Optimized code-books, for enhancing the performance of cVEP Brain Computer Interfaces

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2022-02-15

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en

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Visually evoked potentials (VEPs) can be measured in the EEG as response to a visual stimulus. Commonly, VEPs are displayed by averaging multiple responses to a certain stimulus or a classifier is trained to identify the response to a certain stimulus. Brain-computer interfaces (BCIs) based on code-modulated visual evoked potentials (cVEPs) provide high information transfer rates, which make them a promising alternative communication tool. One of the important components of a BCI is the set of codes that are flashed as a stimulus, eliciting specific responses. Codes that give rise to more differentiable responses, can increase the performance of a BCI significantly. Creating a codebook is not trivial as various chosen mathematical and statistical properties do not necessarily transform to the responses. One way to create a custom codebook is to grow it, taking into account the responses it produces at each step. This guarantees the preservation of chosen differentiating properties, when the codes elicit responses during their use. In this paper, this method of codebook designing was investigated. In addition to this, the influence of the use of prior probabilities (by incorporation) to further guide this generative process, was investigated. An objective metric to simulate BCI trials was constructed and utilized to compared the quality of codebooks generated using the aforementioned procedure, against the codebooks that are common-practice for use in BCIs.

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Faculteit der Sociale Wetenschappen