Is 'gamma' (40 Hz) synchronous activity disturbed in patients with traumatic brain injury?

Objectives: The objective of this work is to determine whether Gamma (40Hz) synchronous activity has disturbed patients with severe traumatic brain injury (TBI). Methods: Using a conventional auditory oddball paradigm, the extent of Gamma synchrony across multiple scalp sites in specific frequency bands as a function of time was examined in 15 patients with severe TBI and 15 age- and sex-matched controls. Averaged Gamma synchrony was analyzed using within and between group multiple analyses of variance with region (left versus right hemisphere, anterior versus posterior region) as the within factor. Results: Compared to controls, subjects with TBI displayed significantly delayed early Gamma latency (from -150 to 150ms) (F_(1,28)=10.28, P<0.003) across all sites in addition to other specific regional disturbances. For late Gamma synchrony, subjects with TBI displayed delayed Gamma latency at the left hemisphere (from 200 to 450ms) (F_(1,28)=8.71, P<0.006) and posterior region (F_(1,28)=9.18, P<0.006) in comparison to controls. Conclusions: Impaired integration of spatially distributed brain activity ('40Hz' electroencephalogram rhythms) may be an important marker of deficits of cortical network binding postulated to be abnormal in people who have survived TBI.