2015年2月28日土曜日

A Common Neural Code for Perceived and Inferred Emotion

Amy E. Skerry and Rebecca Saxe
The Journal of Neuroscience, 26 November 2014, 34(48): 15997-16008

fMRI MVPA。
「他者の情動」の「知覚」と「推測」は前頭前野内側部で「同じ様式」でコードされている。
つまり、「他者情動の知覚」を復元できるようトレーニングした分類器で「他者情動の推測」を復元できる(逆もOK)。

Although the emotions of other people can often be perceived from overt reactions (e.g., facial or vocal expressions), they can also be inferred from situational information in the absence of observable expressions. How does the human brain make use of these diverse forms of evidence to generate a common representation of a target's emotional state? In the present research, we identify neural patterns that correspond to emotions inferred from contextual information and find that these patterns generalize across different cues from which an emotion can be attributed. Specifically, we use functional neuroimaging to measure neural responses to dynamic facial expressions with positive and negative valence and to short animations in which the valence of a character's emotion could be identified only from the situation. Using multivoxel pattern analysis, we test for regions that contain information about the target's emotional state, identifying representations specific to a single stimulus type and representations that generalize across stimulus types. In regions of medial prefrontal cortex (MPFC), a classifier trained to discriminate emotional valence for one stimulus (e.g., animated situations) could successfully discriminate valence for the remaining stimulus (e.g., facial expressions), indicating a representation of valence that abstracts away from perceptual features and generalizes across different forms of evidence. Moreover, in a subregion of MPFC, this neural representation generalized to trials involving subjectively experienced emotional events, suggesting partial overlap in neural responses to attributed and experienced emotions. These data provide a step toward understanding how the brain transforms stimulus-bound inputs into abstract representations of emotion.

2015年2月27日金曜日

Planning activity for internally generated reward goals in monkey amygdala neurons

István Hernádi, Fabian Grabenhorst & Wolfram Schultz
Nature Neuroscience 18, 461–469 (2015)

扁桃体は、報酬に基づく意思決定の「計画」をコードしている。
本当に「計画している」のか、それとも単に「逐一、意思決定をしている」だけなのかを区別するために色々と解析で工夫しているのが面白い。

The best rewards are often distant and can only be achieved by planning and decision-making over several steps. We designed a multi-step choice task in which monkeys followed internal plans to save rewards toward self-defined goals. During this self-controlled behavior, amygdala neurons showed future-oriented activity that reflected the animal's plan to obtain specific rewards several trials ahead. This prospective activity encoded crucial components of the animal's plan, including value and length of the planned choice sequence. It began on initial trials when a plan would be formed, reappeared step by step until reward receipt, and readily updated with a new sequence. It predicted performance, including errors, and typically disappeared during instructed behavior. Such prospective activity could underlie the formation and pursuit of internal plans characteristic of goal-directed behavior. The existence of neuronal planning activity in the amygdala suggests that this structure is important in guiding behavior toward internally generated, distant goals.