Vibrotactile Sensitivity Research Articles

A Vibrotactile Belt for Measuring Vibrotactile Acuities on the Human Torso Using Coin Motors

Accurate measurement of the vibrotactile acuities of the human torso is the key to designing effective torso-worn vibrotactile displays for healthcare applications such as navigation aids for visually impaired persons. Although efforts have been made to measure vibrotactile acuities, there remains a lack of systematic studies addressing the spatial, temporal, and intensity-related aspects of vibrotactile sensitivity on the human torso. In this work, a torso-worn vibrotactile belt consisting of two crossed coin motor arrays was designed and a psychophysical study was carried out to measure the spatial, temporal, and intensity-related vibrotactile acuities of a set of human subjects wearing the designed belt. The objective parameters of vibrational intensity and the timing latency of the coin motor were also determined before measuring the vibrotactile acuities. The experimental results indicated that the tested coin motor was able to generate a median number of five and six available just-noticeable differences in intensity and duration, respectively. Among the four parameters of vibrational intensity, the perceived intensity was the most relevant to vibrational displacement. The spatial acuities measured as the degree of two-point spatial thresholds (TPTs) showed less individual difference than the distance TPTs. The results from the current work provide valuable guidance for the design of a comfortable torso-worn vibrotactile display using coin motors.

Sensitivity to Vibrotactile Stimulation in the Hand and Wrist: Effects of Motion, Temporal Patterns, and Biological Sex.

We investigated the impact of low-tempo, repetitive hand movements on vibrotactile sensitivity by employing various temporal and spatial patterns in the hand and wrist area. The investigation of a human's ability to perceive vibrotactile stimuli during dynamic hand movements remains understudied, despite the prevalence of slow to mild hand motions in applications such as hand navigation or gesture control using haptic gloves in Virtual Reality (VR) and Augmented Reality (AR). We investigated vibrotactile sensitivity, analyzing the impact of various factors, including Motion (static and low-tempo repetitive hand movements), Temporal Patterns (Single or Double vibrations with varying onset times), Tactor Placements (hand and wrist), Spatial Patterns, and Biological Sex. Our study revealed that Motion significantly influences vibrotactile sensitivity in the hand and wrist areas, leading to reduced accuracy rates during dynamic conditions. Additionally, as the stimulus onset approached in Double vibrations, accuracy rates markedly decreased. Notably, Hand Placement resulted in significantly higher accuracy rates compared to the Wrist Placement. Our findings underscore the impact of motion in reducing vibrotactile sensitivity on the back of the hand and around the wrist. This research has wide-ranging practical applications, particularly in the field of VR/AR experiences, rehabilitation programs, and accessibility solutions through the use of haptic gloves. Insights from our study can be harnessed to enhance the efficacy of haptic gloves in conveying vibrotactile cues within these contexts.

Speech-derived haptic stimulation enhances speech recognition in a multi-talker background

Speech understanding, while effortless in quiet conditions, is challenging in noisy environments. Previous studies have revealed that a feasible approach to supplement speech-in-noise (SiN) perception consists in presenting speech-derived signals as haptic input. In the current study, we investigated whether the presentation of a vibrotactile signal derived from the speech temporal envelope can improve SiN intelligibility in a multi-talker background for untrained, normal-hearing listeners. We also determined if vibrotactile sensitivity, evaluated using vibrotactile detection thresholds, modulates the extent of audio-tactile SiN improvement. In practice, we measured participants’ speech recognition in a multi-talker noise without (audio-only) and with (audio-tactile) concurrent vibrotactile stimulation delivered in three schemes: to the left or right palm, or to both. Averaged across the three stimulation delivery schemes, the vibrotactile stimulation led to a significant improvement of 0.41 dB in SiN recognition when compared to the audio-only condition. Notably, there were no significant differences observed between the improvements in these delivery schemes. In addition, audio-tactile SiN benefit was significantly predicted by participants’ vibrotactile threshold levels and unimodal (audio-only) SiN performance. The extent of the improvement afforded by speech-envelope-derived vibrotactile stimulation was in line with previously uncovered vibrotactile enhancements of SiN perception in untrained listeners with no known hearing impairment. Overall, these results highlight the potential of concurrent vibrotactile stimulation to improve SiN recognition, especially in individuals with poor SiN perception abilities, and tentatively more so with increasing tactile sensitivity. Moreover, they lend support to the multimodal accounts of speech perception and research on tactile speech aid devices.

