2013年9月30日月曜日

Opening the black box: dopamine, predictions, and learning

Neir Eshel, Ju Tian, Naoshige Uchida
Trends in Cognitive Sciences, Volume 17, Issue 9, 430-431, 09 July 2013

「ドーパミン・ニューロンは報酬予測誤差に相関して活動する」ことが知られているが、それが本当に連合学習に効いているのか?
オプトジェネティクス・光遺伝学を用いた研究のレビュー。

Dopamine neurons are thought to promote learning by signaling prediction errors, that is, the difference between actual and expected outcomes. Whether these signals are sufficient for associative learning, however, remains untested. A recent study used optogenetics in a classic behavioral paradigm to confirm the role of dopamine prediction errors in learning.

2013年9月26日木曜日

The Basal Ganglia's Contributions to Perceptual Decision Making

Long Ding, Joshua I. Gold
Neuron, Volume 79, Issue 4, 640-649, 21 August 2013

知覚的意思決定についての展望論文。
知覚的意思決定には、運動制御や学習及びその他の認知的処理と同様に、大脳基底核(Basal Ganglia)が重要な役割を果たしているはずだ。

Perceptual decision making is a computationally demanding process that requires the brain to interpret incoming sensory information in the context of goals, expectations, preferences, and other factors. These integrative processes engage much of cortex but also require contributions from subcortical structures to affect behavior. Here we summarize recent evidence supporting specific computational roles of the basal ganglia in perceptual decision making. These roles probably share common mechanisms with the basal ganglia’s other, more well-established functions in motor control, learning, and other aspects of cognition and thus can provide insights into the general roles of this important subcortical network in higher brain function.

2013年9月25日水曜日

Neural Correlates of Interval Timing in Rodent Prefrontal Cortex

Jieun Kim, Jeong-Wook Ghim, Ji Hyun Lee, and Min Whan Jung
J. Neurosci. 2013;33 13834-13847
http://www.jneurosci.org/cgi/content/abstract/33/34/13834?etoc

【背景】
脳はどのように「時間情報」を処理しているのか?
線形?対数スケール?などなど、よく分かっていない。
先行研究により、「前頭葉内側部(mPFC)の働きを阻害すると、時間情報の処理に障害が起こる」ことが知られている。

【手法、結果】
この研究では、ラットを対象とした電気生理学的手法を用いて、mPFCと時間情報処理の関係を詳細に調べた。
その結果、「mPFCのニューロンは時間の情報を対数スケールで保持している」ことが分かった。
→ mPFCが主観的な時間を表す「こころの中の時計」の役割を果たしているのでは?

Time interval estimation is involved in numerous behavioral processes, but its underlying neural mechanisms remain unclear. In particular, it has been controversial whether time is encoded on a linear or logarithmic scale. Based on our previous finding that inactivation of the medial prefrontal cortex (mPFC) profoundly impairs rat's ability to discriminate time intervals, we investigated how the mPFC processes temporal information by examining activity of mPFC neurons in rats performing a temporal bisection task. Many mPFC neurons dconveyed temporal information based on monotonically changing activity profiles over time with negative accelerations, so that their activity profiles were better described by logarithmic than linear functions. Moreover, the precision of time-interval discrimination based on neural activity was lowered in proportion to the elapse of time, but without proportional increase in neural variability, which is well accounted for by logarithmic, but not by linear functions. As a population, mPFC neurons conveyed precise information about the elapse of time with their activity tightly correlated with the animal's choice of target. These results suggest that the mPFC might be part of an internal clock in charge of controlling interval-timing behavior, and that linearly changing neuronal activity on a logarithmic time scale might be one way of representing the elapse of time in the brain.

