Tactile Motion Research Articles

Peles Macias e Peles Ásperas: as cinco peles de Hundertwasser em conversa com a poética pessoal

This article presents an excerpt from the personal poetic production of the artist João Cóser, selected from the portfolio, and which covers five artistic works created between 2016 and 2020. The analysis of João Cóser's artistic process uses the concepts and symbologies about the skin, as constructed by the Austrian artist Hundertwasser, who defines five levels of coverings or skins for the human being: the epidermis, clothing, the home, the social environment and the global environment. The connections between the chosen poetic production and the works of other artists who deal with corporeality and the senses, such as Ernesto Neto, Chiharu Shiota and Hélio Oiticica, are also explored. The analysis also incorporates the phenomenology of the body, as developed by Merleau-Ponty and other authors who support the research. The tactile movement and manipulation of the object, whether of its visible or invisible materiality, are also addressed as prerogatives of the body.

Effect of Normal Force Intensity on Tactile Motion Speed Perception Based on Spatiotemporal Cue.

While the relative motion between the skin and objects in contact with it is essential to everyday tactile experiences, our understanding of how tactile motion is perceived via human tactile function is limited. Previous studies have explored the effect of normal force on speed perception under conditions where multiple motion cues on the skin (spatiotemporal cue, tangential skin deformation cue, and slip-induced vibration cue) were integrated. However, the effect of the normal force on speed perception in terms of each motion cue remains unclear since the multiple motion cues have not been adequately separated in the previously reported experiments. In this study, we aim to elucidate the effect of normal force in situations where the speed perception of tactile motion is based solely on a spatiotemporal cue. We developed a pin-array display which allowed us to vary the intensity of the normal force without causing tangential forces or slip-induced vibrations. Using the display, we conducted two psychophysical experiments. In Experiment 1, we found that the speed of the object was perceived to be 1.12-1.14 times faster when the intensity of the normal force was doubled. In Experiment 2, we did not observe significant differences in the discriminability of tactile speed caused by differences in normal force intensity. Our experimental results are of scientific significance and offer insights for engineering applications when using haptic displays that can only provide spatiotemporal cues represented by normal forces.

A Novel Tactile Sensing System Utilizing Magnetorheological Structures for Dynamic Contraction and Relaxation Motions.

It is well known that the rheological properties of magnetorheological (MR) material change under a magnetic field. So far, most works on MR materials have been oriented toward actuating characteristics instead of sensing functions. In this work, to realize dynamic tactile motion, a spherical MR structure was designed as a sensor, incorporating a magnetic circuit core to provide maximum dynamic motion. After manufacturing a prototype (sample), a sinusoidal magnetic field of varying exciting frequency and magnitude was applied to the sample, and the dynamic contraction and relaxation motion depending on the exciting magnetic field was observed. Among the test results, when 10% deformation occurred, the instantaneous force generated was from 2.8 N to 8.8 N, and the force when relaxed was from 1.2 N to 3.5 N. It is also shown that the repulsive force within this range can be implemented using an acceptable input current. The special tactile sensing structure proposed in this work can be used as a sensor to measure the field-dependent viscoelastic properties of human tissues such as stomach, liver, and overall body. In addition, it could be usefully applied to robot surgery, because it can mimic the dynamic motions of various human organs under various surgical conditions.

The hands’ default location guides tactile spatial selectivity

Our skin is a two-dimensional sheet that can be folded into a multitude of configurations due to the mobility of our body parts. Parts of the human tactile system might account for this flexibility by being tuned to locations in the world rather than on the skin. Using adaptation, we scrutinized the spatial selectivity of two tactile perceptual mechanisms for which the visual equivalents have been reported to be selective in world coordinates: tactile motion and the duration of tactile events. Participants' hand position-uncrossed or crossed-as well as the stimulated hand varied independently across adaptation and test phases. This design distinguished among somatotopic selectivity for locations on the skin and spatiotopic selectivity for locations in the environment, but also tested spatial selectivity that fits neither of these classical reference frames and is based on the default position of the hands. For both features, adaptation consistently affected subsequent tactile perception at the adapted hand, reflecting skin-bound spatial selectivity. Yet, tactile motion and temporal adaptation also transferred across hands but only if the hands were crossed during the adaptation phase, that is, when one hand was placed at the other hand's typical location. Thus, selectivity for locations in the world was based on default rather than online sensory information about the location of the hands. These results challenge the prevalent dichotomy of somatotopic and spatiotopic selectivity and suggest that prior information about the hands' default position -right hand at the right side-is embedded deep in the tactile sensory system.

