2013年8月31日土曜日

海外在住者が日本の運転免許を更新するには?

一時帰国した際に、運転免許を更新しました。
せっかくなので、手順をまとめておきます。
なお、この記事の一番下に「参考にしたWEBページのリンク」を貼っているので、詳細はご自身で確認下さい。

注1:更新は一時滞在先(妻の実家)のある神奈川県運転免許試験場で行いました。
注2:同時に本籍も変更しました。

【到着時刻】
運転免許試験場に9:00-9:50 or 13:00-13:50に到着する。
「更新連絡はがき」を持っていないので、到着時間が限定されるみたいです。
注3:実際の手続きはスムーズに進むので、少し遅れても問題なさそうでした。

【必要書類】
通常の書類:
・運転免許証
・運転免許証更新申請書(試験場の窓口で渡されるので、その場で記入する)
・申請用写真(持参した写真を使いたい場合のみ)

海外在住の場合:
・滞在証明書(日本での一時滞在先を証明する書類)←「ここ」から雛形を入手し、義父に押印してもらいました。
・滞在証明書を書いた人の住民票の写し等(氏名と住所が証明できる書類)←義父の住民票を提出しました。

本籍を変更する場合:
・本籍が記載されている住民票の写し等←日本に住民票がないため戸籍謄本を持参しました。

海外旅行、病気など、やむを得ない理由のため、更新期間中に手続が困難な場合:
・パスポートなどやむを得ない理由を証明する書類←「ここ」をみて「パスポート」を提出しました(今回は妻が該当)。
注4:厳密にはパスポートでは「やむを得ない理由」を説明できないと思うのですが大丈夫でした…

以上です。
手続きは非常にスムーズに進むので、問題はないかと思います。


【参考にしたWEBページの一覧】
神奈川県警・海外居住者の免許更新手続き
http://www.police.pref.kanagawa.jp/mes/mes83005.htm
神奈川県警・運転免許証の更新手続について
http://www.police.pref.kanagawa.jp/mes/mes83002.htm
神奈川県警・更新連絡書(はがき)をお持ちでない方の更新手続
http://www.police.pref.kanagawa.jp/mes/mes83067.htm
神奈川県警・運転免許証の記載事項変更手続について
http://www.police.pref.kanagawa.jp/mes/mes83004.htm#syorui
神奈川県警・滞在証明書について
http://www.police.pref.kanagawa.jp/mes/mes83005.htm#kisai
運転免許総合案内所・更新期間前の更新手続き
http://www.unten-menkyo.com/2008/08/post_20.html

2013年8月29日木曜日

Early Experience Shapes Amygdala Sensitivity to Race: An International Adoption Design

Eva H. Telzer, Jessica Flannery, Mor Shapiro, Kathryn L. Humphreys, Bonnie Goff, Laurel Gabard-Durman, Dylan D. Gee, and Nim Tottenham
J. Neurosci. 2013;33 13484-13488

【背景/実験】
「幼少期に異人種との交流が全くない」ことが、成長後の「異人種に対する行動的/神経科学的反応」にどういう影響を与えるのか?
幼少期を東アジア/東ヨーロッパの児童養護施設で過ごし、その後、アメリカの家庭で育てられた人々を対象に実験。

【結果】
異人種の表情から感情を読み取るのが難しい。
また、異人種の顔に対して扁桃体(amygdala)が活動する。

In the current study, we investigated how complete infant deprivation to out-group race impacts behavioral and neural sensitivity to race. Although monkey models have successfully achieved complete face deprivation in early life, this is typically impossible in human studies. We overcame this barrier by examining youths with exclusively homogenous racial experience in early postnatal development. These were youths raised in orphanage care in either East Asia or Eastern Europe as infants and later adopted by American families. The use of international adoption bolsters confidence of infant exposure to race (e.g., to solely Asian faces or European faces). Participants completed an emotional matching task during functional MRI. Our findings show that deprivation to other-race faces in infancy disrupts recognition of emotion and results in heightened amygdala response to out-group faces. Greater early deprivation (i.e., later age of adoption) is associated with greater biases to race. These data demonstrate how early social deprivation to race shapes amygdala function later in life and provides support that early postnatal development may represent a sensitive period for race perception.

