Vibrotactile Cue Research Articles

A Novel Kinematic Gait Parameter-Based Vibrotactile Cue for Freezing of Gait Mitigation among Parkinson's Patients: A Pilot Study.

Auditory and visual cues have been efficacious in laboratory-based freezing of gait (FoG) mitigation in Parkinson's disease (PD). However, real-life applications of these cues are restricted due to inconvenience to the users. Closed-loop vibrotactile cues based on temporal gait events have overcome the shortcomings of auditory and visual cueing. However, kinematic gait parameter-driven vibrotactile cueing has not been explored yet. Kinematic gait parameter-driven cueing is more effective than temporal cueing, according to FoG pathophysiology studies. Therefore, we developed and pilot-tested a novel cueing scheme in which the foot-to-ground angle at heel strike (FGA_HS) is estimated using indigenous instrumented shoes to drive vibrotactile cueing. Ten PD freezers underwent a 6-meter timed walk test in the off-medication state with and without the cue and after medication without the cue. The proposed system potentially mitigated FoG, quantified by a reduction in the ratio of time spent freezing to the total walking time and the number of FoGs. The FoG mitigation potential of the cue was further supported by increased anteroposterior center of pressure progression and FGA_HS. With a future comprehensive validation in a larger number of participants, the novel cue could likely be used in practice and commercialized.

Haptic Feedback Based on Movement Smoothness Improves Performance in a Perceptual-Motor Task.

In many training scenarios, and in surgery in particular, feedback is provided to the trainee after the task has been performed, and the assessment is often qualitative in nature. In this paper, we demonstrate the effect of real-time objective performance feedback conveyed through a vibrotactile cue. Subjects performed a mirror-tracing task that requires coordination and dexterity similar in nature to that required in endovascular surgery. Movement smoothness, a characteristic associated with skilled and coordinated movement, was measured by spectral arc length, a frequency-domain measure of smoothness. The smoothness-based performance metric was encoded as a vibrotactile cue displayed on the user's arm. Performance on the mirror tracing task with smoothness-based feedback was compared to position-based feedback (where the subject was alerted when they moved outside the path boundary) and to a no vibrotactile feedback control condition. Subjects receiving smoothness-based feedback altered their task completion strategies, resulting in faster task completion times, but their accuracy was slightly worse overall than the other two groups. In procedures such as endovascular surgery, the reduction of procedure time that could be achieved with smoothness-based feedback training may be advantageous, despite the fact that accuracy was inferior to that observed with no feedback or position-based feedback.

Auditory cues for somatosensory targets invoke visuomotor transformations: Behavioral and electrophysiological evidence.

Prior to goal-directed actions, somatosensory target positions can be localized using either an exteroceptive or an interoceptive body representation. The goal of the present study was to investigate if the body representation selected to plan reaches to somatosensory targets is influenced by the sensory modality of the cue indicating the target’s location. In the first experiment, participants reached to somatosensory targets prompted by either an auditory or a vibrotactile cue. As a baseline condition, participants also performed reaches to visual targets prompted by an auditory cue. Gaze-dependent reaching errors were measured to determine the contribution of the exteroceptive representation to motor planning processes. The results showed that reaches to both auditory-cued somatosensory targets and auditory-cued visual targets exhibited larger gaze-dependent reaching errors than reaches to vibrotactile-cued somatosensory targets. Thus, an exteroceptive body representation was likely used to plan reaches to auditory-cued somatosensory targets but not to vibrotactile-cued somatosensory targets. The second experiment examined the influence of using an exteroceptive body representation to plan movements to somatosensory targets on pre-movement neural activations. Cortical responses to a task-irrelevant visual flash were measured as participants planned movements to either auditory-cued somatosensory or auditory-cued visual targets. Larger responses (i.e., visual-evoked potentials) were found when participants planned movements to somatosensory vs. visual targets, and source analyses revealed that these activities were localized to the left occipital and left posterior parietal areas. These results suggest that visual and visuomotor processing networks were more engaged when using the exteroceptive body representation to plan movements to somatosensory targets, than when planning movements to external visual targets.

