Background and objectives: 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.
Methods: 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.
Results: 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.
Conclusions: The excitatory and inhibitory functions in S1 differ between male and female subjects, at least during the early follicular phase.
Keywords: paired-pulse inhibition (PPI); primary somatosensory cortex (S1); sex differences; somatosensory evoked potentials.