2013年1月16日水曜日

Salience Signals in the Right Temporoparietal Junction Facilitate Value-Based Decisions


Thorsten Kahnt and Philippe N. Tobler
J. Neurosci. 2013;33 863-869
http://www.jneurosci.org/cgi/content/abstract/33/3/863?etoc

Value-based decisions optimize the relation of costs and benefits. Costs and benefits confer not only value but also salience, which may influence decision making through attentional mechanisms. However, the computational and neurobiological role of salience in value-based decisions remains elusive. Here we develop and contrast two formal concepts of salience for value-based choices involving costs and benefits. Specifically, global salience (GS) first integrates costs and benefits and then determines salience based on this overall sum, whereas elemental salience (ES) first determines the salience of costs and benefits before integrating them. We dissociate the behavioral and neural effects of GS and ES from those of value using a value-based decision-making task and fMRI in humans. Specifically, we show that value guides choices and correlates with neural signals in the striatum. In contrast, only ES but not GS impacts decision making by speeding up reaction times. Moreover, activity in the right temporoparietal junction (RTPJ) reflects only ES and correlates with its response-accelerating behavioral effects. Finally, we report an ES-dependent change in functional connectivity between the RTPJ and the locus ceruleus, suggesting noradrenergic processes underlying the response-facilitating effects of ES on decision making. Together, these results support a novel concept of salience in value-based decision making and suggest a computational, anatomical, and neurochemical dissociation of value- and salience-based factors supporting value-based choices.

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