Audio-visual multisensory integration and haptic perception are altered in adults with developmental coordination disorder.

Developmental Coordination Disorder (DCD) is a movement disorder in which atypical sensory processing may underly movement atypicality. However, whether altered sensory processing is domain-specific or global in nature, are unanswered questions. Here, we measured for the first time, different aspects of sensory processing and spatiotemporal integration in the same cohort of adult participants with DCD (N = 16), possible DCD (pDCD, N = 12) and neurotypical adults (NT, N = 28). Haptic perception was reduced in both DCD and the extended DCD + pDCD groups when compared to NT adults. Audio-visual integration, measured using the sound-induced double flash illusion, was reduced only in DCD participants, and not the DCD + pDCD extended group. While low-level sensory processing was altered in DCD, the more cognitive, higher-level ability to infer temporal dimensions from spatial information, and vice-versa, as assessed with Tau-Kappa effects, was intact in DCD (and extended DCD + pDCD) participants. Both audio-visual integration and haptic perception difficulties correlated with the degree of self-reported DCD symptoms and were most apparent when comparing DCD and NT groups directly, instead of the expanded DCD + pDCD group. The association of sensory difficulties with DCD symptoms suggests that perceptual differences play a role in motor difficulties in DCD via an underlying internal modelling mechanism.

Objects drawn from haptic perception and vision-based spatial abilities.

Haptic perception is used in the anatomy laboratory with the handling of three-dimensional (3D) prosections, dissections, and synthetic models of anatomical structures. Vision-based spatial ability has been found to correlate with performance on tests of 3D anatomy knowledge in previous studies. The objective was to explore whether haptic-based spatial ability was correlated with vision-based spatial ability. Vision-based spatial ability was measured in a study group of 49 medical graduates with three separate tests: a redrawn Vandenberg and Kuse Mental Rotations Tests in two (MRT A) and three (MRT C) dimensions and a Surface Development Test (SDT). Haptic-based spatial ability was measured using 18 different objects constructed from 10 cubes glued together. Participants were asked to draw these objects from blind haptic perception, and drawings were scored by two independent judges. The maximum score was 24 for each of MRT A and MRT C, 60 for SDT, and 18 for the drawings. The drawing score based on haptic perception [median = 17 (lower quartile = 16, upper quartile = 18)] correlated with MRT A [14 (9, 17)], MRT C [9 (7, 12)] and SDT [44 (36, 52)] scores with a Spearman's rank correlation coefficient of 0.395 (p = 0.0049), 0.507 (p = 0.0002) and 0.606 (p < 0.0001), respectively. Spatial abilities assessed by vision-based tests were correlated with a drawing score based on haptic perception of objects. Future research should investigate the contribution of haptic-based and vision-based spatial abilities on learning 3D anatomy from physical models.

Can Facial Expressions Induce Haptic Perception?

A key challenge in haptics is designing human-human communications involving touch to facilitate positive effects on social interactions. An important consideration in designing social touch is understanding the effect of social stimuli on perception, in addition to that of a physical stimulus, because social touch always involves a partner. This study presents an experiment to demonstrate that facial expressions induce haptic perception. We developed a human-agent interaction system on a display in which participants moved the mouse cursor to click the target icon while the agent behaved as if it pulled the cursor back in the opposite direction, showing either a negative or neutral face. The perceived force during the interaction was quantified by the control display ratio using a psychophysical approach. The results show that the negative face induced a significantly greater perceived force than the neutral face. In addition, the perceived force correlated with the individual's evaluation of the facial expression; that is, the more unpleasant or aroused they perceived the facial expression to be, the more force they perceived. This study sheds light on the design of social touch performed by people who have physical or mediated contact with each other in physical space or cyberspace.

Investigating the Haptic Perception of Directional Information Within a Handle.

This paper studies the perception of 2-dimensional directional cues presented on a hand-held tangible interface that resembles a cylindrical handle. The tangible interface is designed to be comfortably held with one hand and houses five custom electromagnetic actuators composed of coils as stators and magnets as movers. We carried out a human subjects experiment enrolling 24 participants, analysing the recognition rate of directional cues using the actuators either to vibrate or tap in sequence across the user's palm. Results show an impact of the positioning/holding of the handle, the mode of stimulation, and the directional indication sent via the handle. There was also a correlation between the score and the confidence of the participants, showing that participants are more confident when recognising vibration patterns. Overall, results supported the potential of the haptic handle to provide accurate guidance, with recognition rates higher than 70 % in all conditions and higher than 75 % in the precane and power wheelchair configurations.