"I see where this is going": a psychophysical study of directional mid-air haptics and apparent tactile motion.

Mid-air haptic technology can render a plethora of tactile sensations including points, lines, shapes, and textures. To do so, one requires increasingly complex haptic displays. Meanwhile, tactile illusions have had widespread success in the development of contact and wearable haptic displays. In this article, we exploit the apparent tactile motion illusion to display mid-air haptic directional lines; a prerequisite for the rendering of shapes and icons. We present two pilot studies and a psychophysical study that contrasts a dynamic tactile pointer (DTP) to an apparent tactile pointer (ATP) in terms of direction recognition. To that end, we identify optimal duration and direction parameters for both DTP and ATP mid-air haptic lines and discuss the implications of our findings with respect to haptic feedback design, and device complexity.

Cognitive Grasping and Manipulation of Unknown Object with Control Grip Force using Cyber Physical System Approach

Service robots working in human environments must have the ability to grasp a wide variety of unseen objects with ability to grasp a wide variety of unseen objects with appropriate grip force without knowing their properties and its response to action in a human environment. This research uses a novel Cyber Physical System framework to estimate and apply minimum grasping force for unknown objects under a task motion using only tactile motion data captured from sensor-less acceleration-based controlled common gripper. The goal is to use this novel framework for developing functions for position-controlled robots to perform real-time cognitive grasping and enable quick implementation across multiple robots. This paper uses soft sensing inputs from the earlier research to characterize unknown object properties like stiffness, mass and surface interaction and show how a data-based analytics algorithm learns a wide range of object properties and slip status along with task action dynamics features, to propose the grasping action with minimum applied force. We validated that the minimum grasping force is able to hold the object firmly during any task motion. In order to improve the learning, the paper proposes a part of the framework to use virtual simulation to gather more learning data and show results that compare well between simulated results with experimental data. We use the simulated data to train Reinforcement Learning approach and show that small variation in object width can be learnt to identify optimum gripping position.

Selective Enhancement of Post-Sleep Visual Motion Perception by Repetitive Tactile Stimulation during Sleep.

Tactile sensations can bias visual perception in the awake state while visual sensitivity is known to be facilitated by sleep. It remains unknown, however, whether the tactile sensation during sleep can bias the visual improvement after sleep. Here, we performed nap experiments in human participants (n = 56, 18 males, 38 females) to demonstrate that repetitive tactile motion stimulation on the fingertip during slow wave sleep selectively enhanced subsequent visual motion detection. The visual improvement was associated with slow wave activity. The high activation at the high beta frequency was found in the occipital electrodes after the tactile motion stimulation during sleep, indicating a visual-tactile cross-modal interaction during sleep. Furthermore, a second experiment (n = 14, 14 females) to examine whether a hand- or head-centered coordination is dominant for the interpretation of tactile motion direction showed that the biasing effect on visual improvement occurs according to the hand-centered coordination. These results suggest that tactile information can be interpreted during sleep, and can induce the selective improvement of post-sleep visual motion detection.SIGNIFICANCE STATEMENT Tactile sensations can bias our visual perception as a form of cross-modal interaction. However, it was reported only in the awake state. Here we show that repetitive directional tactile motion stimulation on the fingertip during slow wave sleep selectively enhanced subsequent visual motion perception. Moreover, the visual improvement was positively associated with sleep slow wave activity. The tactile motion stimulation during slow wave activity increased the activation at the high beta frequency over the occipital electrodes. The visual improvement occurred in agreement with a hand-centered reference frame. These results suggest that our sleeping brain can interpret tactile information based on a hand-centered reference frame, which can cause the sleep-dependent improvement of visual motion detection.

