Towards sensory substitution and augmentation: Mapping visual distance to audio and tactile frequency.

Multimodal perception is the predominant means by which individuals experience and interact with the world. However, sensory dysfunction or loss can significantly impede this process. In such cases, cross-modality research offers valuable insight into how we can compensate for these sensory deficits through sensory substitution. Although sight and hearing are both used to estimate the distance to an object (e.g., by visual size and sound volume) and the perception of distance is an important element in navigation and guidance, it is not widely studied in cross-modal research. We investigate the relationship between audio and vibrotactile frequencies (in the ranges 47-2,764 Hz and 10-99 Hz, respectively) and distances uniformly distributed in the range 1-12 m. In our experiments participants mapped the distance (represented by an image of a model at that distance) to a frequency via adjusting a virtual tuning knob. The results revealed that the majority (more than 76%) of participants demonstrated a strong negative monotonic relationship between frequency and distance, across both vibrotactile (represented by a natural log function) and auditory domains (represented by an exponential function). However, a subgroup of participants showed the opposite positive linear relationship between frequency and distance. The strong cross-modal sensory correlation could contribute to the development of assistive robotic technologies and devices to augment human perception. This work provides the fundamental foundation for future assisted HRI applications where a mapping between distance and frequency is needed, for example for people with vision or hearing loss, drivers with loss of focus or response delay, doctors undertaking teleoperation surgery, and users in augmented reality (AR) or virtual reality (VR) environments.

From CySkin to ProxySKIN: Design, Implementation and Testing of a Multi-Modal Robotic Skin for Human-Robot Interaction.

The Industry 5.0 paradigm has a human-centered vision of the industrial scenario and foresees a close collaboration between humans and robots. Industrial manufacturing environments must be easily adaptable to different task requirements, possibly taking into account the ergonomics and production line flexibility. Therefore, external sensing infrastructures such as cameras and motion capture systems may not be sufficient or suitable as they limit the shop floor reconfigurability and increase setup costs. In this paper, we present the technological advancements leading to the realization of ProxySKIN, a skin-like sensory system based on networks of distributed proximity sensors and tactile sensors. This technology is designed to cover large areas of the robot body and to provide a comprehensive perception of the surrounding space. ProxySKIN architecture is built on top of CySkin, a flexible artificial skin conceived to provide robots with the sense of touch, and arrays of Time-of-Flight (ToF) sensors. We provide a characterization of the arrays of proximity sensors and we motivate the design choices that lead to ProxySKIN, analyzing the effects of light interference on a ToF, due to the activity of other sensing devices. The obtained results show that a large number of proximity sensors can be embedded in our distributed sensing architecture and incorporated onto the body of a robotic platform, opening new scenarios for complex applications.

Direction-Specific Effects of Artificial Skin-Stretch on Stiffness Perception and Grip Force Control.

When interacting with an object, we use kinesthetic and tactile information to create our perception of the object's properties and to prevent its slippage using grip force control. We previously showed that applying artificial skin-stretch together with, and in the same direction as, kinesthetic force increases the perceived stiffness. Here, we investigated the effect of the direction of the artificial stretch on stiffness perception and grip force control. We presented participants with kinesthetic force together with negative or positive artificial stretch, in the opposite or the same direction of the natural stretch due to the kinesthetic force, respectively. Our results showed that artificial skin-stretch in both directions augmented the perceived stiffness; however, the augmentation caused by the negative stretch was consistently lower than that caused by the positive stretch. Additionally, we proposed a computational model that predicts the perceptual effects based on the preferred directions of the stimulated mechanoreceptors. When examining the grip force, we found that participants applied higher grip forces during the interactions with positive skin-stretch in comparison to the negative skin-stretch, which is consistent with the perceptual results. These results may be useful in tactile technologies for wearable haptic devices, teleoperation, and robot-assisted surgery.

A Survey on Force Sensing Techniques in Robot-Assisted Minimally Invasive Surgery.

