A study of SSVEP from below-the-hairline areas in low-, medium-, and high-frequency ranges

Abstract

Purpose: Recent studies have analyzed steady-state visual evoked potentials (SSVEPs) measured on belowthe-hairline areas, such as behind-the-ears (temporal area) and face (frontal area) using different montages of channels and frequency bands. This study aims to investigate how both reference electrode and frequency ranges (low, medium, and high bands) affect the SSVEP measured on hairless areas of temporal and frontal. Methods: The EEG signals were acquired from 12 individuals, and the elicited SSVEP was evaluated in terms of amplitude and signal-to-noise ratio (SNR). Results: The best electrode combinations for measuring SSVEP on hairless areas are obtained with Fpz-Tp9 and Fpz-Tp10 (up to 40 Hz); however, for stimuli frequencies higher than 40 Hz, the best result is obtained with the temporal area and with the reference electrode located on the ear. Conclusion: The SSVEP amplitude and the SNR depend on the combination of the electrode reference and the range of visual stimulus frequency. These findings can aid in the development of more practical and comfortable SSVEP-based BCIs.