about your issue
のところで、
"Where's my staff?"
"Tracking shows delivered but shipment not received"
を選択します。

最後に、
[3] How would you like to contact us?
と聞かれるので、"Email"を選びます(電話なども選べます)。

ここまで入力すると、メールの内容は自動で入りますが、
If your order qualifies, which would you prefer: a Replacement Order or a Refund?
を決める必要があります。
ホリデー・シーズンで再度の配送トラブルが心配だったので、ぼくは "Refund" を選択しました。

あとはメールを送信すれば、これで終わりです(超簡単!!!)。

小一時間後にはAmazon.comから「返金します」旨のメールが来ました。
あとは、自分のクレジットカードのページで返金されているのを確認するだけです(たぶん数日かかる)。
「本当に品物が届いていないのか?」の確認などややこしいことは一切ありませんでした。
たぶん一定の割合で配送がトラブるのは織り込み済みなのでしょう。

というわけで、とても快適に全ての処理を終えられました。

追伸:
同じような状況の人はいっぱい居るようで。
ぼくは、以下のブログを参考にしました。
http://d.hatena.ne.jp/CSCs/20110513/1305359613

Trial-to-trial, uncertainty-based adjustment of decision boundaries in visual categorization

Ahmad T. Qamar, R. James Cotton, Ryan G. George, Jeffrey M. Beck, Eugenia Prezhdo, Allison Laudano, Andreas S. Tolias, and Wei Ji Ma
PNAS December 10, 2013 vol. 110 no. 50 20332-20337

ヒト、サル心理物理。
ヒト及びサルは刺激の不確実性(曖昧さ)に応じて、知覚のやり方を変えることができる。
具体的には、「知覚情報が溜まって行き、最終的に意思決定に至るまでの閾値」を調整する。

Categorization is a cornerstone of perception and cognition. Computationally, categorization amounts to applying decision boundaries in the space of stimulus features. We designed a visual categorization task in which optimal performance requires observers to incorporate trial-to-trial knowledge of the level of sensory uncertainty when setting their decision boundaries. We found that humans and monkeys did adjust their decision boundaries from trial to trial as the level of sensory noise varied, with some subjects performing near optimally. We constructed a neural network that implements uncertainty-based, near-optimal adjustment of decision boundaries. Divisive normalization emerges automatically as a key neural operation in this network. Our results offer an integrated computational and mechanistic framework for categorization under uncertainty.

2013年12月16日月曜日

Oxytocin enhances brain reward system responses in men viewing the face of their female partner

Dirk Scheele, Andrea Wille, Keith M. Kendrick, Birgit Stoffel-Wagner, Benjamin Becker, Onur Güntürkün, Wolfgang Maier, and René Hurlemann
PNAS December 10, 2013 vol. 110 no. 50 20308-20313

ヒト行動薬理+fMRI実験。
オキシトシンを経鼻投与されると、男性はパートナーの顔をより魅力的だと思うようになる。
また、その変化は脳内報酬系(腹側被蓋野と側坐核)活動の変化と対応している。

The biological mechanisms underlying long-term partner bonds in humans are unclear. The evolutionarily conserved neuropeptide oxytocin (OXT) is associated with the formation of partner bonds in some species via interactions with brain dopamine reward systems. However, whether it plays a similar role in humans has as yet not been established. Here, we report the results of a discovery and a replication study, each involving a double-blind, placebo-controlled, within-subject, pharmaco-functional MRI experiment with 20 heterosexual pair-bonded male volunteers. In both experiments, intranasal OXT treatment (24 IU) made subjects perceive their female partner's face as more attractive compared with unfamiliar women but had no effect on the attractiveness of other familiar women. This enhanced positive partner bias was paralleled by an increased response to partner stimuli compared with unfamiliar women in brain reward regions including the ventral tegmental area and the nucleus accumbens (NAcc). In the left NAcc, OXT even augmented the neural response to the partner compared with a familiar woman, indicating that this finding is partner-bond specific rather than due to familiarity. Taken together, our results suggest that OXT could contribute to romantic bonds in men by enhancing their partner's attractiveness and reward value compared with other women.

2013年12月15日日曜日

Decision Making as a Window on Cognition

Michael N. Shadlen, Roozbeh Kiani
Neuron, Volume 80, Issue 3, 791-806, 30 October 2013

知覚的意思決定についての総説論文。
サル電気生理研究が中心。
意思決定の「速さ」、「正確さ」、「確信度」などを処理する神経メカニズムについて議論。

A decision is a commitment to a proposition or plan of action based on information and values associated with the possible outcomes. The process operates in a flexible timeframe that is free from the immediacy of evidence acquisition and the real time demands of action itself. Thus, it involves deliberation, planning, and strategizing. This Perspective focuses on perceptual decision making in nonhuman primates and the discovery of neural mechanisms that support accuracy, speed, and confidence in a decision. We suggest that these mechanisms expose principles of cognitive function in general, and we speculate about the challenges and directions before the field.

