Frequency-modulated steady-state visual evoked potentials: a new stimulation method for brain-computer interfaces

Abstract

Background: Steady-state visual evoked potentials (SSVEPs) are widely used for brain-computer interfaces. However, users experience fatigue due to exposure to flickering stimuli. High-frequency stimulation has been proposed to reduce this problem. We adapt frequency-modulated (FM) stimulation from the auditory domain, where it is commonly used to evoke steady-state responses, and compare the EEG as well as behavioral flicker perceptibility ratings.

New method: We evoke SSVEPs with a green light-emitting diode (LED) driven by FM signals.

Results: FM-SSVEPs with different carrier and modulation frequencies can reliably be evoked with spectral peaks at the lower FM sideband. Subjective perceptibility ratings decrease with increasing FM carrier frequencies, while the peak amplitude and signal-to-noise ratio (SNR) remain the same.

Comparison with existing method: There are neither amplitude nor SNR differences between SSVEPs evoked rectangularly, sinusoidally or via FM. Perceptibility ratings were lower for FM-SSVEPs with carrier frequencies of 20Hz and above than for sinusoidally evoked SSVEPs.

Conclusions: FM-SSVEPs seem to be beneficial for BCI usage. Reduced flicker perceptibility in FM-SSVEPs suggests reduced fatigue, which leads to an enhanced user experience and performance.

Keywords: Amplitude modulation; Brain–computer interface (BCI); EEG; Frequency modulation; Light-emitting diode (LED); Steady-state visual evoked potential (SSVEP).