Sex-based Differences in Corticospinal Excitability and Inhibition
Abstract
The purpose of this study was to perform a novel exploration of sex-based differences in corticospinal excitability and inhibition, with consideration of hormone phases. Thirty participants (15 females) attended two visits during different phases (low vs high). Responses evoked by single- and paired-pulse transcranial magnetic stimulation were recorded using electromyography from a hand muscle. Excitability was assessed via the motor-evoked potential and intracortical facilitation. Inhibition was assessed via the cortical silent period (CSP), short-interval (SICI), and long-interval intracortical inhibition (LICI). Each measure was compared between phases and sexes. Neither sex differed significantly across phases for excitability, nor inhibition for males. Females displayed significantly greater inhibition in the low phase (CSP: p=0.04). Overall, males and females had similar excitability. Males displayed significantly greater inhibition vs females for SICI (p=0.004) and LICI (p=0.008) but not CSP (p=0.28). Findings suggest both sexes could be equally included in research, during different hormone phases.