2013年9月24日火曜日

Involvement of the Globus Pallidus in Behavioral Goal Determination and Action Specification

Nariko Arimura, Yoshihisa Nakayama, Tomoko Yamagata, Jun Tanji, and Eiji Hoshi
J. Neurosci. 2013;33 13639-13653
http://www.jneurosci.org/cgi/content/abstract/33/34/13639?etoc

淡蒼球(Globus Pallidus)は意思決定において、「ゴール(相対的な場所:左右)の設定」と「行動(実際に触るべき場所)の決定」に関与する。
タスクがエレガント。

Multiple loop circuits interconnect the basal ganglia and the frontal cortex, and each part of the cortico-basal ganglia loops plays an essential role in neuronal computational processes underlying motor behavior. To gain deeper insight into specific functions played by each component of the loops, we compared response properties of neurons in the globus pallidus (GP) with those in the dorsal premotor cortex (PMd) and the ventrolateral and dorsolateral prefrontal cortex (vlPFC and dlPFC) while monkeys performed a behavioral task designed to include separate processes for behavioral goal determination and action selection. Initially, visual signals instructed an abstract behavioral goal, and seconds later, a choice cue to select an action was presented. When the instruction cue appeared, GP neurons started to reflect visual features as early as vlPFC neurons. Subsequently, GP neurons began to reflect goals informed by the visual signals no later than neurons in the PMd, vlPFC, and dlPFC, indicating that the GP is involved in the early determination of behavioral goals. In contrast, action specification occurred later in the GP than in the cortical areas, and the GP was not as involved in the process by which a behavioral goal was transformed into an action. Furthermore, the length of time representing behavioral goal and action was shorter in the GP than in the PMd and dlPFC, indicating that the GP may play an important role in detecting individual behavioral events. These observations elucidate the involvement of the GP in goal-directed behavior.

2013年9月22日日曜日

Delusions and the Role of Beliefs in Perceptual Inference

Katharina Schmack, Ana Gomez-Carrillo de Castro, Marcus Rothkirch, Maria Sekutowicz, Hannes Rossler, John-Dylan Haynes, Andreas Heinz, Predrag Petrovic, and Philipp Sterzer
J. Neurosci. 2013;33 13701-13712
http://www.jneurosci.org/cgi/content/abstract/33/34/13701?etoc

「妄想」に関するfMRI実験。
知覚課題を用いて、妄想の神経基盤を探る。
「知覚」を司る脳領域と「信念/思い込み」を司る脳領域の機能的結合が強いと妄想が生じ易くなる。
研究テーマの設定と実験デザインがユニークで面白かった。

Delusions are unfounded yet tenacious beliefs and a symptom of psychotic disorder. Varying degrees of delusional ideation are also found in the healthy population. Here, we empirically validated a neurocognitive model that explains both the formation and the persistence of delusional beliefs in terms of altered perceptual inference. In a combined behavioral and functional neuroimaging study in healthy participants, we used ambiguous visual stimulation to probe the relationship between delusion-proneness and the effect of learned predictions on perception. Delusional ideation was associated with less perceptual stability, but a stronger belief-induced bias on perception, paralleled by enhanced functional connectivity between frontal areas that encoded beliefs and sensory areas that encoded perception. These findings suggest that weakened lower-level predictions that result in perceptual instability are implicated in the emergence of delusional beliefs. In contrast, stronger higher-level predictions that sculpt perception into conformity with beliefs might contribute to the tenacious persistence of delusional beliefs.

2013年9月19日木曜日

Dopamine Regulates Two Classes of Primate Prefrontal Neurons That Represent Sensory Signals

Simon N. Jacob, Torben Ott, and Andreas Nieder
J. Neurosci. 2013;33 13724-13734
http://www.jneurosci.org/cgi/content/abstract/33/34/13724?etoc

「前頭前野におけるドーパミン活動は、意思決定に必要な知覚プロセスに影響を与える」という仮説を検証。
→ドーパミン活動は、知覚情報の前頭前野への入力を調節し、その情報の保持を促進する。

