Vibrotactile Stimulators Research Articles

Tactile Location Perception Encoded by Gamma-Band Power.

The perception of tactile-stimulation locations is an important function of the human somatosensory system during body movements and its interactions with the surroundings. Previous psychophysical and neurophysiological studies have focused on spatial location perception of the upper body. In this study, we recorded single-trial electroencephalography (EEG) responses evoked by four vibrotactile stimulators placed on the buttocks and thighs while the human subject was sitting in a chair with a cushion. Briefly, 14 human subjects were instructed to sit in a chair for a duration of 1 h or 1 h and 45 min. Two types of cushions were tested with each subject: a foam cushion and an air-cell-based cushion dedicated for wheelchair users to alleviate tissue stress. Vibrotactile stimulations were applied to the sitting interface at the beginning and end of the sitting period. Somatosensory-evoked potentials were obtained using a 32-channel EEG. An artificial neural net was used to predict the tactile locations based on the evoked EEG power. We found that single-trial beta (13-30 Hz) and gamma (30-50 Hz) waves can best predict the tactor locations with an accuracy of up to 65%. Female subjects showed the highest performances, while males' sensitivity tended to degrade after the sitting period. A three-way ANOVA analysis indicated that the air-cell cushion maintained location sensitivity better than the foam cushion. Our finding shows that tactile location information is encoded in EEG responses and provides insights on the fundamental mechanisms of the tactile system, as well as applications in brain-computer interfaces that rely on tactile stimulation.

Opportunities and Pitfalls in Applying Emotion Recognition Software for Persons With a Visual Impairment: Simulated Real Life Conversations.

BackgroundA large part of the communication cues exchanged between persons is nonverbal. Persons with a visual impairment are often unable to perceive these cues, such as gestures or facial expression of emotions. In a previous study, we have determined that visually impaired persons can increase their ability to recognize facial expressions of emotions from validated pictures and videos by using an emotion recognition system that signals vibrotactile cues associated with one of the six basic emotions.ObjectiveThe aim of this study was to determine whether the previously tested emotion recognition system worked equally well in realistic situations and under controlled laboratory conditions.MethodsThe emotion recognition system consists of a camera mounted on spectacles, a tablet running facial emotion recognition software, and a waist belt with vibrotactile stimulators to provide haptic feedback representing Ekman’s six universal emotions. A total of 8 visually impaired persons (4 females and 4 males; mean age 46.75 years, age range 28-66 years) participated in two training sessions followed by one experimental session. During the experiment, participants engaged in two 15 minute conversations, in one of which they wore the emotion recognition system. To conclude the study, exit interviews were conducted to assess the experiences of the participants. Due to technical issues with the registration of the emotion recognition software, only 6 participants were included in the video analysis.ResultsWe found that participants were quickly able to learn, distinguish, and remember vibrotactile signals associated with the six emotions. A total of 4 participants felt that they were able to use the vibrotactile signals in the conversation. Moreover, 5 out of the 6 participants had no difficulties in keeping the camera focused on the conversation partner. The emotion recognition was very accurate in detecting happiness but performed unsatisfactorily in recognizing the other five universal emotions.ConclusionsThe system requires some essential improvements in performance and wearability before it is ready to support visually impaired persons in their daily life interactions. Nevertheless, the participants saw potential in the system as an assistive technology, assuming their user requirements can be met.

Armband with Soft Robotic Actuators and Vibrotactile Stimulators for Bimodal Haptic Feedback from a Dexterous Artificial Hand.

The haptic sense relies upon a plurality of receptors and pathways to produce a complex perceptual experience of contact, pressure, taps, vibrations and flutters. This complexity is yet to be reproduced in haptic feedback interfaces that are used by people controlling a dexterous robotic hand, be it for limb-absence or teleoperation. The goal of the present bimodal haptic armband is to convey both low-frequency pressure changes and high-frequency vibrations from a dexterous robotic hand to a human's upper arm, so as to guide his/her control of the artificial limb. To that end, we design and manufacture four novel soft robotic armbands combining inflatable air chambers and vibrotactile stimulators. We develop control systems for both pathways. We conduct a series of benchtop tests to determine the pneumatic and vibrotactile performance and select from competing designs and materials. We test two of the resulting bimodal haptic armband on human subjects and confirm their ability to use both aspects of this haptic information. Arguing that dexterous artificial hands are presently not used to their fullest capability by the dearth of haptic information in users, this work aims to achieve a more realistic tactile experience for a fluent, more natural usage of robotic artificial hands.

Assessing Command-Following and Communication With Vibro-Tactile P300 Brain-Computer Interface Tools in Patients With Unresponsive Wakefulness Syndrome.

Persons diagnosed with disorders of consciousness (DOC) typically suffer from motor disablities, and thus assessing their spared cognitive abilities can be difficult. Recent research from several groups has shown that non-invasive brain-computer interface (BCI) technology can provide assessments of these patients' cognitive function that can supplement information provided through conventional behavioral assessment methods. In rare cases, BCIs may provide a binary communication mechanism. Here, we present results from a vibrotactile BCI assessment aiming at detecting command-following and communication in 12 unresponsive wakefulness syndrome (UWS) patients. Two different paradigms were administered at least once for every patient: (i) VT2 with two vibro-tactile stimulators fixed on the patient's left and right wrists and (ii) VT3 with three vibro-tactile stimulators fixed on both wrists and on the back. The patients were instructed to mentally count either the stimuli on the left or right wrist, which may elicit a robust P300 for the target wrist only. The EEG data from −100 to +600 ms around each stimulus were extracted and sub-divided into 8 data segments. This data was classified with linear discriminant analysis (using a 10 × 10 cross validation) and used to calibrate a BCI to assess command following and YES/NO communication abilities. The grand average VT2 accuracy across all patients was 38.3%, and the VT3 accuracy was 26.3%. Two patients achieved VT3 accuracy ≥80% and went through communication testing. One of these patients answered 4 out of 5 questions correctly in session 1, whereas the other patient answered 6/10 and 7/10 questions correctly in sessions 2 and 4. In 6 other patients, the VT2 or VT3 accuracy was above the significance threshold of 23% for at least one run, while in 4 patients, the accuracy was always below this threshold. The study highlights the importance of repeating EEG assessments to increase the chance of detecting command-following in patients with severe brain injury. Furthermore, the study shows that BCI technology can test command following in chronic UWS patients and can allow some of these patients to answer YES/NO questions.

Validation of a Vibrotactile Stimulation System Using the Wii Remote for Studies of Tactile Sensitivity

Background: Vibrotactile stimuli are widely used to study the functional characteristics of the haptic sense. Although many vibrotactile stimulators are commercially available, most are expensive. Objective: We developed a low-cost vibrotactile stimulation system using a Nintendo Wii Remote and a personal computer. In the present study, we examined the validity and accuracy of this vibrotactile stimulation system. Method: In the first experiment, we measured the linearity of vibration amplitude and changes in peak vibration frequency generated by the Wii Remote as a function of activation intensity. In the second experiment, the effect of vibrotactile stimuli applied to the dorsal surface of hand on two-point discrimination threshold at the index finger was examined in twelve participants. Results: The peak vibration frequency was about 150 Hz irrespective of vibration intensity, which would effectively activate fast adapting type II (FAII) cutaneous mechanical receptors. The two-point discrimination threshold measured at the third pad of the index finger decreased significantly when a near-threshold vibrotactile stimulus was applied to the dorsal hand, a response termed stochastic resonance (SR). These SR results are consistent with findings in the other sensory systems, such as auditory, visual, and somatosensory systems. Conclusion: This newly developed stimulation system produces controllable vibrotactile stimuli useful for study of the haptic sense.

Time-Discrete Vibrotactile Feedback Contributes to Improved Gait Symmetry in Patients With Lower Limb Amputations: Case Series.

