EEG Asymmetry During Covert Mental Activity

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Abstract
Twenty subjects selected for (overt) task‐induced EEG asymmetry performed 17 different covert mental tasks while EEG was recorded from right and left temporoparietal leads. After each task, subjects rated their experiences on four scales: (covert) verbalization, visual imagery, affect, and concentration. Zero‐order and semipartial correlations between integrated EEG measures and subjective ratings showed that verbalization and concentration were systematically related to EEG asymmetry. The results suggest that verbal processes may be a more important influence on temporoparietal EEG asymmetry than are visual imagery processes, at least during purely covert tasks. The results also demonstrate that EEG asymmetry reflects lateralized cognitive processes occurring in the absence of external stimuli or overt responses.