2012年12月30日日曜日

2012年も終わり

今年も終わろうとしていますね。
お世話になった皆様、ありがとうございました。
そして一年間、お疲れ様でした。

ぼくは一足お先に21日で仕事納めにして、クリスマス休暇を満喫していました。
ラスベガスとか行ってしまいました。
なんか、すみません…(笑)

さて、今年ですが、色々と激動の一年でした。

研究面では、理研で4年間かけて行ってきた研究がNeuron誌から出版されました。
詳しい内容/出版までの経緯は
http://szkshnsk.blogspot.com/2012/06/neuron.html
にまとめたのですが、やはりとっても嬉しい出来事でした。

同業者の皆様へ、
よろしければ、ぜひ引用してやって下さい↓
"Learning to simulate others' decisions"
Shinsuke Suzuki, Norihiro Harasawa, Kenichi Ueno, Justin L Gardner, Noritaka Ichinohe, Masahiko Haruno, Kang Cheng, Hiroyuki Nakahara.
Neuron, Vol. 74, No. 6, pp. 1125-1137, 2012.
http://www.cell.com/neuron/abstract/S0896-6273(12)00427-8

また、論文出版後の10月から、研究の場をカリフォルニア工科大学に移しました。
異動/引越のゴタゴタでなかなか研究は(今のところ)思うようには進んでいないのですが、これから新しい環境で楽しく面白い研究をじゃんじゃんやっていきたいなと思っています。

また、プライベートでは結婚もしました。
渡米直前の入籍で、通称「ビザ婚」というらしいです:笑。
(入籍していないと配偶者ビザの取得が難しいので)

2012年は総合的に見てとても良い一年だったので、来年末も同じように「良い一年だった」と言えるよう、新年一月二日からがんばっていきたいと思います。
元旦は休むけどな!

それでは。
皆様、よいお年を!

2012年12月26日水曜日

Neuronal integration in visual cortex elevates face category tuning to conscious face perception


Johannes J. Fahrenfort, Tineke M. Snijders, Klaartje Heinen, Simon van Gaal, H. Steven Scholte, and Victor A. F. Lamme
PNAS 2012 109 (52) 21504-21509

The human brain has the extraordinary capability to transform cluttered sensory input into distinct object representations. For example, it is able to rapidly and seemingly without effort detect object categories in complex natural scenes. Surprisingly, category tuning is not sufficient to achieve conscious recognition of objects. What neural process beyond category extraction might elevate neural representations to the level where objects are consciously perceived? Here we show that visible and invisible faces produce similar category-selective responses in the ventral visual cortex. The pattern of neural activity evoked by visible faces could be used to decode the presence of invisible faces and vice versa. However, only visible faces caused extensive response enhancements and changes in neural oscillatory synchronization, as well as increased functional connectivity between higher and lower visual areas. We conclude that conscious face perception is more tightly linked to neural processes of sustained information integration and binding than to processes accommodating face category tuning.

2012年12月20日木曜日

HOUSTON'S@PASADENAでアメリカン・ステーキ


昨夜のディナーはステーキ。
以前から美味しいと聞いていた、こちらでは有名なレストランチェーン。
http://www.hillstone.com/#/restaurants/houstons/
予約なしではとても入れないお店です。
我々も五日前に予約してこの日を迎えました(大袈裟)。

お店に着くと駐車場はほぼ満杯。
お店の外、中、ウェイティングバーに人が溢れていました。
予約していて本当に良かったです。


ステーキの見た目と量はアメリカンだけど、お肉も柔らかくて焼き加減もグッド。
とっても美味しかったです。
「アメリカ人、やればできるやん!」っていう感じでした(笑)。
まあ、それなりの値段はしますけどね(笑)。
ただ、量が…やっぱり大き過ぎる…

そして最後に、感動したのが「レセプション(受付)」の人の仕事ぶり。
大量に押し寄せるお客さん・予約の電話を捌きながら、予約客一人一人の名前を覚えたうえで待っている場所(店内、店外、 or ウェイティングバー)を把握し、時間になったら席に案内。
帰り際にも名前を覚えていて「〇〇様、またお会いできるのを楽しみにしています」と挨拶。
まさにプロの仕事でした。
まあ、それなりの値段はしますけどね(←しつこい:笑)。

ということで、半年に一回くらいはがっつり肉を食べに行きたいお店でした。
かしこ。

2012年12月19日水曜日

Prosocial preferences do not explain human cooperation in public-goods games


Maxwell N. Burton-Chellew and Stuart A. West
PNAS December 17, 2012 201210960

公共財ゲームと「同じ状況で他者の存在を知らせない(投資をし報酬を得る:報酬は公共財ゲームと同様に他者と自分の投資額で決まるが、被験者はそのことを知らない)ケース」を比較。協力率に差なし。公共財ゲームでの協力は社会的効用では説明できない。

It has become an accepted paradigm that humans have “prosocial preferences” that lead to higher levels of cooperation than those that would maximize their personal financial gain. However, the existence of prosocial preferences has been inferred post hoc from the results of economic games, rather than with direct experimental tests. Here, we test how behavior in a public-goods game is influenced by knowledge of the consequences of actions for other players. We found that (i) individuals cooperate at similar levels, even when they are not informed that their behavior benefits others; (ii) an increased awareness of how cooperation benefits others leads to a reduction, rather than an increase, in the level of cooperation; and (iii) cooperation can be either lower or higher than expected, depending on experimental design. Overall, these results contradict the suggested role of the prosocial preferences hypothesis and show how the complexity of human behavior can lead to misleading conclusions from controlled laboratory experiments.

