Effects of hyperoxia on human sensorimotor cortex activity produced by electrical stimulation of the median nerve: a functional magnetic resonance imaging study.

This study investigated the effect of hyperoxia on sensorimotorcortical activity resulting from electrical stimulation of the median nerve, using functional magnetic resonance imaging (fMRI). Nine volunteers underwent stimulation at 5 and 100 Hz while breathing 21% FIO(2) (fraction of inspired oxygen) or 100% FIO(2). fMRI data were correlated with a stimulus predictor curve, transformed into Talairach space and averaged by group. Normoxic (21% FIO(2)) and hyperoxic (100% FIO(2)) sensorimotor activation volumes were compared using Student's t-test. There were no significant differences between the primary somatosensory/primary motor/Brodmann area 40 (SI/MI/Ba40) and secondary somatosensory cortex (SII) activation volumes for normoxia and hyperoxia. (P>0.05). There was no difference between SI/MI/Ba40 and SII activations at 5 and 100 Hz. In contrast to results previously reported for primary visual cortex (V1), hyperoxia did not enhance sensorimotor cortical activation in area SI/MI/Ba40 or SII. These results indicate that there is regional heterogeneity of the fMRI response to hyperoxia in the cerebral cortex.