Emerging MXene-Based Flexible Tactile Sensors for Health Monitoring and Haptic Perception.

Due to their potential applications in physiological monitoring, diagnosis, human prosthetics, haptic perception, and human-machine interaction, flexible tactile sensors have attracted wide research interest in recent years. Thanks to the advances in material engineering, high performance flexible tactile sensors have been obtained. Among the representative pressure sensing materials, 2D layered nanomaterials have many properties that are superior to those of bulk nanomaterials and are more suitable for high performance flexible sensors. As a class of 2D inorganic compounds in materials science, MXene has excellent electrical, mechanical, and biological compatibility. MXene-based composites have proven to be promising candidates for flexible tactile sensors due to their excellent stretchability and metallic conductivity. Therefore, great efforts have been devoted to the development of MXene-based composites for flexible sensor applications. In this paper, the controllable preparation and characterization of MXene are introduced. Then, the recent progresses on fabrication strategies, operating mechanisms, and device performance of MXene composite-based flexible tactile sensors, including flexible piezoresistive sensors, capacitive sensors, piezoelectric sensors, triboelectric sensors are reviewed. After that, the applications of MXene material-based flexible electronics in human motion monitoring, healthcare, prosthetics, and artificial intelligence are discussed. Finally, the challenges and perspectives for MXene-based tactile sensors are summarized.

A horizon for haptic perception.

The spatial limits of sensory acquisition (its sensory horizon) are a fundamental property of any sensorimotor system. In the present study, we sought to determine whether there is a sensory horizon for the human haptic modality. At first blush, it seems obvious that the haptic system is bounded by the space where the body can interact with the environment (e.g., the arm span). However, the human somatosensory system is exquisitely tuned to sensing with tools-blind-cane navigation being a classic example of this. The horizon of haptic perception therefore extends beyond body space, but to what extent is unknown. We first used neuromechanical modeling to determine the theoretical horizon, which we pinpointed as 6 m. We then used a psychophysical localization paradigm to behaviorally confirm that humans can haptically localize objects using a 6-m rod. This finding underscores the incredible flexibility of the brain's sensorimotor representations, as they can be adapted to sense an object many times longer than the user's own body.NEW & NOTEWORTHY There are often spatial limits to where an active sensory system can sample information from the environment. Hand-held tools can extend human haptic perception beyond the body, but the limits of this extension are unknown. We used theoretical modeling and psychophysics to determine these spatial limits. We find that the ability to spatially localize objects through a tool extends at least 6 m beyond the user's body.

Physically interacting humans regulate muscle coactivation to improve visuo-haptic perception.

When moving a piano or dancing tango with a partner, how should I control my arm muscles to sense their movements and follow or guide them smoothly? Here we observe how physically connected pairs tracking a moving target with the arm modify muscle coactivation with their visual acuity and the partner's performance. They coactivate muscles to stiffen the arm when the partner's performance is worse and relax with blurry visual feedback. Computational modeling shows that this adaptive sensing property cannot be explained by the minimization of movement error hypothesis that has previously explained adaptation in dynamic environments. Instead, individuals skillfully control the stiffness to guide the arm toward the planned motion while minimizing effort and extracting useful information from the partner's movement. The central nervous system regulates muscle activation to guide motion with accurate task information from vision and haptics while minimizing the metabolic cost. As a consequence, the partner with the most accurate target information leads the movement.NEW & NOTEWORTHY Our results reveal that interacting humans inconspicuously modulate muscle activation to extract accurate information about the common target while considering their own and the partner's sensorimotor noise. A novel computational model was developed to decipher the underlying mechanism: muscle coactivation is adapted to combine haptic information from the interaction with the partner and own visual information in a stochastically optimal manner. This improves the prediction of the target position with minimal metabolic cost in each partner, resulting in the lead of the partner with the most accurate visual information.