Vertical contact forces affect vibration perception in human hairy skin.

Skin is the largest organ of the human body and fulfills many important functions, like detecting mechanical stimuli. Skin can be divided into glabrous (non-hairy) and hairy skin. These two skin types differ with regard to their mechanical properties and in the distribution of mechanoreceptors. Although many investigations focus on glabrous skin, hairy skin still plays a fundamental role in various activities, e.g., with regard to the perception of pleasantness or for developing wearable vibrotactile devices for pattern recognition in persons with disabilities. Unfortunately, investigations on influencing factors, like vertical contactor force, are scarce for hairy skin. Similarly, it would also be interesting to investigate whether regional vibratory sensitivity differences are present across the human torso. Hence, this study investigated the effects of vertical contactor forces and different anatomical locations on vibration perception. Four anatomical torso regions were studied. Based on findings in glabrous skin, we generally hypothesized improved vibration perception with increasing contactor forces and regional sensitivity differences between the anatomical locations. Forty young and healthy individuals participated (23.0 ± 2.0 yrs), and vibration perception thresholds (VPTs) were determined at 30 Hz for three vertical force levels (0.6, 2.4, and 4.8 N) at four torso locations (sternum, deltoid/shoulder, lower back, middle lateral torso side). Higher contactor forces resulted in lower VPTs corresponding to improved vibration perception, regardless of anatomical location. In addition, the sternum region was more sensitive than the remaining three regions, regardless of force level. The reasons for these findings may be a varying number and activation pattern of afferents activated under the different conditions. The findings of this study complement the understanding of vibrotactile sensitivity in hairy skin and may offer implications when developing vibrotactile devices or clothing/textiles, for example.

A common computational principle for vibrotactile pitch perception in mouse and human

We live surrounded by vibrations generated by moving objects. These oscillatory stimuli propagate through solid substrates, are sensed by mechanoreceptors in our body and give rise to perceptual attributes such as vibrotactile pitch (i.e. the perception of how high or low a vibration’s frequency is). Here, we establish a mechanistic relationship between vibrotactile pitch perception and the physical properties of vibrations using behavioral tasks, in which vibratory stimuli were delivered to the human fingertip or the mouse forelimb. The resulting perceptual reports were analyzed with a model demonstrating that physically different combinations of vibration frequencies and amplitudes can produce equal pitch perception. We found that the perceptually indistinguishable but physically different stimuli follow a common computational principle in mouse and human. It dictates that vibrotactile pitch perception is shifted with increases in amplitude toward the frequency of highest vibrotactile sensitivity. These findings suggest the existence of a fundamental relationship between the seemingly unrelated concepts of spectral sensitivity and pitch perception.

Vibrotactile Sensitivity of the Glabrous Hand and Perioral Face in Neurotypical Children and Adults

Neural encoding of tactile features by the somatosensory system serves many important perceptual roles, including texture and object discrimination, feedback for precision grip and manipulation, and orofacial motor control for speech, gesture, and eating...

Detection of Friction-Modulated Textures is Limited by Vibrotactile Sensitivity

Modulation of the frictional force of a fingertip sliding over a surface-haptic device can produce compelling sensations of texture and relief. The virtual sensation is particularly apparent and feel as fixed in space if the stimulus is rigorously correlated with the displacement of the finger. While frictional textures tactually resemble their real counterparts, some exploratory conditions under which the sharpness of the texture declines exist. We postulate that this decline in sharpness is caused by the perceptual limitation of the attempt to interpret the variation in friction as an out-of-plane sinusoidal topography. To investigate these questions, we measured the detection thresholds of sinusoidal friction-modulated gratings for a wide range of spatial periods explored at two different speeds. We compared the results with the detection thresholds, reported in the literature, of real gratings and vibrotactile stimuli. We found that the detection of spatial friction-modulated textures does not follow the same trend as that of real textures but is more similar to the vibrotactile rendering, which is strongly influenced by the exploratory speed. This article provides a better understanding of the perception of friction-modulated textures and provides insight into how to design impactful stimuli on surface-haptic devices.

Гидровибрационная стимуляция в реабилитации детей с тугоухостью высокой степени

Goals of the study were investigation the perception of vibro-acoustic signals, spreading in water, by deaf patients and the possibility of use hydrovibrotactile stimulation for habilitation of deaf children. In the first part of study 5 experienced cochlear implants (CI) users were involved – 2 adults and 3 children with congenital deafness. Participants were presented modulated tones (100-4000 Hz) and natural sounds (horn, pipe, march melody) though underwater loudspeakers in small swimming pool. Each participant was sitting in the swimming pool without CI during the stimulation. It was shown that deaf subjects are able to detect vibro-acoustic signals, spreading in water, which they feel as a vibrotactile sense. The most vibrotactile sensitivity was between 100 and 400 Hz, while stimuli between 1000 Hz and 4000 Hz didn’t evoke any sensation. In the second part of the study 30 early aged children with severe or profound sensorineural hearing loss without hearing aids or CI experience were participated. It was observed typical oriented behavioral reactions in response to test stimuli in water in 15 children from the experimental group, but there weren’t reactions to the acoustic component of stimuli on air (out of water). Hydrovibrotactile stimulation sessions prior amplification and CI processor fitting accelerated the development of oriented and stable condition motor reflex reactions to sounds in children with hearing aids and CI, including even near-threshold stimuli, in comparison with control group children, who got only traditional lessons with speech-language therapist. As a result, an adequate fitting of hearing aids or CI processor and spontaneous development of hearing behavior in everyday situations were achieved significantly faster.

Effects of Contact Force and Vibration Frequency on Vibrotactile Sensitivity During Active Touch.

Humans require precise force control to execute fine manual tasks, which is generally facilitated to a great extent by providing adequate feedback. Currently, such dexterous manual tasks can be an input source of computing. To design appropriate vibrotactile stimuli for manual tasks, it is essential to quantify human vibrotactile sensitivity over a large range of contact forces. In this paper, we report the psychophysical detection thresholds for vibrotactile stimuli measured for five pressing forces that cover the range of forces encountered during ordinary manual tasks. The experimental results showed stark contrasts between stimulus frequencies, depending on actively exerted pressing force. The detection thresholds for 40Hz stimuli first increased and then decreased as the pressing force increased, but the detection threshold for 250Hz stimuli generally decreased as the force increased. These results have immediate consequences on the design of vibrotactile feedback for manual tasks in many applications of tangible interaction, tele-operation, and VR.

Vibrotactile sensitivity of patients with HIV-related sensory neuropathy: An exploratory study.

BackgroundHIV‐associated distal polyneuropathy (HIV‐PN) affects large and small sensory nerve fibers and can cause tactile insensitivity. This exploratory study forms part of an effort to apply subsensory electrical nerve stimulation (SENS) to improve tactile sensitivity of patients with HIV‐PN. This work presented an opportunity to use a robust protocol to quantitatively describe the vibrotactile sensitivity of individuals with HIV‐PN on effective antiretroviral therapy (ART) and correlate these findings with commonly used clinical vibration testing and scoring grades.MethodsThe vibration perception thresholds (VPTs) of 20 patients with HIV‐PN at three vibration frequencies (25, 50, and 128 Hz) were measured. We compare the vibration perception threshold (VPT) outcomes to an age‐ and gender‐matched control cohort. We further correlated VPT findings with 128 Hz tuning fork (TF) assessments performed on the HIV‐PN participants, accrued as part of a larger study. HIV‐PN was defined as having at least one distal symmetrical neuropathic sign, although 18 of 20 had at least two neuropathic signs.ConclusionsHIV‐PN participants were found to have lower VPT sensitivity than controls for all three vibration frequencies, and VPT was more sensitive at higher vibration frequencies for both HIV‐PN and controls. VPT sensitivity was reduced with older age. Years on ART was correlated with VPT‐25 Hz but not with VPT in general. Notably, VPT sensitivity did not correlate with the clinically used 128 Hz TF severity grades. Outcomes of tests for interaction with vibration frequency suggest that HIV‐PN pathology does not affect all mechanoreceptors similarly.