Multidigit tactile perception I: motion integration benefits for tactile trajectories presented bimanually.

Interactions with objects involve simultaneous contact with multiple, not necessarily adjacent, skin regions. Although advances have been made in understanding the capacity to selectively attend to a single tactile element among distracting stimulations, here, we examine how multiple stimulus elements are explicitly integrated into an overall tactile percept. Across four experiments, participants averaged the direction of two simultaneous tactile motion trajectories of varying discrepancy delivered to different fingerpads. Averaging performance differed between within- and between-hands conditions in terms of sensitivity and precision but was unaffected by somatotopic proximity between stimulated fingers. First, precision was greater in between-hand compared with within-hand conditions, demonstrating a bimanual perceptual advantage in multi-touch integration. Second, sensitivity to the average direction was influenced by the discrepancy between individual motion signals, but only for within-hand conditions. Overall, our experiments identify key factors that influence perception of simultaneous tactile events. In particular, we show that multi-touch integration is constrained by hand-specific rather than digit-specific mechanisms.NEW & NOTEWORTHY Object manipulation involves encoding spatially and temporally extended tactile signals, yet most studies emphasize minimal units of tactile perception (e.g., selectivity). Instead, we asked participants to average two tactile motion trajectories delivered simultaneously to two different fingerpads. Our results show strong integration between multiple tactile inputs, but subject to limitations for inputs delivered within a hand. As such, the present study establishes a paradigm for studying unified experience of touch despite distinct stimulus elements.

Direction-selective modulation of visual motion rivalry by collocated tactile motion

Early models of multisensory integration posited that cross-modal signals only converged in higher-order association cortices and that vision automatically dominates. However, recent studies have challenged this view. In this study, the significance of the alignment of motion axes and spatial alignment across visual and tactile stimuli, as well as the effect of hand visibility on visuo-tactile interactions were examined. Using binocular rivalry, opposed motions were presented to each eye and participants were required to track the perceived visual direction. A tactile motion that was either a leftward or rightward sweep across the fingerpad was intermittently presented. Results showed that tactile effects on visual percepts were dependent on the alignment of motion axes: rivalry between up/down visual motions was not modulated at all by left/right tactile motion. On the other hand, visual percepts could be altered by tactile motion signals when both modalities shared a common axis of motion: a tactile stimulus could maintain the dominance duration of a congruent visual stimulus and shorten its suppression period. The effects were also conditional on the spatial alignment of the visual and tactile stimuli, being eliminated when the tactile device was displaced 15 cm away to the right of the visual stimulus. In contrast, visibility of the hand touching the tactile stimulus facilitated congruent switches relative to a visual-only baseline but did not present a significant advantage overall. In sum, these results show a low-level sensory interaction that is conditional on visual and tactile stimuli sharing a common motion axis and location in space.

Interplay of tactile and motor information in constructing spatial self-perception

During active movement, there is normally a tight relation between motor command and sensory representation about the resulting spatial displacement of the body. Indeed, some theories of space perception emphasize the topographic layout of sensory receptor surfaces, while others emphasize implicit spatial information provided by the intensity of motor command signals. To identify which has the primary role in spatial perception, we developed experiments based on everyday self-touch, in which the right hand strokes the left arm. We used a robot-mediated form of self-touch to decouple the spatial extent of active or passive right hand movements from their tactile consequences. Participants made active movements of the right hand between unpredictable, haptically defined start and stop positions, or the hand was passively moved between the same positions. These movements caused a stroking tactile motion by a brush along the left forearm, with minimal delay, but with an unpredictable spatial gain factor. Participants judged the spatial extent of either the right hand's movement, or of the resulting tactile stimulation to their left forearm. Across five experiments, we found that movement extent strongly interfered with tactile extent perception, and vice versa. Crucially, interference in both directions was stronger during active than passive movements. Thus, voluntary motor commands produced stronger integration of multiple sensorimotor signals underpinning the perception of personal space. Our results prompt a reappraisal of classical theories that reduce space perception to motor command information.

