Aim 1: Assess how menstrual cycle phase affects motor cortex plasticity in females. Aim 2: Compare motor cortex plasticity between males and females across the same time points, identifying potential sex differences in TMS response. Aim 3: Examine associations between serum hormone levels and TMS-induced plasticity within and between sexes.
This project will recruit healthy male and female volunteers between the ages of 20-40. Females must who are not on hormonal medications and, if female, have regular menstrual cycles as defined in Table 1. At time of consent, female participants will be send home with given tests that may assess urine estradiol, LH and/or their metabolites. Participants will be asked to complete these tests at home, will be instructed to use these tests in the morning at the first void of the day; the number of days during each cycle that participants will be asked to complete these tests will be based on their report of their regular cycle pattern but will not be longer than half the number of days in each cycle. In addition, female subjects will be given a RedCap survey link at which they will track their menstrual cycle and results from the urine estradiol/LH tests. Subjects will undergo 4 study visits over approximately 1-2 months depending on availability and, if female, menstrual cycle point. At visit 1, subjects will consent to the protocol, fill out surveys including the TMS Adult Safety Screening (TASS) and a questionnaire about past hormonal medication use and if relevant, menstrual cycle history. If female, subjects will be given take-home ovulation tests to use across the study duration. On the following visits, they may undergo the following procedures: 1) venipuncture to collect approximately 45mL 10 mL of blood 2) motor threshold testing, 2) Paired-Pulse Stimulation 3) Single-Pulse TMS to the motor cortex 4) intermittent Theta Burst Stimulation (iTBS) to the motor cortex.
Study Type
OBSERVATIONAL
Enrollment
100
Subjects will receive a series of 60 10s trains that will be presented over the course of the \~3.5 min session. Each train will consist of 2 s of stimulation with an 8 s ITI. During the 2 s of stimulation, 10, 50 Hz bursts will be repeated at intervals of 200 ms (5 Hz). iTBS will be administered at 100% of the motor threshold (MT).
University of Pennsylvania
Philadelphia, Pennsylvania, United States
RECRUITINGSingle-pulse TMS
Single-pulse TMS: Cortical excitability curves will be measured before and after a single 1800-pulse train of iTBS. Motor Evoked Potentials (MEPs) will be recorded from the right FDI muscle at 7 distinct intensities ranging from -20% to + 40% of MT. Single pulses will be delivered once every 10±3 seconds to the left motor cortex at random intensities in the above range to avoid habituation across pulses. Across the session, a total of 70 pulses will be delivered before and after iTBS, 10 at each intensity.
Time frame: Will be collected during 3 visits over the course of a 2 month timeframe during different phases of the menstrual cycle (in females).
Paired pulse stimulation
Paired-pulse stimulation: Subjects will undergo paired-pulse stimulation to measure both intracortical inhibition and intracortical facilitation. For intracortical inhibition, subjects will receive a conditioning pulse at 80% MT 4 seconds before the test pulse at 120% MT. For intracortical facilitation, subjects will receive a conditioning pulse at 120% MT 15s before the test pulse at 120% MT. Across the session, a total of 60 paired pulses will be delivered before and after iTBS, 30 at each ISI.
Time frame: Will be collected during 3 visits over the course of a 2 month timeframe during different phases of the menstrual cycle (in females).
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