Sex-based differences in corticospinal excitability and inhibition

The purpose of this study was to perform a novel exploration of sex-based differences in various single- and paired-pulse transcranial magnetic stimulation (TMS)-based measures of corticospinal excitability and inhibition. Thirty participants (15 females) attended one laboratory visit where responses evoked by single- and paired-pulse TMS were recorded using electromyography from the first dorsal interosseous muscle. Excitability was assessed via the motor-evoked potential (MEP) and intracortical facilitation (ICF). Inhibition was assessed via the cortical silent period (CSP), short-interval intracortical inhibition (SICI), and long-interval intracortical inhibition (LICI). Each measure was compared between sexes. Overall, males and females did not significantly differ in excitability (MEP: P = 0.070; ICF: P = 0.194). Males displayed significantly greater inhibition compared to females for the SICI (P = 0.016) and LICI (P = 0.003) measures but not CSP (P = 0.612). These findings suggest that sex may be an important consideration for some (SICI and LICI), but not all TMS-based measures of corticospinal excitability and inhibition.