A Configurable, Inexpensive, Portable, Multi-channel, Multi-frequency, Multi-chromatic RGB LED System for SSVEP Stimulation

Abstract

Steady state visual evoked potential (SSVEP) is extensively used in the research of brain-computer interface (BCI) and require a controllable and configurable light source. SSVEP requires appropriate control of visual stimulus parameters, such as flicker frequency, light intensity, multi-frequency light source and multi-spectral compositions. Light emitting diodes (LEDs) are extensively used as a light source as they are energy efficient, low power, multi-chromatic, have higher contrast, and support wider frequency ranges. Here, we present the design of a compact versatile visual stimulus which is capable of producing simultaneous multiple frequency RGB LED flicker suitable for a wide range of SSVEP paradigms. The hardware is based upon the open source Arduino platform and supports on-the-fly reprogramming with easily configurable user interface via USB. The design provides fourteen independent high output channels with customisable output voltages. The flicker frequencies can be easily customised within the frequency range of 5-50 Hz, using a look-up table. The LED flickers are generated with single RGB LEDs which generate the required colour or frequency combinations for combined multi-frequency flicker with variable duty cycle to generate SSVEP. Electroencephalogram (EEG) signals have been successfully recorded from five subjects using the stimulator for different frequencies, colours, duty cycle, intensity and multiple frequency RGB source, thereby demonstrating the high usability, adaptability and flexibility of the stimulator. Finally we discuss the possible improvements to the stimulator which could provide real time user feedback to reduce visual fatigue and so increase the level of user comfort.

Toward a reliable PWM‐based light‐emitting diode visual stimulus for improved SSVEP response with minimal visual fatigue

“…Studies have used light-emitting diode (LED)-based visual stimulus designs that can produce visual flickers without any frequency restrictions and can also produce multiple visual stimuli using the same control platform [22,23]. When using multiple visual stimuli flashing at different frequencies, the accuracy of the flicker frequency for visual stimulus plays an important role in SSVEP-based BCI.…”

Sharing an Open Stimulation System for Auditory EEG Experiments Using Python, Raspberry Pi, and HifiBerry

“…The addition of the HiFiBerry has broadened the range of studies that can be performed using a Raspberry Pi. Previous work from Kuziek et al (2017) and Mouli et al (2015) showed that open source stimulation systems could be used to present simple stimulation (beeps). Our solution extends their work by allowing all types of (personalized) audio protocols with good sound quality.…”

“…Another example of a Raspberry Pi use in multisite neuroscientific studies results from multisensory studies on rodent behavior ( Buscher et al, 2020 ). Others have shown that an Arduino could be easily used for steady-state visual evoked potential ( Mouli et al, 2015 ). However, these systems have been developed for very simple protocols and materials (beeps) and could be improved both in timing accuracy and audio quality.…”

Effects of visual flickering stimuli for event-related potential recording

“…Distance is set approximately one meter. Based on the studies in [5]- [7] found that the optimal parameter for the subject to reduce visual fatigue or visual discomfort. For each trial, therefore, we set the duty cycle (D) is 0.7, flickering rate (F) is fixed at 7 Hz, light intensity (I) is 10%, and chromatic color (C) is green.…”