Prefrontal cortex lesions disrupt the contextual control of response conflict

Abstract

The prefrontal cortex has been implicated in multiple forms of goal-directed behavior. Rats with pretraining lesions to the prefrontal cortex (PFC) or specific lesions to the anterior cingulate cortex (ACC) were trained and tested on a novel behavioral procedure measuring aspects of cue and response competition typical of tests of prefrontal function in humans. Rats were trained on two biconditional discrimination tasks, one auditory and one visual, in two discriminably different contexts. At test, they received presentations of audiovisual compounds of these training stimuli in both contexts, in extinction. These compounds were formed in such way that the individual elements had dictated either the same (congruent trials) or different (incongruent trials) responses during training. Sham-operated rats used the contextual cues to disambiguate the conflicting response information provided by incongruent stimulus compounds. ACC lesions impaired the contextual control of instrumental responding during incongruent cues during only the initial period of cue presentation, whereas larger PFC lesions abolished incongruent cue performance completely. Neither biconditional discrimination acquisition, nor test performance during congruent stimulus compounds, were affected by the lesions. These findings are consistent with human and nonhuman primate studies, indicating a role for the PFC in the processes by which cues come to control behavior in the face of conflicting information and the ACC specifically in processes such as detection of response conflict. This procedure provides a good foundation for an improved understanding of the disruption to goal-directed behavior seen with frontal dysfunction in a number of neuropsychological disorders including schizophrenia.

Figure 1.

Representations of the minimum (gray) and maximum (striped) extent and location of damage within the prefrontal cortex. The outlines are reproduced from Paxinos and Watson (1998) and represent sections ranging from 2.2 to 4.7 anterior to bregma.

Figure 2.

Representations of the minimum (gray) and maximum (striped) extent and location of damage within the anterior cingulate cortex. The outlines are reproduced from Paxinos and Watson (1998) and represent sections ranging from 2.2 to 3.7 anterior to bregma.

Figure 3.

Normal acquisition of biconditional discrimination tasks in ACC- and PFC-lesioned animals. Error bars represent 1 SEM.

Figure 4.

Accurate performance to the biconditional training stimuli in extinction in sham, ACC-lesioned, and PFC-lesioned animals. Error bars represent 1 SEM.

Figure 5.

Abolition of context-appropriate responding to incongruent stimulus compounds in animals with PFC and ACC lesions, early (first 10 s) in S_D presentation. Congruent compounds comprised elements that required the same response during training; incongruent compounds comprised elements that required different responses during training. Error bars represent 1 SEM.

Figure 6.

Abolition of context-appropriate responding to incongruent stimulus compounds only in animals with PFC lesions, late (final 50 s) in S_D presentation. Congruent compounds comprised elements that required the same response during training; incongruent compounds comprised elements that required different responses during training. Error bars represent 1 SEM.

Figure 7.

Normal effect of reinforcer devaluation on responding to contextual cues in ACC- and PFC-lesioned animals. For the nondevalued condition, the devalued reinforcer had not been presented previously in the test context, whereas for the devalued condition, the devalued reinforcer had been presented previously in the test context. Error bars represent 1 SEM.