Laterality of 40 HZ EEG and EMG activity during cognitive performance

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Task-dependent lateralization of the 40 Hz EEG rhythm was investigated in 16 right-handed male adults during the performance of verbal analogy and geometric rotation tasks. 40 Hz EMG activity recorded from the neck and temporal muscles was similarly examined. The EEG and EMG signals were analyzed using coincidence detection units, consisting of band-pass filters tuned to center frequencies of 40 Hz and 70 Hz, which were designed to control muscle contamination of the EEG signal. In addition, an algorithm was developed to determine which trials should be discarded because of high muscle interference. Results indicate that the 40 Hz EEG rhythm is asymmetrically distributed during cognitive performance. Specifically, each hemisphere produces relatively greater amounts of 40 Hz EEG when maximally engaged in task relevant cognition. No evidence was obtained to indicate systematic changes in the 40 Hz EEG laterality distribution as a function of task. The results are discussed in relation to previous studies concerning the distribution of 40 Hz EEG. In addition, a neural model of 40 Hz EEG is developed.