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Rypma B, Berger JS, D'Esposito M.

The influence of working-memory demand and subject performance on prefrontal cortical activity during maintenance of working memory

fMRIDC Accession Number: 2-2002-112JG
Journal of Cognitive Neuroscience 2002 Jul ;14(5): p.721-731
View entire article (off-site link)
PubMed ID: 12167257 (off-site link)

Study Meta-Data

Brain imaging and behavioral studies of working-memory (WM) converge to suggest that ventrolateral prefrontal cortex (PFC) mediates a capacity-limited storage buffer and that 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 ventrolateral PFC mediates WM storage and that 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 lateral PFC during maintenance and retrieval. Low-performing subjects showed overall more activation than high-performing subjects but minimal activation increases in 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.

Supplemental Information

Language: English
fMRIDC Comments: Memory load modulation Dataset Size: 2.1G Available on 1 CD
Country: USA
Magnetic Field Strength: 1.5T
Scanner Manufacturer: GE Signa
Analysis Software: Custom
Cognitive Domain: Working Memory
Subjects: 8
Age Range: 21-30
Functional Runs: 9
Has anatomical data
Has raw image data
Has high-res images

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