2011年4月20日水曜日

国際会議等で発表を予定されている方へのご提案

信州大学の小松孝徳さんからの提案です。
http://tkomat-lab.com/logo.html

私も全面的に賛同しています。

-----------------------

研究者の皆様への「ご提案」

東日本大震災のような未曾有の大災害に対して,研究者である私たちができること.それは何も特別なことではなく,自分たちのやるべきことを粛々とこなし続けること,つまり社会で力強く活躍できる人材を世に輩出できるよう教育活動に力を注ぎ,そして研究活動に精進することでその研究成果を世界に向けて発信し続けることしかないのかもしれません.

研究成果の発信手段の一つとして,国際会議にて研究発表を行う研究者の方は多いと思います.そしてその際に,何らかの形で今回の大震災に対する海外からの支援への感謝を表明したいと思っている方も多いと思います.そこで,この感謝の気持ちをスライドやポスター上で示せるようなワンポイントのロゴを作成しました.

国際会議に参加する研究者は,その会議における「日本代表」に他なりません.私は日本代表として,胸を張って,笑顔で,そして堂々と,「ありがとう,日本は元気です!」と,海外からの支援へに対する心からの感謝を,そして「この震災に日本人は絶対に負けない!」「日本人研究者は元気だぜ!」という強い気持ちも発信したいと考えています.

こんな若輩者の私の「気持ち」に少しでも共感いただけましたら,このロゴを発表スライドやポスターの片隅に張り付けて頂けないでしょうか.その会議に参加した日本からの発表者の皆さんの多くがこのロゴを使っていると,「おお,日本人はみんな一体になって頑張ってるんだ!」という強いメッセージになると思います.

なお,このロゴは,明治大学理工学部・宮下芳明先生,T-D-F代表・園山隆輔様,書道家 麗 先生に作成いただきました.こんな私の思いつきを迅速に高いクオリティにて具現化していただいたお三方には,本当に心から感謝です(てか,ぶっちゃけこのロゴ,相当カッコイイですよね!).なお,このロゴの配布については特に著作権などは主張いたしませんが,ここに記した目的以外の使用についてはお手数ですが私までご一報を頂けますと幸いです.

「日本代表」となる研究者の皆様のご理解,ご協力を心よりお願い申し上げます.

最後に,東日本大震災にてお亡くなりになられた方々のご冥福を心からお祈りし,被災された皆さまおよびそのご家族の皆様に心からお見舞いを申しあげます.

We will never walk alone!

平成23年4月21日
小松 孝徳
信州大学ファイバーナノテク国際若手研究者育成拠点
e-mail: tkomat@acm.org

2011年4月12日火曜日

Social rejection shares somatosensory representations with physical pain

Ethan Kross, Marc G. Berman, Walter Mischel, Edward E. Smith, and Tor D. Wager
PNAS April 12, 2011 vol. 108 no. 15 6270-6275

How similar are the experiences of social rejection and physical pain? Extant research suggests that a network of brain regions that support the affective but not the sensory components of physical pain underlie both experiences. Here we demonstrate that when rejection is powerfully elicited by having people who recently experienced an unwanted break-up view a photograph of their ex-partner as they think about being rejected areas that support the sensory components of physical pain (secondary somatosensory cortex; dorsal posterior insula) become active. We demonstrate the overlap between social rejection and physical pain in these areas by comparing both conditions in the same individuals using functional MRI. We further demonstrate the specificity of the secondary somatosensory cortex and dorsal posterior insula activity to physical pain by comparing activated locations in our study with a database of over 500 published studies. Activation in these regions was highly diagnostic of physical pain, with positive predictive values up to 88%. These results give new meaning to the idea that rejection “hurts.” They demonstrate that rejection and physical pain are similar not only in that they are both distressing?they share a common somatosensory representation as well.

