ACTIVITY OF RAT DORSAL STRIATAL MEDIUM SPINY NEURONS DURING ODOUR SAMPLING IN A WORKING MEMORY CAPACITY TASK

Abstract

Working memory is an important cognitive function that allows us to perform everyday tasks including language comprehension and reasoning. It is, therefore, unsurprising that working memory dysfunction has been detected in many neurodegenerative and psychiatric disorders, such as schizophrenia. The striatum is an important brain region for working memory in both humans and rats, but its role remains unclear. While increased striatal activity has been shown during information updating in human working memory tasks, assessment of striatal activity during information maintenance, the retention of information for cognitive processes, have generated mixed results. No previous studies were examined striatal activity in rats completing a working memory task, although medium spiny neurons have been shown to increase activity after a reward was received in short-term memory tasks. Therefore, in the present study, I examined the activity of medium spiny neurons of the dorsomedial striatum when receiving a reward and also, when rats approached familiar and novel odours during the odour span task. Rats were then administered MK801, an N-Methyl-D-Aspartate receptor antagonist, and observed for any putative changes in neural activity during the odour span task. I observed significantly increased activity in a population of medium spiny neurons after a reward was received, while no changes of activity were detected in response to rats approaching a familiar odour. The results from the activity of medium spiny neurons in response to novel odours was inconclusive. Neural activity was recorded 30 minutes following MK801 administration. During the last 10 minutes of the recording, medium spiny neurons significantly increased activity compared to a baseline recording pre-injection. By increasing our knowledge regarding the neural activity underlying working memory and how it is affected by psychoactive drugs, our understanding of how to treat working memory dysfunction may improve.