Sex differences in attentional visual processing but not in plasticity-related modulation of visually evoked potentials

Impaired neuroplasticity is a core feature underlying many psychiatric disorders. Long-term potentiation (LTP)-like modulation of visually evoked potentials (VEPs), measured via EEG, represents a promising approach to assess plasticity in humans. Recent evidence indicates potential sex differences in VEP-based plasticity. This study investigated sex differences in visual cortical processing and plasticity by quantifying LTP-like modulation of VEPs. We analysed 96 available recordings from 61 women (mean age = 26.53 ± 6.87 years) and 35 men (mean age = 28.77 ± 8.63 years). VEPs were elicited using a checkerboard reversal stimulus (20 s at 2 Hz), presented before and after a 10-minute visual modulation. Post-modulation VEPs were recorded at 2, 8, 12, 18, 22, and 28 min. Amplitude changes from baseline to post-modulation were assessed. Predefined VEP components were analysed using linear mixed-effects models (LMEM), and time-resolved sex differences were evaluated via cluster-based permutation testing. LTP-like modulation was evident in early VEP components-specifically C1, P1, and P1N1 peak-to-peak amplitude indicating dynamic changes in early visual processing from 2 to 8 min post-stimulation. LMEM did not reveal any sex-specific effects in these components. However, time-course analyses identified discrete, significant sex differences in late VEP components in late VEP components at baseline (350-390 ms; p = .043) and 18 min post-modulation (388-426 ms; p = .048). Our findings demonstrate robust LTP-like modulation in early VEP components independent of sex. Subtle sex differences emerged in late, unmodulated VEP components (350-426 ms), likely reflecting variations in attention-related processing rather than plasticity per se.