The lateral prefrontal cortex (PFC), a hub of higher-level cognitive processing, is strongly modulated by midbrain dopamine (DA) neurons. The cellular mechanisms have been comprehensively studied in the context of short-term memory, but little is known about how DA regulates sensory inputs to PFC that precede and give rise to such memory activity. By preparing recipient cortical circuits for incoming signals, DA could be a powerful determinant of downstream cognitive processing. Here, we tested the hypothesis that prefrontal DA regulates the representation of sensory signals that are required for perceptual decisions. In rhesus monkeys trained to report the presence or absence of visual stimuli at varying levels of contrast, we simultaneously recorded extracellular single-unit activity and applied DA to the immediate vicinity of the neurons by micro-iontophoresis. We found that DA modulation of prefrontal neurons is not uniform but tailored to specialized neuronal classes. In one population of neurons, DA suppressed activity with high temporal precision but preserved signal/noise ratio. Neurons in this group had short visual response latencies and comprised all recorded narrow-spiking, putative interneurons. In a distinct population, DA increased excitability and enhanced signal/noise ratio by reducing response variability. These neurons had longer visual response latencies and were composed exclusively of broad-spiking, putative pyramidal neurons. By gating sensory inputs to PFC and subsequently strengthening the representation of sensory signals, DA might play an important role in shaping how the PFC initiates appropriate behavior in response to changes in the sensory environment.

2013年9月18日水曜日

The Ventral Striato-Pallidal Pathway Mediates the Effect of Predictive Learning on Choice between Goal-Directed Actions

Beatrice K. Leung and Bernard W. Balleine
J. Neurosci. 2013;33 13848-13860

腹側線条体(側座核)と腹側淡蒼球(ventral pallidum)の経路が「パブロフ型条件づけと道具的条件づけの転移(Pavlovian-instrumental transfer)」に重要な役割を果たす。

The nucleus accumbens shell (NAc-S) plays an important role in the way stimuli that predict reward affect the performance of, and choice between, goal-directed actions in tests of outcome-specific Pavlovian-instrumental transfer (PIT). The neural processes involved in PIT downstream of the ventral striatum are, however, unknown. The NAc-S projects prominently to the ventral pallidum (VP), and in the current experiments, we assessed the involvement of the NAc-S to VP projection in specific PIT in rats. We first compared expression of the immediate-early gene c-Fos in the medial (VP-m) and lateral (VP-l) regions of the VP and in addition, used the retrograde tracer Fluoro-gold combined with c-Fos to assess the involvement of these pathways during PIT. Although there was no evidence of differential activation in neurons in the VP-l, the VP-m showed a selective increase in activity in rats tested for PIT compared with appropriate controls, as did NAc-S neurons projecting to the VP-m. To confirm that VP-m activity is important for PIT, we inactivated this region before test and found this inactivation blocked the influence of predictive learning on choice. Finally, to confirm the functional importance of the NAc-S to VP-m pathway we used a disconnection procedure, using asymmetrical inactivation of the NAc-S and either the ipsilateral or contralateral VP-m. Specific PIT was blocked but only by inactivation of the NAc-S and VP-m in contralateral hemispheres. These results suggest that the NAc-S and VP-m form part of a circuit mediating the effects of predictive learning on choice.

2013年9月17日火曜日

Optogenetic Stimulation of Lateral Orbitofronto-Striatal Pathway Suppresses Compulsive Behaviors

Eric Burguière, Patrícia Monteiro, Guoping Feng, Ann M. Graybiel
Science 7 June 2013: Vol. 340 no. 6137 pp. 1243-1246

マウス・オプトジェネティクス(光遺伝学)。
外側眼窩前頭皮質と線条体の経路は「強迫神経症的/衝動的な行動の抑制」に重要な役割を果たしている。

Dysfunctions in frontostriatal brain circuits have been implicated in neuropsychiatric disorders, including those characterized by the presence of repetitive behaviors. We developed an optogenetic approach to block repetitive, compulsive behavior in a mouse model in which deletion of the synaptic scaffolding gene, Sapap3, results in excessive grooming. With a delay-conditioning task, we identified in the mutants a selective deficit in behavioral response inhibition and found this to be associated with defective down-regulation of striatal projection neuron activity. Focused optogenetic stimulation of the lateral orbitofrontal cortex and its terminals in the striatum restored the behavioral response inhibition, restored the defective down-regulation, and compensated for impaired fast-spiking neuron striatal microcircuits. These findings raise promising potential for the design of targeted therapy for disorders involving excessive repetitive behavior.

