2013年2月6日水曜日

Ventromedial Prefrontal and Anterior Cingulate Cortex Adopt Choice and Default Reference Frames during Sequential Multi-Alternative Choice


Erie D. Boorman, Matthew F. Rushworth, and Tim E. Behrens
The Journal of Neuroscience, 6 February 2013, 33(6):2242-2253; doi:10.1523/JNEUROSCI.3022-12.2013

Although damage to the medial frontal cortex causes profound decision-making impairments, it has been difficult to pinpoint the relative contributions of key anatomical subdivisions. Here we use function magnetic resonance imaging to examine the contributions of human ventromedial prefrontal cortex (vmPFC) and dorsal anterior cingulate cortex (dACC) during sequential choices between multiple alternatives—two key features of choices made in ecological settings. By carefully constructing options whose current value at any given decision was dissociable from their longer term value, we were able to examine choices in current and long-term frames of reference. We present evidence showing that activity at choice and feedback in vmPFC and dACC was tied to the current choice and the best long-term option, respectively. vmPFC, mid-cingulate, and posterior cingulate cortex encoded the relative value between the chosen and next best option at each sequential decision, whereas dACC encoded the relative value of adapting choices from the option with the highest value in the longer term. Furthermore, at feedback we identify temporally dissociable effects that predict repetition of the current choice and adaptation away from the long-term best option in vmPFC and dACC, respectively. These functional dissociations at choice and feedback suggest that sequential choices are subject to competing cortical mechanisms.

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