Illusory tactile movement crosses arms and legs and is coded in external space

Humans often misjudge where on the body a touch occurred. Theoretical accounts have ascribed such misperceptions to local interactions in peripheral and primary somatosensory neurons, positing that spatial-perceptual mechanisms adhere to limb boundaries and skin layout. Yet, perception often reflects integration of sensory signals with prior experience. On their trajectories, objects often touch multiple limbs; therefore, body–environment interactions should manifest in perceptual mechanisms that reflect external space.Here, we demonstrate that humans perceived the cutaneous rabbit illusion – the percept of multiple identical stimuli as hopping across the skin – along the Euclidian trajectory between stimuli on two body parts and regularly mislocalized stimuli from one limb to the other. A Bayesian model based on Euclidian, as opposed to anatomical, distance faithfully reproduced key aspects of participants' localization behavior.Our results suggest that prior experience of touch in space critically shapes tactile spatial perception and illusions beyond anatomical organization.

Identification of unknown object properties based on tactile motion sequence using 2-finger gripper robot

The purpose of service robots is to work and handle a wide range of objects in a human environment. Therefore, they must have the ability to grasp unknown objects with the appropriate force, by dynamically identifying their stiffness, mass, and surface-interaction properties. To ensure the successful grasping of unknown objects, it is significant to estimate the object response properties. In this paper, the cognitive functions to efficiently perform such operations with only tactile motion data and supervised learning using limited data, have been demonstrated. The study uses pinch-grasping performed by a 2-fingered robot experimental setup with a pre-designed motion sequence, over 7 different objects having a wide range of properties to capture the motion data. The proposed approach avails pre-processed motion data to train neural networks for accurately predicting object response properties for 3 unseen test objects. We have done a comparative study among three neural network architectures CNN, LSTM, and CNN-LSTM and we found that novel CNN-LSTM outperforms the other two models in terms of accuracy. The CNN-LSTM regression model achieves 0.98 and 0.97 of R2 value for the prediction of stiffness and mass, respectively and the CNN classification model achieves 94% of accuracy for the surface interaction classification.

A new patterned air-flow device to reveal the network for tactile motion coding using fMRI

BackgroundStudying brain processes underlying tactile perception induced by natural-like stimulation is challenging yet crucial to closely match real-world situations. New methodWe developed a computer-controlled pneumatic device that allows the delivery of complex airflow patterns on subject’s body, through a MR-compatible system fixed on an independent clippable mounting device. The intensity of stimulation as well as the timing of each of the four air channels are completely programmable and independent, allowing the precise control and modularity of the airflow delivery. ResultsAn analysis of signal-to-noise ratio (SNR) measurements did not show any impact of the PAF device on anatomical or functional scan acquisitions. A psychophysical experiment was also performed on 24 volunteers to evaluate the perception of different airflow patterns delivered over the lower part of their face. It revealed that all participants were able to finely discriminate the direction of these leftward to rightward flow motions. The fMRI experiment, which consisted in presenting to 20 participants four different airflow patterns, shed light on the brain network associated with tactile motion perception. A multivariate analysis further showed a specific coding of the different patterns inside this tactile brain network including the primary and secondary somatosensory cortex Comparison with existing method(s)The Patterned Air-Flow (PAF) is an easy-to-set-up, portable, adaptable device, which can be spatially and temporally modulated to provide complex tactile stimuli. ConclusionsThis device will be useful to further explore complex dynamic touch exerted over various body parts and can also be combined with visual or auditory stimulation to study multisensory mechanisms.

Visual pursuit biases tactile velocity perception.