Minimally invasive surgery (MIS) is commonly used in some robotic-assisted surgery (RAS) systems. However, many RAS lack the strength and tactile sensation of surgical tools. Therefore, researchers have developed various force sensing techniques in robot-assisted minimally invasive surgery (RMIS). This paper provides a systematic classification and review of force sensing approaches in the field of RMIS, with a particular focus on direct and indirect force sensing. In this survey, the relevant literature on various sensing principles, haptic sensor design standards, and sensing technologies between 2000 and 2022 is reviewed. This survey can also serve as a roadmap for future developments by identifying the shortcomings of the field and discussing the emerging trends in force sensing methods.

Ion trap and release dynamics enables nonintrusive tactile augmentation in monolithic sensory neuron.

An iontronic-based artificial tactile nerve is a promising technology for emulating the tactile recognition and learning of human skin with low power consumption. However, its weak tactile memory and complex integration structure remain challenging. We present an ion trap and release dynamics (iTRD)-driven, neuro-inspired monolithic artificial tactile neuron (NeuroMAT) that can achieve tactile perception and memory consolidation in a single device. Through the tactile-driven release of ions initially trapped within iTRD-iongel, NeuroMAT only generates nonintrusive synaptic memory signals when mechanical stress is applied under voltage stimulation. The induced tactile memory is augmented by auxiliary voltage pulses independent of tactile sensing signals. We integrate NeuroMAT with an anthropomorphic robotic hand system to imitate memory-based human motion; the robust tactile memory of NeuroMAT enables the hand to consistently perform reliable gripping motion.

Applying cosmetic oil with added aromatic compounds improves tactile sensitivity and skin properties.

Tactile sensitivity generally decreases with aging and is associated with impairments in skin properties. Products that hydrate the skin can combat touch deficits and aromatic compounds have been shown to improve skin mechanical properties. Thus, we tested a base cosmetic oil against a perfumed oil, applied to the skin of females aged 40-60 years, on tactile sensitivity and skin properties after repeated application. Tactile detection thresholds were assessed using calibrated monofilaments applied at the index finger, palm, forearm, and cheek. Spatial discrimination on the finger was assessed using pairs of plates with different inter-band spaces. These tests were performed before and after 1 month of base or perfumed oil use. We found that tactile detection thresholds and spatial discrimination improved only in perfumed oil group. A complementary immunohistological study using human skin was conducted to estimate the expression of olfactory receptor OR2A4 and elastic fiber length. Further, the expression of OR2A4 intensity and the length of elastic fibers increased significantly with oil application, where larger effects were seen with the perfumed oil. We conclude that the application of a perfumed oil may be of additional benefit and could repair, and even prevent, tactile decline with aging by ameliorating skin condition.

Aß-CT Affective Touch: Touch Pleasantness Ratings for Gentle Stroking and Deep Pressure Exhibit Dependence on A-Fibers.

Gentle stroking of the skin is a common social touch behavior with positive affective consequences. A preference for slow versus fast stroking of hairy skin has been closely linked to the firing of unmyelinated C-tactile (CT) somatosensory afferents. Because the firing of CT afferents strongly correlates with touch pleasantness, the CT pathway has been considered a social-affective sensory pathway. Recently, ablation of the spinothalamic pathway- thought to convey all C-fiber sensations- in patients with cancer pain impaired pain, temperature, and itch, but not ratings of pleasant touch. This suggested integration of afferent A and CT fiber input in the spinal cord, or mechanoreceptive A-fiber contributions to computations of touch pleasantness in the brain. However, contribution of mechanoreceptive A-fibers to touch pleasantness, in humans without pain, remains unknown. In the current, single-blinded study, we performed two types of peripheral nerve blocks in healthy adults to temporarily eliminate the contribution of A-fibers to touch perception. Our findings show that when mechanoreceptive A-fiber function is greatly diminished, the perceived intensity and pleasantness of both gentle stroking and deep pressure are nearly abolished. These findings demonstrate that explicit perception of the pleasantness of CT-targeted brushing and pressure both critically depend on afferent A-fibers.