2013年8月28日水曜日

Distinct Basal Ganglia Circuits Controlling Behaviors Guided by Flexible and Stable Values

Hyoung F. Kim, and Okihide Hikosaka
Neuron in Press
10.1016/j.neuron.2013.06.044

サル電気生理。
適切な意思決定を行うためには、「モノや行動、選択肢の価値」を「A. 柔軟に更新」しつつ「B. 長期間保持」している必要がある。
→ この二つの処理には、尾状核の別々の部位が関わっている。尾状核前部はAに、後部はBに関与。

Choosing valuable objects is critical for survival, but their values may change flexibly or remain stable. Therefore, animals should be able to update the object values flexibly by recent experiences and retain them stably by long-term experiences. However, it is unclear how the brain encodes the two conflicting forms of values and controls behavior accordingly. We found that distinct circuits of the primate caudate nucleus control behavior selectively in the flexible and stable value conditions. Single caudate neurons encoded the values of visual objects in a regionally distinct manner: flexible value coding in the caudate head and stable value coding in the caudate tail. Monkeys adapted in both conditions by looking at objects with higher values. Importantly, inactivation of each caudate subregion disrupted the high-low value discrimination selectively in the flexible or stable context. This parallel complementary mechanism enables animals to choose valuable objects in both flexible and stable conditions.

2013年8月27日火曜日

Kin Recognition Protects Cooperators against Cheaters

Hsing-I Ho, Shigenori Hirose, Adam Kuspa, Gad Shaulsky
Current Biology, Volume 23, Issue 16, 1590-1595, 01 August 2013

「各個体が血縁者を見分けられる、協力(利他)行動は進化することができる」と言われていた。
それでを、Dictyostelium discoideum(キイロタマホコリカビ)で実証。

The evolution of sociality and altruism is enigmatic because cooperators are constantly threatened by cheaters who benefit from cooperation without incurring its full cost [1,2]. Kin recognition is the ability to recognize and cooperate with genetically close relatives. It has also been proposed as a potential mechanism that limits cheating [3,4], but there has been no direct experimental support for that possibility. Here we show that kin recognition protects cooperators against cheaters. The social amoebae Dictyostelium discoideum cooperate by forming multicellular aggregates that develop into fruiting bodies of viable spores and dead stalk cells. Cheaters preferentially differentiate into spores while their victims die as stalk cells in chimeric aggregates. We engineered syngeneic cheaters and victims that differed only in their kin-recognition genes, tgrB1 and tgrC1, and in a single cheater allele and found that the victims escaped exploitation by different types of nonkin cheaters. This protection depends on kin-recognition-mediated segregation because it is compromised when we disrupt strain segregation. These findings provide direct evidence for the role of kin recognition in cheater control and suggest a mechanism for the maintenance of stable cooperative systems.

2013年8月26日月曜日

The Head-Direction Signal Is Critical for Navigation Requiring a Cognitive Map but Not for Learning a Spatial Habit

Brett Gibson, William N. Butler, Jeffery S. Taube
Current Biology, Volume 23, Issue 16, 1536-1540, 25 July 2013

適切な方向への移動には、「自分がどちらを向いているか、つまり頭の向き(Head-direction:HD)」をコードするニューロンの情報と「自分が居る場所」をコードするニューロンの情報を組み合わせる事が重要。
ただし、移動自体がすでに習慣化(habit-associated directional strategyを使用)している場合は、HDニューロンが活動していなくても適切な方向選択ができる。

