Individualized Gabor Flicker for Well-Tolerated Neural Entrainment During Working Memory

Rhythmic visual stimulation offers a non-invasive means of modulating oscillatory brain activity, but conventional flicker may induce considerable visual discomfort. We developed an individualized Gabor flicker stimulation designed to balance neural entrainment and tolerability. In Experiment 1, thirty-four participants passively viewed Plain and Gabor flickers presented at their individual alpha frequency (IAF), IAF - 2 Hz, or IAF + 2 Hz, and at threshold-adjusted or full intensity. Steady-state visual evoked potential signal-to-noise ratio (SNR) was highest at IAF and increased with intensity. Plain and Gabor flickers produced comparable overall SNR, but Gabor flicker was rated as substantially more comfortable and less mentally fatiguing, with stimulation at IAF providing the most favorable balance between neural entrainment and tolerability. In Experiment 2, the optimized stimulation parameters were applied during a retro-cue working memory task using individualized theta and alpha frequency flickers. Stimulation increased SNR and inter-trial phase coherence relative to a non rhythmic Natural condition. No behavioral benefit was observed in the full sample. However, an exploratory subgroup analysis indicated higher accuracy with theta stimulation of cued representations and alpha stimulation of uncued representations than in the Natural condition among participants who showed limited baseline retro-cue benefits. These findings show that individualized Gabor flicker can provide robust and well-tolerated neural entrainment during passive viewing and working memory retention, although its behavioral effects may vary across individuals according to their cognitive performance.