Neuromodulation with transparent textured flicker preserves Alpha-band entrainment and improves visual comfort: A...

Rhythmic visual flicker entrains cortical oscillations and can modulate selective attention, yet its practical use is often hampered by discomfort. We compared alpha-band (10 Hz) with a high-frequency control (30 Hz) flickers under three contrast conditions: full-contrast, near-threshold low-contrast, and a textured low-contrast "ricker". Twenty adults performed a modified Eriksen flanker task while recording occipital steady-state visually evoked potentials (SSVEPs). Across all intensities, 10 Hz flickers yielded SSVEPs approximately three times larger than 30 Hz, confirming its efficacy in alpha entrainment. At the behavioral level, alpha stimulation selectively reduced flanker interference - without evidence of a uniform suppression of flanker processing - compared to 30 Hz stimulation. Importantly, stimulus design had a marked impact on user comfort: the ricker flicker elicited reliable alpha-band entrainment while being rated as the most comfortable. These results demonstrate that visual entrainment in the alpha-band can enhance attentional control and that textured low-contrast flicker provides a promising pathway for comfortable and effective neuromodulation.