Brain-computer interfacing using modulations of alpha activity induced by covert shifts of attention

Abstract

BackgroundVisual brain-computer interfaces (BCIs) often yield high performance only when targets are fixated with the eyes. Furthermore, many paradigms use intense visual stimulation, which can be irritating especially in long BCI sessions. However, BCIs can more directly directly tap the neural processes underlying visual attention. Covert shifts of visual attention induce changes in oscillatory alpha activity in posterior cortex, even in the absence of visual stimulation. The aim was to investigate whether different pairs of directions of attention shifts can be reliably differentiated based on the electroencephalogram. To this end, healthy participants (N = 8) had to strictly fixate a central dot and covertly shift visual attention to one out of six cued directions.ResultsCovert attention shifts induced a prolonged alpha synchronization over posterior electrode sites (PO and O electrodes). Spectral changes had specific topographies so that different pairs of directions could be differentiated. There was substantial variation across participants with respect to the direction pairs that could be reliably classified. Mean accuracy for the best-classifiable pair amounted to 74.6%. Furthermore, an alpha power index obtained during a relaxation measurement showed to be predictive of peak BCI performance (r = .66).ConclusionsResults confirm posterior alpha power modulations as a viable input modality for gaze-independent EEG-based BCIs. The pair of directions yielding optimal performance varies across participants. Consequently, participants with low control for standard directions such as left-right might resort to other pairs of directions including top and bottom. Additionally, a simple alpha index was shown to predict prospective BCI performance.

On the control of brain-computer interfaces by users with cerebral palsy

“…This is common practice in BCI research and provides some measure of both the best performance and the performance over time (Treder et al, 2011;Fazli et al, 2012;Allison et al, 2010a). However, it may be argued that peak accuracy alone does not provide a complete measure of statistically significant performance.…”

An online EEG BCI based on covert visuospatial attention in absence of exogenous stimulation

“…Initial offline studies aimed at possible BCI usage followed these basic findings. They have demonstrated the potential feasibility of single-trial (real-time) classification-the hallmark of BCI operation [19,20]. However, an operational online BCI based on self-initiated, top-down EEG correlates of CVSA has not been built until now.…”

Covert Attention as a Paradigm for Subject-Independent Brain-Computer Interfacing

“…Data from the experiment of Treder et al [14] was used. In the main experiment, eight healthy participants performed a cued visual attention task.…”

“…Two vertical and horizontal EOG bipolar channels were used to monitor eye-movements. In this paper we only consider the trials which were 2000 ms long and we used the same preprocessing steps as the ones taken in [14].…”

“…Covert attention has been introduced as a paradigm for gaze-independent brain computer interfacing (BCI) [6,7,17,15,2,14].As we know that the applicability of a BCI system depends on the consistency of its paradigm over a group of subjects, one important feature of a BCI is its subject-independence. To generalize a BCI to be applicable for new users, one can think of either to use a machine learning algorithm above a standard BCI to improve the generalization or to choose a more appropriate paradigm.…”