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 oxygenation and hemodynamics of the brain hemispheres due to three different types of mental stimulation. The variations were observed with a four-channel optical imaging system using tissue-transparent near-infrared light and described changes from baseline of both the hemoglobin oxygenation state and blood volume during three kinds of psychological or mental tasks. During the mirror drawing task, a lateralized hemisphere response (the dominant hemisphere response pattern) was observed in 57% of 14 right handed volunteers in the frontal region (Brodmann's area 10), while in the temporal region (area 38), 80% showed the bilateral response pattern. A large majority of the subjects showed the bilateral response pattern in the frontal and temporal regions while calculating. A smaller majority showed this while looking at anatomical charts, though 30% did not show any response at all in the temporal region. This showed that there were region-dependent asymmetrical or symmetrical variations of the oxygen delivery-oxygen utilization relationship due to different types of mental stimuli.