High Frequency SSVEP-BCI With Hardware Stimuli Control and Phase-Synchronized Comb Filter.

Anna Chabuda,Piotr Durka,Jaroslaw Zygierewicz

doi:10.1109/tnsre.2017.2734164

Abstract

We present an efficient implementation of brain-computer interface (BCI) based on high-frequency steady state visually evoked potentials (SSVEP). Individual shape of the SSVEP response is extracted by means of a feedforward comb filter, which adds delayed versions of the signal to itself. Rendering of the stimuli is controlled by specialized hardware (BCI Appliance). Out of 15 participants of the study, nine were able to produce stable response in at least eight out of ten frequencies from the 30-39 Hz range. They achieved on average 96±4% accuracy and 47±5 bit/min information transfer rate (ITR) for an optimized simple seven-letter speller, while generic full-alphabet speller allowed in this group for 89±9% accuracy and 36±9 bit/min ITR. These values exceed the performances of high-frequency SSVEP-BCI systems reported to date. Classical approach to SSVEP parameterization by relative spectral power in the frequencies of stimulation, implemented on the same data, resulted in significantly lower performance. This suggests that specific shape of the response is an important feature in classification. Finally, we discuss the differences in SSVEP responses of the participants who were able or unable to use the interface, as well as the statistically significant influence of the layout of the speller on the speed of BCI operation.

Highlights

B RAIN Computer Interface (BCI) is a non-muscular communication pathway, commonly based upon electroencephalogram (EEG).Steady state visually evoked potential (SSVEP, [1]) is the response of the brain to regularly flickering light, observed in the EEG signal over visual areas of the scalp
In this paper we propose a novel state visually evoked potentials (SSVEP)-based BCI which makes a direct use of the phase relations between the stimuli and SSVEP responses
BCI Appliance [9] used in this study consists of liquid crystal display (LCD) backlit by an array of LEDs

Summary

Introduction

Steady state visually evoked potential (SSVEP, [1]) is the response of the brain to regularly flickering light, observed in the EEG signal over visual areas of the scalp. SSVEP is frequency-following, its spectrum exhibits characteristic peaks in the stimulation frequency and its harmonics, stable over time [2]. Apart from these purely spectral properties, SSVEP is phase-locked to the stimulus and has a specific, subjectdependent structure, reflected in specific ratios of the harmonic components [3]. Contrary to the spectral properties of Manuscript received October 7, 2016; revised February 27, 2017 and June 7, 2017; accepted July 9, 2017.

Methods

Discussion

Conclusion