The Roles of Prefrontal Brain Regions in Components of Working Memory: Effects of Memory Load and Individual Differences

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 96; no. 11; pp. 6558 - 6563
• Main Authors: Rypma, Bart, D'Esposito, Mark
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 25.05.1999; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: Adult; Biological Sciences; Brain; Brain Mapping; Evoked Potentials - physiology; Female; Hemispheres; Humans; Imaging; Magnetic Resonance Imaging; Male; Memory; Memory - physiology; Memory encoding; Memory recall; Prefrontal Cortex - physiology; Propagation delay; Psychology; Reaction Time; Regression Analysis; Statistical variance; Time series; Working memory
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.96.11.6558

Using an event-related functional MRI design, we explored the relative roles of dorsal and ventral prefrontal cortex (PFC) regions during specific components (Encoding, Delay, Response) of a working memory task under different memory-load conditions. In a group analysis, effects of increased memory load were observed only in dorsal PFC in the encoding period. Activity was lateralized to the right hemisphere in the high but not the low memory-load condition. Individual analyses revealed variability in activation patterns across subjects. Regression analyses indicated that one source of variability was subjects' memory retrieval rate. It was observed that dorsal PFC plays a differentially greater role in information retrieval for slower subjects, possibly because of inefficient retrieval processes or a reduced quality of mnemonic representations. This study supports the idea that dorsal and ventral PFC play different roles in component processes of working memory.