Sex Differences in Excitatory and Inhibitory Function in the Primary Somatosensory Cortex during the Early Follicular Phase: A Preliminary Study.

Abstract

We examined sex differences in the excitatory and inhibitory functions of the primary somatosensory cortex (S1) between males and females during the early follicular phase, when estradiol hormones are unaffected. Fifty participants (25 males and 25 females) underwent measurement of somatosensory evoked potentials (SEPs) and paired-pulse inhibition (PPI) in the S1; SEPs and PPI were elicited by constant current square-wave pulses (0.2 ms duration) delivered to the right median nerve by electrical stimulation. Paired-pulse stimulation occurred at 30- and 100-ms interstimulus intervals. Participants were randomly presented with 1500 (500 stimuli each) single- and paired-pulse stimuli at 2 Hz. The N20 amplitude was significantly larger in female subjects than in male subjects, and the PPI-30 ms was significantly potentiated in female subjects compared to that in male subjects. The excitatory and inhibitory functions in S1 differ between male and female subjects, at least during the early follicular phase.