Head-direction (HD) cells fire as a function of an animal’s directional heading in the horizontal plane during two-dimensional navigational tasks [1]. The information from HD cells is used with place and grid cells to form a spatial representation (cognitive map) of the environment [2,3]. Previous studies have shown that when rats are inverted (upside down), they have difficulty learning a task that requires them to find an escape hole from one of four entry points but that they can learn it when released from one or two start points [4]. Previous reports also indicate that the HD signal is disrupted when a rat is oriented upside down [5,6]. Here we monitored HD cell activity in the two-entry-point version of the inverted task and when the rats were released from a novel start point. We found that despite the absence of direction-specific firing in HD cells when inverted, rats could successfully navigate to the escape hole when released from one of two familiar locations by using a habit-associated directional strategy. In the continued absence of normal HD cell activity, inverted rats failed to find the escape hole when started from a novel release point. The results suggest that the HD signal is critical for accurate navigation in situations that require a flexible allocentric cognitive mapping strategy, but not for situations that utilize habit-like associative spatial learning.

2013年8月22日木曜日

Ant colonies outperform individuals when a sensory discrimination task is difficult but not when it is easy

Takao Sasaki, Boris Granovskiy, Richard P. Mann, David J. T. Sumpter, and Stephen C. Pratt
PNAS August 20, 2013 vol. 110 no. 34 13769-13773

アリの集団は、単独個体と比べて、より良い意思決定ができるのか(より良い営巣地を見つける)?
課題が難しい(二つに営巣地の候補が似ている)場合、集団の方がより良い意思決定ができる。
一方、課題が簡単(より優れた営巣地が明らかに分かる)な場合は単独個体の意思決定の方が優れている。

“Collective intelligence” and “wisdom of crowds” refer to situations in which groups achieve more accurate perception and better decisions than solitary agents. Whether groups outperform individuals should depend on the kind of task and its difficulty, but the nature of this relationship remains unknown. Here we show that colonies of Temnothorax ants outperform individuals for a difficult perception task but that individuals do better than groups when the task is easy. Subjects were required to choose the better of two nest sites as the quality difference was varied. For small differences, colonies were more likely than isolated ants to choose the better site, but this relationship was reversed for large differences. We explain these results using a mathematical model, which shows that positive feedback between group members effectively integrates information and sharpens the discrimination of fine differences. When the task is easier the same positive feedback can lock the colony into a suboptimal choice. These results suggest the conditions under which crowds do or do not become wise.

2013年8月21日水曜日

Outcome evaluations in group decision making using the majority rule: An electrophysiological study

Kenta Kimura, Jun'ichi Katayama
Psychophysiology Volume 50, Issue 9, pages 848–857, September 2013

集団的意思決定の事象関連電位(ERP)研究。
ヒトが失敗をした際に起こる「エラー関連陰性電位(ERN)」に注目している。

【実験】
単純なギャンブル課題において、各グループ三人の被験者が独立に選択を行い多数決で「グループの選択」を決める。
グループの選択に応じて被験者には報酬/損失が与えられる。

【結果】
・損失に反応して起こるERNは、自分が少数派であった(つまり、自分の意見が採用されなかった)時には減少する。
(自分の選択が損失をもたらした訳ではないから?)
・また、ERNに似た活動が「自分が少数派である時」に見られた。

Event-related brain potential (ERP) reflecting outcome evaluation is called feedback-related negativity (FRN). The present study examined the evaluative processes for two different types of outcomes by recording ERPs from three participants during a group decision task. First, we examined the evaluative processing of outcomes associated with group decisions using the majority rule. Second, we investigated whether the majority rule influenced the evaluation of conflicts related to individual opinions among group members. We found that FRN for monetary loss associated with the group decision was reduced when the participant's opinion was in the minority. In addition, conflict of opinions among group members elicited FRN-like negativity, and greater amplitudes were observed when the participant's opinion was in the minority. The present results suggested that the majority rule can modulate outcome evaluations in group decision making.

