Instant classification for the spatially-coded BCI

The spatially-coded SSVEP BCI exploits changes in the topography of the steady-state visual evoked response to visual flicker stimulation in the extrafoveal field of view. In contrast to frequency-coded SSVEP BCIs, the operator does not gaze into any flickering lights; therefore, this paradigm can r...

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Bibliographic Details
Published in:PloS one 2022-04, Vol.17 (4), p.e0267548-e0267548
Main Authors: Maÿe, Alexander, Rauterberg, Raika, Engel, Andreas K
Format: Article
Language:English
Subjects:
Accuracy
Analysis
Biology and Life Sciences
Brain
Brain - physiology
Brain stimulation
Brain-Computer Interfaces
Classification
Dynamic response
Electroencephalography - methods
Engineering and Technology
Evaluation
Evoked Potentials, Visual
Evoked response (psychophysiology)
Experiments
Fatigue
Field of view
Flicker
Information transfer
Intervals
Medicine and Health Sciences
Methods
Neurophysiology
Pathophysiology
Photic Stimulation - methods
Physical Sciences
Research and Analysis Methods
Response time
Social Sciences
Stimulation
Visual evoked potentials
Visual stimuli
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Summary:The spatially-coded SSVEP BCI exploits changes in the topography of the steady-state visual evoked response to visual flicker stimulation in the extrafoveal field of view. In contrast to frequency-coded SSVEP BCIs, the operator does not gaze into any flickering lights; therefore, this paradigm can reduce visual fatigue. Other advantages include high classification accuracies and a simplified stimulation setup. Previous studies of the paradigm used stimulation intervals of a fixed duration. For frequency-coded SSVEP BCIs, it has been shown that dynamically adjusting the trial duration can increase the system's information transfer rate (ITR). We therefore investigated whether a similar increase could be achieved for spatially-coded BCIs by applying dynamic stopping methods. To this end we introduced a new stopping criterion which combines the likelihood of the classification result and its stability across larger data windows. Whereas the BCI achieved an average ITR of 28.4±6.4 bits/min with fixed intervals, dynamic intervals increased the performance to 81.1±44.4 bits/min. Users were able to maintain performance up to 60 minutes of continuous operation. We suggest that the dynamic response time might have worked as a kind of temporal feedback which allowed operators to optimize their brain signals and compensate fatigue.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0267548