Bayes-Like Integration of a New Sensory Skill with Vision

Humans are effective at dealing with noisy, probabilistic information in familiar settings. One hallmark of this is Bayesian Cue Combination: combining multiple noisy estimates to increase precision beyond the best single estimate, taking into account their reliabilities. Here we show that adults also combine a novel audio cue to distance, akin to human echolocation, with a visual cue. Following two hours of training, subjects were more precise given both cues together versus the best single cue. This persisted when we changed the novel cue’s auditory frequency. Reliability changes also led to a re-weighting of cues without feedback, showing that they learned something more flexible than a rote decision rule for specific stimuli. The main findings replicated with a vibrotactile cue. These results show that the mature sensory apparatus can learn to flexibly integrate new sensory skills. The findings are unexpected considering previous empirical results and current models of multisensory learning.

A Phantom-Sensation Based Paradigm for Continuous Vibrotactile Wrist Guidance in Two-Dimensional Space

Vibrotactile feedback has long been used to improve the human motor learning process through information transfer. However, in most of the approaches described in the literature, only the joint angles of the limb are guided. To guide motions that involve multiple degrees of freedom (DOFs), the user needs to interpret multiple simultaneous vibrotactile cues (at least one cue per joint), which is difficult. In this letter, we guide the position of a user's wrist in space by producing a vibrotactile cue at any place around the wrist by using a vibrotactile illusion known as “Phantom Sensation” (PS). In a user study that involved 10 male participants, the vibrotactile cues produced by PS were reasonably accurately located with an average error of $\boldsymbol{7.9^\circ }$ . To maintain consistency between the vibrotactile cue location and the global frame, we measured the user's wrist rotation and adjusted the position of the vibrotactile cue accordingly. When rotating their hand, the participants recognized the location of the vibrotactile cue with an average error of $\boldsymbol{9.3^\circ }$ . By using the proposed feedback paradigm, we guided users’ wrists in space under two conceptual mappings (“push” and “pull”). This experiment examined the participants’ motion path efficiency (ME), which measures the directness with which the user's wrist moves toward the desired position. The participants reached the desired positions under the vibrotactile feedback alone. The average MEs of the “push” and “pull” mappings were 44.3% and 52.4%, respectively. We will apply the proposed method under the “pull” mapping to guide real life tasks, such as book classification or rehabilitation.

The role of forelimb motor cortex areas in goal directed action in mice

Mammalian motor cortex consists of several interconnected subregions thought to play distinct roles in voluntary movements, yet their specific role in decision making and execution is not completely elucidated. Here we used transient optogenetic inactivation of the caudal forelimb area (CFA) and rostral forelimb area (RFA) in mice as they performed a directional joystick task. Based on a vibrotactile cue applied to their forepaw, mice were trained to push or pull a joystick after a delay period. We found that choice and execution are temporally segregated processes. CFA and RFA were both essential during the stimulus delivery for correct choice and during the answer period for motor execution. Fine, distal motor deficits were restricted to CFA inactivation. Surprisingly, during the delay period neither area alone, but only combined inactivation was able to affect choice. Our findings suggest transient and partially distributed neural processing of choice and execution across different subregions of the motor cortex.

Gaze Cueing with a Vibrotactile Headband for a Visual Search Task

Augmented attention, assisting the user in noticing important things, is one of the ways human action can be enhanced with technologies. We investigated how vibrotactile stimulation given to the forehead could be used to cue gaze direction. We built a vibrotactile headband with an array of six actuators that presented short, tap-like cues. In the first experiment, the participant was instructed to look at the point on a horizontal line that they thought the vibrotactile cue was pointing to. Analysis of the participant’s gaze points showed that for the majority there were statistically significant differences between cues from different actuators. This indicated that the six actuators could successfully direct the participant’s gaze to different areas of the visual field. In addition, vibrotactile cueing of gaze direction could be used for directing visual attention and providing navigation cues with wearable headbands. To strengthen our findings, we investigated how effective the vibrotactile stimulation would be to cue gaze direction in a visual search task. Participant’s were asked to find a deviant shape (a target) from a display full of simple shapes. The vibrotactile cueing implemented with the headband device was used to inform the participants of the approximate horizontal position of the target in three different experimental conditions. In the most informative condition, six actuators were used to inform the participant of the horizontal area where the target would be found, in the second condition two actuators were used to inform the participant of the target side on the display (left or right), and in the least informative condition no directional information was given. Analysis of the trial completion times showed that there were statistically significant differences between the least informative condition and the two other conditions. However, we did not find significant differences in trial completion times between the two conditions where information of the target location was given. This indicated that while the actuators could successfully direct the participant’s attention to different areas of the visual field to help in the search task, the simple approach of just adding actuators and dividing the visual field to more sub-areas did not improve the results. The findings of this study showed that while there is potential in using vibrotactile cueing of gaze direction, more research is needed to fully exploit it.