Abstract Background Reduced sensory feedback from lower leg prostheses results in harmful gait patterns and entails a significant cognitive burden because users have to visually monitor their locomotion. Objectives The purpose of this study was to validate a sensory feedback device designed to help elderly patients with transfemoral amputation to improve their temporal gait symmetry after a training program aimed at associating the vibrotactile patterns with symmetrical walking. Design This was a prospective quasi-experimental study including 3 elderly patients walking with lower leg prostheses. Methods During training sessions, participants walked on a treadmill equipped with a feedback device that controlled vibrotactile stimulators based on signals from a sensorized insole while provided with visual feedback about temporal gait symmetry. The vibrotactile stimulators delivered short-lasting, low-intensity vibrations synchronously with certain gait-phase transitions. During pretraining and posttraining sessions, participants walked without visual feedback about gait symmetry under 4 conditions: with or without vibrotactile feedback while performing or not performing a secondary cognitive task. The primary outcome measure was temporal gait symmetry. Results With ≤2 hours of training, the participants improved their temporal gait symmetry from 0.82 to 0.84 during the pretraining evaluation session to 0.98 to 1.02 during the follow-up session across all conditions. Following training, participants were able to maintain good temporal gait symmetry, without any evidence of an increased cognitive burden. Limitations The small sample size and short follow-up time do not allow straightforward extrapolations to larger populations or extended time periods. Conclusions Low-cost, gait phase–specific vibrotactile feedback after training combined with visual feedback may improve the temporal gait symmetry in patients with transfemoral amputation without representing an additional cognitive burden.

Tactile Situation Awareness System

Recent system development efforts have been made concerning a Tactile Situation Awareness System (TSAS). TSAS is a garment containing vibrotactile stimulators that provide aircraft flight control feedback to the torso. TSAS is intended to improve human factors during flight by reducing workload, increasing situation awareness, and reducing the likelihood of brownout mishaps. During simulation and flight tests, pilots using TSAS have demonstrated the ability to non-visually hover helicopters, while consistently reporting reduced workload and increased situation awareness. The current effort enlarged the surface area of the garment to extend the capability beyond hovering to include complete forward flight control (pitch and roll) so that the technology could be transitioned to the helicopter pilot community and effect a reduction of brownout mishaps. The following describes the delivery of this new suite of capabilities, including the cueing garments, avionics interfaces, and software compatible with military helicopter platforms.

P131. Vibrotactile stimulation as a novel method to detect malingered attention or sensory deficits

Introduction To our knowledge there exist no objective methods for the clinical validation of reactions after tactile stimulation although the prevalence of symptom aggravation is high in compensation seeking context (18–40%, Axelrod et al., 2000; Binder, 1993; Mittenberg et al., 2002). In order to develop an electrophysiological method for symptom validation after vibrotactile stimulation we investigated the tactile stimulation of mechanical receptors of single sensory qualities with varied stimulation principles (mechanical pulse, vibration, coating, indentation, passive movement) and established a clinical routine. Methods In the present work LRP (lateralized readiness potentials) and NIRS (near-infrared spectroscopy) were recorded after vibrotactile stimulation of the thumb (60 Hz) in 40 healthy controls and 40 subjects with an episode of depression. Tactile SEP (somatosensory evoked potentials) were conducted to make sure that the stimuli were perceived by the subjects. In condition I the subjects were instructed to react to a vibrational stimulus with least possible delay by pushing a button, in condition II an additional time delay or a lack of reaction was asked to be executed. Stimulus- and response-locked LRP and activation patterns of the NIRS signal (Oxy-Hb and Deoxy-Hb) were compared statistically between both the conditions and the subject groups. Results In condition II the reaction-time was significantly longer and its dispersion was greater ( p p p p Conclusion If our results can be replicated in subjects with substantial brain lesions, a novel objective validation method for both sensory deficits and malingered attention deficits might result. As vibrotactile stimulators have only limited availability yet, EEG and surface myography are used as common techniques. If available, this novel method can be easily implemented to routine procedures.

P125. mindBEAGLE: A BCI for communication and assessment of consciousness for patients with disorders of consciousness

Introduction In this publication we present a tool for assessment and communication with patients suffering Disorder of Consciousness (DOC). Four different Brain–Computer Interface (BCI) approaches are used: An auditory P300 approach, a vibrotactile P300 approach with two or three tactile stimulators, and a Motor Imagery (MI) based approach. The vibrotactile P300 and the MI based approaches can be used for both, the assessment of consciousness and communication with patients. The auditory P300 approach can be used only for assessment of consciousness. System overview Fig. 1 shows an overview of the system. The user wears an EEG cap with 16 electrodes, distributed to fit for all three BCI approaches. The laptop controls the paradigms, performs the signal processing and displays the results to the user. Three vibrotactile stimulators are used for the tactile P300 approach, earphones are used for the auditory P300. The cues that are needed for the MI approach are also played via the earphones. System validation Table 1 shows results of five healthy users, controlling mindBEAGLE. The vibrotactile P300 approach was already tested on a group of six Locked-In Patients showing a average accuracy of 80% for two tactors and 55.3% for three tactors ( Lugo et al., 2014 ). The feasibility of auditory P300 for cognitive assessment was also proved in previous studies ( Cipresso et al., 2012 , Kubler et al., 2009 ). In future studies, all approaches of the device system will be validated on both: healthy users and patients.

Contextual cueing: implicit memory of tactile context facilitates tactile search.

In visual search, participants detect and subsequently discriminate targets more rapidly when these are embedded in repeatedly encountered distractor arrangements, an effect termed contextual cueing (Chun & Jiang Cognitive Psychology, 36, 28–71, 1998). However, whereas previous studies had explored contextual cueing exclusively in visual search, in the present study we examined the effect in tactile search using a novel tactile search paradigm. Participants were equipped with vibrotactile stimulators attached to four fingers on each hand. A given search array consisted of four stimuli (i.e., two items presented to each hand), with the target being an odd-one-out feature singleton that differed in frequency (Exps. 1 and 2) or waveform (Exp. 3) from the distractor elements. Participants performed a localization (Exps. 1 and 2) or discrimination (Exp. 3) task, delivering their responses via foot pedals. In all three experiments, reaction times were faster when the arrangement of distractor fingers predicted the target finger. Furthermore, participants were unable to explicitly discriminate repeated from nonrepeated tactile configurations (Exps. 2 and 3). This indicates that the tactile modality can mediate the formation of configural representations and use these representations to guide tactile search.

Vibrotactile stimulation promotes embodiment of an alien hand in amputees with phantom sensations.

Tactile feedback is essential to intuitive control and to promote the sense of self-attribution of a prosthetic limb. Recent findings showed that amputees can be tricked to experience this embodiment, when synchronous and modality-matched stimuli are delivered to biological afferent structures and to an alien rubber hand. Hence, it was suggested to exploit this effect by coupling touch sensors in a prosthesis to an array of haptic tactile stimulators in the prosthetic socket. However, this approach is not clinically viable due to physical limits of current haptic devices. To address this issue we have proposed modality-mismatched stimulation and demonstrated that this promotes self-attribution of an alien hand on normally limbed subjects. In this work we investigated whether similar effects could be induced in transradial amputees with referred phantom sensations in a series of experiments fashioned after the Rubber Hand Illusion using vibrotactile stimulators. Results from three independent measures of embodiment demonstrated that vibrotactile sensory substitution elicits body-ownership of a rubber hand in transradial amputees. These results open up promising possibilities in this field; indeed miniature, safe and inexpensive vibrators could be fitted into commercially available prostheses and sockets to induce the illusion every time the prosthesis manipulates an object.

Evaluation of the attention network test using vibrotactile stimulations.

