REGION-DEPENDENT ASYMMETRICAL OR SYMMETRICAL VARIATIONS IN THE OXYGENATION AND HEMODYNAMICS OF THE BRAIN DUE TO DIFFERENT MENTAL STIMULI

The present paper demonstrates region-dependent variations in the oxyg enation and hemodynamics of the brain hemispheres due to three differe nt types of mental stimulation. The variations were observed with a fo ur-channel optical imaging system using tissue-transparent near-infrar ed light and described changes from baseline of both the hemoglobin ox ygenation state and blood volume during three kinds of psychological o r mental tasks. During the mirror drawing task, a lateralized hemisphe re response (the dominant hemisphere response pattern) was observed in 57% of 14 right handed volunteers in the frontal region (Brodmann's a rea 10), while in the temporal region (area 38), 80% showed the bilate ral response pattern. A large majority of the subjects showed the bila teral response pattern in the frontal and temporal regions while calcu lating. A smaller majority showed this while looking at anatomical cha rts, though 30% did not show any response at all in the temporal regio n. This showed that there were region-dependent asymmetrical or symmet rical variations of the oxygen delivery-oxygen utilization relationshi p due to different types of mental stimuli.