Not only motor skill performance but also haptic function is impaired in children with developmental language disorder.

BACKGROUND: Previous studies have found an association between motor immaturity and developmental language impairment in children. However, systematic investigations of somatosensory dysfunctions that might be linked to motor deficits in children with developmental language disorder (DLD) are lacking. AIMS: Examined haptic perception and motor skills in school-age children with DLD and typically-developing (TD) children. METHODS: Sixteen children with DLD and sixteen age-matched TD children performed a curvature detection task measuring haptic sensitivity and a curvature discrimination task measuring haptic acuity. The Movement Assessment Battery for Children, 2nd edition (MABC-2) was also conducted to evaluate children's motor ability. RESULTS: The results revealed elevated thresholds of both haptic detection (67.5%) and haptic discrimination (67.9%) in the DLD group when compared to the TD group. In addition, the children with DLD performed significantly less well on the manual dexterity of MABC-2. Finally, a lower haptic acuity was associated with poorer manual dexterity scores of MABC-2. CONCLUSIONS: This study demonstrates for the first time that not only motor skills, but also haptic function is altered in children with DLD. The observed association between manual dexterity and haptic acuity suggests a close relationship between haptic and motor skills in school-age children.

Neural Correlates of Oral Stereognosis-An fMRI Study.

Oral stereognosis is the ability to recognize, discriminate and localize a bolus in the oral cavity. Clinical observation indicates deficits in oral stereognosis in patients with vascular or neurodegenerative diseases particularly affecting the parietal lobes. However, the precise neural representation of oral stereognosis remains unclear whereas the neural network of manual stereognosis has already been identified. We hypothesize that oral and manual stereognosis share common neuronal substrates whilst also showing somatotopic distribution. Functional magnetic resonance images (fMRI; Siemens Prisma 3 T) from 20 healthy right-handed participants (11 female; mean age 25.7 years) using a cross-modal task of oral and manual spatial object manipulation were acquired. Data were analyzed using FSL software using a block design and standard analytical and statistical procedures. A conjunction analysis targeted the common neuronal substrate for stereognosis. Activations associated with manual and oral stereognosis were found in partially overlapping fronto-parietal networks in a somatotopic fashion, where oral stereognosis is located caudally from manual stereognosis. A significant overlap was seen in the left anterior intraparietal sulcus. Additionally, cerebellar activations were shown particularly for the oral condition. Spatial arrangement of shaped boli in the oral cavity is associated with neuronal activity in fronto-parietal networks and the cerebellum. These findings have significant implications for clinical diagnostics and management of patients with lesions or atrophy in parietal lobule (e.g. Alzheimer's disease, stroke). More studies are required to investigate the clinical effect of damage to these areas, such as loss of oral stereognosis or an impaired oral phase.

Haptic perception using optoelectronic robotic flesh for embodied artificially intelligent agents.

Flesh encodes a variety of haptic information including deformation, temperature, vibration, and damage stimuli using a multisensory array of mechanoreceptors distributed on the surface of the human body. Currently, soft sensors are capable of detecting some haptic stimuli, but whole-body multimodal perception at scales similar to a human adult (surface area ~17,000 square centimeters) is still a challenge in artificially intelligent agents due to the lack of encoding. This encoding is needed to reduce the wiring required to send the vast amount of information transmitted to the processor. We created a robotic flesh that could be further developed for use in these agents. This engineered flesh is an optical, elastomeric matrix "innervated" with stretchable lightguides that encodes haptic stimuli into light: temperature into wavelength due to thermochromic dyes and forces into intensity due to mechanical deformation. By exploiting the optical properties of the constitutive materials and using machine learning, we infer spatiotemporal, haptic information from light that is read by an image sensor. We demonstrate the capabilities of our system in various assemblies to estimate temperature, contact location, normal and shear force, gestures, and damage from temporal snapshots of light coming from the entire haptic sensor with errors <5%.