2013年9月16日月曜日

Reward-Modulated Motor Information in Identified Striatum Neurons

Yoshikazu Isomura, Takashi Takekawa, Rie Harukuni, Takashi Handa, Hidenori Aizawa, Masahiko Takada, and Tomoki Fuqua
J. Neurosci. 2013;33 10209-10220
http://www.jneurosci.org/cgi/content/abstract/33/25/10209?etoc

背側線条体が直接(D1受容体に発現)/間接(D2受容体に発現)という二つの経路を通じて自発的運動に関与することは知られていたが、報酬予測との関係はよく分かっていなかった。
今回、この論文で分かったことは…後で読む。

It is widely accepted that dorsal striatum neurons participate in either the direct pathway (expressing dopamine D1 receptors) or the indirect pathway (expressing D2 receptors), controlling voluntary movements in an antagonistically balancing manner. The D1- and D2-expressing neurons are activated and inactivated, respectively, by dopamine released from substantia nigra neurons encoding reward expectation. However, little is known about the functional representation of motor information and its reward modulation in individual striatal neurons constituting the two pathways. In this study, we juxtacellularly recorded the spike activity of single neurons in the dorsolateral striatum of rats performing voluntary forelimb movement in a reward-predictable condition. Some of these neurons were identified morphologically by a combination of juxtacellular visualization and in situ hybridization for D1 mRNA. We found that the striatal neurons exhibited distinct functional activations before and during the forelimb movement, regardless of the expression of D1 mRNA. They were often positively, but rarely negatively, modulated by expecting a reward for the correct motor response. The positive reward modulation was independent of behavioral differences in motor performance. In contrast, regular-spiking and fast-spiking neurons in any layers of the motor cortex displayed only minor and unbiased reward modulation of their functional activation in relation to the execution of forelimb movement. Our results suggest that the direct and indirect pathway neurons cooperatively rather than antagonistically contribute to spatiotemporal control of voluntary movements, and that motor information is subcortically integrated with reward information through dopaminergic and other signals in the skeletomotor loop of the basal ganglia.

2013年9月12日木曜日

Signals in inferotemporal and perirhinal cortex suggest an untangling of visual target information

Marino Pagan, Luke S Urban, Margot P Wohl & Nicole C Rust
Nature Neuroscience (2013) doi:10.1038/nn.3433
Received 09 January 2013 Accepted 08 May 2013 Published online 23 June 2013

複数の(視覚)目標の中からお目当てのモノを探すには、「何を探しているのか?という記憶情報」と「何がどこにあるのか?という視覚情報」を組み合わせて処理する必要がある。
このような処理は「inferotemporal cortex(下側頭皮質:IT)」から「perirhinal cortex(鼻周囲皮質:PRH)」へ情報が受け渡されることで行われている。

Finding sought visual targets requires our brains to flexibly combine working memory information about what we are looking for with visual information about what we are looking at. To investigate the neural computations involved in finding visual targets, we recorded neural responses in inferotemporal cortex (IT) and perirhinal cortex (PRH) as macaque monkeys performed a task that required them to find targets in sequences of distractors. We found similar amounts of total task-specific information in both areas; however, information about whether a target was in view was more accessible using a linear read-out or, equivalently, was more untangled in PRH. Consistent with the flow of information from IT to PRH, we also found that task-relevant information arrived earlier in IT. PRH responses were well-described by a functional model in which computations in PRH untangle input from IT by combining neurons with asymmetric tuning correlations for target matches and distractors.

