Reward expectancy increases the sensitivity of mPFC neurons to sensory-motor information.
ARL NSMA, Univ. Arizona, Tucson, AZ
Subsets of neurons in the medial prefrontal cortex (mPFC) of the rat are highly sensitive to sensory-motor information (Gemmell et al., 2002; Euston and McNaughton, 2006). The connection of the mPFC to numerous neuromodulatory centers raises the possibility that such sensitivity may be modulated by motivational factors. We describe a subset of prefrontal neurons that expressed enhanced tuning to head position during periods of high reward expectancy and less sensitivity to head position when reward delivery was uncertain. Simultaneous activity from multiple neurons in the mPFC was recorded as animals performed a stimulus-sequence discrimination task. A delay of 700 msec separated the presentation of the first and second stimulus, and an 800 msec delay separated the presentation of the second stimulus and reward delivery. The capacity of the second stimulus to predict reward delivery was manipulated: in one condition, the presence of the second stimulus predicted reward delivery during 100% of trials; while in a second condition, reward delivery was random (delivered on 50% of trials) following the presentation of CS2. Neurons sensitive to head position were significantly more responsive to head position during delay intervals that preceded the predictable delivery of reward. Together, these results support the hypothesis that the access of mPFC neurons to sensory-motor information is influenced by reward expectancy and suggest that the functional consequences of such expectancy may be the 'gating' of sensory-motor information into mPFC networks.
Grant/Other Support: NS020331
Keyword (Complete): medial prefrontal cortex; attention; associative learning; movement; prediction