During a smooth pursuit eye movement of a target stimulus, a briefly flashed stationary background appears to move in the opposite direction as the eye's motion-an effect known as the Filehne illusion. Similar illusions occur in audition, in the vestibular system, and in touch. Recently, we found that the movement of a surface perceived from tactile slip was biased if this surface was sensed with the moving hand. The analogy between these two illusions suggests similar mechanisms of motion processing between the vision and touch. In the present study, we further assessed the interplay between these two sensory channels by investigating a novel paradigm that associated an eye pursuit of a visual target with a tactile motion over the skin of the fingertip. We showed that smooth pursuit eye movements can bias the perceived direction of motion in touch. Similarly to the classical report from the Filehne illusion in vision, a static tactile surface was perceived as moving rightward with a leftward eye pursuit movement, and vice versa. However, this time the direction of surface motion was perceived from touch. The biasing effects of eye pursuit on tactile motion were modulated by the reliability of the tactile and visual stimuli, consistently with a Bayesian model of motion perception. Overall, these results support a modality- and effector-independent process with common representations for motion perception.NEW & NOTEWORTHY The study showed that smooth pursuit eye movement produces a bias in tactile motion perception. This phenomenon is modulated by the reliability of the tactile estimate and by the presence of a visual background, in line with the predictions of the Bayesian framework of motion perception. Overall, these results support the hypothesis of shared representations for motion perception.

Sexual Not Sexualized: Remembering Black Girlhood Using Tactile Motion

Abstract Black girls live at the nexus of anti-Black racism, heteronormative patriarchy, and capitalism. They are placed in binaries of silent/loud, obedient/disruptive, and sexual/asexual. This research intends to nuance these binaries by integrating creative technologies to capture how affect and tactile motion can describe the full complexities of Black girlhood lived reality. This study explores how Black girl youth ages 18-21 in the southeastern United States affectively interpret their sexuality using tactile braiding of plastic lanyard string to remember their girlhood. It is necessary to locate the ways sexual agency and affirmation manifest when examining the aspects that encroach upon Black girls’ understanding of their bodies, personhood, and sexuality. Stretching how research understands and articulates the everyday lives and sexual embodiments of Black girls, this experimental study seeks to affirm and nuance conversation of sexuality through creative methodology to feel, remember, and explore the dimensions of Black girlhood through the sense of touch.

Performance Assessment Through Motion Literation to Assess The Motoric Skill of Junior High School Students Based on Laban Notation

Motor skills integrate physical functions and coordination between the brain as a center for information and control through visual activities (reading) and tactile (writing) movement symbols. Symbols and motion codes are found in labanotation, so the ability to read symbols and write symbol patterns is called motion literacy. It can be done through continuous assessment continuously in an effort to diagnose their abilities. The results of the study describe a change in the condition of students’ motor skills after intervention through labanotation-based motion literacy work assessment, namely the change in conditions from the intervention condition (B) to the final baseline condition (A’) decreases the students’ adaptability. However, at the final baseline condition (A’), the motor ability score improved better than in the phase before baseline (A). The total average score obtained in this condition was 62.86%. Thus it can be concluded that the effect of performance appraisal through motion literacy provides benefits for improving brain function because structured and programmed motion exercises are useful in stimulating various learning centers in the brain. This also impacts on improving motor skills in students to undergo the learning process at a later stage.

Directional biases in whole hand motion perception revealed by mid-air tactile stimulation

Many emerging technologies are attempting to leverage the tactile domain to convey complex spatiotemporal information translated directly from the visual domain, such as shape and motion. Despite the intuitive appeal of touch for communication, we do not know to what extent the hand can substitute for the retina in this way. Here we ask whether the tactile system can be used to perceive complex whole hand motion stimuli, and whether it exhibits the same kind of established perceptual biases as reported in the visual domain. Using ultrasound stimulation, we were able to project complex moving dot percepts onto the palm in mid-air, over 30 cm above an emitter device. We generated dot kinetogram stimuli involving motion in three different directional axes (‘Horizontal’, ‘Vertical’, and ‘Oblique’) on the ventral surface of the hand. Using Bayesian statistics, we found clear evidence that participants were able to discriminate tactile motion direction. Furthermore, there was a marked directional bias in motion perception: participants were both better and more confident at discriminating motion in the vertical and horizontal axes of the hand, compared to those stimuli moving obliquely. This pattern directly mirrors the perceptional biases that have been robustly reported in the visual field, termed the ‘Oblique Effect’. These data demonstrate the existence of biases in motion perception that transcend sensory modality. Furthermore, we extend the Oblique Effect to a whole hand scale, using motion stimuli presented on the broad and relatively low acuity surface of the palm, away from the densely innervated and much studied fingertips. These findings highlight targeted ultrasound stimulation as a versatile method to convey potentially complex spatial and temporal information without the need for a user to wear or touch a device.

