Journal of the International Neuropsychological Society



Parametric manipulation of working memory load in traumatic brain injury: Behavioral and neural correlates


WILLIAM M.  PERLSTEIN  a1 a2 a3 c1 , MICHAEL A.  COLE  a1 , JASON A.  DEMERY  a1 , PAUL J.  SEIGNOUREL  a1 , NEHA K.  DIXIT  a1 , MICHAEL J.  LARSON  a1 and RICHARD W.  BRIGGS  a4
a1 Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida
a2 Department of Psychiatry, University of Florida, Gainesville, Florida
a3 McKnight Brain Institute, University of Florida, Gainesville, Florida
a4 Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas

Article author query
perlstein wm   [PubMed][Google Scholar] 
cole ma   [PubMed][Google Scholar] 
demery ja   [PubMed][Google Scholar] 
seignourel pj   [PubMed][Google Scholar] 
dixit nk   [PubMed][Google Scholar] 
larson mj   [PubMed][Google Scholar] 
briggs rw   [PubMed][Google Scholar] 

Abstract

Traumatic brain injury (TBI) is often associated with enduring impairments in high-level cognitive functioning, including working memory (WM). We examined WM function in predominantly chronic patients with mild, moderate and severe TBI and healthy comparison subjects behaviorally and, in a small subset of moderate-to-severe TBI patients, with event-related functional magnetic resonance imaging (fMRI), using a visual n-back task that parametrically varied WM load. TBI patients showed severity-dependent and load-related WM deficits in performance accuracy, but not reaction time. Performance of mild TBI patients did not differ from controls; patients with moderate and severe TBI were impaired, relative to controls and mild TBI patients, but only at higher WM-load levels. fMRI results show that TBI patients exhibit altered patterns of activation in a number of WM-related brain regions, including the dorsolateral prefrontal cortex and Broca's area. Examination of the pattern of behavioral responding and the temporal course of activations suggests that WM deficits in moderate-to-severe TBI are due to associative or strategic aspects of WM, and not impairments in active maintenance of stimulus representations. Overall, results demonstrate that individuals with moderate-to-severe TBI exhibit WM deficits that are associated with dysfunction within a distributed network of brain regions that support verbally mediated WM. (JINS, 2004, 10, 724–741.)

(Received June 6 2003)
(Revised February 14 2004)
(Accepted March 16 2004)


Key Words: Traumatic brain injury; Working memory; Functional magnetic resonance imaging.

Correspondence:
c1 Reprint requests to: William M. Perlstein, Ph.D., Department of Clinical and Health Psychology, HSC Box 100165, University of Florida, Gainesville, FL 32610. E-mail: wmp@grove.ufl.edu


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