Changes in task-associated cerebral blood induced by role lettering: measurement by multichannel near-infrared spectroscopy.

Using optical topography (near-infrared spectroscopy: NIRS), relative changes in oxidized hemoglobin (oxy-Hb) were measured before and after the introduction of Role lettering. Tasks performed during measurements included antegrade (from the subject to other persons) and retrograde (from other persons to the subject) mental imaging and writing tasks. All subjects were junior high school students. Relative changes in oxy-Hb were measured before and 3, 6, and 12 months after the start of Role lettering. The region of interest (ROI) was determined based upon the motor cortex region of hand movement and upon relative oxy-Hb changes noted before any Role lettering. For antegrade mental tasks, oxy-Hb increased significantly in right-sided ROI after 3 months; this increase persisted at 1 year. For retrograde mental tasks, oxy-Hb significantly increased bilaterally at 3 months, an effect that also persisted at 1 year. With the antegrade writing task, no significant difference was observed throughout the study; with the retrograde writing task, oxy-Hb level decreased significantly in right lateral ROI after 6 months; the decrease persisted at 1 year. The number of words produced after Role lettering increased significantly in both antegrade and retrograde writing tasks at 1 year, compared with the number before Role lettering. Role lettering thus altered mental activity, particularly in the right hemisphere. Retrograde writing tasks, similar to those employed in the actual practice of Role lettering, reduced right hemispheric function; continuation of the task enhanced performance. Role lettering studies using NIRS may provide useful psychophysiologic indices.