Near-infrared spectroscopy study of language activated hyper- and hypo-oxygenation in human prefrontal cortex.

Oxygenation changes in the left prefrontal cortex during language processing were assessed with near-infrared spectroscopy (NIRS). Oxyhemoglobin and deoxyhemoglobin concentrations at the Fp1 site during 5 min of resting with eyes closed (control), followed by 5 min of reading aloud, were monitored. A statistically significant change in the oxyhemoglobin concentration was observed by NIRS in all the subjects after execution of the experimental task. The observations of hyper-oxygenation as well as hypo-oxygenation in the present investigation extend past studies and suggest a complex phenomenon of activation that may be the result of a vascular steal mechanism, attenuated activation baselines, or active cortical deactivation.