Improving Steady State Visual Evoked Potentials Responses from LED Stimuli Through Orientation Analysis

This article focuses on different orientations of LED visual stimulus configurations which could be used to elicit Steady State Visual Evoked Potentials (SSVEP). SSVEP is extensively used in the research for various biomedical applications and require a configurable light source flickering at a constant frequency that would induce responses in corresponding frequencies in the EEG recorded over the visual cortex area of the scalp. The present study investigated the SSVEP amplitude dependence of horizontal and vertical LED visual stimulus orientations. SSVEP amplitudes were compared for five healthy subjects from five sessions of 30 seconds each and the recorded EEG signals were analysed. Individual recording sessions were carried out with horizontal and vertical orientation with 10 Hz visual stimulus for analysing the SSVEP responses and also to evaluate the viewing comfort in each orientation. The signals were processed with band-pass filtering and analysed with Fast Fourier Transform (FFT) and autoregressive spectral analysis. The sign rank statistical results showed horizontal visual stimulus gave the higher response and viewing comfort in all subjects in comparison to vertical orientation.