2013年5月24日金曜日

Stimulus Value Signals in Ventromedial PFC Reflect the Integration of Attribute Value Signals Computed in Fusiform Gyrus and Posterior Superior Temporal Gyrus

Seung-Lark Lim, John P. O'Doherty, and Antonio Rangel
J. Neurosci. 2013;33 8729-8741
http://www.jneurosci.org/cgi/content/abstract/33/20/8729?etoc

我々が意思決定を行う際、選択肢の様々な側面(例:Tシャツの色、柄など)を評価する必要がある。
過去の行動実験では「ヒトは各側面の価値を別々に計算し、それらを統合して最終的な価値を決める」ことが示唆されている。
しかし、神経メカニズムはよく分かっていなかった。

ヒトfMRI。
Tシャツの「色の価値(好み)」は紡錘状回(fusiform gyrus;視覚情報を処理)で、「柄(ハングル文字)の価値」は後部上側頭回(posterior superior temporal gyrus;文字の意味などを処理)で保持されており、その二つを統合した最終的な「Tシャツの価値」は腹内側前頭前野(vmPFC)にコードされている。
つまり、それぞれの側面の価値は異なる脳部位で計算され、最終的には腹内側前頭前野(vmPFC)で統合される。

We often have to make choices among multiattribute stimuli (e.g., a food that differs on its taste and health). Behavioral data suggest that choices are made by computing the value of the different attributes and then integrating them into an overall stimulus value signal. However, it is not known whether this theory describes the way the brain computes the stimulus value signals, or how the underlying computations might be implemented. We investigated these questions using a human fMRI task in which individuals had to evaluate T-shirts that varied in their visual esthetic (e.g., color) and semantic (e.g., meaning of logo printed in T-shirt) components. We found that activity in the fusiform gyrus, an area associated with the processing of visual features, correlated with the value of the visual esthetic attributes, but not with the value of the semantic attributes. In contrast, activity in posterior superior temporal gyrus, an area associated with the processing of semantic meaning, exhibited the opposite pattern. Furthermore, both areas exhibited functional connectivity with an area of ventromedial prefrontal cortex that reflects the computation of overall stimulus values at the time of decision. The results provide supporting evidence for the hypothesis that some attribute values are computed in cortical areas specialized in the processing of such features, and that those attribute-specific values are then passed to the vmPFC to be integrated into an overall stimulus value signal to guide the decision.

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