We report a vibrotactile version of the attention network test (ANT)-the tactile ANT (T-ANT). It has been questioned whether attentional components are modality specific or not. The T-ANT explores alertness, orienting, cognitive control, and their relationships, similar to its visual counterpart, in the tactile modality. The unique features of the T-ANT are in utilizing stimuli on a single plane-the torso-and replacing the original imperative flanker task with a tactile Simon task. Subjects wore a waist belt mounted with two vibrotactile stimulators situated on the back and positioned to the right and left of the spinal column. They responded by pressing keys with their right or left hand in reaction to the type of vibrotactile stimulation (pulsed/continuous signal). On a single trial, an alerting tone was followed by a short tactile (informative/noninformative) peripheral cue and an imperative tactile Simon task target. The T-ANT was compared with a variant of the ANT in which the flanker task was replaced with a visual Simon task. Experimental data showed effects of orienting over control only when the peripheral cues were informative. In contrast to the visual task, interactions between alertness and control or alertness and orienting were not found in the tactile task. A possible rationale for these results is discussed. The T-ANT allows examination of attentional processes among patients with tactile attentional deficits and patients with eyesight deficits who cannot take part in visual tasks. Technological advancement would enable implementation of the T-ANT in brain-imaging studies.

HyVE-hybrid vibro-electrotactile stimulation-is an efficient approach to multi-channel sensory feedback.

An important reason for the abandonment of commercial actuated hand prostheses by the users is the lack of sensory feedback. Wearable afferent interfaces capable of providing electro- or vibro-tactile stimulation have high potential to restore the missing tactile and/or proprioceptive information to the user. By definition, these devices can elicit single modality (i.e., either vibrotactile or electrotactile) substitute sensations. In a recent research we have presented a novel approach comprising hybrid vibro-electrotactile (HyVE) combined stimulation, in order to provide multimodal sensory feedback. An important advantage of this approach is in the size of the design: the HyVE interface is much more compact than two separated single-modality interfaces, since electro- and vibro-tactile stimulators are placed one on top of the other. The HyVE approach has been previously tested in healthy subjects and has shown to provide a range of hybrid stimuli that could be properly discriminated. However, this approach has never been assessed as a method to provide multi-channel stimuli, i.e., stimuli from a variety of stimulators, mapping information from a multitude of sensors on a prosthesis. In this study, the ability of ten healthy subjects to discriminate stimuli and patterns of stimuli from four different five-channel interfaces applied on their forearms was evaluated. We showed that multiple HyVE units could be used to provide multi-channel sensory information with equivalent performance (∼95 percent for single stimuli and ∼80 percent for pattern) to single modality interfaces (vibro- or electro-tactile) larger in size and with better performance than vibrotactile interfaces (i.e., 73 percent for single stimuli and 69 percent for pattern) with the same size. These results are promising in relation to the current availability of multi-functional prostheses with multiple sensors.

InerTouchHand System - iTH - Demonstration of a Glove Device with Distributed Inertial Sensors and Vibro-tactile Feedback

The InerTouchHand System shows the usage of an instrumented glove-like device for HMI-Human Machine Interaction applications. We explored the use of distributed inertial sensors and vibro-tactile stimulators on the hand. Distributed Inertial Measurement Units (IMUs) can be used to infer structure and reconstruct 6D pose of nodes, as well as relative motion. Our system uses MEMS IMUs on each fingertip for providing relative angular pose by using gravity as a vertical reference for acceleration measurements. Although not always fully observable it can be complemented by the IMUsâ?? gyro rotation and magnetometer measurements. When combined with vibro-tactile stimulators a hand worn device or glove can provide spatial aware feedback. At exp.atâ??13 (2nd Experiment@ International Conference) an interactive demo presented InerTouchHand (iTH), the hand device for gesture recognition and HMI with touch feedback.

Hand-opening feedback for myoelectric forearm prostheses: Performance in virtual grasping tasks influenced by different levels of distraction

Sensory feedback and the required attentional demands are important aspects in prosthesis acceptance. In this study, hand-opening feedback is provided and the performance in a virtual grasping task is investigated. Simultaneously, a secondary task was performed to investigate the attentional demands. Ten nondisabled subjects performed the tasks with and without feedback about the hand opening through an array of eight vibrotactile stimulators on the forearm. Activation of one stimulator corresponded to one hand-opening position. For the dual-task experiments, subjects simultaneously performed a secondary auditory counting task. The addition of vibrotactile feedback increased the performance (expressed in percentages of correct hand positions, mean absolute errors in position, and percentages of deviations up to one hand-opening position), but the duration of the tasks was also increased. Three levels of distraction (no distraction, counting task, count and subtract task) were applied, which did not influence the performance in the grasping tasks except for the highest level of distraction. We concluded that the proposed method to provide hand-opening feedback through an array of eight vibrotactile stimulators is successful because the performance in a grasping task increases but it is not significantly attention demanding.

A novel device for the study of somatosensory information processing

Current methods for applying multi-site vibratory stimuli to the skin typically involve the use of multiple, individual vibrotactile stimulators. Limitations of such an arrangement include difficulty with both positioning the stimuli as well as ensuring that stimuli are delivered in a synchronized and deliberate manner. Previously, we reported a two-site tactile stimulator that was developed in order to solve these problems (Tannan et al., 2007a). Due to both the success of that novel stimulator and the limitations that were inherent in that device, we designed and fabricated a four-site stimulator that provides a number of advantages over the previous version. First, the device can stimulate four independent skin sites and is primarily designed for stimulating the digit tips. Second, the positioning of the probe tips has been re-designed to provide better ergonomic hand placement. Third, the device is much more portable than the previously reported stimulator. Fourth, the stimulator head has a much smaller footprint on the table or surface where it resides. To demonstrate the capacity of the device for delivering tactile stimulation at four independent sites, a finger agnosia protocol, in the presence and absence of conditioning stimuli, was conducted on seventeen healthy control subjects. The study demonstrated that with increasing amplitudes of vibrotactile conditioning stimuli concurrent with the agnosia test, inaccuracies of digit identification increased, particularly at digits D3 and D4. The results are consistent with prior studies that implicated synchronization of adjacent and near-adjacent cortical ensembles with conditioning stimuli in impacting TOJ performance (Tommerdahl et al., 2007a,b).

Tactile Working Memory Outside our Hands

The haptic perception of 2D images is believed to make heavy demands on working memory. During active exploration, we need to store not only the current sensory information, but also to integrate this with kinesthetic information of the hand and fingers in order to generate a coherent percept. The question that arises is how much tactile memory we have for tactile stimuli that are no longer in contact with the skin during active touch? We examined working memory using a tactile change detection task with active exploration. Each trial contained two stimulation arrays. Participants engaged in unconstrained active tactile exploration of an array of vibrotactile stimulators. In half of the trials, one of the vibrating tactors that was active in the first stimulation turned off and another started vibrating in the second stimulation. Participants had to report whether the arrays were the same or different. Performance was near-perfect when up to two tactors were used and dropped linearly as the number of the ...