A hierarchical sensorimotor control framework for human-in-the-loop robotic hands.

Human manual dexterity relies critically on touch. Robotic and prosthetic hands are much less dexterous and make little use of the many tactile sensors available. We propose a framework modeled on the hierarchical sensorimotor controllers of the nervous system to link sensing to action in human-in-the-loop, haptically enabled, artificial hands.

"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.

Deconstructing Haptic Feedback Information in Robot-Assisted Needle Insertion in Soft Tissues.

This paper evaluates the role and effectiveness of different types of haptic feedback in presenting relevant feedback information during needle insertion in soft tissues through a remotely operated robot. We carried out three experiments with human subjects to analyze the effect of grounded kinesthetic feedback, cutaneous vibrotactile feedback, and cutaneous pressure feedback for rendering the elastic and the viscous force components of a simplified needle-tissue interaction model in a simulated environment. Results showed that providing the two pieces of feedback information through different channels, i.e., kinesthetic and cutaneous, led to the best performance, yielding an improvement in detecting a different tissue layer with respect to providing both information through the same commercial grounded kinesthetic interface. Moreover, results indicate that cutaneous pressure feedback is more suited for rendering the elastic component of the interaction with respect to vibrotactile cutaneous sensations. Finally, results suggest that rendering this elastic component where the user holds the input interface is not so important, confirming that delocalized cutaneous sensations can be an effective solution.

Precise Monitoring of Returning Sensation in Digital-Nerve Lesions by Three-Dimensional Imaging: A Proof-of-Concept Study.

SUMMARY: Digital-nerve lesions result in a loss of tactile sensation reflected by an anesthetic area (AA) at the radial or ulnar aspect of the respective digit. Available tools to monitor the recovery of tactile sense have been criticized for their lack of validity. Precise quantification of AA dynamics by three-dimensional (3D) imaging could serve as an accurate surrogate to monitor recovery after digital-nerve repair. For validation, AAs were marked on digits of healthy volunteers to simulate the AA of an impaired cutaneous innervation. The 3D models were composed from raw images that had been acquired with a 3D camera to precisely quantify relative AA for each digit (3D models, n = 80). Operator properties varied with regard to individual experience in 3D imaging and image processing. In addition, the concept was applied in a clinical case study. Results showed that images taken by experienced photographers were rated as better quality ( P < 0.001) and needed less processing time ( P = 0.020). Quantification of the relative AA was not altered significantly, regardless of experience level of the photographer ( P = 0.425) or image assembler ( P = 0.749). The proposed concept allows precise and reliable surface quantification of digits and can be performed consistently without relevant distortion by lack of examiner experience. Routine 3D imaging of the AA has the great potential to provide visual evidence of various returning states of sensation and to convert sensory nerve recovery into a metric variable with high responsiveness to temporal progress.

Effects of sickness manipulation on disgust and pleasantness in interpersonal touch.

The theory of the behavioral immune system (BIS) describes a set of behaviors that protect the individual from infectious diseases and that are motivated by disgust and the perceived vulnerability to disease. As interpersonal touch is one of the most common situations of potential transmission of infectious diseases in our everyday life, it seems likely that being touched by an apparently sick individual activates disgust. Our aim was to determine if risk of contamination from interpersonal touch alters the pleasantness of interpersonal touch and modulates facially expressed emotions. In total, 64 participants received interpersonal stroking by either a healthy or by sick-appearing experimenter. Half the strokes were performed at a slow velocity of 3 cm/s and half at a faster velocity of 30 cm/s, to modulate the degree of C-tactile fiber activation in the touch perceiver. While the experimental sickness manipulation did not influence the reported touch pleasantness, there was a tendency for a diminished expression of happiness in the slow stroking condition. In addition, the desire to clean the arm after stroking correlated positively to disgust sensitivity and to germ aversion, which is a subscale of the perceived vulnerability to disease. Contrary to previous studies, participants did not prefer the slow over the fast stroking velocity, irrespective of sickness induction. Our results lead us to assume that disgust in interpersonal touch depends especially on the touch receiver and we speculate that a rather conservative reactivity of the BIS allows for an adaptive behavioral balance in interpersonal relations. This balance may be needed to weight the risks of contamination against the benefits of interpersonal touch for social interaction.

Challenges faced by undergraduate dental students during root canal treatment: a survey study / Desafios enfrentados por estudantes de graduação em odontologia durante o tratamento de canal radicular: um estudo de pesquisa

Introduction: root canal treatment is a challenging procedure often first encountered by undergraduate dental students, leading to various difficulties and mistakes. Objective: this study aimed to identify the specific difficulties encountered by undergraduate dental students during root canal treatment and the frequency of mistakes they committed in relation to these difficulties. Material and method: this study employed a cross-sectional survey design. A cohort of 60 third-year students completed a self-administered questionnaire consisting of 27 questions addressing various aspects of endodontic treatment and 11 key areas of root canal procedures. The response options for each question were based on a 4-point Likert scale. Data analysis was performed using Python programming language and heatmaps were created using the seaborn library to better understand the distribution of the data. Result: students encounter challenges in developing tactile sensation, accessory cone placement, and accurately reaching the apex during canal location. Dental schools should focus on improving students' tactile skills and methods to reach the apex to enhance the effectiveness of root canal treatment education. In contrast, students reported fewer mistakes in rubber dam application and safety measures during treatment. Dental educators should emphasize proper instrument use and safety precautions during root canal treatment. Interestingly, students did not perceive these areas as problematic despite committing mistakes. Conclusion: this study provides valuable insights into the challenges and mistakes encountered by undergraduate dental students during root canal treatment. Dental educators should address these issues to improve students' skills and techniques and provide optimal patient care.

Introdução: o tratamento endodôntico é um procedimento desafiador, frequentemente encontrado pela primeira vez por estudantes de odontologia, levando a diversas dificuldades e erros. Objetivo: este estudo teve como objetivo identificar as dificuldades específicas encontradas por estudantes de graduação em Odontologia durante o tratamento endodôntico e a frequência de erros cometidos por eles em relação a essas dificuldades. Material e método: este estudo empregou um desenho de pesquisa transversal. Um grupo de 60 estudantes do terceiro ano respondeu a um questionário autoaplicável composto por 27 perguntas abordando vários aspectos do tratamento endodôntico e 11 áreas-chave dos procedimentos de canal radicular. As opções de resposta para cada questão foram baseadas em uma escala Likert de 4 pontos. A análise dos dados foi realizada utilizando a linguagem de programação Python e mapas de calor foram criados utilizando a biblioteca seaborn para melhor compreender a distribuição dos dados. Resultado: os alunos encontram desafios no desenvolvimento da sensação tátil, na colocação do cone acessório e no alcance preciso do ápice durante a localização do canal. As escolas de odontologia devem se concentrar em melhorar as habilidades táteis e os métodos dos alunos para alcançar o ápice e aumentar a eficácia do ensino sobre tratamento de canal radicular. Em contrapartida, os estudantes relataram menos erros na aplicação do dique de borracha e nas medidas de segurança durante o tratamento. Os educadores odontológicos devem enfatizar o uso adequado dos instrumentos e as precauções de segurança durante o tratamento do canal radicular. Curiosamente, os alunos não consideraram estas áreas problemáticas, apesar de cometerem erros. Conclusão: este estudo fornece informações valiosas sobre os desafios e erros encontrados por estudantes de odontologia durante o tratamento endodôntico. Os educadores odontológicos devem abordar essas questões para melhorar as habilidades e técnicas dos alunos e fornecer o melhor atendimento ao paciente.

Directional touch sensing for stiffness singularity search in an object using microfinger with tactile sensor.

