Single-channel EEG measurement of engagement in virtual rehabilitation: a validation study

Stroke rehabilitation suffers from low levels of patient engagement, impeding recovery. Virtual rehabilitation (VR) approaches can improve patient outcomes; however, there is limited understanding of the participant's user experience and the field lacks a validated, objective measure of VR engagement. A neurophysiological measure of engagement in healthy adults was therefore examined, to inform future clinical studies. Twenty-four participants (M(age)26.7 years, range 18-47) interacted with a tabletop VR system (ElementsDNA, or EDNA), after which they rated their experience on the presence questionnaire (PQ). Separately, participants completed tasks eliciting low (restingeyes-open and -closed) and high (EDNA VR and roller coastersimulation) levels of engagement while continuous electroencephalogram (EEG) was recorded from a single, left pre-frontal electrode. EEG differences between therestingandsimulationconditions included an increase in theta power (p < 0.01) and a decrease in alpha power (p < 0.01). Importantly, theta power insimulationconditions correlated with PQ scores expressing the hands-on EDNA VR experience (r(s) = 0.38-0.48). In conclusion, the current results provide proof of concept that increased frontal theta power in healthy adults provides a valid measure of user engagement in VR simulation and participation. As the practical potential of VR is increasingly realised in stroke rehabilitation, objective EEG-based measures of engagement may provide a convenient and sensitive technique to assist in evaluating these interventions.