Changes in Two Eeg Rhythms during Mental Activity.

2 sets of tasks—mental addition tasks and concept tasks—were given to 12 Ss and the effects of these tasks on 2 EEG rhythms—kappa and alpha—observed. On the mental addition tasks the difficulty of the task was shown to increase the output of kappa significantly but not the output of alpha. On the concept task, however, the difficulty of the task was shown to depress the output of alpha significantly. The results for kappa, although highly consistent for each individual, did not show any consistent pattern from one individual to another. It is suggested that the effects of mental tasks on kappa and alpha are specific to the sense modality involved in the task.