TY - JOUR
T1 - The influence of working-memory demand and subject performance on prefrontal cortical activity
AU - Rypma, Bart
AU - Berger, Jeffrey S.
AU - D'Esposito, Mark
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2002/7/1
Y1 - 2002/7/1
N2 - Brain imaging and behavioral studies of working memory (WM) converge to suggest that the ventrolateral prefrontal cortex (PFC) mediates a capacity-limited storage buffer and that the dorsolateral PFC mediates memory organization processes that support supracapacity memory storage. Previous research from our laboratory has shown that the extent to which such memory organization processes are required depends on both task factors (i.e., memory load) and subject factors (i.e., response speed). Task factors exert their effects mainly during WM encoding while subject factors exert their effects mainly during WM retrieval. In this study, we sought to test the generalizability of these phenomena under more difficult memory-demand conditions than have been used previously. During scanning, subjects performed a WM task in which they were required to maintain between 1 and 8 letters over a brief delay. Neural activity was measured during encoding, maintenance, and retrieval task periods using event-related functional magnetic resonance imaging. With increasing memory load, there were reaction time increases and accuracy rate decreases, ventrolateral PFC activation decreases during encoding, and dorsolateral PFC activation increases during maintenance and retrieval. These results suggest that the ventrolateral PFC mediates WM storage and that the dorsolateral PFC mediates strategic memory organization processes that facilitate supracapacity WM storage. Additionally, high-performing subjects showed overall less activation than low-performing subjects, but activation increases with increasing memory load in the lateral PFC during maintenance and retrieval. Low-performing subjects showed overall more activation than high-performing subjects, but minimal activation increases in the dorsolateral PFC with increasing memory load. These results suggest that individual differences in both neural efficiency and cognitive strategy underlie individual differences in the quality of subjects' WM performance.
AB - Brain imaging and behavioral studies of working memory (WM) converge to suggest that the ventrolateral prefrontal cortex (PFC) mediates a capacity-limited storage buffer and that the dorsolateral PFC mediates memory organization processes that support supracapacity memory storage. Previous research from our laboratory has shown that the extent to which such memory organization processes are required depends on both task factors (i.e., memory load) and subject factors (i.e., response speed). Task factors exert their effects mainly during WM encoding while subject factors exert their effects mainly during WM retrieval. In this study, we sought to test the generalizability of these phenomena under more difficult memory-demand conditions than have been used previously. During scanning, subjects performed a WM task in which they were required to maintain between 1 and 8 letters over a brief delay. Neural activity was measured during encoding, maintenance, and retrieval task periods using event-related functional magnetic resonance imaging. With increasing memory load, there were reaction time increases and accuracy rate decreases, ventrolateral PFC activation decreases during encoding, and dorsolateral PFC activation increases during maintenance and retrieval. These results suggest that the ventrolateral PFC mediates WM storage and that the dorsolateral PFC mediates strategic memory organization processes that facilitate supracapacity WM storage. Additionally, high-performing subjects showed overall less activation than low-performing subjects, but activation increases with increasing memory load in the lateral PFC during maintenance and retrieval. Low-performing subjects showed overall more activation than high-performing subjects, but minimal activation increases in the dorsolateral PFC with increasing memory load. These results suggest that individual differences in both neural efficiency and cognitive strategy underlie individual differences in the quality of subjects' WM performance.
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U2 - 10.1162/08989290260138627
DO - 10.1162/08989290260138627
M3 - Article
C2 - 12167257
AN - SCOPUS:0036646615
SN - 0898-929X
VL - 14
SP - 721
EP - 731
JO - Journal of Cognitive Neuroscience
JF - Journal of Cognitive Neuroscience
IS - 5
ER -