Longitudinal analysis of EEG and behavior in learning disabled children



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Brain electrical activity and concurrent performance on behavioral tasks was Investigated In twenty Learning Disabled children and In twenty age and IQ matched children making normal school progress. All children were boys from the same school district. Longitudinal changes In EEG and performance on behavioral tasks for a twenty month period were Investigated for the Learning Disabled children. Leads recorded were P[lowered 3]-C[lowered z], P[lowered 4]-C[lowered z], O[lowered 1]-C[lowered z], O[lowered 2]-C[lowered z], F[lowered 3]-C[lowered z] and F[lowered 4]-C[lowered z]. EEG recordings were made during a resting, eyes open, baseline condition and during the performance of three behavioral tasks; a Verbal-Visual task, a Verbal-Auditory task and a Tactile-Kinesthetic task which had been developed at the University of Houston Psychological Laboratories. Two equated forms of the tasks were used, one for the Pretest Phase and the other for the Posttest Phase. Magnetic taped stored analog cortical signals for the parietal and occipital leads were digitized at a 512 samples per second sampling rate and Fast Fourier transformations were calculated on sequential four second segments of EEG recorded during the baseline and task conditions. Percent of energy was calculated for nine frequency bands 1) 1.5-3.5 hz, 2) 3.75-7.5 hz, 3) 7.75-9.5 hz, 4) 9.75-12.5 hz, 5) 12.75-17.5 hz, 6) 17.75-27.5 hz, 7) 27.75-35.5 hz, 8) 35.75-44.5 hz 9) 44.75-56.0 hz. The percent of energy was calculated by using the total energy from 1.5-27.5 hz as the denominator for Bands 1-6, and. total energy from 1.5-56-0 hz as the denominator for Bands 7, 8 and 9- The percent of 'slow activity' was calculated for a window from 1.5-9-5 hz and for 'beta' activity from 12.75-27.5 hz. It was found on closer inspection of the activity in beta band that most of the significant differences between the LD and Control children were in the 12.75-17-5 window (Band 5), so Band 5 activity was considered separately. It was found that the LD children had significantly more slow activity and less beta (Band 5) activity, and committed substantially more errors on performance tasks than did the Control group during the Pretest Phase. During the Posttest Phase, the LD children formed a bimodal distibution ; those who made substantial and consistent improvement on performance tasks and those who did not. There was a significant overlap between those children who Improved in performance and those who showed substantial decreases in slow activity and Increases In beta(Band 5) activity. The results were Interpreted within a framework of the EEG reflecting a continuum of state of cortical arousal with a higher arousal state necessary for the learning process. The results would be consistent with a cerebral maturatlonal lag etiology being appropriate for some Learning Disabled children.