title: Inactivation of the medial prefrontal cortex of the rat impairs strategy set-shifting, but not reversal learning, using a novel, automated procedure.
abstract: The medial prefrontal cortex (mPFC) of the rat plays an essential role in behavioral flexibility, as lesions or inactivations of this region impair shifting between strategies or attentional sets using a variety of different behavioral tests. In the present study, we assessed the effects of inactivation of the mPFC on strategy set-shifting and reversal learning, using a novel, automated procedure conducted in an operant chamber. In Experiment 1, inactivation of the mPFC with bupivacaine did not impair the initial learning of a visual-cue (i.e.; always press the lever with a cue light illuminated above it) or a response (i.e.; always press the left lever) discrimination. Control rats required greater number of trials to shift from using a visual-cue to a response strategy than the opposite shift. mPFC inactivation impaired performance of a visual-cue-response set-shift, but not the easier response-visual-cue shift. In Experiment 2, pre-exposure to the visual-cue stimulus lights increased the difficulty of the response-visual-cue shift, reflected by a greater number of trials required by control rats to achieve criterion relative to those in Experiment 1. Under these conditions, inactivation of the mPFC did impair performance of this set-shift. In contrast, mPFC inactivation did not affect reversal learning of a response discrimination. These findings highlight the utility of this automated procedure for assessing set-shifting mediated by the mPFC. Furthermore, they reveal that the relative difficulty of the type of shift rats are required to perform has a direct impact on whether or not the mPFC contributes to this form of behavioral flexibility.
authors: Department of Psychology and Brain Research Centre, University of British Columbia, 2136 West Mall, Vancouver, B.C., Canada. floresco@psych.ubc.ca
authors: Stan B
authors: SB
authors: Floresco
authors: Annie E
authors: AE
authors: Block
authors: Maric T L
authors: MT
authors: Tse
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D001289:Attention Deficit Disorder with Hyperactivity / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D001522:Behavior, Animal / Q000502:physiology; D002045:Bupivacaine / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology*; D003463:Cues; D004192:Discrimination, Psychological / Q000187:drug effects / Q000502:physiology; D010775:Photic Stimulation; D017397:Prefrontal Cortex / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D012193:Reversal Learning / Q000187:drug effects / Q000502:physiology*
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine