Vibrotactile Research Articles

ID:15943 Somatosensory Evoked Potentials: Comparison of Median Nerve Stimulation to Vibro-tactile Fingertip Stimulation

Median nerve stimulation (MNS) can localize the somatosensory cortex involving cortical surface recordings in patients who are awake or under general anesthesia (GA). The temporal shape and amplitude distribution of the somatosensory evoked potentials (SEPs) vary systematically as a function of spatial location relative to the hand representation area. Phase reversals in SEP are used to determine the location of the central sulcus (CS). This study investigates if similar effects can be observed, when finger digits are stimulated in a vibro-tactile (VT) manner instead of MNS.

Movement Variability and Accuracy Within the Temporal and Spatial Domains When Provided a Vibrotactile Stimulus

Different means of informing body movements can include visual, auditory, and vibrotactile (VT) stimuli. Each method may guide movements within the temporal (TEMP) and spatial (SPAT) domains in varying ways. As VT stimuli has become more accessible, it is important to understand how users interpret this method of instruction to promote patterned movements. PURPOSE: Determine the effects of VT stimulus pattern speed on TEMP and SPAT movement variability (VAR) and accuracy (ACC). METHODS: Sixteen young healthy subjects were recruited. Participants completed a continuous wrist flexion and extension activity. The task involved matching wrist motion with two different VT pattern speeds (FAST, SLOW) provided via motors attached to the forearm. An electrogoniometer captured wrist movement. Five 20s trials with 2min rest periods were completed for the two speeds. Flexion/extension movements were combined for further analysis. Absolute (STDEV) and relative (CV) VAR, and ACC (mean absolute error) for TEMP and SPAT domains were calculated within individuals. 5x2 linear mixed models accounting for repeated measures compared the variables across pattern speeds and trial numbers. Post-hoc Tukey HSDs identified differences for trial effects. RESULTS: No significant interactions were found in either domain. Significant pattern speed effects were observed in the TEMP domain for VAR (STDEV: FAST 0.07s, SLOW 0.13s, p < .05; CV: FAST 12.9%, SLOW 16.8%, p < .05), and ACC (FAST 0.05s, SLOW 0.10s, p < .05). VAR in the both domains and TEMP ACC changed significantly over the 5 trials (all, p < .05; ACC SPAT, p > .05). Post-hoc tests revealed trial 1 to be different from all subsequent trials for TEMP and SPAT VAR (STDEV TEMP: #1: 0.15s, #5: 0.08s, p < .05; STDEV SPAT: #1: 7.7deg, #5: 4.7deg, p < .05; CV TEMP: #1: 20.8%, #5: 13.2%, p < .05; CV SPAT: #1: 11.9%, #5: 5.9%, p < .05), and ACC TEMP (#1: 0.11s, #5: 0.07s, p < .05). CONCLUSIONS: VT stimulus appears capable of producing a desired continuous wrist movement at multiple pattern speeds. TEMP VAR was lower and TEMP ACC was higher for the FAST speed, while SPAT measures did not differ between speeds. Lower TEMP and SPAT VAR, and higher TEMP ACC were observed by trial 2, with improved performance maintained in the remaining trials. A lack of change in SPAT ACC may reflect limited SPAT guidance provided to subjects.

Usability Evaluation of a VibroTactile Feedback System in Stroke Subjects.

To increase the functional capabilities of stroke subjects during activities of daily living, patients receive rehabilitative training to recover adequate motor control. With the goal to motivate self-training by use of the arm in daily life tasks, a sensor system (Arm Usage Coach, AUC) was developed that provides VibroTactile (VT) feedback if the patient does not move the affected arm above a certain threshold level. The objective of this study is to investigate the usability of this system in stroke subjects. The study was designed as a usability and user acceptance study of feedback modalities. Stroke subjects with mild to moderate arm impairments were enrolled. The subjects wore two AUC devices one on each wrist. VT feedback was given by the device on the affected arm. A semi-structured interview was performed before and after a measurement session with the AUC. In addition, the System Usability Scale (SUS) questionnaire was given. Ten ischemic chronic stroke patients (39 ± 38 months after stroke) were recruited. Four out of 10 subjects have worn the VT feedback on their dominant, affected arm. In the pre-measurement interview, eight participants indicated a preference for acoustic or visual over VT feedback. In the post evaluation interview, nine of 10 participants preferred VT over visual and acoustic feedback. On average, the AUC gave VT feedback six times during the measurement session. All participants, with the exception of one, used their dominant arm more then the non-dominant. For the SUS, eight participants responded above 80%, one between 70 and 80%, and one participant responded below 50%. More patients accepted and valued VT feedback after the test period, hence VT is a feasible feedback modality. The AUC can be used as a telerehabilitation device to train and maintain upper extremity use in daily life tasks.

The relationship between clinical and standardized tests for hand-arm vibration syndrome.

Standardized laboratory tests are undertaken to assist the diagnosis and staging of hand-arm vibration syndrome (HAVS), but the strength of the relationship between the tests and clinical stages of HAVS is unknown. To assess the relationship between the results of thermal aesthesiometry (TA), vibrotactile (VT) thresholds and cold provocation (CP) tests with the modified Stockholm scales for HAVS and to determine whether the relationship is affected by finger skin temperature. Consecutive records of workers referred to a Tier 5 HAVS assessment centre from 2006 to 2015 were identified. The diagnosis and staging of cases was undertaken from the clinical information contained in the records. Cases with alternative or mixed diagnoses were excluded and staging performed according to the modified Stockholm scale without knowledge of the results of the standardized laboratory tests. A total of 279 cases of HAVS were analysed. Although there was a significant trend for sensorineural (SN) and vascular scores to increase with clinical stage (P < 0.01), there was no significant difference in scores between 2SN early and 2SN late or between 2SN late and 3SN. There was moderate correlation between the TA and VT scores and the clinical SN stages (r = 0.6). This correlation did not change when subjects were divided into those with a finger skin temperature <30 and >30°C. CP scores distributed bimodally and correlated poorly with clinical staging (r = 0.2). Standardized SN tests distinguish between the lower Stockholm stages, but not above 2SN early. This has implications for health surveillance and UK policy.

Multiscale layered biomechanical model of the pacinian corpuscle.

This paper describes a multiscale analytical model of the lamellar structure and the biomechanical response of the Pacinian Corpuscle (PC). In order to analyze the contribution of the PC lamellar structure for detecting high-frequency vibrotactile (VT) stimuli covering 10Hz to a few kHz, the model response is studied against trapezoidal and sinusoidal stimuli. The model identifies a few generalizable features of the lamellar structure which makes it scalable for different sizes of PC with different number of lamellae. The model describes the mechanical signal conditioning of the lamellar structure in terms of a recursive transfer-function, termed as the Compression-Transmittance-Transfer-Function (CTTF). The analytical results show that with the increase of the PC layer index above 15, the PC inner core (IC) relaxes within 1ms against step compression of the outermost layer. This model also considers the mass of each PC layer to investigate its effect on the biomechanical response of the lamellar structure. The interlamellar spacing and its biomechanical properties along with the model response are validated with experimental data in the literature. The proposed model can be used for simulating a network of PCs considering their diversity for analyzing the high-frequency VT sensitivity of the human skin.

Vibrotactile sensitivity threshold: nonlinear stochastic mechanotransduction model of the Pacinian Corpuscle.

Based on recent discoveries of stretch and voltage activated ion channels in the receptive area of the Pacinian Corpuscle (PC), this paper describes a two-stage mechanotransduction model of its near threshold Vibrotactile (VT) sensitivity valid over 10Hz to a few kHz. The model is based on the nonlinear and stochastic behavior of the ion channels represented as dependent charge sources loaded with membrane impedance. It simulates the neural response of the PC considering the morphological and statistical properties of the receptor potential and action potential with the help of an adaptive relaxation pulse frequency modulator. This model also simulates the plateaus and nonmonotonic saturation of spike rate characteristics. The stochastic simulation based on the addition of mechanical and neural noise describes that the VT Sensitivity Threshold (VTST) at higher frequencies is more noise dependent. Above 800Hz even a SNR = 150 improves the neurophysiological VTST more than 3dBμ. In that frequency range, an absence of the entrainment threshold and a lower sensitivity index near the absolute threshold make the upper bound of the psychophysical VTST more dependent on the experimental protocol and physical set-up. This model can be extended to simulate the neural response of a group of PCs.

Idiosyncratic Heart Rate Response in Men during Sexual Arousal

Heart rate, sensitive to sympathetic activation, is known to change during sexual arousal and therefore may be a useful tool for investigating psychosomatic differences between sexually functional and dysfunctional men. However, heart rate during arousal also tends to be highly variable across individual men, making its predictability based on group patterns relatively poor. We wanted to determine whether individual men show idiosyncratic heart rate patterns during sexual arousal, that is, whether they exhibit consistent patterns across similar (though not identical) stimulus situations. Agreement between heart rates under the two conditions, visual sexual stimulation (VSS) and VSS + vibrotactile (VIB), was assessed using the concordance correlation coefficient (CCC). Thirty-eight men, 25 of whom were diagnosed with premature ejaculation (PE), were monitored for penile response and heart rate under two similar (though not identical) conditions: a 9-minute erotic video (VSS), then a 9-minute erotic video combined with vibrotactile penile stimulation (VSS + VIB). CCC for men with PE was 0.65; for the sexually functional comparison group, CCC was 0.82. For both groups combined, CCC was 0.71. For all groupings, the CCC was relatively high, indicating agreement in heart rate from one session to the next within individual men. Despite high intersubject variation in heart rate patterns, individual men show signature heart rates across similar sexual stimulus sessions. Such stereotypy helps explain previous inconsistent findings and may also serve as a marker for the effectiveness of treatments designed to improve ejaculatory control in men with PE.

Recovery functions of human cortical potentials evoked by tones, shocks, vibration, and flashes12

Averaged evoked “Vpotentials” were obtained from four Ss at five interstimulus intervals from 0.5 to 10.0 sec. Amplitude-recovery functions for vibro tactile, electric shock, auditory, and visual stimulation were quite similar in form but differed in slope. In the range from 1.0 to 5.0 sec, the percentage increase in amplitude for doubling of the interstimulus interval was: for vibration, 48; for shocks, 41; for tones, 35; and for flashes, 16.