A comparison of covert and overt attention as a control option in a steady-state visual evoked potential-based brain computer interface

[jinglescode]

Paper

Link: https://pubmed.ncbi.nlm.nih.gov/17271364/
Year: 2004

Summary

• The average accuracy is found to be reduced by ~20% in the switch from overt to covert attention
• SSVEPs resulting from stimuli located in foveal vision are known to be of large amplitude and very robust
• stimuli located in peripheral vision generate SSVEPs of much smaller amplitude

SSVEPs resulting from stimuli located in foveal vision are known to be of large amplitude and very robust; stimuli located in peripheral vision generate SSVEPs of much smaller amplitude. Kelly et al. /cite{kelly2004comparison} suggested that stimulus presentation should not be locked to the refresh rate in order to elicit an SSVEP of an amplitude greater than the background EEG.

EEG data were recorded from occipital scalp regions of subjects who attended to an alternating checkerboard stimulus in one visual field while ignoring a similar stimulus of a different frequency in the opposite visual field. Classification of left/right spatial attention is attempted by extracting steady-state visual evoked potentials (SSVEPs) elicited by the stimuli to assess the potential use of such a spatial selective attention paradigm in a brain computer interface (BCI). Experimental setup and analysis procedure in a previous study in which eye movement is permitted are replicated in order to quantify differences in classification performance using overt and covert attention. Four variations of the basic paradigm, involving both feedback and addition of extra mental load, are studied for comparison. The average accuracy is found to be reduced by approximately 20% in the switch from overt to covert attention when no other specifications of the task are changed.