The electrophysiological effects of a brain injury on auditory memory functioning The QEEG correlates of impaired memory

Abstract

The effect of a brain injury on the quantitative EEG (QEEG) variables during an auditory memory activation condition was examined with 56 normal subjects and 85 mild traumatic brain-injured (MTBI) subjects. An analysis was conducted on the different response patterns of the two groups, the variables which were correlated with memory performance in the brain-injured group, and the variables which predicted the memory score for the combined two groups (normal and brain injured). The three conditions included the input task, the immediate recall, and the delayed recall task. The consistent effect of a brain injury was a lowering of the connectivity patterns in the beta1 and beta2 frequencies (phase and coherences) and increases predominantly in the relative power of beta1 (13-32Hz), which were correlated with the differences in recall. There is a subtle shift to right hemisphere/right temporal functioning and employment of the higher beta1 and beta2 frequencies (phase and coherence) in the response pattern of the MTBI subject. Memory functioning is predominantly positively correlated with connection activity (phase and coherence) and negatively correlated with beta activation at specific locations.

Traumatic Brain Injury Rehabilitation: QEEG Biofeedback Treatment Protocols

“…The head injured group relative to controls had increased EEG amplitudes and amplitude variances particularly in the beta band, with no significant differences in relative power of the bands between the two groups. In other studies of long term effects, Thornton (1999Thornton ( , 2000Thornton ( , 2003 reported significantly lowered values in the TBI group (with a post injury time frame ranging from \1 to 43 years), compared to normal controls in SCC and phase beta2 (32-64 Hz) relations under eyes closed condition (1999), auditory and visual attention (2000) and listening to paragraphs condition (2003), predominantly from frontal locations. Previous research (Thatcher et al 1989) with the eyes closed condition had not examined these relations.…”

“…Thus, in the previous two cognitive activation studies cited (Randolph and Miller 1988;Thornton 2003), the TBI subject shows increased beta (amplitudes and/or relative power) compared to normals. The three eyes closed comparisons reported specific decreases in beta (20.5-36 Hz) and high alpha (10.5-13.5 Hz; Tebano et al 1988), alpha (8-13 Hz;Thatcher et al 1989), and increases in low alpha (8-10 Hz; Tebano et al 1988) and theta (4-8 Hz; Thornton 1999).…”

“…The reader is referred to Collura (2008) for a more thorough discussion of these differences. This article focuses mainly on two specific formulations of these relations; classical or ''pure'' coherence as defined by Thatcher et al (2001) and the SCC (Lexicor) algorithm, which was employed in the Thornton (1999Thornton ( , 2000Thornton ( , 2003 TBI research and is referred to as SCC in this article. The concept of phase employs the Lexicor definition and is sensitive to timing issues between the signals.…”

“…There have been only two QEEG approaches, the eyes closed and the activation tasks, which have systematically examined the brain activity differences between the TBI patient and a normal population. Thatcher et al (1989) employed an eyes closed normative database with TBI subjects and a 0.5-22 Hz frequency range while Thornton (2003) examined the differences between TBI subjects and a normal group under cognitive activation tasks with the frequency range of 0.0-64 Hz. Other available activation databases for reading and math conditions have been developed (SKIL 2008) but have not been employed in research with the TBI population.…”

“…The quantitative electroencephalography (QEEG) involves the digitization of the EEG signal, which is saved to the hard disk and subsequently analyzed mathematically. One study (Nuwer et al 2005) asserts that there are no clear unique TBI, EEG or QEEG features, despite the research report (Thatcher et al 1989) that validated a discriminant function equation across three independent samples of TBI patients and obtained a hit rate above 90% and the research reports of Thornton (1999Thornton ( , 2000Thornton ( , 2003 which reported similar results. QEEG differences were reported between concussed athletes (mean assessment time was 89 days post concussion) and control subjects under the postural task condition of standing up (Thompson et al 2005).…”