Modulation of tactile detection threshold with rhythmic somatosensory entrainment

Abstract

Ongoing neural activity in human somatosensory cortex has a strong impact on the detectability of weak tactile stimuli. Recent studies suggest that brain oscillations, which determine the state of excitability of a cortical area, play a crucial role in this process. Mainly two frequency bands have been reported to be involved in conscious sensory perception: alpha (8 - 12 Hz) and beta (15 - 30 Hz). In addition to correlative findings, more recent studies investigated causality by measuring the extent to which directly modulating brain oscillations affects sensory perception. While most of these studies use transcranial alternating current stimulation (tACS), rhythmic sensory stimulation has been suggested as a simple and safe alternative to entrain ongoing neural activity. However, convincing findings demonstrating the modulation of neural signals and related behavioral function are scarce.\n\nHere, we investigated whether rhythmically induced brain oscillations by means of vibrotactile stimulation (i.e. sensory entrainment) modulate tactile detection. In line with previous findings, we show in trials without sensory entrainment that preceding alpha power and phase-angles in beta oscillations predict the detection rate of a weak tactile stimulus. Further, we reveal a masking effect induced by sensory entrainment stimulation resulting in higher perception thresholds. Intriguingly, we find that the masking effect is modulated by the strength of neural entrainment resulting from 20 Hz stimulation. Our data provide evidence for the possibility to modulate sensory processing with rhythmic sensory stimulation. However, in light of the induced masking effects, the feasibility of this entrainment method to modulate human behavior remains questionable.