2013年8月20日火曜日

Laterality Effect for Faces in Chimpanzees (Pan troglodytes)

Christoph D. Dahl, Malte J. Rasch, Masaki Tomonaga, and Ikuma Adachi
J. Neurosci. 2013;33 13344-13349
http://www.jneurosci.org/cgi/content/abstract/33/33/13344?etoc

チンパンジーも、ヒトと同様に、脳の右半球を使って他者の顔を認知している。

・他者を同定するのに「他者の顔の左半分の情報」を主に用いている
・「他者の顔の左半分の情報」は「自分の脳の右半球」に入る(視覚経路は交叉しているので)
→ 脳の右半球を使って他者の顔を認知している
というロジック。

Face perception in humans is governed more by right-hemispheric than left-hemispheric neural correlate. Some but not all neurophysiological studies depict a right-side dominance for face responsive neurons in the brains of macaques. Hence, it is an open question whether and to what extent a right-hemisphere preference of processing faces exists across primate brains. We investigated chimpanzees discriminating chimeric faces of chimpanzees and humans, i.e., the combination of either left or right sides of a face vertically flipped and merged into a whole face. We found an effect of choosing the left-chimeric face more often than the right-chimeric face as being the one of the two that is closer to the original face, reflecting an advantage for the right side of the brain to process faces, as reported in humans. Moreover, we found a modulation by age of the participants, suggesting that the exposure history with a particular category shapes the right-hemispheric neural correlate to a configural/holistic processing strategy. In other words, the findings in chimpanzee participants parallel those in human participants and are suggestive for similar neural machineries in the occipital-temporal cortices in both species.

2013年8月15日木曜日

Emergent Sensing of Complex Environments by Mobile Animal Groups

Andrew Berdahl1, Colin J. Torney, Christos C. Ioannou, Jolyon J. Faria, Iain D. Couzin
Science 1 February 2013:
Vol. 339 no. 6119 pp. 574-576

群れがどのように「最適な場所」を探し当てるのか?
魚の群れを用いた実験とコンピュータ・シミュレーションを組み合わせることにより、
各個体が「環境の情報」と「多個体の移動方向の情報」を使って自分の移動方向/スピードを決める時、群れ全体として(個体単独の場合と比べて)よりうまく最適な場所を探し当てられる、ことが分かった。

The capacity for groups to exhibit collective intelligence is an often-cited advantage of group living. Previous studies have shown that social organisms frequently benefit from pooling imperfect individual estimates. However, in principle, collective intelligence may also emerge from interactions between individuals, rather than from the enhancement of personal estimates. Here, we reveal that this emergent problem solving is the predominant mechanism by which a mobile animal group responds to complex environmental gradients. Robust collective sensing arises at the group level from individuals modulating their speed in response to local, scalar, measurements of light and through social interaction with others. This distributed sensing requires only rudimentary cognition and thus could be widespread across biological taxa, in addition to being appropriate and cost-effective for robotic agents.

2013年8月14日水曜日

Diversity and Homogeneity in Responses of Midbrain Dopamine Neurons

Christopher D. Fiorillo, Sora R. Yun, and Minryung R. Song
The Journal of Neuroscience, 13 March 2013, 33(11):4693-4709; doi:10.1523/JNEUROSCI.3886-12.2013

嫌悪刺激に対するドーパミン・ニューロンの活動(DA)。
- DAは嫌悪刺激によって抑制され、報酬刺激によって促進される(従来の報酬予測誤差仮説と一致)。
- 黒質稠密部(SNc)の腹側及び前方にあるニューロンほど嫌悪刺激によって強く抑制される。
- 嫌悪刺激によって活動が促進されるニューロンも見つかっているが、それらは「嫌悪」とは関係のない「刺激の知覚強度」をコードしているだけである。

Dopamine neurons of the ventral midbrain have been found to signal a reward prediction error that can mediate positive reinforcement. Despite the demonstration of modest diversity at the cellular and molecular levels, there has been little analysis of response diversity in behaving animals. Here we examine response diversity in rhesus macaques to appetitive, aversive, and neutral stimuli having relative motivational values that were measured and controlled through a choice task. First, consistent with previous studies, we observed a continuum of response variability and an apparent absence of distinct clusters in scatter plots, suggesting a lack of statistically discrete subpopulations of neurons. Second, we found that a group of “sensitive” neurons tend to be more strongly suppressed by a variety of stimuli and to be more strongly activated by juice. Third, neurons in the “ventral tier” of substantia nigra were found to have greater suppression, and a subset of these had higher baseline firing rates and late “rebound” activation after suppression. These neurons could belong to a previously identified subgroup of dopamine neurons that express high levels of H-type cation channels but lack calbindin. Fourth, neurons further rostral exhibited greater suppression. Fifth, although we observed weak activation of some neurons by aversive stimuli, this was not associated with their aversiveness. In conclusion, we find a diversity of response properties, distributed along a continuum, within what may be a single functional population of neurons signaling reward prediction error.

