Progressive Tactile Perception and Peripheral Hemodynamic Responses Induced by LIFUS on Fingertip
Liuni Qin, Yinshen Huang, Jin Xie, Lili Niu, Laixin Huang, Fei Li, Shichun Bao, Guanglin Li, Yanjuan Geng
IEEE Transactions on Neural Systems and Rehabilitation Engineering 2026, 34, 1305-1317 · 10.1109/tnsre.2026.3664418
Abstract
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.
Abstract via europepmc.
Exposures
Exposure 1: LIFUS-250
Target: digital nerve — “right index fingertip”
Device: custom-built · Pantsd Inc. · HN81C-750-250KC ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 250 | ✓✓✓ |
| Pulse duration (ms) | not reported | ⚑ |
| Pulse repetition frequency (Hz) | 4, 7, 14, 24, 63, 72, 80, 88swept | ✓✓✓⚑ |
| Duty cycle (%) | 3 | ✓✓✓⚑ |
| Sonication duration (s) | 2 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | 10.28, 12.26, 22.82, 25.92, 10.28, 13.91, 20.86, 28.02swept | ✓?⚑ |
| Free-field Ispta (W/cm²) | 0.25, 0.37, 0.69, 0.78, 0.22, 0.42, 0.63, 0.84swept | ✓? |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
Four distinct PRF ranges (4-7, 14-24, 63-72, 80-88 Hz) were paired with a moderate or strong acoustic intensity (AI, 30-40% or 60-70% of each participant's individually determined [AImin, AImax] threshold range) to elicit tapping, vibration, electrical, and pressure sensations, respectively, each delivered for a 2-s trial. A separate pretest to determine AI thresholds used a fixed PRF of 50 Hz, a fixed duty cycle of 3%, and a 2-s stimulation duration; duty cycle for the four main sensation-eliciting conditions is not stated.
Exposure 2: LIFUS-500
Target: digital nerve — “right index fingertip”
Device: custom-built · NDT Inc. · IBP0.512 ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | not reported | |
| Pulse repetition frequency (Hz) | 4, 7, 14, 24, 63, 72, 80, 88swept | ✓✓✓ |
| Duty cycle (%) | 3 | ✓✓✓ |
| Sonication duration (s) | 2 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | 10.28, 16.36, 31.51, 35.33, 12.78, 15.03, 31.68, 35.33swept | ✓? |
| Free-field Ispta (W/cm²) | 0.31, 0.49, 0.95, 1.06, 0.38, 0.45, 1.04, 1.15swept | ✓? |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
Four distinct PRF ranges (4-7, 14-24, 63-72, 80-88 Hz) were paired with a moderate or strong acoustic intensity (AI, 30-40% or 60-70% of each participant's individually determined [AImin, AImax] threshold range) to elicit tapping, vibration, electrical, and pressure sensations, respectively, each delivered for a 2-s trial. A separate pretest to determine AI thresholds used a fixed PRF of 50 Hz, a fixed duty cycle of 3%, and a 2-s stimulation duration; duty cycle for the four main sensation-eliciting conditions is not stated.
Flags from extraction
n_subjects— Abstract states '14 healthy volunteers' but Methods states '16 healthy right-handed volunteers ... were recruited'; the more detailed Methods count (16) is used.exposures[0].timing.duty_cycle_pct— A fixed duty cycle of 3% is stated only for the separate AI-threshold pretest (PRF 50 Hz, 2 s); duty cycle for the four main sensation-eliciting stimuli (Table I) is not stated.exposures[0].timing.pulse_duration_ms— Not stated; only PRF and intensity are given for the sensation-eliciting stimuli, and duty cycle needed to derive pulse duration is not reported for these conditions.exposures[0].timing.pulse_repetition_frequency_hz— Table I gives four separate PRF ranges (one per tactile sensation type); recorded as the flattened list of the eight range boundaries in table order (tapping, vibration, electrical, pressure).exposures[0].free_field.isppa_w_cm2— Isppa/Ispta were measured with a needle hydrophone in a degassed water bath (device characterization), then delivered directly onto the acoustically transparent skin with no intervening skull; classified as free-field, and recorded as the eight table values (one per sensation type/level) in table order.auditory_control— Participants wore eye masks and earmuffs during testing to avoid visual and auditory distraction; classified as masking_sound.sham_type— A 'no stimulation' condition was included as one of the five randomly-ordered trial types within each block, functioning as a within-session no-stimulation control; classified as none because no separate sham transducer/control arm is described.