2013年9月11日水曜日

Context-dependent hierarchies in pigeons

Máté Nagy, Gábor Vásárhelyi, Benjamin Pettit, Isabella Roberts-Mariani, Tamás Vicsek, and Dora Biro
PNAS August 6, 2013 vol. 110 no. 32 13049-13054

ハトの社会階層の話。
「日頃の社会的支配/被支配関係(例:誰が餌を先に食べる権利を持つか)」と「群れで移動する際のリーダー/フォロワー関係(例:誰が行き先を決めるのか」は一致しなかった。言い換えると、「日頃の社会的関係において優位な個体」と「移動の際にリーダーとなる個体」は異なっていた。
つまり、ハトの社会階層は固定されたものではなく、状況によって柔軟に変わり得る。

Hierarchical organization is widespread in the societies of humans and other animals, both in social structure and in decision-making contexts. In the case of collective motion, the majority of case studies report that dominant individuals lead group movements, in agreement with the common conflation of the terms “dominance” and “leadership.” From a theoretical perspective, if social relationships influence interactions during collective motion, then social structure could also affect leadership in large, swarm-like groups, such as fish shoals and bird flocks. Here we use computer-vision–based methods and miniature GPS tracking to study, respectively, social dominance and in-flight leader–follower relations in pigeons. In both types of behavior we find hierarchically structured networks of directed interactions. However, instead of being conflated, dominance and leadership hierarchies are completely independent of each other. Although dominance is an important aspect of variation among pigeons, correlated with aggression and access to food, our results imply that the stable leadership hierarchies in the air must be based on a different set of individual competences. In addition to confirming the existence of independent and context-specific hierarchies in pigeons, we succeed in setting out a robust, scalable method for the automated analysis of dominance relationships, and thus of social structure, applicable to many species. Our results, as well as our methods, will help to incorporate the broader context of animal social organization into the study of collective behavior.

2013年9月10日火曜日

Why skill matters

Okihide Hikosaka, Shinya Yamamoto, Masaharu Yasuda, Hyoung F. Kim
Trends in Cognitive Sciences, 02 August 2013

スキル学習についての総説論文。
単位時間当たりの報酬量を最大化するための手段として「意思決定/行動のスピードアップ(つまり、スキル学習)」がある。その学習には、「最適な意思決定方法/行動を見つける(objects skill)」ことと「それを実行する(action skill)」が重要である。

Maximizing rewards per unit time is ideal for success and survival in humans and animals. This goal can be approached by speeding up behavior aiming at rewards and this is done most efficiently by acquiring skills. Importantly, reward-directed skills consist of two components: finding a good object (i.e., object skill) and acting on the object (i.e., action skill), which occur sequentially. Recent studies suggest that object skill is based on high-capacity memory for object–value associations. When a learned object is encountered the corresponding memory is quickly expressed as a value-based gaze bias, leading to the automatic acquisition or avoidance of the object. Object skill thus plays a crucial role in increasing rewards per unit time.

2013年9月9日月曜日

Prolonged dopamine signalling in striatum signals proximity and value of distant rewards

Mark W. Howe, Patrick L. Tierney, Stefan G. Sandberg, Paul E. M. Phillips & Ann M. Graybiel
Nature (2013) doi:10.1038/nature12475
Received 25 January 2013 Accepted 17 July 2013 Published online 04 August 2013

ラットの迷路課題。
ドーパミンはゴール(報酬が貰える地点)までの「距離(所要時間ではなく)」をコードしている(TD強化学習における「価値」とは異なる変数なのかな?)。
→ モチベーションのコントロールに重要な役割を果たすと考えられる。

Predictions about future rewarding events have a powerful influence on behaviour. The phasic spike activity of dopamine-containing neurons, and corresponding dopamine transients in the striatum, are thought to underlie these predictions, encoding positive and negative reward prediction errors1, 2, 3, 4, 5. However, many behaviours are directed towards distant goals, for which transient signals may fail to provide sustained drive. Here we report an extended mode of reward-predictive dopamine signalling in the striatum that emerged as rats moved towards distant goals. These dopamine signals, which were detected with fast-scan cyclic voltammetry (FSCV), gradually increased or—in rare instances—decreased as the animals navigated mazes to reach remote rewards, rather than having phasic or steady tonic profiles. These dopamine increases (ramps) scaled flexibly with both the distance and size of the rewards. During learning, these dopamine signals showed spatial preferences for goals in different locations and readily changed in magnitude to reflect changing values of the distant rewards. Such prolonged dopamine signalling could provide sustained motivational drive, a control mechanism that may be important for normal behaviour and that can be impaired in a range of neurologic and neuropsychiatric disorders.