The electrophysiological timecourse of postural remapping of somatosensory space

Event Abstract Back to Event The electrophysiological timecourse of postural remapping of somatosensory space Silvia Rigato1*, José Van Velzen1, Robert Davis1 and Andrew J. Bremner1 1 Goldsmiths, University of London, United Kingdom To locate a tactile stimulus in multisensory space one must both register the tactile location on the body surface, and also take account of the current posture of the relevant limbs in order to remap the relationship of the tactile location with respect to the body (e.g., Lloyd et al., 2003). Azañón and Soto-Faraco (2008) have investigated the behavioural timecourse of this remapping and found that tactile location is first coded with respect to a somatotopic frame of reference and later remapped to an external representation. This study investigated the electrophysiological correlates of this somatosensory spatial processing. Somatosensory evoked potentials (SEPs) were recorded from adults who were asked to hold two vibrotactile stimulators in their palms, in an uncrossed-hands and crossed-hands posture. On each trial (of which there were 40 in each posture) participants received a sequence of 6 vibrotactile stimuli. Statistical analyses of the SEPs revealed a late interaction between posture (crossed hands / uncrossed hands) and hemisphere with respect to the stimulated hand in anatomical coordinates (ipsilateral / contralateral) occurring at frontal sites around 500ms. The N140 component is initially of larger amplitude contralaterally rather than the ipsilaterally in both posture conditions. However, at 500ms posture influences somatosensory coding such that the SEP was of larger (negative) amplitude ipsilaterally than contralaterally when the hands were uncrossed, but larger contralaterally than ipsilaterally when the hands were crossed. These findings corroborate behavioural evidence that somatosensory stimuli are coded in anatomical coordinates before being remapped to an external frame of reference (Azañón & Soto-Faraco, 2008). Funding: Supported by European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013) / ERC Grant agreement no. 241242. Keywords: Perception, SEP Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Neurophysiology of Sensation and Perception Citation: Rigato S, Van Velzen J, Davis R and Bremner AJ (2011). The electrophysiological timecourse of postural remapping of somatosensory space. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00338 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Silvia Rigato, Goldsmiths, University of London, London, United Kingdom, srigato@essex.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Silvia Rigato José Van Velzen Robert Davis Andrew J Bremner Google Silvia Rigato José Van Velzen Robert Davis Andrew J Bremner Google Scholar Silvia Rigato José Van Velzen Robert Davis Andrew J Bremner PubMed Silvia Rigato José Van Velzen Robert Davis Andrew J Bremner Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The design and evaluation of a multi-sensory vibrotactile feedback system for a myoelectric prosthetic hand

Upper-limb amputees have reported that one of their main dissatisfactions with current commercialised prosthetic arms is a lack of sensory feedback. The current study investigates the feasibility of providing feedback of grip force, slippage, and finger position through vibrotactile stimulators to the prosthetic users. Tests are performed to determine subject’s spatial sensitivity as well as their abilities to differentiate discrete vibration intensity levels. We find that human subjects can correctly identify discrete sensory levels (with 90% accuracy) from 62 Hz to 250 Hz for tactors placed at least 3 cm apart. The accuracy of the EMG classifier system would decrease if all three tactors are activated. Even though a multivariable vibrotactile feedback system may not be feasible initially due to information overload, the user performance may improve with training. Multi-tactor system can be implemented with a slight decrease in electromyographic signal classification for the control of a neuroprosthetic hand.

Vibrotactile stimulators and virtual 3-D audio countermeasures, training and motion sickness symptoms with a simulated graveyard spin illusion

The vestibular system by itself is incapable of effectively compensating for the graveyard spin illusion. We examined two countermeasures, i.e., efficacy of vibrotactile stimulation around the waist and virtual 3-D audio presented independently and jointly for controlling a simulated graveyard spin. We also examined: a) additional training with these countermeasures to improve "intuitiveness;" b) included non-perturbation trials along with perturbation trials; and c) monitored changes in well-being as measured by a motion sickness scale from pre- to post-test and immediately following each trial. Ten volunteers received two training and two test sessions. The somatogyral illusion was generated by accelerating a chair for 24 s until it attained a peak rotation of 120 degrees /s and then stopped. Over the ensuing 40 s the chair rotated in one of two random perturbation patterns or remained stationary. During this period, participants were required to eliminate all movements of the chair by turning a knob in the opposite direction of perceived rotation. For the control trials, participants relied solely on vestibular signals to cancel perceived movements. For the experimental trials, vibrotactile stimulation around the waist, virtual 3-D audio, or both were presented. The mean Cancellation Error (CE) for the control trials was 52 degrees /s. The application of the countermeasures significantly reduced the CE. Additional training and testing did not improve intuitiveness. Perturbations to the chair resulted in a higher CE than no perturbations. Motion sickness symptoms showed no differences from pre- to post-test and very rarely reported after each trial.