Right Dorsolateral Prefrontal Cortex is Engaged During Post-retrieval Processing of Both Episodic and Semantic Information

Post-retrieval processes are engaged when the outcome of a retrieval attempt must be monitored or evaluated. Functional neuroimaging studies have implicated right dorsolateral prefrontal cortex (DLPFC) as playing a role in post-retrieval processing. The present study used fMRI to investigate whether retrieval-related neural activity in DLPFC is associated specifically with monitoring the episodic content of a retrieval attempt. During study, subjects were cued to make one of two semantic judgments on serially presented pictures. One study phase was followed by a source memory task, in which subjects responded 'new' to unstudied pictures, and signaled the semantic judgment made on each studied picture. A separate study phase was followed by a task in which the studied items were subjected to a judgment about their semantic attributes. Both tasks required that retrieved information be evaluated prior to response selection, but only the source memory task required evaluation of retrieved episodic information. In both tasks, activity in a common region of right DLPFC was greater for studied than for unstudied items, and the magnitude of this effect did not differ between the tasks. Together with the results of a parallel event-related potential study [Hayama, H. R., Johnson, J. D., & Rugg, M. D. (2008). The relationship between the right frontal old/new ERP effect and post-retrieval monitoring: Specific or non-specific? Neuropsychologia, 46(5), 1211-1223, doi:S0028-3932(07)00390-9], the present findings indicate that putative right DLPFC correlates of post-retrieval processing are not associated exclusively with monitoring or evaluating episodic content. Rather, the effects likely reflect processing associated with monitoring or decision-making in multiple cognitive domains.