Functional role of rat prelimbic-infralimbic cortices in spatial memory: evidence for their involvement in attention and behavioural flexibility

The involvement of the medial prefrontal cortex (mPFC), and more particular ly the prelimbic and infralimbic cortices (PL-IL area), in spatial memory r emains controversial. The present study investigates the effects of neuroto xic lesions restricted to the PL-IL area of the mPFC in rats trained in two different spatial tasks. In experiment I: PL-IL lesioned rats showed norma l acquisition of a delayed non-matching to position task. They were also ab le to plan their responses for a prospective strategy but were transiently disrupted when the initial delay was extended. In experiment 2, rats were t rained to locate one baited box among 13 identical boxes distributed on a c ircular arena. Lesioned rats performed normally when trained from a single start position but were severely disrupted when four start positions were u sed. A probe trial showed this deficit was not due to failure to learn the goal location. The addition of a proximal cue signalling the goal box helpe d lesioned rats to directly open the goal box, but did not compensate for g reater distances that they travelled to reach it. Results from both experim ents indicate that the PL-IL area is directly involved neither in allocentr ic spatial representations nor prospective,memory and is not specifically i nvolved in working memory. This area seems more likely to be involved in bo th attentional processes and behavioural flexibility that may be important for processing information for working memory as well as for spatial memory . (C) 2000 Elsevier Science B.V. All rights reserved.