title: A functional MRI study of the influence of practice on component processes of working memory.
abstract: Previous neuroimaging studies have shown that neural activity changes with task practice. The types of changes reported have been inconsistent, however, and the neural mechanisms involved remain unclear. In this study, we investigated the influence of practice on different component processes of working memory (WM) using a face WM task. Event-related functional magnetic resonance imaging (fMRI) methodology allowed us to examine signal changes from early to late in the scanning session within different task stages (i.e., encoding, delay, retrieval), as well as to determine the influence of different levels of WM load on neural activity. We found practice-related decreases in fMRI signal and effects of memory load occurring primarily during encoding. This suggests that practice improves encoding efficiency, especially at higher memory loads. The decreases in fMRI signal we observed were not accompanied by improved behavioral performance; in fact, error rate increased for high WM load trials, indicating that practice-related changes in activation may occur during a scanning session without behavioral evidence of learning. Our results suggest that practice influences particular component processes of WM differently, and that the efficiency of these processes may not be captured by performance measures alone.
authors.affiliation: Henry H. Wheeler Brain Imaging Center, Helen Wills Neuroscience Institute, and Department of Psychology, University of California at Berkeley, 3210 Tolman Hall #1650, Berkeley, CA 94720-1650, USA. slandau@socrates.berkeley.edu
authors.forename: Susan M
authors.initials: SM
authors.lastname: Landau
authors.forename: Eric H
authors.initials: EH
authors.lastname: Schumacher
authors.forename: Hugh
authors.initials: H
authors.lastname: Garavan
authors.forename: T Jason
authors.initials: TJ
authors.lastname: Druzgal
authors.forename: Mark
authors.initials: M
authors.lastname: D'Esposito
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D003071:Cognition / Q000502:physiology; D003627:Data Interpretation, Statistical; D005145:Face; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D005222:Mental Fatigue; D011214:Practice, Psychological; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology