Progressive Tactile Perception and Peripheral Hemodynamic Responses Induced by LIFUS on Fingertip

Peripherally applied low-intensity focused ultrasound stimulation (LIFUS) has emerged as a new modality of tactile restoration recently. If repetitive LIFUS would cause perceptual adaptation, like transcutaneous electrical nerve stimulation (TENS) does, has been rarely investigated. To address this issue, 14 healthy volunteers received LIFUS-based fine tactile stimulation on their right index fingertip in this work. To evaluate their perceptual stability, both subjective perceptual ratings and peripheral local hemodynamic responses were deployed. The sensory-level TENS was also included for comparison. Our results showed that the LIFUS brought better perceptual acuity and perceptual stability than TENS in terms of subjective perception and judgement. Moreover, the LIFUS induced an increase of local blood perfusion volume (BPV) since stimulation onset, while the TENS caused a decrease of BPV, both followed by a slow rebound to the baseline. Notably, repetitive LIFUS didn't cause obvious progressive decrease of BPV responses with increasing dose, i.e., temporal accumulation, whereas TENS did. These findings would facilitate the development of non-invasive sensory feedback technique in multiple human-machine interaction scenarios, and shed valuable insights on neuromodulation mechanisms of peripherally applied LIFUS.