Motion Direction Discrimination with Tactile Random-Dot Kinematograms.

Motion detection is a fundamental sensory function for multiple modalities, including touch, but the mechanisms underlying tactile motion detection are not well understood. While previous findings supported the existence of high-level feature tracking, it remains unclear whether there also exist low-level motion sensing that directly detects a local spatio-temporal correlation in the skin-stimulation pattern. To elucidate this mechanism, we presented, on braille displays, tactile random-dot kinematograms, similar to those widely used in visual motion research, which enables us to independently manipulate feature trackability and various parameters of local motion. We found that a human observer is able to detect the direction of difficult-to-track tactile motions presented to the fingers and palms. In addition, the direction-discrimination performance was better when the stimuli were presented along the fingers than when presented across the fingers. These results indicate that low-level motion sensing, in addition to high-level tracking, contribute to tactile motion perception.

Cross-modal motion aftereffects transfer between vision and touch in early deaf adults

Previous research on early deafness has primarily focused on the behavioral and neural changes in the intact visual and tactile modalities. However, how early deafness changes the interplay of these two modalities is not well understood. In the current study, we investigated the effect of auditory deprivation on visuo-tactile interaction by measuring the cross-modal motion aftereffect. Consistent with previous findings, motion aftereffect transferred between vision and touch in a bidirectional manner in hearing participants. However, for deaf participants, the cross-modal transfer occurred only in the tactile-to-visual direction but not in the visual-to-tactile direction. This unidirectional cross-modal motion aftereffect found in the deaf participants could not be explained by unisensory motion aftereffect or discrimination threshold. The results suggest a reduced visual influence on tactile motion perception in early deaf individuals.

Anisotropic Psychophysical Trends in the Discrimination of Tactile Direction in a Precision Grip.

Tactile cues arising from interactions with objects have a sense of directionality which affects grasp. Low latency responses to varied grip perturbations indicate that grasp safety margins are exaggerated in certain directions and conditions. In a grip with the ulnar-radial axis vertical, evidence suggests that distal and downward directions are more sensitive to task parameters and have larger safety margins. This suggests that, for the purpose of applying forces with the fingers, reference frames with respect to the hand and gravity are both in operation. In this experiment, we examined human sensitivities to the direction of tactile movement in the context of precision grip in orientations either orthogonal to or parallel to gravity. Subjects performed a two-alternative-forced-choice task involving a textured cube which moved orthogonal to their grip axis. Subjects’ arms were placed in a brace that allowed for finger movement but minimized arm movement. Movement of thumb and index joints were monitored via PhaseSpace motion capture. The subject was presented with a textured cube and instructed to lightly grasp the cube, as if it were slipping. In each trial the object was first translated 1 cm in 0° (proximal), 90° (radial), 180° (distal), or 270° (ulnar) and returned to its origin. This primary stimulus was immediately followed by a 10 mm secondary stimulus at a random 5° interval between −30° and 30° of the primary stimulus. Response from the subject after each pair of stimuli indicated whether the test direction felt the same as or different from the primary stimulus. Traditional bias and sensitivity analyses did not provide conclusive results but suggested that performance is best in the ulnar-radial axis regardless of gravity. Modeling of the response curve generated a detection threshold for each primary stimulus. Lower thresholds, indicating improved detection, persisted in the ulnar-radial axis. Anisotropic thresholds of increased detection appear to coincide with digit displacement and appear to be independent of the grasp orientation.