Parametric manipulation of working memory load in traumatic brain injury: behavioral and neural correlates.
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.
Perlstein
William M
WM
Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida 32610, USA. wmp@grove.ufl.edu
Cole
Michael A
MA
Demery
Jason A
JA
Seignourel
Paul J
PJ
Dixit
Neha K
NK
Larson
Michael J
MJ
Briggs
Richard W
RW
D000328:Adult; D001930:Brain Injuries / Q000473:pathology / Q000503:physiopathology* / Q000523:psychology; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000098:blood supply / Q000503:physiopathology*; D003710:Demography; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D011930:Reaction Time / Q000502:physiology; D013647:Task Performance and Analysis
D010100:Oxygen