Right prefrontal cortex and episodic memory retrieval: a functional MRI test of the monitoring hypothesis

Though the right prefrontal cortex is often activated in neuroimaging studi es of episodic memory retrieval, the functional significance of this activa tion remains unresolved, In this functional MRI study of 12 healthy volunte ers, we tested the hypothesis that one role of the right prefrontal cortex is to monitor the information retrieved from episodic memory in order to ma ke an appropriate response. The critical comparison was between two word re cognition tasks that differed only in whether correct responses did or did not require reference to the spatiotemporal context of words presented duri ng a previous study episode. Activation in a dorsal midlateral region of th e right prefrontal cortex was associated with increased contextual monitori ng demands, whereas a more ventral region of the right prefrontal cortex sh owed retrieval-related activation that was independent of task instructions . This functional dissociation of dorsal and ventral right prefrontal regio ns is discussed in relation to a theoretical framework for the control of e pisodic memory retrieval.