2011年4月6日水曜日

Neural Correlates of Forward Planning in a Spatial Decision Task in Humans

The Journal of Neuroscience, 6 April 2011, 31(14): 5526-5539
Dylan Alexander Simon and Nathaniel D. Daw

Although reinforcement learning (RL) theories have been influential in characterizing the mechanisms for reward-guided choice in the brain, the predominant temporal difference (TD) algorithm cannot explain many flexible or goal-directed actions that have been demonstrated behaviorally. We investigate such actions by contrasting an RL algorithm that is model based, in that it relies on learning a map or model of the task and planning within it, to traditional model-free TD learning. To distinguish these approaches in humans, we used functional magnetic resonance imaging in a continuous spatial navigation task, in which frequent changes to the layout of the maze forced subjects continually to relearn their favored routes, thereby exposing the RL mechanisms used. We sought evidence for the neural substrates of such mechanisms by comparing choice behavior and blood oxygen level-dependent (BOLD) signals to decision variables extracted from simulations of either algorithm. Both choices and value-related BOLD signals in striatum, although most often associated with TD learning, were better explained by the model-based theory. Furthermore, predecessor quantities for the model-based value computation were correlated with BOLD signals in the medial temporal lobe and frontal cortex. These results point to a significant extension of both the computational and anatomical substrates for RL in the brain.

Signals in Human Striatum Are Appropriate for Policy Update Rather than Value Prediction

The Journal of Neuroscience, 6 April 2011, 31(14): 5504-5511
Jian Li and Nathaniel D. Daw

Influential reinforcement learning theories propose that prediction error signals in the brain's nigrostriatal system guide learning for trial-and-error decision-making. However, since different decision variables can be learned from quantitatively similar error signals, a critical question is: what is the content of decision representations trained by the error signals? We used fMRI to monitor neural activity in a two-armed bandit counterfactual decision task that provided human subjects with information about forgone and obtained monetary outcomes so as to dissociate teaching signals that update expected values for each action, versus signals that train relative preferences between actions (a policy). The reward probabilities of both choices varied independently from each other. This specific design allowed us to test whether subjects' choice behavior was guided by policy-based methods, which directly map states to advantageous actions, or value-based methods such as Q-learning, where choice policies are instead generated by learning an intermediate representation (reward expectancy). Behaviorally, we found human participants' choices were significantly influenced by obtained as well as forgone rewards from the previous trial. We also found subjects' blood oxygen level-dependent responses in striatum were modulated in opposite directions by the experienced and forgone rewards but not by reward expectancy. This neural pattern, as well as subjects' choice behavior, is consistent with a teaching signal for developing habits or relative action preferences, rather than prediction errors for updating separate action values.

2011年4月2日土曜日

Watching My Mind Unfold versus Yours: An fMRI Study Using a Novel Camera Technology to Examine Neural Differences in Self-projection of Self versus Other Perspectives

Peggy L. St. Jacques, Martin A. Conway, Matthew W. Lowder, and Roberto Cabeza
Journal of Cognitive Neuroscience
June 2011, Vol. 23, No. 6, Pages 1275-1284

Self-projection, the capacity to re-experience the personal past and to mentally infer another person's perspective, has been linked to medial prefrontal cortex (mPFC). In particular, ventral mPFC is associated with inferences about one's own self, whereas dorsal mPFC is associated with inferences about another individual. In the present fMRI study, we examined self-projection using a novel camera technology, which employs a sensor and timer to automatically take hundreds of photographs when worn, in order to create dynamic visuospatial cues taken from a first-person perspective. This allowed us to ask participants to self-project into the personal past or into the life of another person. We predicted that self-projection to the personal past would elicit greater activity in ventral mPFC, whereas self-projection of another perspective would rely on dorsal mPFC. There were three main findings supporting this prediction. First, we found that self-projection to the personal past recruited greater ventral mPFC, whereas observing another person's perspective recruited dorsal mPFC. Second, activity in ventral versus dorsal mPFC was sensitive to parametric modulation on each trial by the ability to relive the personal past or to understand another's perspective, respectively. Third, task-related functional connectivity analysis revealed that ventral mPFC contributed to the medial temporal lobe network linked to memory processes, whereas dorsal mPFC contributed to the fronto-parietal network linked to controlled processes. In sum, these results suggest that ventral–dorsal subregions of the anterior midline are functionally dissociable and may differentially contribute to self-projection of self versus other.