Síndrome de la mano inútil con astereognosia secundaria a un astrocitoma cervical / Useless hand syndrome with astereognosis secondary to a cervical astrocytoma

Resumen El presente caso es un ejemplo del síndrome de la mano inútil de Oppenheim secundario a un astrocitoma cervical alto. La pérdida sensorial propioceptiva y discriminativa suspendida con conservación de la termoalgesia y el tacto crudo en ambas extremidades superiores es secundaria al daño a la entrada de la raíz dorsal y al núcleo cuneiforme. La torpeza y las dificultades para una prensión precisa con la mano se deben al daño del núcleo proprioespinal en las astas dorsales a nivel C3-C4. Este núcleo integra influencias excitadoras descendentes del tracto corticoespinal e interneuronas inhibitorias controladas por los sistemas descendentes y las aferencias de las extremidades anteriores. Probablemente la pérdida de las aferentes cervicales propioceptivas inhibitorias sea la culpable de las dificultades para agarrar con las manos.

The present case is an example of the useless hand syndrome of Oppenheim secondary to a high cervical astrocytoma. The suspended proprioceptive and discriminative sensory loss with conservation of thermoalgesia and crude touch in both upper extremities is secondary to damage to dorsal root entry and cuneate nucleus. The clumsiness and difficulties in precise grasping with the hand are due to damage of the propriospinal nucleus in the dorsal horns at C3-C4 level. This nucleus integrates descending excitatory influences from corticospinal tract and inhibitory interneurons controlled by descending systems and the forelimb afferents. Probably the loss of the inhibitory proprioceptive cervical afferents is the culprit of the difficulties in grasping by the hands.

Global surface features contribute to human haptic roughness estimations.

Previous studies have paid special attention to the relationship between local features (e.g., raised dots) and human roughness perception. However, the relationship between global features (e.g., curved surface) and haptic roughness perception is still unclear. In the present study, a series of roughness estimation experiments was performed to investigate how global features affect human roughness perception. In each experiment, participants were asked to estimate the roughness of a series of haptic stimuli that combined local features (raised dots) and global features (sinusoidal-like curves). Experiments were designed to reveal whether global features changed their haptic roughness estimation. Furthermore, the present study tested whether the exploration method (direct, indirect, and static) changed haptic roughness estimations and examined the contribution of global features to roughness estimations. The results showed that sinusoidal-like curved surfaces with small periods were perceived to be rougher than those with large periods, while the direction of finger movement and indirect exploration did not change this phenomenon. Furthermore, the influence of global features on roughness was modulated by local features, regardless of whether raised-dot surfaces or smooth surfaces were used. Taken together, these findings suggested that an object's global features contribute to haptic roughness perceptions, while local features change the weight of the contribution that global features make to haptic roughness perceptions.

Effect of Tactile Masking on Multi-Sensory Haptic Perception.

Multi-sensory wearable haptic devices are able to encode a variety of information using multiple haptic cues. However, simultaneous cues can be misperceived due to tactile masking effects. In this paper, we investigate the effect of masking on the perception of skin stretch and squeeze. We performed three experiments measuring the just-noticeable difference (JND) and the absolute threshold of skin stretch and squeeze alone and in the presence of simultaneous haptic cues. Additionally, we investigate the relative perceptual amplitudes of these haptic cues. Results indicate that the JND for a skin stretch cue increases with a masking squeeze cue, while the JND for a squeeze cue does not change with a masking stretch cue. Also, masking has a significant effect on the absolute threshold of both skin stretch and squeeze. These results suggest that the effect of masking diminishes as haptic cues become larger in amplitude. The results from the subjective equality experiment suggest a potential nonlinear relationship between perceptual magnitudes. Further testing should be carried out to investigate this relationship. Future multi-sensory devices can use these perceptual experiment findings to ensure the delivery of salient cues to users.

Isolated post-traumatic astereognosis: a case-based review.

