ABSTRACT
The major current theory relating brain mechanisms in prefrontal cortex (PFC) to memory for discrete events (episodic memory) emphasizes the role of right PFC during retrieval. Using event-related fMRI, we found both right and left PFC activity during episodic remembering, but only the left PFC activity was related to the amount of episodic detail required at test. We suggest that right PFC subserves relatively simple, heuristic, cognitive processes and that left PFC is recruited for more reflectively demanding, systematic, processes. Episodic remembering often requires such systematic processes and, under those circumstances, recruits left, as well as right, PFC.
Subject(s)
Functional Laterality/physiology , Memory/physiology , Prefrontal Cortex/physiology , Acoustic Stimulation , Cognition/physiology , Evoked Potentials/physiology , Humans , Magnetic Resonance Imaging , Photic Stimulation , Reaction Time/physiologyABSTRACT
Recent studies of episodic memory using functional neuroimaging techniques indicate that right prefrontal cortex (PFC) is activated while people remember events. Our review suggests that left PFC is also activated during remembering, depending on the reflective demands of the task. As more, or more complex, reflective processes are required (e.g. when criteria for evaluation have to be established and maintained, when the complexity of the evaluation required increases, and when retrieval of additional information is required beyond that activated by an initial cue), left PFC activity is more likely to occur. Our `cortical asymmetry of reflective activity' (CARA) hypothesis summarizes available findings and suggests directions for future research.
ABSTRACT
To investigate brain mechanisms involved in identifying the origin of memories, event-related potentials (ERPs) were recorded as participants discriminated previously presented (old) from new items or identified their earlier source (picture, word, or new). Differences in ERPs between old-new recognition and source identification were focused at frontal sites. For source identification, prominent negative deflections at occipital or frontal sites occurred depending on encoding task. These results support a model in which memory attributes are distributed neocortically and the frontal lobes are critical for source monitoring.
Subject(s)
Discrimination Learning/physiology , Frontal Lobe/physiology , Memory/physiology , Reality Testing , Evoked Potentials/physiology , Female , Humans , Male , Reference ValuesABSTRACT
To investigate brain mechanisms involved in identifying the origin of memories, event-related potentials (ERPs) were recorded as participants discriminated previously presented (old) from new items or identified their earlier source (picture, word, or new). Differences in ERPs between old-new recognition and source identification, were focused at frontal sites. For source identification, prominent negative deflections at occipital or frontal sites occurred depending on encoding task. These results support a model in which memory attributes are distributed neocortically and the frontal lobes are critical for source monitoring.
