40Hz activity in MBI, LLD and normal children: a comparative EEG study



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EEGs were recorded on three groups of children classified as Normals (N=22, mean age=10.08, mean IQ=102.32), Language-Learning Disability (LLD, N=29, mean age=9.91, mean IQ=99.36) and Minimal Brain Injured (MBI, N=25, mean age=10.63, mean IQ=90.56) by the Aldine School District during resting and performance of verbal and nonverbal tasks. Mean errors for the Verbal-Visual (VV) task were 2.41 for Normals, 4.62 for LLDs and 6.12 for MBIs. Mean errors for the Verbal-Auditory (VA) task were 1.91 for Normals, 5.34 for LLDs, and 6.94 for MBIs. Mean errors for the Tactile-Kinesthetic (TK) task were 3.86 for Normals, 5.38 for LLDs, and 5.12 for MBIs. Normals performed better than both learning disability groups on all tasks but no differences were found between the LLDs and MBIs. Computer analysis of the P[lowered 3]-C[lowered z] and P[lowered 4]-C[lowered z] leads divided the EEG into four 23% 1/3 octave bands centered at 30, 40, 50, and 70Hz. Activity of interest was 40Hz. with 30 and 50Hz. serving as control frequencies and 70Hz. used as a muscle detector. Normals had increases during the VV task in both leads in 40 and 50Hz. activity, during the VA task in both leads in 40Hz. activity, and during the TK task in the P[lowered 4]-C[lowered z] lead in 40Hz. activity. MBIs had increases during the TK task in the P[lowered 3]-C[lowered z]. lead in 40 and 50Hz. activity. LLDs had increases during the W task in P[lowered 4]-C[lowered z] in 50Hz. activity and decreases in 30Hz. activity in both leads during the VV task and in P[lowered 3]-C[lowered z], during the VA and TK tasks. Subgroups were formed using psychoeducational test data from school records and behavioral and EEG comparisons were made between the subgroups and between the subgroups and Normals. Hyperactivity, WRAT (Reading, Mathematics, and Spelling), and WISC Performance variables were not as effective as WRAT Reading subtest, WISC Verbal and the Bender-Gestalt test in predicting the degree of 40Hz. deficit as measured by the number of subjects showing 40Hz. increases within a subgroup compared to Nonaals. Findings were discussed in terms of "focused arousal," right-left hemisphere processing differences, the delayed maturation hypothesis, and prognosis for improvement resulting from 40Hz. conditioning as a treatment for learning disabilities. LLDs were selected as the group most likely to benefit from 40Hz. conditioning.