INTRODUCTION: Astereognosis is the tactile inability to recognize objects placed in the palms by touch with the eyes closed or blind-folded in the presence of intact primary sensory modalities. Stereognosis is usually considered a function of the contralateral sensory cerebral cortex. However, lesions of several anatomic areas and pathologic entities have been reported to be associated with astereognosis. Only two previous reports linked traumatic injury to isolated astereognosis: following surgical evacuation of traumatic parietal extradural hematoma and following bullet injury in the neck in 1992 and 1919, respectively. METHODS AND RESULTS: All the pertinent literature was analyzed, focusing on the relevant definitions, clinical spectra, pathoanatomical processes, assessment, management, and outcomes of astereognosis. Also, an illustrative case was presented. The case highlights isolated post-traumatic left hand astereognosis in a 17-year-old boy following a blunt trauma to the head which resulted in a non-hemorrhagic contusion of the right post-central gyrus. CONCLUSIONS: Post-traumatic isolated astereognosis is a rare and probably underreported sequel of traumatic brain injury. Neurosurgeons need to be more sensitive to the assessment and detection of subtle stereognostic deficits in general and in trauma patients in particular. Other anatomical areas, in addition to the contralateral post-central gyrus, may be considered in the pathogenesis of astereognosis with the involvement of the dorsal column medial lemniscus tract such as the brainstem, foramen magnum, and the cervical spinal cord. To the best of our knowledge, this rare case report is considered the second report on astereognosis following head trauma, and the third report on astereognosis following trauma in general.

Validation of Spanish Erasmus-Modified Nottingham Sensory Assessment Stereognosis Scale in Acquired Brain Damage.

Acquired brain injury (ABI) is the third leading cause of death in Spain. The disability derived from ABI can include considerable difficulties in upper-limb use due to somatosensory deficits. One of the assessments most commonly used to evaluate ABI is the Nottingham Sensory Assessment (NSA); however, there is no complete psychometric analysis or standardized version in Spanish. We aimed to develop and validate a Spanish version of the stereognosis component of the NSA for evaluating Spanish adults with ABI via a single-center, observational, cross-sectional study. The Spanish version of the NSA was developed in two steps. The first was based on the standardization and collection of normative data in 120 asymptomatic participants. For the second, we recruited 25 participants with ABI to establish concurrent criterion-related validity, internal consistency, and floor/ceiling effects. Criterion validity was assessed against two-point discrimination and tactile-localization tests. Our normative data showed significant differences among the various age groups (p < 0.05), supporting the validity of the Spanish-version assessment. For the ABI sample, we also found further evidence of validity with Spearman's rho coefficient between the total scores and the two-point discrimination and tactile-localization tests, which showed low and moderate correlations (rho = 0.50-0.75, p < 0.05). Internal consistency was excellent, with a Cronbach's alpha of 0.91. No ceiling or floor effects were found. We conclude that the stereognosis component of the NSA in its Spanish version is a valid scale that can be used to comprehensively and accurately assess stereognosis capacity in adults with ABI. As a low-cost evaluation, this assessment has great potential to be widely used in clinical practice and research settings.

Effects of visual and visual-haptic perception of material rigidity on reaching and grasping in the course of development.

The development of material property perception for grasping objects is not well explored during early childhood. Therefore, we investigated infants', 3-year-old children's, and adults' unimanual grasping behavior and reaching kinematics for objects of different rigidity using a 3D motion capture system. In Experiment 1, 11-month-old infants and for purposes of comparison adults, and in Experiment 2, 3-year old children were encouraged to lift relatively heavy objects with one of two handles differing in rigidity after visual (Condition 1) and visual-haptic exploration (Condition 2). Experiment 1 revealed that 11-months-olds, after visual object exploration, showed no significant material preference, and thus did not consider the material to facilitate grasping. After visual-haptic object exploration and when grasping the contralateral handles, infants showed an unexpected preference for the soft handles, which were harder to use to lift the object. In contrast, adults generally grasped the rigid handle exploiting their knowledge about efficient and functional grasping in both conditions. Reaching kinematics were barely affected by rigidity, but rather by condition and age. Experiment 2 revealed that 3-year-olds no longer exhibit a preference for grasping soft handles, but still no adult-like preference for rigid handles in both conditions. This suggests that material rigidity plays a minor role in infants' grasping behavior when only visual material information is available. Also, 3-year-olds seem to be on an intermediate level in the development from (1) preferring the pleasant sensation of a soft fabric, to (2) preferring the efficient rigid handle.

Adapting the visuo-haptic perception through muscle coactivation.