2013年12月12日木曜日

Toward a Neural Basis for Social Behavior

Damian A. Stanley, Ralph Adolphs
Neuron, Volume 80, Issue 3, 816-826, 30 October 2013

社会的行動の神経基盤についての総説論文。
過去25年の研究動向と今後25年の研究の展望を紹介。

Nearly 25 years ago, the shared interests of psychologists and biologists in understanding the neural basis of social behavior led to the inception of social neuroscience. In the past decade, this field has exploded, in large part due to the infusion of studies that use fMRI. At the same time, tensions have arisen about how to prioritize a diverse range of questions and about the authority of neurobiological data in answering them. The field is now poised to tackle some of the most interesting and important questions about human and animal behavior but at the same time faces uncertainty about how to achieve focus in its research and cohesion among the scientists who tackle it. The next 25 years offer the opportunity to alleviate some of these growing pains, as well as the challenge of answering large questions that encompass the nature and bounds of diverse social interactions (in humans, including interactions through the internet); how to characterize, and treat, social dysfunction in psychiatric illness; and how to compare social cognition in humans with that in other animals.

2013年12月11日水曜日

Right supramarginal gyrus is crucial to overcome emotional egocentricity bias in social judgments

Giorgia Silani, Claus Lamm, Christian C Ruff, and Tania Singer
The Journal of Neuroscience, 25 September 2013, 33(39): 15466-15476

ヒト、行動+fMRI+rTMS実験。
ヒトは「自分の感情を投影して他者の感情を判断する」クセがある。
そして、そのクセは縁上回(Supramarginal Gyrus)が活動しているときに抑えられる。
実際、rTMSで縁上回の活動を一時的に抑制してやると、「自分の感情を投影して他者の感情を判断するクセ」が強くなった。

Humans tend to use the self as a reference point to perceive the world and gain information about other people's mental states. However, applying such a self-referential projection mechanism in situations where it is inappropriate can result in egocentrically biased judgments. To assess egocentricity bias in the emotional domain (EEB), we developed a novel visuo-tactile paradigm assessing the degree to which empathic judgments are biased by one's own emotions if they are incongruent to those of the person we empathize with. A first behavioral experiment confirmed the existence of such EEB, and two independent fMRI experiments revealed that overcoming biased empathic judgments is associated with increased activation in the right supramarginal gyrus (rSMG), in a location distinct from activations in right temporoparietal junction reported in previous social cognition studies. Using temporary disruption of rSMG with repetitive transcranial magnetic stimulation resulted in a substantial increase of EEB, and so did reducing visuo-tactile stimulation time as shown in an additional behavioral experiment. Our findings provide converging evidence from multiple methods and experiments that rSMG is crucial for overcoming emotional egocentricity. Effective connectivity analyses suggest that this may be achieved by early perceptual regulation processes disambiguating proprioceptive first-person information (touch) from exteroceptive third-person information (vision) during incongruency between self- and other-related affective states. Our study extends previous models of social cognition. It shows that although shared neural networks may underlie emotional understanding in some situations, an additional mechanism subserved by rSMG is needed to avoid biased social judgments in other situations.

2013年12月10日火曜日

Neuronal Origins of Choice Variability in Economic Decisions

Camillo Padoa-Schioppa
Neuron, Volume 80, Issue 5, 1322-1336, 4 December 2013

眼窩前頭野(OFC)には「選択肢の価値を保持するニューロン」、「実際に選択された選択肢の価値を保持するニューロン」がある。
二つの選択肢の価値がほぼ等しい際の選択はそれらのニューロンの活動で説明できる?
前者のタイプのニューロンの活動では説明できないが、後者のタイプのニューロンの意思決定の直前で説明できる。

To investigate the mechanisms through which economic decisions are formed, I examined the activity of neurons in the orbitofrontal cortex while monkeys chose between different juice types. Different classes of cells encoded the value of individual offers (offer value), the value of the chosen option (chosen value), or the identity of the chosen juice (chosen juice). Choice variability was partly explained by the tendency to repeat choices (choice hysteresis). Surprisingly, near-indifference decisions did not reflect fluctuations in the activity of offer value cells. In contrast, near-indifference decisions correlated with fluctuations in the preoffer activity of chosen juice cells. After the offer, the activity of chosen juice cells reflected the decision difficulty but did not resemble a race-to-threshold. Finally, chosen value cells presented an “activity overshooting” closely related to the decision difficulty and possibly due to fluctuations in the relative value of the juices. This overshooting was independent of choice hysteresis.

2013年12月9日月曜日

The Irrationality of Categorical Perception

Stephen M. Fleming, Laurence T. Maloney, and Nathaniel D. Daw
J. Neurosci. 2013;33 19060-19070
http://www.jneurosci.org/cgi/content/abstract/33/49/19060?etoc

ヒト心理物理。
知覚の不確実性と運動の不確実性。
ヒトは前者を過大に評価してしまう。

Perception is often categorical: the perceptual system selects one interpretation of a stimulus even when evidence in favor of other interpretations is appreciable. Such categorization is potentially in conflict with normative decision theory, which mandates that the utility of various courses of action should depend on the probabilities of all possible states of the world, not just that of the one perceived. If these probabilities are lost as a result of categorization, choice will be suboptimal. Here we test for such irrationality in a task that requires human observers to combine perceptual evidence with the uncertain consequences of action. Observers made rapid pointing movements to targets on a touch screen, with rewards determined by perceptual and motor uncertainty. Across both visual and auditory decision tasks, observers consistently placed too much weight on perceptual uncertainty relative to action uncertainty. We show that this suboptimality can be explained as a consequence of categorical perception. Our findings indicate that normative decision making may be fundamentally constrained by the architecture of the perceptual system.