PREFRONTAL HYPOOXYGENATION DURING LANGUAGE PROCESSING ASSESSED WITH NEAR-INFRARED SPECTROSCOPY

Near-infrared spectroscopy (NIRS) is a noninvasive optical method whic h allows in vivo measurements of relative concentrations of oxygenated (O(2)Hb) and desoxygenated hemoglobin (HHb). It has been successfully applied to assess the blood oxygenation changes during cerebral ische mia in man. An interesting application of NIRS is the investigation of regional cerebral blood oxygenation during physiological brain functi ons. In the present study, left and right anterior prefrontal brain ar eas of 10 healthy subjects were investigated with 2-channel NIRS durin g language processing treading aloud). Nonverbal visual perception (pi cture observation) was performed as a control condition. Compared to t he respective baseline conditions, a significant HHb increase and an O (2)Hb decrease as a trend were found during language processing but no t during the nonverbal perceptual task, and no hemispheric differences were found. The metabolic activation patterns differed significantly between the tasks indicating the changes due to the language-related e fforts but not to visual perception. Based on previous findings of met abolic brain imaging studies the results are best explained as a compl ementary phenomenon consisting in relative anterior prefrontal hypoper fusion due to a blood volume redistribution which favors language-rela ted temporal areas.