Abstract
Introduction The main drawback of a Brain-computer Interface based on Steady-State Visual Evoked Potential (SSVEP-BCI) that detects the emergence of visual evoked potentials (VEP) in reaction to flickering stimuli is its muscular dependence due to users must redirect their gaze to put the target stimulus in their field of view. In this work, a novel setup is evaluated in which two stimuli are placed together in the center of users' field of view, but with dissimilar distances from them, so that the target selection is performed by focus shifting instead of head, neck and/or eyeball movements. Methods A model of VEP generation for the novel setup was developed. The Spectral F-test based on Bartett periodogram was used to evaluate the null hypothesis of absence of effects of the non-focused stimulus (NFS) within the VEP elicited by the focused stimulus (FS). To reinforce that there is not statistical evidence to support the presence of NFS effects, the PSDA detection method was employed to find the frequency of FS. Electroencephalographic signals of nine subjects were recorded. Results Approximately in 80% of the tests, the null hypothesis with 5% level of significance was non-rejected at the fundamental frequency of NFS. The average of the accuracy rate attained with PSDA detection method was 79.4%. Conclusion Results of this work become further evident to state that if the focused stimulus (FS) will be able to elicit distinguishable VEP pattern regardless the non-focused stimulus (NFS) is also present.
Highlights
The main drawback of a Brain-computer Interface based on Steady-State Visual Evoked Potential (SSVEP-Brain-Computer Interfaces (BCI)) that detects the emergence of visual evoked potentials (VEP) in reaction to flickering stimuli is its muscular dependence due to users must redirect their gaze to put the target stimulus in their field of view
Spectral F-test (SFT) can be evaluated along the frequency domain to find where the null hypothesis is rejected
An alternative manner of presenting state visual evoked potentials (SSVEP) stimuli was evaluated, in which two flickering stimuli are placed together in the center of users’ field of view, but with dissimilar distances. These distances play an important role because blurriness degree of a non-focused object depends on the Depth-of-Field of a focused object, which in turn depends on the distances between focused and non-focused objects
Summary
The main drawback of a Brain-computer Interface based on Steady-State Visual Evoked Potential (SSVEP-BCI) that detects the emergence of visual evoked potentials (VEP) in reaction to flickering stimuli is its muscular dependence due to users must redirect their gaze to put the target stimulus in their field of view. In BCI systems, particular features are extracted from recorded brain signals for the purpose of translating them into artificial outputs. These outputs act coherently on the environment or the person’s body itself, helping to restore useful functions for people in which the central nervous system is severely disabled. Steady-state visual evoked potentials (SSVEP) are periodic signals present in the EEG produced by repetitive presentation of visual stimuli
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