Orbital prefrontal cortex mediates reversal learning and not attentional set shifting in the rat.

It has been demonstrated previously that lesions to medial prefrontal cortex in rats impair the shifting of attentional set between perceptual features of complex stimuli [J. Neurosci. 20 (2000) 4320], a result that mirrors the deficit found in humans and monkeys [Nature 380 (1996) 69; Behav. Neurosci. 110 (1996) 872; J. Neurosci. 17 (1997) 9285; Neuropsychologia 29 (1991) 993]. These data imply functional homology between rat medial prefrontal cortex and primate prefrontal cortex.In marmoset monkeys, there is a double dissociation between the effects of lesions of lateral prefrontal cortex, which impair shifting of attentional set, and lesions of orbital prefrontal cortex, which result in impairments of reversal of stimulus-reward contingencies, leaving attentional set-shifting capacities intact [Nature 380 (1996) 69; Behav. Neurosci. 110 (1996) 872; J. Neurosci. 17 (1997) 9285]. The present investigation examined whether lesions to rat orbital prefrontal cortex would produce deficits in reversal learning in the absence of deficits in shifting attentional set, as seen in monkeys. Rats were trained to perform an attentional set-shifting task that is formally the same as that used in monkeys and humans. In a single session, rats performed a series of discriminations, including acquisitions and reversals. Damage to orbital prefrontal cortex in the rats did not disrupt the ability to acquire, maintain or shift attentional set. We report here the same selective impairment in reversal learning in rats as seen in primates with orbital prefrontal cortex lesions.