2013年9月5日木曜日

Dopamine Modulates Risk-Taking as a Function of Baseline Sensation-Seeking Trait

Agnes Norbury, Sanjay Manohar, Robert D. Rogers, and Masud Husain
J. Neurosci. 2013;33 12982-12986 Open Access
http://www.jneurosci.org/cgi/content/abstract/33/32/12982?etoc

ドーパミンとリスク選好の関係。
D2/D3 agonistを用いて「ドーパミンD2/D3レセプターの感受性を高める」と、ヒトは「リスク愛好的」になる。
また、この効果は「元々リスク回避的なヒト」で顕著であった。

Trait sensation-seeking, defined as a need for varied, complex, and intense sensations, represents a relatively underexplored hedonic drive in human behavioral neuroscience research. It is related to increased risk for a range of behaviors including substance use, gambling, and risky sexual practice. Individual differences in self-reported sensation-seeking have been linked to brain dopamine function, particularly at D2-like receptors, but so far no causal evidence exists for a role of dopamine in sensation-seeking behavior in humans. Here, we investigated the effects of the selective D2/D3 agonist cabergoline on performance of a probabilistic risky choice task in healthy humans using a sensitive within-subject, placebo-controlled design. Cabergoline significantly influenced the way participants combined different explicit signals regarding probability and loss when choosing between response options associated with uncertain outcomes. Importantly, these effects were strongly dependent on baseline sensation-seeking score. Overall, cabergoline increased sensitivity of choice to information about probability of winning; while decreasing discrimination according to magnitude of potential losses associated with different options. The largest effects of the drug were observed in participants with lower sensation-seeking scores. These findings provide evidence that risk-taking behavior in humans can be directly manipulated by a dopaminergic drug, but that the effectiveness of such a manipulation depends on baseline differences in sensation-seeking trait. This emphasizes the importance of considering individual differences when investigating manipulation of risky decision-making, and may have relevance for the development of pharmacotherapies for disorders involving excessive risk-taking in humans, such as pathological gambling.

2013年9月4日水曜日

The Basolateral Amygdala Is Critical for Learning about Neutral Stimuli in the Presence of Danger, and the Perirhinal Cortex Is Critical in the Absence of Danger

Nathan M. Holmes, Shauna L. Parkes, A. Simon Killcross, and R. Frederick
Westbrook
J. Neurosci. 2013;33 13112-13125
http://www.jneurosci.org/cgi/content/abstract/33/32/13112?etoc

ラット損傷研究。
「刺激間(音と光)の連合形成/学習」に perirhinal cortex(PRh:日本語だと?)と扁桃体(basolateral amygdala)が果たす役割。
一方の刺激が「危険(電気ショック)」と関連付けられている場合は、扁桃体が連合形成/学習に効いており(PRhは効いていない)、刺激が危険に関連付けられていない場合は逆の結果になる。
つまり、危険のあるなしによって、「刺激間の連合形成」には異なる脳部位が関わる。

