Summary and Comment

Traditional behavioral neurology taught that memory is dependent on Papez's circuit but that the frontal lobes are important for attention. An explosion of functional neuroimaging studies using PET and fMRI have recently elucidated the role of the frontal lobes in memory, and the evidence suggests that these structures are critical in accurate encoding and retrieval. These authors review the literature and offer a model of the activation of 3 areas of the frontal lobes in working memory (the ability to maintain and manipulate information "online" over periods of seconds) and episodic memory (the ability to store and retrieve information for much longer intervals). In the authors' model, ventrolateral frontal cortex (VLFC; inferior to the inferior frontal sulcus and roughly Brodmann areas 44, 45, and 47) is important in updating and maintaining information in working memory so that it can be processed further by other brain systems. In studies of episodic memory, VLFC was found to be active during successful encoding, suggesting that information must first be maintained in working memory before it can enter more long-term storage. VLFC was also found to be active during the initial stage of retrieval when information is transferred from long-term stores into working memory. Dorsolateral frontal cortex (DLFC; superior to the inferior frontal sulcus and roughly Brodmann areas 9 and 46) is important in the selection, manipulation, and monitoring of information that is already active in working memory. Thus, although DLFC may be activated in complex encoding tasks, it is more likely to be active during the second stage of episodic memory retrieval, when the information obtained from the initial search is evaluated. Anterior frontal cortex (AFC; anterior to the anterior edge of the inferior frontal gyrus and roughly Brodmann areas 8 and 10) is important in selecting goals and coordinating the activities of VLFC and DLFC to achieve these goals. AFC activation may be seen during intentional (rather than incidental) retrieval, and, in particular, when a participant needs to adopt or change specific strategies of memory retrieval to assist in goal-directed behavior.

Comment: This review provides a useful synthesis of recent functional neuroimaging studies in the cognitive neuroscience of memory. Neurologists will find this synthesis immediately applicable to their patients with frontal lesions from strokes or tumors.

— AE Budson

Published in Journal Watch Neurology August 9, 2001

Source: Fletcher PC and Henson RN. Frontal lobes and human memory: Insights from functional neuroimaging. Brain 2001 May; 124:849-881.