title: The Effects of Sex Hormonal Fluctuations during Menstrual Cycle on Cortical Excitability and Manual Dexterity (a Pilot Study).
abstract: OBJECTIVE
  To investigate whether hormonal fluctuations during the menstrual cycle affect corticospinal excitability, intracortical inhibition (ICI) or facilitation (ICF) in primary motor cortex, and also whether the hormonal fluctuations have any effect on manual dexterity in neurologically intact women.
  
  
  METHODS
  Twenty volunteers (10 Female, 10 Male) were included in this study. The levels of progesterone and estradiol were measured from saliva during the women's menstrual follicular, ovulation and mid-luteal phases. Motor evoked potentials were recorded from the right first dorsal interosseous muscle. Single and paired-pulse Transcranial Magnetic Stimulation (TMS) were delivered in a block of 20 stimuli. With paired-pulse technique, 3ms and 10ms inter-stimulus intervals were used to assess ICI and ICF, respectively. The Grooved Pegboard Test (GPT) was completed in each session before the TMS assessments. Male participants were tested at similar time intervals as female participants.
  
  
  RESULTS
  Mixed design ANOVA revealed that GPT score in female participants was significantly lower at the mid-luteal phase compared to the ovulation phase (p = 0.017). However, it was not correlated with progesterone or estrogen fluctuations during the menstrual cycle. The results also showed that the effect of phase, sex and the interaction of phase by sex for resting motor threshold, ICI or ICF were not significant (p > 0.05).
  
  
  CONCLUSIONS
  Manual dexterity performance fluctuates during the menstrual cycle in neurologically intact women, which might be due to the balance of the neuromodulatory effects of P4 and E2 in the motor cortex during different phases.
authors: Department of Medicine (Royal Melbourne Hospital), The University of Melbourne, Parkville, Melbourne, Australia.
authors: Maryam
authors: M
authors: Zoghi
authors: School of Primary Health Care, Faculty of Medicine, Nursing and Health Sciences, Monash University, Frankston, Melbourne, Australia.
authors: Bita
authors: B
authors: Vaseghi
authors: Department of Medicine (Royal Melbourne Hospital), The University of Melbourne, Parkville, Melbourne, Australia.
authors: Andisheh
authors: A
authors: Bastani
authors: School of Primary Health Care, Faculty of Medicine, Nursing and Health Sciences, Monash University, Frankston, Melbourne, Australia.
authors: Shapour
authors: S
authors: Jaberzadeh
authors: Department of Medicine (Royal Melbourne Hospital), The University of Melbourne, Parkville, Melbourne, Australia.
authors: Mary P
authors: MP
authors: Galea
mesh_terms: D000328:Adult; D004958:Estradiol / Q000494:pharmacology*; D019054:Evoked Potentials, Motor / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008597:Menstrual Cycle / Q000187:drug effects / Q000502:physiology*; D009044:Motor Cortex / Q000187:drug effects / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D010865:Pilot Projects; D011374:Progesterone / Q000494:pharmacology*; D012463:Saliva / Q000737:chemistry; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
chemical_list: D011374:Progesterone; D004958:Estradiol