An investigation of the effects of different pulse patterns of transcutaneous electrical nerve stimulation (TENS) on perceptual embodiment of a rubber hand in healthy human participants with intact limbs

Objectives The aim of this study was to investigate the strength of perceptual embodiment achieved during a adapted version of the rubber hand illusion(RHI) in response to a series of modified TENS pulse patterns with dynamic temporal and spatial characteristics which are more akin to the mechanical brush stroke in the original RHI. Materials and Method A repeated-measures counter balanced experimental study was conducted where each participant was exposed to four TENS interventions: Continuous pattern TENS; Burst pattern TENS (fixed frequency of 2 bursts per second of 100 pulses per second); Amplitude modulated pattern TENS (intensity increasing from zero to a pre-set level then back to zero again in a cyclical fashion); and Sham (no current) TENS. Participants rated the intensity of the RHI using a three item numerical rating scale (each item was ranked from 0-10). Friedman’s analysis of ranks (one-factor repeated measure) were used to test the differences in perceptual embodiment between TENS interventions; alpha was set at p<0.05. Results There were statistically significant differences in the intensity of misattribution and perceptual embodiment between sham and active TENS interventions but no significant differences between the three active TENS interventions (amplitude-modulated TENS, burst TENS and continuous TENS). Amplitude-modulated and burst TENS produced significantly higher intensity scores for misattribution sensation and perceptual embodiment compared with sham (no current) TENS, whereas continuous TENS did not. Discussion The findings provide tentative, but not definitive, evidence that TENS parameters with dynamic spatial and temporal characteristics may produce more intense misattribution sensations and intense perceptual embodiment than parameters with static characteristics (e.g. continuous pulse patterns).