Lesions of medial prefrontal cortex disrupt the acquisition but not the expression of goal-directed learning

Sean B Ostlund, Bernard W Balleine, Sean B Ostlund, Bernard W Balleine

Abstract

Several studies have established that pretraining lesions of the medial prefrontal cortex (mPFC) render instrumental actions insensitive to devaluation of the instrumental outcome and degradation of the action-outcome contingency. Nevertheless, it remains to be assessed whether the involvement of the mPFC in goal-directed action is limited to the acquisition or to the expression of the action-outcome association in performance. The current series of experiments investigated this issue by comparing the effects of mPFC lesions made either before or after initial training using sensitivity to outcome devaluation as an assay of goal-directed performance. Whereas pretraining lesions left performance insensitive to outcome devaluation, posttraining lesions spared this effect. To determine whether the effect of mPFC lesions on outcome devaluation was the result of a more fundamental deficit in response selection, experiment 2 assessed the impact of pretraining and posttraining lesions on the ability of the instrumental outcome to selectively reinstate the performance of its associated action after a period of extinction. Although both lesions attenuated the magnitude of instrumental reinstatement generally, they left intact the ability of the instrumental outcome to influence response selection. Experiment 3 investigated the relationship between the outcome-selective devaluation and reinstatement effects and found evidence that these effects are both behaviorally and neurally dissociable at the level of the mPFC. These results indicate that the mPFC is selectively involved in the acquisition, but not the permanent storage or expression, of action-outcome associations in instrumental conditioning.

Figures

Figure 1.
Figure 1.
Schematic representation of minimum (black) and maximum (gray) extent of mPFC damage. Coronal sections are modified from Paxinos and Watson (1998). The number next to each section refers to its position in the anteroposterior plane relative to bregma (in millimeters).
Figure 2.
Figure 2.
Reacquisition of instrumental performance. The mean number of lever presses per minute (±1 SEM), averaged across daily sessions, are shown for the last 3 d of training (left) and 3 d of retraining after surgery (right). The data are plotted separately for the sham and mPFC group.
Figure 3.
Figure 3.
Extinction and selective reinstatement of instrumental performance. Left, The mean number of lever presses per minute (±1 SEM) during consecutive 5 min blocks of extinction for the sham and mPFC groups. Right, The mean percentage of total responses (±1 SEM) made on each lever after the noncontingent outcome delivery for the sham and mPFC group. The data are plotted according to whether the action was trained with the outcome delivered during reinstatement (Reinst) or other outcome (Other).
Figure 4.
Figure 4.
Sensitivity of instrumental performance to outcome devaluation. The mean number of lever presses per minute during the outcome devaluation test for the sham and mPFC group is shown. The data are plotted according to whether the action was trained with the outcome devalued at test (Deval) or the other outcome (Other). The vertical bars represent 1 SE of the difference between means across actions for each group.
Figure 5.
Figure 5.
Sensitivity of instrumental performance to outcome devaluation. The mean number of lever presses per minute during the outcome devaluation test for groups sham, pre, and post is shown. The data are plotted according to whether the action was trained with the outcome devalued at test (Deval) or the other outcome (Other). The vertical bars represent 1 SE of the difference between means across actions for each group.
Figure 6.
Figure 6.
Extinction and selective reinstatement of instrumental performance. Left, The mean number of lever presses per minute (±1 SEM) during consecutive 5 min blocks of extinction for the sham and mPFC groups. Right, The mean percentage of total responses (±1 SEM) made on each lever after the noncontingent outcome delivery for groups sham, pre, and post. The data are plotted according to whether the action was trained with the outcome delivered during reinstatement (Reinst) or the other outcome (Other).
Figure 7.
Figure 7.
Extinction (baseline) during devalued reinstatement testing. The mean number of lever presses per minute during consecutive 5 min blocks of extinction for the sham and mPFC group. The data are plotted according to whether the action was trained with the outcome devalued at test (Deval) or the other outcome (Other). Note that the devalued outcome was also used to reinstate instrumental performance (see Fig. 8).
Figure 8.
Figure 8.
Impact of a devalued, noncontingently delivered outcome on response selection. The mean percentage of total responses made on each lever before (Extinction) and after (Reinstatement) the noncontingent outcome delivery for the sham group (left) and mPFC group (right). The data are plotted according to whether the action was trained with the outcome delivered during reinstatement (Reinst) or other outcome (Other). Note that the reinstating outcome had been devalued immediately before the test. Error bars represent SEM.

Source: PubMed

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