Traumatic Brain Injury (TBI) patients often have persistent cognitive deficits, particularly in attention and executive function. We used Magnetoencephalography (MEG) to examine the timecourse of ...neural activity during a Color Naming Stroop Task with beamforming source localization. Data were acquired from 19 adult patients with chronic symptomatic mild or moderate TBI and 14 healthy controls using a 275-channel whole-head biomagnetometer (CTF Systems, Vancouver BC) and analyzed in the time-frequency domain using Nutmeg (bil.ucsf.edu/nutmeg). Activity was defined as power fluctuations in each voxel over time in theta (4-7 Hz), alpha (8-12 Hz), beta (12-30 Hz), low gamma (30-55 Hz), and high gamma (63-117 Hz) bands for Incongruent versus Congruent trials and submitted to within- and between-group analyses. Control subjects had significant conflict-related activity in prefrontal and temporal regions in all frequency bands, including Dorsolateral Prefrontal Cortex (DLPFC) and Anterior Cingulate Cortex (ACC), beginning at 50 msec post-stimulus and extending throughout a 700 msec window. In all regions exhibiting significant conflict-related activity in healthy controls, TBI patients had equivalent or reduced activity. However, TBI patients had extensive significantly increased activity in other frontal, temporal and occipital brain regions in each frequency band. High Gamma activity, in right prefrontal cortex from 350-450 msec and right ACC from 350-400 msec, was associated with conflict processing scores in TBI patients. This activity in right prefrontal cortex was correlated with the Extended Glasgow Outcome Scale, a measure of clinical status. These results suggest large scale compensatory reorganization due to TBI within the oscillatory networks subserving conflict.
Traumatic Brain Injury (TBI) often produces chronic deficits in cognitive function that affect patients' quality of life. To investigate attention-related neural activity differences associated with ...TBI, we measured whole-head magnetoencephalography (MEG) signals during a cued visuospatial attention task. MEG data from nineteen patients with mild-to-moderate symptomatic TBI and eighteen healthy control participants were analyzed using an adaptive spatial filtering technique (NUTMEG, http://bil.ucsf.edu/nutmeg), and co-registered to individual brain anatomy prior to normalizing images for within-and between-group comparisons. We examine high gamma band activity (63-117 Hz) arising from Incongruently-versus Congruently-cued target stimuli. Using Family-wise Error (FWE) correction for comparisons across voxels, in healthy participants we observe activations in Left Middle Frontal Gyrus (LMFG) from 100 to 175 ms, followed by largely-concurrent Right hemisphere activity from 175 to 300 ms in areas of Inferior Parietal Sulcus (RIPS), Insula, Putamen, and Superior Temporal Cortex and, subsequently, at ~325ms Left Inferior Frontal Cortex for a 50 ms period. In these regions, TBI patients exhibited reduced activity relative to healthy participants and, as a group, showed no alternate compensatory pattern of activity that survived the FWE correction threshold. Linear discriminant analyses revealed that activity levels in just 2 of these 5 regions, LMFG and RIPS, reliably predicted injury status. Furthermore, activity in LMFG showed negative correlation with both the Head Injury Symptom Checklist for post-concussive syndrome (HISC-PCS) and a measure of Cognitive Failures. These results suggest reduced activation due to TBI within a frontotemporal high-gamma oscillatory network subserving spatial attention.
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