Novel electrotactile brain-computer interface with somatosensory event-related potential based control

Abstract

ObjectiveA brain computer interface (BCI) allows users to control external devices using non-invasive brain recordings, such as electroencephalography (EEG). We developed and tested a novel electrotactile BCI prototype based on somatosensory event-related potentials (sERP) as control signals, paired with a tactile attention task as a control paradigm.ApproachA novel electrotactile BCI comprises commercial EEG device, an electrical stimulator and custom software for EEG recordings, electrical stimulation control, synchronization between devices, signal processing, feature extraction, selection, and classification. We tested a novel BCI control paradigm based on tactile attention on a sensation at a target stimulation location on the forearm. Tactile stimuli were electrical pulses delivered at two proximal locations on the user’s forearm for stimulating branches of radial and median nerves, with equal probability of the target and distractor stimuli occurrence, unlike in any other ERP-based BCI design. We proposed a compact electrical stimulation electrodes configuration for delivering electrotactile stimuli (target and distractor) using 2 stimulation channels and 3 stimulation electrodes. We tested the feasibility of a single EEG channel BCI control, to determine pseudo-online BCI performance, in ten healthy subjects. For optimizing the BCI performance we compared the results for two classifiers, sERP averaging approaches, and novel dedicated feature extraction/selection methods via cross-validation procedures.Main resultsWe achieved a single EEG channel BCI classification accuracy in the range of 75.1 to 88.1% for all subjects. We have established an optimal combination of: single trial averaging to obtain sERP, feature extraction/selection methods and classification approach.SignificanceThe obtained results demonstrate that a novel electrotactile BCI paradigm with equal probability of attended (target) and unattended (distractor) stimuli and proximal stimulation sites is feasible. This method may be used to drive restorative BCIs for sensory retraining in stroke or brain injury, or assistive BCIs for communication in severely disabled users.

Somatosensory Event-Related Potential as an Electrophysiological Correlate of Endogenous Spatial Tactile Attention: Prospects for Electrotactile Brain-Computer Interface for Sensory Training

“…The results of this study are the first to show that the sERP morphology associated with a novel sustained spatial electrotactile attention task, first introduced in our recent work exploring electrotactile BCI for sensory training [17]. Our results on the sERP components when stimulating mixed nerve branches revealed that the ERP morphology is similar to previous reports on components obtained by the stimulation of exclusively sensory nerves, i.e., we validated the presence of P100, N140, P3a, and P3b peaks for mixed radial and median nerve stimulation.…”

“…Moreover, we discuss the effects of the sustained endogenous spatial attention task on the sERP features. Finally, we discuss the immediate implications of these findings for the design of electrotactile BCIs generally, and more specifically, the implications of the current results for further improvements in the control of our recently presented novel electrotactile BCI prototype [17].…”

“…A common indifferent electrode was placed on the volar aspect of the right wrist. Electrical stimulation setup and fine-tuning was already described in detail in our previous publication [17].…”

“…This limitation should be addressed in future basic studies exploring the effects of endogenous spatial tactile attention on sERP. The selection of the EEG channels in our current study was constrained to the analysis of sensorimotor areas since the effects of our recently presented electrotactile BCI for sensory training [17] are expected to be reflected in the reorganization of sensorimotor cortex. The lower number of channels was in line with intended applications in tactile BCIs where the control paradigms based on smaller subset of channels are favorable.…”

“…We have previously designed and presented an electrotactile BCI system that enables online detection of tactile attention, directed towards one of the two proximal stimulation locations on the user's forearm [17]. However, the presentation and analysis of sERP morphology and topographic differences over the sensorimotor cortex during this task wasn't previously conducted.…”