2011年6月22日水曜日

Neurobiology of Value Integration: When Value Impacts Valuation

Soyoung Q Park, Thorsten Kahnt, Jörg Rieskamp, and Hauke R. Heekeren
The Journal of Neuroscience, 22 June 2011, 31(25): 9307-9314


お金と電気ショックの効用をどう統合しているのか?独立に加算?交互作用ある?選択モデルを行動データにフィットしても判定できなかったが、前頭前野(報酬関連部位)の神経活動(fMRI)にフィットしたら「交互作用を含んだモデル」が支持された。

選択(意思決定)モデルをfMRI信号にフィットして「モデル比較」をするという発想は面白いけど、モデル内の変数(効用、価値とか)が神経活動レベルでどう表象されているのか分からない以上、難しいと思う。


Everyday choice options have advantages (positive values) and disadvantages (negative values) that need to be integrated into an overall subjective value. For decades, economic models have assumed that when a person evaluates a choice option, different values contribute independently to the overall subjective value of the option. However, human choice behavior often violates this assumption, suggesting interactions between values. To investigate how qualitatively different advantages and disadvantages are integrated into an overall subjective value, we measured the brain activity of human subjects using fMRI while they were accepting or rejecting choice options that were combinations of monetary reward and physical pain. We compared different subjective value models on behavioral and neural data. These models all made similar predictions of choice behavior, suggesting that behavioral data alone are not sufficient to uncover the underlying integration mechanism. Strikingly, a direct model comparison on brain data decisively demonstrated that interactive value integration (where values interact and affect overall valuation) predicts neural activity in value-sensitive brain regions significantly better than the independent mechanism. Furthermore, effective connectivity analyses revealed that value-dependent changes in valuation are associated with modulations in subgenual anterior cingulate cortex–amygdala coupling. These results provide novel insights into the neurobiological underpinnings of human decision making involving the integration of different values.

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