Separate value comparison and learning mechanisms in macaque medial and lateral orbitofrontal cortex.
Uncertainty about the function of orbitofrontal cortex (OFC) in guiding decision-making may be a result of its medial (mOFC) and lateral (lOFC) divisions having distinct functions. Here we test the hypothesis that the mOFC is more concerned with reward-guided decision making, in contrast with the lOFC's role in reward-guided learning. Macaques performed three-armed bandit tasks and the effects of selective mOFC lesions were contrasted against lOFC lesions. First, we present analyses that make it possible to measure reward-credit assignment--a crucial component of reward-value learning--independently of the decisions animals make. The mOFC lesions do not lead to impairments in reward-credit assignment that are seen after lOFC lesions. Second, we examined how the reward values of choice options were compared. We present three analyses, one of which examines reward-guided decision making independently of reward-value learning. Lesions of the mOFC, but not the lOFC, disrupted reward-guided decision making. Impairments after mOFC lesions were a function of the multiple option contexts in which decisions were made. Contrary to axiomatic assumptions of decision theory, the mOFC-lesioned animals' value comparisons were no longer independent of irrelevant alternatives.
Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, United Kingdom. maryann.noonan@psy.ox.ac.uk
M P
MP
Noonan
M E
ME
Walton
T E J
TE
Behrens
J
J
Sallet
M J
MJ
Buckley
M F S
MF
Rushworth
D000818:Animals; D001522:Behavior, Animal; D003657:Decision Making / Q000502:physiology*; D007858:Learning / Q000502:physiology*; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D017397:Prefrontal Cortex / Q000473:pathology / Q000502:physiology*; D012201:Reward