Dissertation

Frontopolar signaling of inferred value

Cox, Karin

2011

Overview

Adaptive decision-making requires that options be weighed according to the predicted value of the outcomes that they are likely to produce. Cognitive neuroscientific research has frequently emphasized the importance of the ventromedial prefrontal cortex (VMPFC) for encoding value information. As measured via functional MRI, VMPFC activity has been shown to correlate with the subjective values of explicitly-presented options (e.g., monetary gambles, offered foods) and also with the learned values of stimuli or actions that have been arbitrarily paired with rewards or punishments. Additional work has confirmed VMPFC sensitivity to abrupt changes in option values, particularly when these may be inferred on the basis of regular fluctuations in and/or interrelationships between option-outcome contingencies (e.g., as in serial reversal learning). The use of fixed option alternatives in these settings (e.g., constant choice stimuli) raises the question of whether such rapid updating of value activity can only occur when inferences can rely upon concretely-encoded sensory and motor information. To determine whether any brain region tracks values that may only be inferred via abstract rules, we scanned 17 participants as they completed a series of unique, two-trial discrimination problems in which the stimulus chosen on each Trial 1 was replaced with a novel stimulus of the same reward status on the following Trial 2. Under this protocol, optimal responding required inferences regarding the valence of each unsampled Trial 1 stimulus. Additional problem-wise manipulation of the magnitude of the available gains and losses created a situation in which the specific values of the unsampled stimuli could also be inferred. BOLD-signal analyses revealed activity in the right lateral frontopolar cortex (FPC) that varied linearly with the inferable values of the unsampled Trial 1 stimuli; follow-up analyses confirmed that this effect was not attributable to the influence of the recently-delivered Trial 1 outcomes. Therefore, the results indicate that the brain does encode values that may only be inferred via abstract deduction. The frontopolar focus of this inferred-value activity corroborates and expands upon recent accounts of FPC function, which posit a broader role for this region in monitoring the value of re-directing behavior towards postponed response options.

• Publisher: ProQuest Dissertations & Theses
• Subject: Cognitive psychology / Psychobiology
• ISBN: 9781267230690, 126723069X