2012年12月18日火曜日

Neural and behavioral bases of age differences in perceptions of trust


Elizabeth Castle, Naomi I. Eisenberger, Teresa E. Seeman, Wesley G. Moons, Ian A. Boggero, Mark S. Grinblatt, and Shelley E. Taylor
PNAS December 18, 2012 vol. 109 no. 51 20848-20852

高齢者は、若者に比べ、(他者の顔を見て「信頼できるか」を評定する課題で)他者を信頼しやすい。また、他者の顔を見ている際の(リスク知覚に関連すると考えられている)前島皮質の活動も低い。

Older adults are disproportionately vulnerable to fraud, and federal agencies have speculated that excessive trust explains their greater vulnerability. Two studies, one behavioral and one using neuroimaging methodology, identified age differences in trust and their neural underpinnings. Older and younger adults rated faces high in trust cues similarly, but older adults perceived faces with cues to untrustworthiness to be significantly more trustworthy and approachable than younger adults. This age-related pattern was mirrored in neural activation to cues of trustworthiness. Whereas younger adults showed greater anterior insula activation to untrustworthy versus trustworthy faces, older adults showed muted activation of the anterior insula to untrustworthy faces. The insula has been shown to support interoceptive awareness that forms the basis of “gut feelings,” which represent expected risk and predict risk-avoidant behavior. Thus, a diminished “gut” response to cues of untrustworthiness may partially underlie older adults’ vulnerability to fraud.

2012年12月6日木曜日

The Interaction of Bayesian Priors and Sensory Data and Its Neural Circuit Implementation in Visually Guided Movement


Jin Yang, Joonyeol Lee, and Stephen G. Lisberger
J. Neurosci. 2012;32 17632-17645
http://www.jneurosci.org/cgi/content/abstract/32/49/17632?etoc

Sensory-motor behavior results from a complex interaction of noisy sensory data with priors based on recent experience. By varying the stimulus form and contrast for the initiation of smooth pursuit eye movements in monkeys, we show that visual motion inputs compete with two independent priors: one prior biases eye speed toward zero; the other prior attracts eye direction according to the past several days' history of target directions. The priors bias the speed and direction of the initiation of pursuit for the weak sensory data provided by the motion of a low-contrast sine wave grating. However, the priors have relatively little effect on pursuit speed and direction when the visual stimulus arises from the coherent motion of a high-contrast patch of dots. For any given stimulus form, the mean and variance of eye speed covary in the initiation of pursuit, as expected for signal-dependent noise. This relationship suggests that pursuit implements a trade-off between movement accuracy and variation, reducing both when the sensory signals are noisy. The tradeoff is implemented as a competition of sensory data and priors that follows the rules of Bayesian estimation. Computer simulations show that the priors can be understood as direction-specific control of the strength of visual-motor transmission, and can be implemented in a neural-network model that makes testable predictions about the population response in the smooth eye movement region of the frontal eye fields.

Critical Roles for Anterior Insula and Dorsal Striatum in Punishment-Based Avoidance Learning


Stefano Palminteri, Damian Justo, Céline Jauffret, Beth Pavlicek, Aurélie Dauta, Christine Delmaire, Virginie Czernecki, Carine Karachi, Laurent Capelle, Alexandra Durr, Mathias Pessiglione
Neuron, Volume 76, Issue 5, 6 December 2012, Pages 998–1009

前島皮質または背側線条体に障害のある患者は損失回避学習が(報酬獲得学習に比べて)うまくできない。強化学習モデルを行動にフィットした結果、「健常者に比べて、前者の患者は損失に鈍感であり、後者の患者は行動選択の精度が低い」ことが分かった。

The division of human learning systems into reward and punishment opponent modules is still a debated issue. While the implication of ventral prefrontostriatal circuits in reward-based learning is well established, the neural underpinnings of punishment-based learning remain unclear. To elucidate the causal implication of brain regions that were related to punishment learning in a previous functional neuroimaging study, we tested the effects of brain damage on behavioral performance, using the same task contrasting monetary gains and losses. Cortical and subcortical candidate regions, the anterior insula and dorsal striatum, were assessed in patients presenting brain tumor and Huntington disease, respectively. Both groups exhibited selective impairment of punishment-based learning. Computational modeling suggested complementary roles for these structures: the anterior insula might be involved in learning the negative value of loss-predicting cues, whereas the dorsal striatum might be involved in choosing between those cues so as to avoid the worst.