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Detection of Steady-State Visual Evoked Potentials in the EEG

A brain computer interface (BCI) is a communication or control system which does not need any neuromuscular activity to produce the message or action. Therefore it can be a communication solution for those people with severe neuromuscular disorders as well as for healthy people in practical applications in entertainment, and communication restoration. SSVEPs are oscillatory responses elicited by a flickering light stimulus that can be recorded in the electroencephalogram(EEG). It is a repetitive evoked potential whose constituent discrete frequency components remain constant in amplitude and phase over aninfinitive long time period. The SSVEP response consists of a number of sinusoids with frequencies given by the stimulus flickering frequency and a number of harmonics. This study is based on brain computer interfaces based on steady-state-visual-evoked-potentials. Thebrain regions where the response is produced has been demonstrated along this work to be stable for a certain frequency and so on spatial filters that discriminate the regions responsible of the SSVEP response have been consider a good solution. We present an approach to automatically obtain the optimum spatial filter to detect the SSVEP at a given stimulation frequency using short signal segments where the stimulation is presented at intermittent periods interspersed with breaks. The best harmonic combination is calculated and asan output all the necessary tools for a suitable detection, thresholdand detection filters.