2013年8月13日火曜日

Multiphasic Temporal Dynamics in Responses of Midbrain Dopamine Neurons to Appetitive and Aversive Stimuli

Christopher D. Fiorillo, Minryung R. Song, and Sora R. Yun
The Journal of Neuroscience, 13 March 2013, 33(11):4710-4725; doi:10.1523/JNEUROSCI.3883-12.2013

「報酬予測誤差をコードしていると言われているドーパミン・ニューロン」の活動は、その潜時によって役割が違う。
特に、短い潜時(40〜120ミリ秒)の活動は「刺激の知覚強度」をコードしており、「報酬予測/モチベーション」などとは関係がない。
一方、中程度の潜時(150〜250ミリ秒)の活動は、従来の報酬予測誤差仮説と矛盾なく、「報酬予測/モチベーション」をコードしている。

The transient response of dopamine neurons has been described as reward prediction error (RPE), with activation or suppression by events that are better or worse than expected, respectively. However, at least a minority of neurons are activated by aversive or high-intensity stimuli, casting doubt on the generality of RPE in describing the dopamine signal. To overcome limitations of previous studies, we studied neuronal responses to a wider variety of high-intensity and aversive stimuli, and we quantified and controlled aversiveness through a choice task in which macaques sacrificed juice to avoid aversive stimuli. Whereas most previous work has portrayed the RPE as a single impulse or “phase,” here we demonstrate its multiphasic temporal dynamics. Aversive or high-intensity stimuli evoked a triphasic sequence of activation-suppression-activation extending over a period of 40–700 ms. The initial activation at short latencies (40–120 ms) reflected sensory intensity. The influence of motivational value became dominant between 150 and 250 ms, with activation in the case of appetitive stimuli, and suppression in the case of aversive and neutral stimuli. The previously unreported late activation appeared to be a modest “rebound” after strong suppression. Similarly, strong activation by reward was often followed by suppression. We suggest that these “rebounds” may result from overcompensation by homeostatic mechanisms in some cells. Our results are consistent with a realistic RPE, which evolves over time through a dynamic balance of excitation and inhibition.

2013年8月12日月曜日

Social Influence Bias: A Randomized Experiment

Lev Muchnik, Sinan Aral, Sean J. Taylor
Science 9 August 2013:
Vol. 341 no. 6146 pp. 647-651

口コミサイト(例:食べログ、Yelpなど)のように「みんなの意見を蓄積する」ことは「評価におけるバイアス」を減少させるのか?
実際のWEBサイトのデータを解析。
結果は、悪い方へのバイアスはみんなの意見を集計することで解消出来るが、良い方へのバイアスは解消出来ない。
個々人の意見が「他人の良い評価」に引っ張られて(悪い評価には引っ張られない)、ポジティブ・フィードバックがかかるから。

含意は「食べログなどでは、良い評価はバイアスがかかっている可能性あり」ということ?

Our society is increasingly relying on the digitized, aggregated opinions of others to make decisions. We therefore designed and analyzed a large-scale randomized experiment on a social news aggregation Web site to investigate whether knowledge of such aggregates distorts decision-making. Prior ratings created significant bias in individual rating behavior, and positive and negative social influences created asymmetric herding effects. Whereas negative social influence inspired users to correct manipulated ratings, positive social influence increased the likelihood of positive ratings by 32% and created accumulating positive herding that increased final ratings by 25% on average. This positive herding was topic-dependent and affected by whether individuals were viewing the opinions of friends or enemies. A mixture of changing opinion and greater turnout under both manipulations together with a natural tendency to up-vote on the site combined to create the herding effects. Such findings will help interpret collective judgment accurately and avoid social influence bias in collective intelligence in the future.

