Thursday, August 28, 2014,
- Location: Wilson Hall • 111 21St Ave S • Nashville, TN 37240
- Room: 316
Peter Kaskan, Section on Neurobiology of Learning and Memory, LN, NIMH
12:10 p.m. Room 316, Wilson Hall
fMRI activation of cortical and subcortical regions in macaque monkeys associated with anticipation and receipt of reward
Cues that have been paired with reward can elicit approach behaviors. These cues are said to acquire incentive salience; the cues themselves are sought as a means of acquiring their associated reward. In an effort to bridge a gap between rodent and human models of reward processing, we developed a behavioral task and fast event-related fMRI paradigm to distinguish BOLD responses to visual cues that predicted reward (anticipation) from responses due to receipt of reward. Monkeys learned to associate images of miscellaneous objects with a high (75%) and low probability (25%) of water reward in choice trials (two cues) and viewing trials (one cue). Monkeys chose high probability cues following two days of training on about 90 percent of choice trials. Monkeys also showed increased licking at the reward delivery spout for high probability cues. Trial start times and reward delivery times were randomized such that BOLD responses due to visual cues could be distinguished from receipt of reward responses. To create a map of reward anticipation, we contrasted fMRI responses from viewing trials of images that had been paired with high probability of reward to those that had been paired with low probability. To create a map of reward receipt, we contrasted responses due to reward delivery to a baseline measurement. In baseline scans, where all cues predicted the same probability of reward, cues that later became paired with a high probability of reward did not elicit greater BOLD responses than cues that later became paired with a low probability of reward. Monkeys showed no choice preferences during baseline scans nor did they demonstrate increased licking. Following training, brain regions responsive to reward anticipation included the dorsal striatum, amygdala, anterior insula, orbital areas 11 and 12, and medial prefrontal area 32. Also, as expected, regions responsive to receipt of reward included the ventral striatum, gustatory cortex, and orbital area 13. Unexpectedly, we identified patches of IT and cortex within the superior temporal sulcus that showed greater BOLD responses to high probability cues than low probability cues. These results corroborate fMRI findings in humans and electrophysiological findings in monkeys demonstrating that the amygdala and striatum are core components of an incentive salience network, and suggest that IT may play a role in representing some aspect of reward predictive visual cues. Experiments designed to test the role of the amygdala in learning from reward feedback and representing reward predictive stimuli are underway.