The perirhinal cortex (PRh) and basolateral amygdala (BLA) appear to mediate distinct aspects of learning and memory. Here, we used rats to investigate the involvement of the PRh and BLA in acquisition and extinction of associations between two different environmental stimuli (e.g., a tone and a light) in higher-order conditioning. When both stimuli were neutral, infusion of the GABAA, muscimol, or the NMDA receptor (NMDAR) antagonist ifenprodil into the PRh impaired associative formation. However, when one stimulus was neutral and the other was a learned danger signal, acquisition and extinction of the association between them was unaffected by manipulations targeting the PRh. Temporary inactivation of the BLA had the opposite effect: formation and extinction of an association between two stimuli was spared when both stimuli were neutral, but impaired when one stimulus was a learned danger signal. Subsequent experiments showed that the experience of fear per se shifts processing of an association between neutral stimuli from the PRh to the BLA. When training was conducted in a dangerous environment, formation and extinction of an association between neutral stimuli was impaired by BLA inactivation or NMDAR blockade in this region, but was unaffected by PRh inactivation. These double dissociations in the roles of the PRh and BLA in learning under different stimulus and environmental conditions imply that fear-induced activation of the amygdala changes how the brain processes sensory stimuli. Harmless stimuli are treated as potentially harmful, resulting in a shift from cortical to subcortical processing in the BLA.

2013年9月3日火曜日

Brain Activity in Valuation Regions while Thinking about the Future Predicts Individual Discount Rates

Nicole Cooper, Joseph W. Kable, B. Kyu Kim, and Gal Zauberman
J. Neurosci. 2013;33 13150-13156
http://www.jneurosci.org/cgi/content/abstract/33/32/13150?etoc

「未来のことを考えている」際の前頭前野腹内側部(vmPFC)及び腹側線条体(ventral striatum)の活動から、その被験者が「将来の報酬をどの程度割り引くのか」を予測できる。
報酬や意思決定とは必ずしも関係ない「未来のこと」という一般的な思考を行っている際の脳活動から「異時点間の報酬割引率」を予測できたのがポイント。

People vary widely in how much they discount delayed rewards, yet little is known about the sources of these differences. Here we demonstrate that neural activity in ventromedial prefrontal cortex (VMPFC) and ventral striatum (VS) when human subjects are asked to merely think about the future—specifically, to judge the subjective length of future time intervals—predicts delay discounting. High discounters showed lower activity for longer time delays, while low discounters showed the opposite pattern. Our results demonstrate that the correlation between VMPFC and VS activity and discounting occurs even in the absence of choices about future rewards, and does not depend on a person explicitly evaluating future outcomes or judging their self-relevance. This suggests a link between discounting and basic processes involved in thinking about the future, such as temporal perception. Our results also suggest that reducing impatience requires not suppression of VMPFC and VS activity altogether, but rather modulation of how these regions respond to the present versus the future.

2013年9月2日月曜日

Distinct Representations of Cognitive and Motivational Signals in Midbrain Dopamine Neurons

Masayuki Matsumotosend, Masahiko Takada
Neuron, 08 August 2013

【背景】
ドーパミンは「報酬予測」だけではなく「種々の認知機能」にも重要な役割を果たすことが知られているが、詳細はよく分かっていなかった。

【実験】
サル電気生理。
サルに「ワーキングメモリと視覚刺激探索が必要な課題」を行わせ、その際の中脳ドーパミン・ニューロンの活動を記録。

【結果】
「認知に関わるニューロン(「覚えておくべき視覚刺激」に反応する)」と「報酬予測に関わるニューロン」が見つかった。
前者は中脳の背外側部(黒質稠密部、SNc)に多く存在し、後者は腹内側部(腹側被蓋野、VTA)に存在する。
これらの結果は「中脳の中で背外側部から腹内側部にかけて、ドーパミン・ニューロンの機能が異なる」ことを示唆する。

Dopamine is essential to cognitive functions. However, despite abundant studies demonstrating that dopamine neuron activity is related to reinforcement and motivation, little is known about what signals dopamine neurons convey to promote cognitive processing. We therefore examined dopamine neuron activity in monkeys performing a delayed matching-to-sample task that required working memory and visual search. We found that dopamine neurons responded to task events associated with cognitive operations. A subset of dopamine neurons were activated by visual stimuli if the monkey had to store the stimuli in working memory. These neurons were located dorsolaterally in the substantia nigra pars compacta, whereas ventromedial dopamine neurons, some in the ventral tegmental area, represented reward prediction signals. Furthermore, dopamine neurons monitored visual search performance, becoming active when the monkey made an internal judgment that the search was successfully completed. Our findings suggest an anatomical gradient of dopamine signals along the dorsolateral-ventromedial axis of the ventral midbrain.

