CEREBRAL OXYGENATION CHANGES IN RESPONSE TO MOTOR STIMULATION

We studied cerebral hemodynamic response to a sequential motor task in 56 subjects to investigate the time course and distribution of blood oxygenation changes as monitored by near-infrared spectroscopy (NIRS). To address whether response is modulated by different performance vel ocities, a group of subjects (n = 12) was examined while performing th e motor task at 1, 2, and 3 Hz, The results demonstrate that 2) the NI RS response reflects localized changes in cerebral hemodynamics, 2) th e response, consisting of an increase in oxygenated hemoglobin concent ration [oxy-Hb] and a decrease in deoxygenated hemoglobin concentratio n ([deoxy-Hb]), is lateralized and increases in amplitude with higher performance rates, and 3) changes in [oxy-Hb] and [deoxy-Hb] differ in time course. Changes in [oxy-Hb] are biphasic, with a fast initial in crease and a pronounced poststimulus undershoot. The stimulus-associat ed decrease in [deoxy-Hb] is monophasic, and response latency is great er. We conclude that NIRS is able to detect even small changes in cere bral hemodynamic response to functional stimulation.