Prelimbic/infralimbic inactivation impairs memory for multiple task switches, but not flexible selection of familiar tasks.
Behavioral flexibility, in the form of strategy switching or set shifting, helps animals cope with changing contingencies in familiar environments. The prelimbic (PL) and infralimbic (IL) regions of the rat prefrontal cortex (PFC) contribute to this ability so that rats trained to use one strategy have difficulty learning a new one if the PL/IL is inactivated. Thus, the PL/IL mediates learning new tasks in place of old ones, but it may also be required to switch between familiar tasks. To test this hypothesis, we trained rats to perform multiple task switches on a plus-shaped maze, alternating between two familiar tasks. Muscimol inactivation of the PL/IL never impaired switch acquisition, but did impair memory for the recently acquired switch 24 h later. Additional experiments determined that control rats continued to perform the new task 24 h after a switch, but rats with PL/IL inactivation had impaired memory and performed the same task that was learned before inactivation. This impairment was observed in multiple switches, demonstrating that PL/IL activity was required to remember which of two familiar tasks was most recently successful. After many switches, however, muscimol no longer impaired performance, and both saline- and muscimol-infused rats appeared to use immediate task contingencies rather than memory to select among familiar tasks. This strategy may account for the decreased effect of PL/IL inactivation observed after extensive training. Thus, although PL/IL activity contributed to memory for multiple task switches, it was not required for flexibly selecting among highly familiar tasks.
Rich
Erin L
EL
Fishberg Department of Neuroscience and Alfred B. and Gudrun J. Kastor Neurobiology of Aging Laboratories, Mount Sinai School of Medicine, New York, New York 10029-6574, USA.
Shapiro
Matthew L
ML
D000818:Animals; D002404:Catheterization; D018755:GABA Agonists / Q000494:pharmacology; D008032:Limbic System / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D009118:Muscimol / Q000494:pharmacology; D017397:Prefrontal Cortex / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D012193:Reversal Learning / Q000187:drug effects / Q000502:physiology
D018755:GABA Agonists; D009118:Muscimol