Medial frontal cortex mediates perceptual attentional set shifting in the rat

Abstract

If rodents do not display the behavioral complexity that is subserved in primates by prefrontal cortex, then evolution of prefrontal cortex in the rat should be doubted. Primate prefrontal cortex has been shown to mediate shifts in attention between perceptual dimensions of complex stimuli. This study examined the possibility that medial frontal cortex of the rat is involved in the shifting of perceptual attentional set. We trained rats to perform an attentional set-shifting task that is formally the same as a task used in monkeys and humans. Rats were trained to dig in bowls for a food reward. The bowls were presented in pairs, only one of which was baited. The rat had to select the bowl in which to dig by its odor, the medium that filled the bowl, or the texture that covered its surface. In a single session, rats performed a series of discriminations, including reversals, an intradimensional shift, and an extradimensional shift. Bilateral lesions by injection of ibotenic acid in medial frontal cortex resulted in impairment in neither initial acquisition nor reversal learning. We report here the same selective impairment in shifting of attentional set in the rat as seen in primates with lesions of prefrontal cortex. We conclude that medial frontal cortex of the rat has functional similarity to primate lateral prefrontal cortex.

Fig. 1.

A series of coronal sections (adapted from Paxinos and Watson, 1997) at 3.7, 2.7, and 1.0 mm anterior to bregma. The extent of the area of damage common to all lesioned rats is shown inblack, whereas the area of damage common to 50% of rats is shown shaded. The maximum extent of any damage is shown as a dotted line.

Fig. 2.

Bar graph showing number of trials to a criterion (six consecutive correct trials) for each discrimination. ID shifts were learned more rapidly than ED shifts. The lesions resulted in a selective impairment in the ED shift; *p < 0.05 compared with control.