Palpation is widely used as the initial medical diagnosis. Integration of micro tactile sensors and artificial muscles enables a soft microfinger for active touch sensing using its bending actuation. Active touch sensing by pushing-in motion of microfinger enables to evaluate stiffness distribution on an elastic object. Due to its compactness, the microfinger can enter a narrow space, such as gastrointestinal and abdominal spaces in a body. However, a microfinger can only touch and sense limited points. We aim at efficient method for searching a stiffness singular part in an elastic object by the directional touch sensing of a microfinger. This study presents a microfinger for active touch sensing using bending and push-in actuation and proposes an algorithm utilizing directivity in touch sensing by a microfinger for efficient localization of the stiffness singular part in an object. A gelatin block structure with a small rigid ball was prepared and touch sensed by the microfinger. Consequently, the position of the buried rigid ball could be efficiently identified based on the proposed algorithm. This result implies that the proposed method has potential applications in endoscopic medical diagnosis, particularly in identifying tumor positions.

Short-term improvements in the body schema can modulate pain perception in fibromyalgia syndrome.

OBJECTIVES: This study aimed to evaluate the pain perception and several aspects of disrupted body schema, in a sample of patients suffering from fibromyalgia (FM) syndrome. METHODS: Twenty-six patients were organised into two groups: the tactile discrimination group and control group (exposed to tactile stimulation alone). Outcome measures were the pain intensity in body regions commonly described as painful (visual analogue scale) and clinical status, body esteem scale (BES), interoceptive awareness. Tactile acuity was measured by the two-point discrimination test (TPD), hits in the location of the stimulus, the probe size discrimination and the graphesthesia task. RESULTS: The group exposed to tactile discrimination experienced a significant improvement in all tactile acuity outcome measures. The decrease of the Fibromyalgia Impact Questionnaire variable was relevant (81.58, SEM 3.29 vs. 72.91, SEM 6.43; p=0.07). Likewise, pain perception was lower in all of the body regions evaluated (reduction of 12.2% in the stimulated body region (cervical VAS) with a large effect size, a pain reduction of 11.3% in the wrists and 9.2% in the knees. The correlation index showed association between the cervical VAS and TPD (ρ=0.53; p<0.05). CONCLUSIONS: There was no improvement in pain scores in the control group but the TPD was decreased also. The BES scores did not show differences between groups. However, interoceptive awareness showed a slight reduction in the group exposed to tactile discrimination (3.68, SEM 0.15 vs. 3.35, SEM 0.19; p=0.01). After short-term tactile discrimination protocol, the group exposed to tactile discrimination experienced a significant improvement in all tactile acuity outcome measures: pain perception, tactile acuity and body perception, compatible with adjustments in the body schema. The tactile stimulation alone group did not show the same improvement.

The Effect of Kinesthetic and Artificial Tactile Noise and Variability on Stiffness Perception.

Robot-assisted minimally invasive surgeries (RAMIS) have many benefits. A disadvantage, however, is the lack of haptic feedback. Haptic feedback is comprised of kinesthetic and tactile information, and we use both to form stiffness perception. Applying both kinesthetic and tactile feedback can enable more precise feedback than kinesthetic feedback alone. However, during remote surgeries, haptic noises and variations can be present. Therefore, toward designing haptic feedback for RAMIS, it is important to understand the effect of haptic manipulations on stiffness perception. We assessed the effect of two manipulations using stiffness discrimination tasks in which participants received force feedback and artificial skin stretch. In Experiment 1, we added sinusoidal noise to the artificial tactile signal, and found that the noise did not affect participants' stiffness perception or uncertainty. In Experiment 2, we varied either the kinesthetic or the artificial tactile information between consecutive interactions with an object. We found that the both forms of variability did not affect stiffness perception, but kinesthetic variability increased participants' uncertainty. We show that haptic feedback, comprised of force feedback and artificial skin stretch, provides robust haptic information even in the presence of noise and variability, and hence can potentially be both beneficial and viable in RAMIS.

Ether anesthetics prevents touch-induced trigger hair calcium-electrical signals excite the Venus flytrap.