2013年9月1日日曜日

J1ビザ更新

日本に一時帰国してJ1ビザを更新してきました。

今回は更新ですが、手順は新規申し込みの時とほぼ同じです。
詳細は去年のエントリー「J1ビザ面接@アメリカ大使館」を見て下さい。
http://szkshnsk.blogspot.jp/2012/09/j1.html
なお、今回はビザ申請料金をクレジットカードで支払ったため、「ビザ申請費用振込証明(ATMのPayEasy使用:明細をDS160の確認ページに貼付)」は不要でした。今はATMで支払っても貼付は不要なのかもしれません?

それで、今回、躓いたのは「面接の予約」でした。
更新の場合は「面接」と「郵送での申請(色々と条件があるのでご自身で確認して下さい)」を選択できるのですが、そこにトラップが…

面接/郵送の予約は基本的に、
1.クレジットカードでビザ申請料金を支払う
2.受付(レシート)番号が表示されるので、それを書き留める
3.受付番号を入力して、面接 or 郵送での申請を予約する
という手順で進みます。

今回、ぼくは「書類不備などのトラブルがあった場合、ビザの更新/入手が大幅に遅れる」可能性を考え、面接での更新をしようと思っていました。
しかし、手順3.で表示される一連の質問に適当に「Yes」と答えたところ、自動的に郵送申請に…(「ドロップボックス確認書」なるモノが表示されます)。

その後、面接の予約を取り直そうとしたのですが、「ビザ申請料支払いの受付番号が確認できない」と言われてどうしようもなくなってしまいました(←間違えて行った郵送申請の予約で受付番号を使ってしまったため)。

ということで、どうしようもないのでサポートに問い合わせ。
「面接予約ページの問い合わせフォームへの記入」か「support-japan@ustraveldocs.comへのメール」だった思います(忘れた…)。
その結果、非常に迅速に対応していただき、翌日には面接予約ができました!
本当にアメリカ大使館様々です…

ちなみに、やりとりは以下のような感じです。

ぼくからサポート・センターへのメール:
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現在、自分と妻のJ1/J2 VISAの更新手続きを行っています。
面接の予約をしようとしたところ、間違えて「郵送申請」で申し込んでしまいました。
なお、その際にVISA申請料金をクレジットカードで支払い「受付番号:************(自分と妻と共通)」を取得しました。

それで、改めて面接の予約を試みたのですが、「ご入力された受付番号ではデータが見つかりません」と言われ、それ以上先には進めなくなってしまいました。

どのようにすれば、面接の予約を取れるのでしょうか?
そのために新たな受付番号を発行していただくことは可能でしょうか?
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すぐにサポート・センターからの返信(1)が来ました:
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アメリカビザサービスデスクにお問い合わせ誠に有難うございます。

ステップ7の郵送申請の確認画面に「いいえ」とクリックするべきところで間違えて「はい」を選択しましたので、システムが自動的に郵送申請に選択し、有効な受付番号を無効にされました。お客様のケースはすでに担当者に報告してレシート番号の解除手続きをしています。後ほど担当者から返事いたしますのでしばらくお待ちいただけないでしょうか?
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翌日にはサポート・センターからの返信(2)が来ました:
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お問い合わせありがとうございます。

現在、予約可能な状態ですので、ご確認をお願い致します。
受付番号が有効な状態になっていない場合は、2回目のお支払いは行なわず、コールセンターまで、ご連絡ください。
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というわけで、無事に面接の予約を取り直すことができました!
皆様、本当にお気を付けて下さい。
質問に適当に答えたら後々面倒なことになります…
めちゃくちゃ焦りました(汗)。