PubMed1980
Lateralized functional specialization of cortical processing of linguistic and spatial information and anatomical lateralization of processing of hemiretinal stimuli were investigated with a randomized factorial design in 14 right-handed male undergraduates using EEG alpha-contingent visual stimulation. Words or geometric designs of equal luminosity and size were presented by computer to randomly selected visual half-fields contingent on the occurrence of alpha at one of 4 placements (left and right occipital and left and right temporal). The replicative reliability of alpha block and, by implication, the control of each stimulus type over different cortical sites, was assessed with the alpha control ratio (mean alpha duration/standard deviation of alpha durations). The alpha control ratio was significantly greater for alpha-contingent vs. random (non-contingent) stimulation. Within alpha-contingent data alone, cerebral lateralization was significantly demonstrated in the 2-way interactions of EEG hemisphere X visual field of stimulation, and of EEG hemisphere X type of stimulus (verbal or spatial). The alpha control ratio was higher for contralateral visual half-field stimulation compared to ipsilateral stimulation. Control was also significantly higher for cognitively appropriate stimulus-hemisphere combinations (verbal stimuli and left cerebral hemisphere, or spatial stimuli and right hemisphere) vs. inappropriate combinations (verbal, right hemisphere, or spatial, left hemisphere). These electrophysiological data corroborate in normal subjects the previous conceptions of hemispheric specialization ascertained with brain-damaged patients.