Relative vibrotactile spatial acuity of the torso

While tactile acuity for pressure has been extensively investigated, far less is known about acuity for vibrotactile stimulation. Vibrotactile acuity is important however, as such stimulation is used in many applications, including sensory substitution devices. We tested discrimination of vibrotactile stimulation from eccentric rotating mass motors with in-plane vibration. In 3 experiments, we tested gradually decreasing center-to-center (c/c) distances from 30 mm (experiment 1) to 13 mm (experiment 3). Observers judged whether a second vibrating stimulator (‘tactor’) was to the left or right or in the same place as a first one that came on 250 ms before the onset of the second (with a 50-ms inter-stimulus interval). The results show that while accuracy tends to decrease the closer the tactors are, discrimination accuracy is still well above chance for the smallest distance, which places the threshold for vibrotactile stimulation well below 13 mm, which is lower than recent estimates. The results cast new light on vibrotactile sensitivity and can furthermore be of use in the design of devices that convey information through vibrotactile stimulation.

Effect of Waveform on Tactile Perception by Electrovibration Displayed on Touch Screens.

In this study, we investigated the effect of input voltage waveform on our haptic perception of electrovibration on touch screens. Through psychophysical experiments performed with eight subjects, we first measured the detection thresholds of electrovibration stimuli generated by sinusoidal and square voltages at various fundamental frequencies. We observed that the subjects were more sensitive to stimuli generated by square wave voltage than sinusoidal one for frequencies lower than 60 Hz. Using Matlab simulations, we showed that the sensation difference of waveforms in low fundamental frequencies occurred due to the frequency-dependent electrical properties of human skin and human tactile sensitivity. To validate our simulations, we conducted a second experiment with another group of eight subjects. We first actuated the touch screen at the threshold voltages estimated in the first experiment and then measured the contact force and acceleration acting on the index fingers of the subjects moving on the screen with a constant speed. We analyzed the collected data in the frequency domain using the human vibrotactile sensitivity curve. The results suggested that Pacinian channel was the primary psychophysical channel in the detection of the electrovibration stimuli caused by all the square-wave inputs tested in this study. We also observed that the measured force and acceleration data were affected by finger speed in a complex manner suggesting that it may also affect our haptic perception accordingly.

Women's finger pressure sensitivity at rest and recalled body awareness during partnered sexual activity.

Greater vibrotactile sensitivity has been related to better erectile function in men, and vibrotactile and pressure tactile sensitivity have been related to better sexual function in women. Our previous study found that, for both sexes, greater recalled body awareness during last sexual relation correlated with greater recalled desire and arousal. Using the same sample of that study (68 women and 48 men, recruited in the Lisbon area, Portugal), we tested if greater recalled body awareness during last sexual relation correlates with tactile pressure sensitivity, as assessed by von Frey microfilaments. In simple and partial correlations controlling for social desirability and smoking before last sex, the hypothesis was confirmed for women, but not for men. Greater tactile sensitivity might enhance sexual arousal through greater awareness of the body during sex, and/or more frequent and pleasant body sensations during sex might lead to greater tactile sensitivity in nonsexual situations. Pressure sensitivity might be more closely linked to sexual arousal in women than in men.

Spatial patterns of cutaneous vibration during whole-hand haptic interactions

We investigated the propagation patterns of cutaneous vibration in the hand during interactions with touched objects. Prior research has highlighted the importance of vibrotactile signals during haptic interactions, but little is known of how vibrations propagate throughout the hand. Furthermore, the extent to which the patterns of vibrations reflect the nature of the objects that are touched, and how they are touched, is unknown. Using an apparatus comprised of an array of accelerometers, we mapped and analyzed spatial distributions of vibrations propagating in the skin of the dorsal region of the hand during active touch, grasping, and manipulation tasks. We found these spatial patterns of vibration to vary systematically with touch interactions and determined that it is possible to use these data to decode the modes of interaction with touched objects. The observed vibration patterns evolved rapidly in time, peaking in intensity within a few milliseconds, fading within 20-30 ms, and yielding interaction-dependent distributions of energy in frequency bands that span the range of vibrotactile sensitivity. These results are consistent with findings in perception research that indicate that vibrotactile information distributed throughout the hand can transmit information regarding explored and manipulated objects. The results may further clarify the role of distributed sensory resources in the perceptual recovery of object attributes during active touch, may guide the development of approaches to robotic sensing, and could have implications for the rehabilitation of the upper extremity.

