EEG correlates of hemisphere differences during a rapid calculation task

Twenty male subjects performed a continuous task involving response to digit sets. The subject was required to respond to sets containing only odd numbers, and whose sum was greater than or equal to 20. Abundance of both left and right hemisphere EEG was inversely related to the number of odd digits in a set, showing accumulation of cortical arousal in response to cue value. This effect was stronger for the left hemisphere in some of the frequency bands. Reaction time correlated with EEg parameters for the left hemisphere only. This study overcomes many of the methodological flaws of earlier work. Differences obtained between hemispheres are thought to reflect both the exertion of mental effort in general and rapid calculation in particular.