Dissociable aspects of performance on the 5-choice serial reaction time task following lesions of the dorsal anterior cingulate, infralimbic and orbitofrontal cortex in the rat: differential effects on selectivity, impulsivity and compulsivity.

It is becoming increasingly apparent that multiple functions of the frontal cortex such as inhibitory control and executive attention are likely sustained by its functionally distinct and interacting sub-regions but the precise localization of dissociable executive processes has proved difficult and controversial. In the present series of studies, we investigated the behavioural effects of bilateral excitotoxic lesions of different regions of the rat neocortex in the 5-choice serial reaction time task. Whereas lesions of the dorsal anterior cingulate cortex (ACC) impaired performance of the task as revealed by a reduction in discriminative accuracy, lesions made to distinct ventral regions of the frontal cortex showed selective deficits in inhibitory measures of control. Specifically, the infralimbic lesion produced increases in premature responding that was accompanied by fast response latencies. By comparison, the orbitofrontal lesion showed perseverative tendencies particularly when the inter-trial interval was made long and unpredictable, a challenge that would normally promote premature responding instead. These different behavioural effects following dorsal and ventral lesions of the rodent frontal cortex signifies the integrity of the frontal cortex in multiple executive mechanisms that work independently and complementarily by which performance is optimized. Furthermore, these data provide new insights into the functional organization of the rodent frontal cortex with a particular emphasis on localization of function.