Plants do not have neurons but operate transmembrane ion channels and can get electrical excited by physical and chemical clues. Among them the Venus flytrap is characterized by its peculiar hapto-electric signaling. When insects collide with trigger hairs emerging the trap inner surface, the mechanical stimulus within the mechanosensory organ is translated into a calcium signal and an action potential (AP). Here we asked how the Ca2+ wave and AP is initiated in the trigger hair and how it is feed into systemic trap calcium-electrical networks. When Dionaea muscipula trigger hairs matures and develop hapto-electric excitability the mechanosensitive anion channel DmMSL10/FLYC1 and voltage dependent SKOR type Shaker K+ channel are expressed in the sheering stress sensitive podium. The podium of the trigger hair is interface to the flytrap's prey capture and processing networks. In the excitable state touch stimulation of the trigger hair evokes a rise in the podium Ca2+ first and before the calcium signal together with an action potential travel all over the trap surface. In search for podium ion channels and pumps mediating touch induced Ca2+ transients, we, in mature trigger hairs firing fast Ca2+ signals and APs, found OSCA1.7 and GLR3.6 type Ca2+ channels and ACA2/10 Ca2+ pumps specifically expressed in the podium. Like trigger hair stimulation, glutamate application to the trap directly evoked a propagating Ca2+ and electrical event. Given that anesthetics affect K+ channels and glutamate receptors in the animal system we exposed flytraps to an ether atmosphere. As result propagation of touch and glutamate induced Ca2+ and AP long-distance signaling got suppressed, while the trap completely recovered excitability when ether was replaced by fresh air. In line with ether targeting a calcium channel addressing a Ca2+ activated anion channel the AP amplitude declined before the electrical signal ceased completely. Ether in the mechanosensory organ did neither prevent the touch induction of a calcium signal nor this post stimulus decay. This finding indicates that ether prevents the touch activated, glr3.6 expressing base of the trigger hair to excite the capture organ.

Effects of body ownership illusion during exposure to disgusting stimuli.

BACKGROUND: The Rubber Hand Illusion (RHI) refers to the feeling of ownership of a rubber hand by synchronously stroking the rubber hand and the own hand of a person. Previous research has shown that RHI can be used to simulate skin contact with a disgust-eliciting stimulus. We used a primary disgust elicitor (a living maggot) to replicate this finding and to gather data on disgust habituation during RHI, and effects on in-vivo exposure. METHODS: A total of 82 healthy participants (25 males, 57 females) were randomly assigned to one of two conditions; synchronous stroking or asynchronous stroking (control condition) of the rubber/own hand. Subsequently, a maggot was placed on the rubber hand for five minutes. Participants rated experienced disgust at the beginning and end of the exposure. They were also asked if the maggot could be placed on their own hand. RESULTS: Synchronous stroking successfully elicited RHI, which was associated with higher disgust ratings for the maggot at the beginning of exposure compared to asynchronous stroking. The two conditions did not differ in disgust habituation and the willingness to expose the own hand to the maggot. CONCLUSION: RHI successfully simulated skin contact with a disgust stimulus. Future studies should apply longer exposure intervals and test individuals with higher disgust propensity to detect possible RHI effects on disgust habituation.

Tactile disgust: Post-contact can be more disgusting than contact.

Several studies have examined if disgust can be evoked by contacting an object-yet none have examined if reported disgust changes when the hand leaves the object. This is surprising given that post-contact tactile disgust is probably a driver of hand hygiene. We examined contact and post-contact tactile disgust and its sensory origins. Participants were asked to touch several objects, making sensory, disgust, and desire-to-handwash evaluations. These ratings were made at three stages-of-contact: object-contact (just touch), post-contact (just touch), and visual post-contact (touch, vision). Disgust was typically highest at post-contact (when the hand left the object). Stickiness and wetness were uniquely predictive of object-contact disgust. Only stickiness drove post-contact disgust, and only wetness visual post-contact disgust. Hand-washing desire was primarily driven by quantity of residue perceived on the hand. These findings suggest that tactile disgust is a multisensory and iterative process relating to object- and residue-adhesiveness.