Steady State Visual Evoked Potentials in the Delta Range (0.5-5 Hz)

The usually ‘accepted’ limits of Steady State Visual Evoked Potentials are in the 3-60 Hz range. Recent studies reported SSVEP activities below 3 Hz, which remains a matter of debate. We recorded EEG responses to stimuli from 0.5 to 13 Hz. We first confirm the possibility to elicit SSVEP below 3 Hz. Afterwards, for the first time, we show that SSVEP recorded in the δ (0.5-5 Hz) range seem to describe several subsystems, with peaks near 1, 2.5 and 5 Hz (close to subharmonics of 10 Hz). Finally, we report surprising results in the lower frequency ranges, with responses for almost all harmonics (e.g. 15 peak responses between 0.5 and 14.5 Hz for stimuli at 1 hz).