2013年8月8日木曜日

Orbitofrontal and striatal circuits dynamically encode the shift between goal-directed and habitual actions

Christina M. Gremel & Rui M. Costa
Nature Communications 4, Article number: 2264 doi:10.1038/ncomms3264

マウスの道具的条件づけ。
Devaluationパラダイムを用いることで、「目的指向(Goal directed)行動」と「習慣化(Habitual)行動」、それぞれを司る脳領域を調べた。

損傷研究の結果から、眼窩前島皮質(OFC)、背側線条体内側部(Dorsomedial Striatum)は目的指向行動に、背側線条体外側部(Dorsolateral Striatum)は習慣化行動に関与。さらに電気生理/光遺伝学的手法を用い、「それぞれの(同一の)ニューロンが活動パターンを変化させることで、目的指向行動から習慣化行動へ切り替わる」ことまで明らかにした。

損傷研究、電気生理、光遺伝学を併用…←すごい。

Shifting between goal-directed and habitual actions allows for efficient and flexible decision making. Here we demonstrate a novel, within-subject instrumental lever-pressing paradigm, in which mice shift between goal-directed and habitual actions. We identify a role for orbitofrontal cortex (OFC) in actions following outcome revaluation, and confirm that dorsal medial (DMS) and lateral striatum (DLS) mediate different action strategies. Simultaneous in vivo recordings of OFC, DMS and DLS neuronal ensembles during shifting reveal that the same neurons display different activities depending on whether presses are goal-directed or habitual, with DMS and OFC becoming more and DLS less engaged during goal-directed actions. Importantly, the magnitude of neural activity changes in OFC following changes in outcome value positively correlates with the level of goal-directed behavior. Chemogenetic inhibition of OFC disrupts goal-directed actions, whereas optogenetic activation of OFC specifically increases goal-directed pressing. These results also reveal a role for OFC in action revaluation, which has implications for understanding compulsive behavior.

2013年8月7日水曜日

Two Dimensions of Value: Dopamine Neurons Represent Reward But Not Aversiveness

Christopher D. Fiorillo
Science 2 August 2013: Vol. 341 no. 6145 pp. 546-549

ドーパミン・ニューロンは「報酬に関する予測誤差」のみをコードしている(罰の予測誤差はコードしていない)。この結果は、我々の脳の中で「報酬」と「罰」はそれぞれ独立に処理されていることを意味する。ポイントは罰の効果を厳密に統制したこと。 http://www.sciencemag.org/content/341/6145/546

これまでの研究では「罰」を扱うのは難しかったが、この研究では色々と工夫している。
・罰を与えるのに使うエアーパフそのものが、ドーパミンニューロンを発火させてしまう → 神経活動の反応潜時から「罰関連の活動」と区別。
・罰の強度をどうやって「報酬の強度」と合わせる? → 通常の古典的条件づけ課題に加え、選択課題を設け「罰(エアーパフ/苦いジュース)を避けるために、サルが支払うジュースの量、つまり罰の価値」を測定。
これらの工夫により、ドーパミン・ニューロンの活動に対する罰の影響を厳密に測定できた。

Whereas reward (appetitiveness) and aversiveness (punishment) have been distinguished as two discrete dimensions within psychology and behavior, physiological and computational models of their neural representation have treated them as opposite sides of a single continuous dimension of “value.” Here, I show that although dopamine neurons of the primate ventral midbrain are activated by evidence for reward and suppressed by evidence against reward, they are insensitive to aversiveness. This indicates that reward and aversiveness are represented independently as two dimensions, even by neurons that are closely related to motor function. Because theory and experiment support the existence of opponent neural representations for value, the present results imply four types of value-sensitive neurons corresponding to reward-ON (dopamine), reward-OFF, aversive-ON, and aversive-OFF.

