To demonstrate this, we performed unilateral ACC lesions with ipsilateral DMS recordings to determine if the resolution of directional signals in DMS is dependent on ACC [connections are largely ipsilateral (13)]. Instead of bilateral lesions, we performed unilateral lesions to minimize the impact on behavior (i.e., the degree of impairment is likely less because one hemisphere remained intact) to assess changes in DMS firing without excessive changes to behavior or potential engagement of redundant systems (14). The task was selected because previous work has shown that single neurons in ACC are highly active prior to and during the resolution of directional signals in DMS (11). We found that, after ACC lesions, firing in DMS did not accurately represent the appropriate response direction on STOP-change trials and that, when rats made errors, firing strongly represented the incorrect, unresolved response. Consistent with these neural response patterns, rats with ACC lesions showed a significant reduction in accuracy on STOP-change trials and were slower to shift to a new response. This demonstrates that the ACC is necessary for appropriate response signaling in downstream regions as proposed by several computational and theoretical models (15–23).