While the nervous system can coordinate muscles' activation to shape the mechanical interaction with the environment, it is unclear if and how the arm's coactivation influences visuo-haptic perception and motion planning. Here we show that the nervous system can voluntarily coactivate muscles to improve the quality of the haptic percept. Subjects tracked a randomly moving visual target they were physically coupled to through a virtual elastic band, where the stiffness of the coupling increased with wrist coactivation. Subjects initially relied on vision alone to track the target, but with practice they learned to combine the visual and haptic percepts in a Bayesian manner to improve their tracking performance. This improvement cannot be explained by the stronger mechanical guidance from the elastic band. These results suggest that with practice the nervous system can learn to integrate a novel haptic percept with vision in an optimal fashion.

Salient Properties in Bimanual Haptic Volume Perception: Influence of Object Shape, Finger Pair, and Schizotypal Personality Traits.

Bimanual haptic volume perception refers to somatosensory access to volume information through both hands, and the characteristics that influence this perception remain unclear. This article investigated the influence of target object shapes and finger pairs on bimanual haptic perception; in addition, associations of bimanual haptic impairment and schizotypal features in nonpsychotic individuals were investigated. Twenty blindfolded participants bimanually discriminated volume variations in regular solid objects under different shape (tetrahedron, cube, or sphere) and finger pair (high- or low-sensitivity pairs) conditions using a newly developed bimanual haptic volume presentation device. Discrimination thresholds were then associated with schizotypal traits using the Chinese version of the Schizotypal Personality Questionnaire. Target object shape and finger pairs significantly influenced bimanual haptic volume perception. Volume discrimination thresholds were significantly higher with the tetrahedron stimuli than the cubic or spherical stimuli in high-sensitivity pair conditions, but no significant differences among shapes were found in low-sensitivity pair conditions. Moreover, volume discrimination thresholds with high-sensitivity pairs were correlated with the paranoid score of the schizotypal personality questionnaire. The findings provide initial evidence toward understanding the nature of bimanual haptic volume perception, including the properties of objects, individuals, and object-individual interfaces.

Effect of complete dentures on oral stereognostic ability in edentulous patients: A systematic review.

Aim: Oral stereognosis is an important sensation for a human being to percept any type of materials that are introduced in the oral cavity. It is defined as the ability of an individual to recognize objects using only tactile sensation without using vision, audition, balance, somatic function, taste, or smell. The primary purpose of this review was to evaluate the effect of complete dentures on oral stereognostic ability in edentulous subjects. Settings and Design: Systematic review based on PRISMA guidelines. Materials and Methods: A systematic search of the electronic databases like PubMed and Web of Science was done using keywords - "stereognosis," "oral stereognosis," "complete denture," and "complete edentulism." In addition to this, a manual search of references mentioned in the articles and gray literature was done. Data extraction and assessment were done by two independent reviewers. Statistical Analysis Used: Qualitative analysis. Results: The literature search yielded a total of 61 articles. Thirteen duplicate articles were removed and 36 articles were rejected after initial screening of titles and abstracts. A total of 12 articles were selected for full text reading and 5 of them were included for qualitative analysis. Conclusion: All the included studies showed complete denture treatment therapy improved stereognostic ability in terms of correct identification of test pieces and time taken to identify the objects. There is also a direct relationship between the adaptability of dentures and stereognostic ability.

The impact of movement sonification on haptic perception changes with aging.

Combining multisensory sources is crucial to interact with our environment, especially for older people who are facing sensory declines. Here, we examined the influence of textured sounds on haptic exploration of artificial textures in healthy younger and older adults by combining a tactile device (ultrasonic display) with synthetized textured sounds. Participants had to discriminate simulated textures with their right index while they were distracted by three disturbing, more or less textured sounds. These sounds were presented as a real-time auditory feedback based on finger movement sonification and thus gave the sensation that the sounds were produced by the haptic exploration. Finger movement velocity increased across both groups in presence of textured sounds (Rubbing or Squeaking) compared to a non-textured (Neutral) sound. While young adults had the same discrimination threshold, regardless of the sound added, the older adults were more disturbed by the presence of the textured sounds with respect to the Neutral sound. Overall, these findings suggest that irrelevant auditory information was taken into account by all participants, but was appropriately segregated from tactile information by young adults. Older adults failed to segregate auditory information, supporting the hypothesis of general facilitation of multisensory integration with aging.