Participant
Participants exist only as random pseudonyms; no names are stored. Stimulation unlocks after photosensitivity screening and recorded consent.
Calibrate
Record eyes open, then eyes closed. The individual alpha frequency (IAF) is the spectral peak after removing the 1/f background; alpha should rise clearly when the eyes close.
Phase sweep
Four target phases and two controls with the same flash rate (open-loop flicker at the IAF, random phase), repeated in randomised blocks. Alpha is measured in the stimulus-free gap after each block, where there is no steady-state visual response.
Stimulate
The endpoint-corrected Hilbert transform estimates the alpha phase at every sample and one flash is scheduled per cycle at the target phase. Dots on the dial show where recent flashes landed, measured afterwards with a non-causal Hilbert transform.
Results
Post-block alpha power by condition (mean ± SEM, relative to the session mean). A permutation test checks for a one-cycle dependence on stimulation phase.