Invisible Spectral Flicker

Conventional luminance flicker (LF) — simple binary "on-off" pulsations of light — can entrain brainwaves at 40 Hz, but produces significant visual discomfort. Unmasked stroboscopic flicker can trigger dizziness, migraines, nausea, and in rare cases photosensitive epilepsy.

For gamma stimulation to be clinically viable as a daily home treatment, it must be tolerated over weeks without adverse effects. This requires a different strategy for entraining gamma brainwaves — one that entrains the target 40 Hz response while eliminating the perceptible flicker.

Invisible Spectral Flicker is a dual-modality flicker system that combines luminance flicker with a synchronous spectral masking. The device uses two precisely calibrated colour phases — Phase 1 and Phase 2 — that alternate at 40 Hz.

The two phases are represented as closely positioned chromaticity coordinates in the CIE 1931 colour space. They constitute two subtly differentiated spectral compositions — in practice, two nearly identical shades of white light. The phases are engineered to be metamerically matched: they appear visually identical to the human eye under typical viewing conditions, yet their spectral profiles differ sufficiently to induce the desired 40 Hz modulation.

As the light oscillates between these phases, the perceived brightness remains stable. The overt luminance change is concealed by the spectral shifts, creating an "almost imperceptible flicker effect" — while the 40 Hz rhythm penetrates the visual system and entrains neural oscillations in the brain's gamma band.