Prefrontal cortex delay activity: Sample code or reward code?
Prefrontal cortex (PFC) delay activity found in working memory tasks has been said to be a neural correlate of memory. However, similar PFC delay activity has been found in reward tasks. Given that a reward usually follows a correct response in a working memory task, it is unclear whether delay activity found in these tasks is actually a memory trace. We examined whether delay activity in the avian equivalent of the prefrontal cortex represents a neural correlate of a to-be-remembered sample or an upcoming reward. Birds were trained on a directed forgetting paradigm in which sample stimuli (red and white) were either followed by cues to remember (high tone) or a cue to forget (low tone). In addition, the task also incorporated a differential outcomes procedure in which a correct response on the memory test following a red (remember) sample was rewarded with food, but correct responses on the memory test following the white (remember) sample were not. If delay activity represents a sample code, then it should be seen on both red-remember and white-remember trials. On the other hand, if delay activity represents a reward code, then delay activity should be seen only on red-remember trial, but not white-remember trials. The findings suggest that activity in the avian prefrontal cortex represents the outcome associated with each sample (reward or no reward) rather than memory for the sample itself.
Advisor: Colombo, Mike
Degree Name: Master of Science
Degree Discipline: Psychology
Publisher: University of Otago
Keywords: Prefrontal cortex; memory code
Research Type: Thesis