Non-Colocated Kinesthetic Display Limits Compliance Discrimination in the Absence of Terminal Force Cues.

An important goal of haptic display is to make available the action/reaction relationships that define interactions between the body and the physical world. While in physical world interactions reaction cues invariably impinge on the same part of the body involved in action (reaction and action are colocated), a haptic interface is quite capable of rendering feedback to a separate body part than that used for producing exploratory actions (non-colocated action and reaction). This most commonly occurs with the use of vibrotactile display, in which a cutaneous cue has been substituted for a kinesthetic cue (a kind of sensory substitution). In this paper, we investigate whether non-colocated force and displacement cues degrade the perception of compliance. Using a custom non-colocated kinesthetic display in which one hand controls displacement and the other senses force, we ask participants to discriminate between two virtual springs with matched terminal force and adjustable non-linearity. An additional condition includes one hand controlling displacement while the other senses force encoded in a vibrotactile cue. Results show that when the terminal force cue is unavailable, and even when sensory substitution is not involved, non-colocated kinesthetic displays degrade compliance discrimination relative to colocated kinesthetic displays. Compliance discrimination is also degraded with vibrotactile display of force. These findings suggest that non-colocated kinesthetic displays and, likewise, cutaneous sensory substitution displays should be avoided when discrimination of compliance is necessary for task success.

Demonstration and Evaluation of an Eyes-Free Mobile Navigation System

Loss of awareness in one’s immediate surroundings can have devastating results when navigating. For instance, military operators must often navigate in unfamiliar environments and must be able to detect nearby threats to survive. Visual displays such as paper or digital maps can draw visual attention away from one’s environment. We developed a navigation display that guides a user through a series of waypoints by playing a 3D audio tone over headphones or vibrating a tactor on an array around the torso. We evaluated the navigation display by having participants navigate through 32 waypoints in an open field. In addition to evaluating auditory and vibrotactile cues, we considered an analog visual cue, an allocentric map, and an egocentric map. Participants were able to reach all waypoints in every condition. Results suggest that the participants reached waypoints fastest with the egocentric map. Additionally, participants were slightly faster with the auditory cue than with the vibrotactile cue. Subjective workload and usability questionnaires found that both of these conditions were not mentally demanding and highly usable. These results help support the development of eye-free mobile navigation tools.

Real-time sensory substitution to enable players who are blind to play video games using whole body gestures

Gesture-based interaction adds a new level of immersion to video games, but players who are blind are unable to play them as these games use visual cues to indicate what gesture to provide and when. Though visual cues can be substituted with audio or haptic cues, this often requires access to the source code, which is not attainable for commercial games. We present a solution that uses real-time video analysis to detect the presence of a particular visual cue, which is then substituted with a vibrotactile cue that is provided with an external controller. A user study with 28 sighted participants with a popular commercial gesture based game showed no significant difference in performance between visual and vibrotactile feedback. A follow up study with seven visually impaired participants revealed no significant difference in performance between both groups of users. Both studies demonstrate the feasibility of real-time sensory substitution as a cost-effective approach for making gesture-based video games accessible to players who are blind.

T-Hive: Bilateral Haptic Interface Using Vibrotactile Cues for Presenting Spatial Information

The primary purpose of this research is to determine which is more effective, kinesthetic or vibrotactile cues, when presenting spatial information with haptic devices. Recent studies have explored the use of tactile cues; however, they were confined to a unilateral display device. Although many kinesthetic bilateral haptic devices have been developed to provide force feedback on an input handle, a vibrotactile stimulus has not been utilized when presenting directional information on the input handle. This paper attempts to adopt vibrotactile cues to design a bilateral device. In addition, a new six degrees of freedom bilateral haptic device, which provides a spatial sensation on the handle, is proposed. The sphere-shaped handle is, especially, designed to be covered by several vibrating panels. When a specific panel is activated, the user perceives the spatial location of the vibrotactile stimulus from that panel during the input operation. Control schemes that are based on the phantom sensation, one of haptic illusory phenomena, are proposed to achieve fine resolution with a limited number of tactors. Two experiments were conducted, in an effort to compare performance between a kinesthetic and a vibrotactile haptic device. The results showed that the vibrotactile cue provides a better method of perceiving the directional information as compared with kinesthetic feedback.