2013年8月6日火曜日

Multisensory Control of Hippocampal Spatiotemporal Selectivity

Pascal Ravassard, Ashley Kees, Bernard Willers, David Ho, Daniel Aharoni, Jesse Cushman, Zahra M. Aghajan, and Mayank R. Mehta
Science 2013 vol. 340 (6138) pp. 1342-1346

「ヴァーチャルリアリティ」と「実際の環境」で、海馬Plece-Cellの活動は異なる。
つまり、海馬が場所を特定/処理するためには視覚以外の様々な感覚情報も重要である。

The hippocampal cognitive map is thought to be driven by distal visual cues and self-motion cues. However, other sensory cues also influence place cells. Hence, we measured rat hippocampal activity in virtual reality (VR), where only distal visual and nonvestibular self-motion cues provided spatial information, and in the real world (RW). In VR, place cells showed robust spatial selectivity; however, only 20% were track active, compared with 45% in the RW. This indicates that distal visual and nonvestibular self-motion cues are sufficient to provide selectivity, but vestibular and other sensory cues present in RW are necessary to fully activate the place-cell population. In addition, bidirectional cells preferentially encoded distance along the track in VR, while encoding absolute position in RW. Taken together, these results suggest the differential contributions of these sensory cues in shaping the hippocampal population code. Theta frequency was reduced, and its speed dependence was abolished in VR, but phase precession was unaffected, constraining mechanisms governing both hippocampal theta oscillations and temporal coding. These results reveal cooperative and competitive interactions between sensory cues for control over hippocampal spatiotemporal selectivity and theta rhythm.

2013年8月5日月曜日

A Mixture of Delta-Rules Approximation to Bayesian Inference in Change-Point Problems

Robert C. Wilson, Matthew R. Nassar, Joshua I. Gold
PLoS Comput Biol 9(7): e1003150. doi:10.1371/journal.pcbi.1003150

不安定な環境(例:報酬確率、株価)を試行錯誤しながらどうやって学習するか?
最適な方法はベイズ推定を行うことだが、数学的にはかなりややこしい。また、神経科学的な裏付けもあまりない。
一方、単純な学習方法であるデルタ・ルール(報酬予測誤差学習、強化学習)は神経科学的な裏付けはあるが、最適な学習方法ではない。

本論文で著者らは「単純なデルタ・ルールを組み合わせる事で、最適なベイズ学習を近似できる」ことを示した。
この結果は「我々の脳が単純な計算を組み合わせる事で難しい問題を(近似的に)解いている」可能性を示唆する。

Error-driven learning rules have received considerable attention because of their close relationships to both optimal theory and neurobiological mechanisms. However, basic forms of these rules are effective under only a restricted set of conditions in which the environment is stable. Recent studies have defined optimal solutions to learning problems in more general, potentially unstable, environments, but the relevance of these complex mathematical solutions to how the brain solves these problems remains unclear. Here, we show that one such Bayesian solution can be approximated by a computationally straightforward mixture of simple error-driven ‘Delta’ rules. This simpler model can make effective inferences in a dynamic environment and matches human performance on a predictive-inference task using a mixture of a small number of Delta rules. This model represents an important conceptual advance in our understanding of how the brain can use relatively simple computations to make nearly optimal inferences in a dynamic world.

2013年8月1日木曜日

Information for decision-making and stimulus identification is multiplexed in sensory cortex

David H Gire, Jennifer D Whitesell, Wilder Doucette & Diego Restrepo
Nature Neuroscience (2013) doi:10.1038/nn.3432
Received 23 March 2013 Accepted 08 May 2013 Published online 23 June 2013

嗅覚経路の初期段階(上流)に位置する前部梨状皮質(piriform)は、「匂いの種類」だけではなく「その匂いの後に得られる報酬("Is the odor rewarded?")」もコードしている。
つまり、(嗅覚)知覚システムは「後の意思決定に用いられる情報」を最初の段階から保持している。

In recordings from anterior piriform cortex in awake behaving mice, we found that neuronal firing early in the olfactory pathway simultaneously conveyed fundamentally different information: odor value (is the odor rewarded?) and identity (what is the smell?). Thus, this sensory system performs early multiplexing of information reflecting stimulus-specific characteristics with that used for decision-making.