Peak visual gamma frequency is modified across the healthy menstrual cycle

Area of Science:

• Neuroscience
• Hormonal Regulation
• Brain Oscillations

Background:

• Gonadal hormone fluctuations during the menstrual cycle influence brain function.
• Progesterone's metabolite, allopregnanolone, modulates GABA_A receptors, affecting cortical excitation-inhibition balance.
• Previous research suggests hormonal shifts impact neural processing.

Purpose of the Study:

• To investigate the effect of menstrual cycle phase on gamma oscillations in the visual cortex.
• To explore how hormonal changes (progesterone, estradiol) influence neural microcircuitry.
• To determine if menstrual cycle phase impacts gamma-band activity and synaptic connections.

Main Methods:

• Electroencephalography (EEG) recorded visual cortex gamma oscillations in 20 females.
• Recordings were performed during the mid-luteal (high hormones) and early follicular (low hormones) phases.
• Dynamic causal modeling (DCM) analyzed synaptic microcircuitry changes.

Main Results:

• Significantly higher gamma frequency (∼5 Hz) observed during the luteal phase compared to the follicular phase.
• Dynamic causal modeling indicated stronger superficial pyramidal cell self-inhibition in the luteal phase.
• A stronger connection from inhibitory interneurons to deep pyramidal cells was found in the follicular phase.

Conclusions:

• Menstrual cycle phase induces complex functional changes in synaptic microcircuitry.
• Hormonal fluctuations across the menstrual cycle alter gamma oscillations and neural inhibition.
• Menstrual cycle phase is a critical factor to consider in research involving female participants and gamma-band oscillations.