Corticolimbic mechanisms in the control of trial and error learning.

As learning progresses, human and animal studies suggest that a frontal executive system is strongly involved early in learning, whereas a posterior monitoring and control system comes online as learning progresses. In a previous study, we employed dense array EEG methodology to delineate the involvement of these two systems as human participants learn, through trial and error, to associate manual responses with arbitrary digit codes. The results were generally consistent with the dual-system learning model, pointing to the importance of both systems as learning progressed. In the present study, we replicate and extend the previous findings by examining the brain responses to error trials as well as examine the activity of these two systems' response to feedback processing. The results confirmed the role of these two systems in learning but they also provide a more complex view of their makeup and function. The frontal system includes ventral (inferior frontal gyrus, ventral anterior cingulate cortex, anterior temporal lobe) corticolimbic structures that are involved early in learning whereas the posterior system includes dorsal (anterior and posterior cingulate and medial temporal lobe) corticolimbic circuits that are engaged later in learning. Importantly, the engagement of each system during the course of learning is dependent on the nature of the events within the learning task.