Sex hormonal modulation of interhemispheric transfer time

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Endocrinology

Background:

• Debate exists on sex differences in functional cerebral asymmetries (FCA).
• Women's FCA may be influenced by fluctuating gonadal steroid hormones across the menstrual cycle.
• Interhemispheric communication, potentially modulated by hormones, influences brain lateralization.

Purpose of the Study:

• To directly measure interhemispheric communication during different menstrual cycle phases.
• To investigate the impact of hormonal changes on brain plasticity and lateralization.

Main Methods:

• Utilized visual-evoked EEG potentials to assess interhemispheric communication.
• Estimated interhemispheric transfer time (IHTT) using the N170 component latency.
• Tested 19 right-handed women during low-hormone (menstrual) and high-hormone (luteal) phases.
• Measured plasma steroid levels via immunoassay.

Main Results:

• Interhemispheric transfer time (IHTT), particularly right-to-left, was longer during the luteal phase compared to the menstrual phase.
• This change was linked to slowed N170 latency in the indirect pathway and shortened latency in the direct pathway during the luteal phase.
• Hormonal effects extend beyond interhemispheric processes to cortical interactions, especially within the right hemisphere.

Conclusions:

• Menstrual cycle-related hormonal fluctuations influence brain communication and cortical interactions in women.
• These findings support the concept of short-term brain plasticity in the female brain across the menstrual cycle.