Visual cortical plasticity depends on stimulus structure and temporal dynamics

Modulation of visually evoked potentials (VEPs) is increasingly used as a putative biomarker of cortical plasticity in neuropsychiatric disorders and treatment response. However, commonly used paradigms differ in stimulus structure, temporal dynamics, and analytical readout, limiting interpretation and comparability. We compared established checkerboard (CB) reversal and sine grating (SG) stimulation protocols, along with their respective control conditions, to assess whether they elicit shared or paradigm-specific VEP modulation profiles. A total of 180 VEP recordings were acquired using EEG from healthy participants across six experimental conditions. CB reversal stimulation (2 rps for 10 min) elicited a robust and sustained increase in occipital P1N1 amplitude relative to a grey-screen control. The canonical SG protocol (8.6 Hz for 2 min) produced stimulus-specific N1b modulation, most pronounced early after stimulation, whereas the SG grey-screen control condition, prolonged 2 Hz SG stimulation, and a mixed 2 Hz/8.6 Hz protocol did not produce frequency- or stimulus-specific effects. Additional cross-component analyses indicated partially overlapping modulation profiles: CB stimulation also induced weaker parietal N1b modulation, whereas SG stimulation affected occipital P1N1 responses, though less specifically and partly in the control condition. These findings suggest that CB and SG paradigms do not map onto entirely separate mechanisms, but emphasize different aspects of visual cortical response modulation. CB stimulation may provide a robust readout of Hebbian- or LTP-like response modulation, whereas SG stimulation is more sensitive to stimulus-specific and frequency-dependent dynamics. This distinction may inform rational protocol selection in future biomarker-oriented applications, including patient stratification and treatment prediction.