Lesions of rat infralimbic cortex enhance renewal of extinguished appetitive Pavlovian responding


Dr A.S Killcross, as above.
E-mail: KillcrossAS@cardiff.ac.uk


It is well established that extinction is highly context dependent, and several behavioural phenomena associated with the expression of extinction (spontaneous recovery, reinstatement and renewal) have been described as resulting from this context dependency. It has previously been shown that lesions of the infralimbic (IL) region of the medial prefrontal cortex result in increased levels of spontaneous recovery and reinstatement of an extinguished appetitive Pavlovian conditioned response. The current study shows that lesions of the IL cortex also result in increased renewal of a conditioned response when tested in the acquisition context. Thirteen IL-lesioned and 14 sham-lesioned rats were trained on an appetitive Pavlovian task in one context (Context A) followed by extinction in a different context (Context B); animals were then tested for renewal of responding in both Context A and B. Both groups demonstrated similarly low levels of responding when tested in the extinction context (B), and greater responding (i.e. renewal) when tested in the acquisition context (A). Further, the level of response renewal was greater in IL-lesioned animals. The results are discussed in relation to the possible role of the IL cortex in contextual control of extinction.