The dorsolateral striatum selectively mediates extinction of habit memory
Previous research has indicated a role for the dorsolateral striatum (DLS) in acquisition and retrieval of habit memory. However, the neurobiological mechanisms guiding extinction of habit memory have not been extensively investigated. The present study examined whether the dorsolateral striatum (DLS) is involved in extinction of habit memory in a food rewarded response learning version of the plus maze in adult male Long Evans rats (experiment 1) In addition, to determine whether the role of this brain region in extinction is selective to habit memory, we also examined whether the DLS is required for extinction of hippocampus dependent spatial memory in a place learning version of the plus maze (experiment 2) Following acquisition in either task, rats received two days of extinction training, in which the food reward was removed from the maze. The number of perseverative trials (a trial in which the rat made the same previously reinforced body turn) and latency to reach the previously correct food well were used as measures of extinction. Animals were given immediate post training intra DLS administration of the sodium channel blocker bupivacaine or vehicle to determine the effect of DLS inactivation on consolidation of extinction memory in each task. In the response learning task, post training DLS inactivation impaired consolidation of extinction memory. Injections of bupivacaine delayed 2 h post training did not affect extinction, indicating a time dependent effect of neural inactivation on consolidation of extinction memory in this task. In contrast, post training DLS inactivation did not impair, but instead slightly enhanced, extinction memory in the place learning task. The present findings indicate a critical role for the DLS in extinction of habit memory in the response learning task, and may be relevant to understanding the neural mechanisms through which maladaptive habits in human psychopathologies (e.g. drug addiction) may be suppressed.
Neurobiology of Learning and Memory