Title: Localized near–infrared spectroscopy and functional optical imaging of brain activity
Abstract: Changes in cerebral blood flow (CBF) and cerebral metabolic rates (CMRO2) have been used as indices for changes in neuronal activity. Near-infrared spectroscopy (NIRS) can also measure cerebral haemodynamics and metabolic changes, enabling the possible use of multichannel recording of NIRS for functional optical imaging of human brain activity. Spatio-temporal variations of brain regions were demonstrated during various mental tasks. Non-synchronous behaviour of cerebral haemodynamics during the neuronal activation was observed. Gender- and handedness-dependent lateralization of the function between right and left hemispheres was demonstrated by simultaneous measurement using two NIR instruments during the mirror-drawing task. A lack of interhemispheric integration was observed with schizophrenic patients. These observations suggest an application for NIRS in psychiatric disease management, as an addition to clinical monitoring at the bedside. A time resolved 64-channel optical imaging system was constructed. This consisted of three picosecond laser diodes and 64 channels of TAC and CFD systems. Image reconstruction for phantom model systems was performed. Time-resolved quantitative optical imaging will become real in the very near future.