Sensory Functions, Balance, and Mobility in Older Adults With Type 2 Diabetes Without Overt Diabetic Peripheral Neuropathy: A Brief Report.

This study examined possible subtle degradation in sensory functions, balance, and mobility in older adults with type 2 diabetes (T2D) prior to overt development of diabetic peripheral neuropathy (DPN). Twenty-five healthy controls (HC group, age = 74.6 ± 5.4) and 35 T2D elderly without DPN (T2D group, age = 70.6 ± 4.7) were recruited. Sensory assessment included vibrotactile sensitivity, bilateral caloric weakness, and visual contrast sensitivity. Self-report measures comprised of Activity-Specific Balance Confidence (ABC), Human Activity Profile-adjusted activity scores (HAP-AAS), falls, and mobility disability. Performance measures included modified Timed-Up and Go (mTUG), Clinical Test of Sensory Integration for Balance (mCTSIB), and Frailty and Injuries (FICSIT-4) balance test. T2D group demonstrated significantly worse bilateral caloric weakness, marginally higher threshold of vibrotactile sensitivity and lower visual contrast sensitivity, and as well as signifcantly lower HAP-AAS. A significantly higher proportion of the T2D group failed mCTSIB Condition 4 than in the HC group. Subtle changes in multiple sensory systems of older adults with T2D may reduce redundancy available for balance control while performing challenging activities much before DPN development.

Вибро-тактилна чувствителност и зрително възприемане на речта при лица с предлингвистична глухота

Вибро-тактилна чувствителност и зрително възприемане на речта при лица с предлингвистична глухота

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.

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.

Age- and sex-related changes in vibrotactile sensitivity of hand and face in neurotypical adults

Sensory perception decreases with age, and is altered as a function of sex. Very little is known about the age- and sex-related changes in vibrotactile detection thresholds (VDTs) of the face relative to the glabrous hand. This study utilized a single-interval up/down (SIUD) adaptive procedure to estimate the VDT for mechanical stimuli presented at 5, 10, 50, 150, 250, and 300 Hz at two sites on the face, including the right non-glabrous surface of the oral angle and the right lower lip vermilion; and on the hand on the glabrous surface of the distal phalanx of the right dominant index finger. Eighteen right-handed healthy younger adults and 18 right-handed healthy older adults participated in this study. VDTs were significantly different between the three stimulus sites (p < 0.0001), and dependent on stimulus frequency (p < 0.0001) and the sex of the participants (p < 0.005). VDTs were significantly higher for older adults when compared to younger adults for the finger stimulation condition (p < 0.05). There were significant differences (p < 0.05) in cheek and lower lip VDTs between male and female subjects. Difference in the VDTs between the three stimulation sites is presumed to reflect the unique typing and distribution of mechanoreceptors in the face and hand. Age-related differences in finger skin sensitivity are likely due to changes in the physical structure of skin, changes in the number and morphology of the mechanoreceptors, differences in the functional use of the hand, and its central representation. Sex-related differences in the VDTs may be due to the differences in tissue conformation and thickness, mechanoreceptor densities, skin hydration, or temperature characteristics.

Tactile Experience Does Not Ameliorate Age-Related Reductions in Sensory Function

Background/Study Context: Sensory function degrades with age, with well-established reductions in tactile spatial acuity, vibrotactile sensitivity, and thermosensation, to name but three aspects of perception. Such age-related losses might be partially stemmed by ongoing experience with tasks requiring high levels of manual dexterity or analogous tactile expertise; individuals who are highly expert in skills that have a fundamental tactile component can show improved tactile function as compared with nonexperts. Methods: Eighty individuals (17 males, 63 females) in the 18–58 age range were assessed on their tactile experience, as measured by self-assessment on a variety of tasks and competencies, each of which required a high level of skill with the hands. Tactile sensory performance, manual dexterity (“haptic efficiency”), and the subjective response to tactile stimulation were quantified. Results: Degradation in tactile sensory acuity with age was confirmed, but no strong evidence was found for variations in acuity contingent on the tactile expertise of participants. In contrast to the performance measures, differences in tactile experience were associated with differences in the subjective response to touch. Greater tactile experience was associated with the provision of richer descriptions of textured materials manipulated with the digits. Conclusion: The range of tactile experience reported in a convenience sample of the population was apparently insufficient to preserve sensory function during aging.