2013年1月3日木曜日

Impulsivity and Self-Control during Intertemporal Decision Making Linked to the Neural Dynamics of Reward Value Representation


Koji Jimura, Maria S. Chushak, and Todd S. Braver
The Journal of Neuroscience, 2 January 2013, 33(1):344-357; doi:10.1523/JNEUROSCI.0919-12.2013

A characteristic marker of impulsive decision making is the discounting of delayed rewards, demonstrated via choice preferences and choice-related brain activity. However, delay discounting may also arise from how subjective reward value is dynamically represented in the brain when anticipating an upcoming chosen reward. In the current study, brain activity was continuously monitored as human participants freely selected an immediate or delayed primary liquid reward and then waited for the specified delay before consuming it. The ventromedial prefrontal cortex (vmPFC) exhibited a characteristic pattern of activity dynamics during the delay period, as well as modulation during choice, that is consistent with the time-discounted coding of subjective value. The ventral striatum (VS) exhibited a similar activity pattern, but preferentially in impulsive individuals. A contrasting profile of delay-related and choice activation was observed in the anterior PFC (aPFC), but selectively in patient individuals. Functional connectivity analyses indicated that both vmPFC and aPFC exerted modulatory, but opposite, influences on VS activation. These results link behavioral impulsivity and self-control to dynamically evolving neural representations of future reward value, not just during choice, but also during postchoice delay periods.

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