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A recently published paper in the Journal of Cognitive Neuroscience titled Neural and Behavioral Evidence for Vibrotactile Beat Perception and Bimodal Enhancement by Sean Gilmore and Dr Frank Russo of Ryerson University used SUBPAC to look at how tactile stimulus can improve “beat perception” or the ability to perceive temporal regularity in musical rhythm. “The ability to synchronize movements to a rhythmic stimulus, referred to as sensorimotor synchronization (SMS), is a behavioral measure of beat perception. Although SMS is generally superior when rhythms are presented in the auditory modality, recent research has demonstrated near-equivalent SMS for vibrotactile presentations of isochronous rhythms.” The study also took EEG measurements to study how each modality affects neural entrainment to a target frequency.
“It turns out that the brain does a good job of tracking beats through vibration and that we may be able to enhance beat perception by combining vibrotactile + audio” says Dr Frank Russo.
The study consisted of three types of stimulation: auditory, vibrotactile, and bimodal (both at the same time). “In the auditory condition, stimuli were presented using 3M E-A-RTONE 3A insert earphones, a piezoelectric earphone that minimizes interference with EEG signals. In the vibrotactile condition, rhythms were presented using the SUBPAC S2, a backpack containing a matrix of vocal coils that cover the entire thoracic region.” In the bimodal condition both auditory and vibrotactile stimuli were applied.
While the EEG results only show a statistically significant change in mean entrainment at 2.5hz between auditory and bimodal stimulation, there was an observed systematic increase in entrainment across all target frequencies under the bimodal condition:
“Overall, these findings support the idea of an auditory advantage underpinned by auditory–motor connectivity as well as the notion that vibrotactile presentations of rhythm are fully capable of supporting beat perception. Our exploratory analysis of neural entrainment in harmonic frequencies is also suggestive of a bimodal advantage.” (Gilmore & Russo, 2021).