Noninvasive assessment of cerebral hemodynamics and tissue oxygenation during activation of brain cell function in human adults using near infrared spectroscopy.

Near Infrared Spectroscopy (NIRS) was employed to noninvasively and continuously (temporal resolution 0.5 s) assess changes in cerebral hemodynamics and oxygenation during various functional states of the adult human brain. During cognitive stimulation (performing calculations) a frontal increase in local cerebral blood volume and oxygenated hemoglobin concentration was observed in most (10 of 12) subjects. During visual stimulation (observing a picture) this was demonstrated in the occipital region in all three subjects. Deoxygenated hemoglobin either decreased, remained unchanged or slightly increased during these procedures. Epileptic patients were examined during spontaneously occurring complex-partial seizures. During these seizures extremely large increases in blood volume and oxygenated hemoglobin concentration were measured. In conclusion, this feasibility study indicates that NIRS might become a useful and simple bedside tool to assess brain function.