Vibrotactile “On-Thigh” Alerting System in the Cockpit

Alerts in the cockpit must be robust, difficult to ignore, and easily recognized. Tactile alerts can provide means to direct the pilot's attention in the already visual-auditory overloaded cockpit environment. This research examined the thigh as a placement for vibrotactile display in the cockpit. The authors (a) report initial findings concerning the loci and properties of the display, (b) evaluate the added value of tactile cuing with respect to the existing audiovisual alerting system, and (c) address the issue of tactile orienting--whether the cue should display "flight" or "fight" orienting. The tactor display prototype was developed by a joint venture of Israel Aerospace Industries, Lahav Division, and the Ben Gurion University of the Negev (patent pending 11/968,405). A vibrotactile display mounted on the thigh provided directional cues in the vertical plane. Two vibrotactile display modes (eight and four tactors) and two response modes (compatible, i.e., fight [toward vibrotactile cue], and inverse, i.e., flight [away from vibrotactile cue]) were evaluated. Vertical directional orienting can be achieved by a vibrotactile display assembled on the thigh. The four-tactor display mode and the compatible response mode produced more accurate results. Tactile cues can provide directional orienting in the vertical plane. The benefit of adding compatible tactile cues compared with visual and auditory cues alone has yet to be reinforced. Nevertheless, fight mode, that is, directing the way to escape from hazardous situations, was preferred. Potential applications include providing directional collision alerts within the vertical plane, assisting pilot's elevation control, or navigation.

Contrasting neuronal activity in supplementary and precentral motor cortex of monkeys. I. Responses to instructions determining motor responses to forthcoming signals of different modalities.

The present report contrasts neuronal activity in two motor cortical fields after instructions that determine which of two sensory signals will trigger a movement and which will not. The goal of the study was to determine possible differential roles of the two cortical fields in the process of preparing to move in response to one external cue and to ignore another. Single-cell recordings were made from the supplementary motor area (SMA) and the precentral motor area (PCM) of monkeys trained to perform key-press movements in two different modes. In the auditory mode, an instruction signal warned the animal to prepare to start the movement promptly in response to a forthcoming 1,000-Hz tone burst (trigger signal), but to remain motionless if the signal was vibrotactile (nontrigger signal). In the tactile mode, the trigger and nontrigger signals were reversed: a different instruction signal warned the animal to prepare to perform the key-press movement in response to the vibrotactile cue, but to withhold it in response to the 1,000-Hz tone. The instruction signals were auditory tones of 300 Hz for the auditory mode and 100 Hz for the tactile mode. Out of 259 task-related SMA neurons, 128 (49%) responded to instructions. Three types of instruction responses were observed: 1) 95 neurons showed continuous instruction-induced activity changes lasting until the occurrence of the movement-triggering signal, regardless of whether an intervening nontrigger signal occurred. 2) 24 neurons showed increased activity until the occurrence of the nontriggering signal, after which the activity subsided. When there was no nontrigger signal, the activity increased during a period when the nontrigger signal might have been given. 3) Nine neurons responded with a transient, short-latency discharge after the instruction. The responses of SMA neurons to two instructions were often different. Forty-four SMA neurons exhibited a selective response to only one of the two instructions. In 43 neurons the response was differential, with the magnitude of activity increase or decrease being at least three times greater after one instruction than the other. In the remaining 41 neurons the response was nondifferential. Out of 112 task-related PCM neurons, 25 (22%) responded to the instructions. In the majority of them (21 neurons), the instruction response was nondifferential.(ABSTRACT TRUNCATED AT 400 WORDS)

Discrimination of Fricatives by Hearing Impaired Children Using A Vibrotactile Cue

An experiment was carried out to determine whether a vibrotactile cue would help profoundly hearing-impaired children discriminate fricative sounds. Ten profoundly hearing-impaired boys were tested under two conditions: (1) audition supplemented by lipreading, and (2) audition and lipreading supplemented by the vibrotactile cue. Speech reception was superior when a tactile cue was provided.