FEAR LEARNING AND HORMONAL FLUCTUATIONS: A MULTIMODAL NEUROPHYSIOLOGICAL STUDY

The present study investigates brain activity during fear learning, focusing on hormonal fluctuations across the menstrual cycle and sex differences. Healthy young adults will be recruited. Women are allocated to four groups: early follicular (EF; low estrogen, low progesterone), late follicular (LF; high estrogen, low progesterone), mid‑luteal (ML; mid estrogen, high progesterone), and oral contraceptive users (OC; exogenous hormones), plus a comparison group of men (M). Participants complete a two-day fear learning paradigm, comprising fear acquisition (Day1) and delayed extinction (24h later). Fear responses are assessed via skin conductance responses (SCR) and fear-potentiated startle (FPS). Contingency awareness is included as an index of risk-related learning. Affective state is assessed with the State-Trait Anxiety Inventory – State (STAI‑S) before and after the experiment on both days. Neural correlates of fear processing and regulation are examined using electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS), targeting prefrontal regions. Preliminary analyses are expected to show enhanced fear modulation and extinction in the LF group compared to EF, reflected in stronger conditioned stimulus (CS+/CS-) differentiation and improved extinction retention, accompanied by increased medial prefrontal activation. Compared with naturally cycling women, OC users are expected to exhibit impaired fear inhibition and altered prefrontal activation patterns. Behaviourally, sex comparisons are expected to reveal similar fear-learning profiles in LF women and men, outperforming EF and OC groups. Preliminary findings are anticipated to highlight the critical role of endogenous and exogenous estrogens in modulating fear learning and its neural regulation, with implications for sex-specific vulnerability to anxiety-related disorders.