Task dependent lateralization of the 40 hertz EEG rhythm



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Task dependent lateralization of the 40 Hz. EEG rhythm was investigated in 24 right handed subjects. Each subject was administered four tests; verbal, mathematical, geometric figure recognition and facial recognition. Subjects' EEGs were recorded during each of the tests and amounts of 40 Hz. EEG activity present over each hemisphere during each test were compared to baseline, resting levels. Forty Hz. EMG activity was also recorded bilaterally from the neck and temporal muscles. Online comparators prevented 40 Hz. EMG from being counted as 40 Hz. EEG. Significant increases in 40 Hz. EEG activity were found over the left hemisphere during performance of the verbal test, and over the right hemisphere during performance of the geometric figure recognition test. Forty Hertz EEG activity was found to be uncorrelated with 40 Hz. EMG activity. Further, decreases in alpha and beta activity were found in all leads for all tests except the facial recognition test which failed to show any significant change in beta activity. The failure of the mathematical and facial recognition tests to show any pattern of lateralization of 40 Hz. EEG activity is discussed, and behavioral and cortical models of the 40 Hz, EEG rhythm as focused arousal are presented.