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Thesis (M.S.)--Boston University

This thesis focuses on tactile perception and aims at a comprehensive analysis of its characteristics over the time-course of various goal-directed movements. Tactile perception is assessed by means of discrimination and detection paradigms, as well as event-related potentials (ERPs). The main question investigated throughout the thesis is: ‘What changes in tactile perception, if any, take place over the time course of a goal-directed movement?’ In Chapter 2, the mechanisms related to such identified changes are examined: a facilitatory one – attention, and an inhibitory one – suppression. The experiment in Chapter 3 tests, at a brain level, amongst several explanations of the experimental results outlined in Chapter 2: timing-based, effector-based, and modality-based attentional/suppressive influences. In Chapter 4, other naturalistic movements are investigated (i.e., the movements involved in juggling and throwing/catching a basketball). The results indicate a lack of facilitation in the processing of tactile information during the preparatory phase of the movement. Furthermore, differential changes are identified in tactile perception over the execution phase of the movement: At a behavioural level, tactile sensitivity significantly declines over the execution phase of the movement (though the detection of incoming tactile stimulation is enhanced), while at a neuronal level the same period exhibits significantly enhanced responses to somatosensory stimulation. The experiments reported here thus bring evidence in favour of a dissociation between detecting and discriminating what is felt while moving. These results suggest that the quality of what is felt while moving may not be important for movement and, at the same time, that different pathways in the brain may be responsible for detecting and discriminating what is felt over the time course of a goal-directed movement. Based on these findings, in Chapter 5, the implications of these results are discussed and directions for further research are outlined.

An occupational exposure to hand-arm vibration can cause a complex of neurological, vascular and musculo-skeletal disturbances, known as the 'vibration syndrome'. However, the underlying pathophysiological mechanisms are not at all clear. Early signs of an incipient vibration syndrome are often intermittent disturbances in the cutaneous sensibility of the fingers, i.e. numbness and/or tactile paresthesias. At later stages, a vasoconstrictive phenomenon appears, usually as episodes of finger blanching. When using a vibratory tool, all mechanical energy entering the body has to be transmitted through, or absorbed by, the glabrous skin in contact with the handle. Therefore, the aims of this study was to investigate: (i) mechanical responses of the skin to vibrations, (ii) the response properties of cutaneous mechanoreceptors to vibrations, and (iii) influences of vibration exposure on touch perception. It was found by measuring the mechanical point impedance (0.02-10 kHz) that the skin is easy to make vibrate within the range of 80 to 200 Hz. Within or close to this range are the dominant frequencies of many vibratory tools. Thus, strong mechanical loads, such as compressive and/or tensile strain, can appear in the skin which, in turn, may induce temporary or permanent injuries. Recordings of impulses in single mechanoreceptive afferents, while the skin as exposed to vibrations, were obtained using needle electrodes inserted into the median nerve. The 4 types of mechanoreceptive afferents (FA I, FA II, SA I, and SA II) in the glabrous skin exhibited different response characteristics to vibrations. The FA I units were most easily excited at vibratory frequencies between ca 8 and 64 Hz and the FA II units between ca 64 and 400 Hz. The SA units were most sensitive at lower frequencies. At high stimulus amplitudes, such as may occur while using vibratory tools, a considerable overlap existed between the frequency ranges at which the units were exited. Evidence was also provided, that mechanical skin stimuli produced by edges of a vibrating object, compared to flat surfaces, more vigorously excited the FA I and particularly the SA I units. Thus, a marked edge enhancement, essential for tactile gnosis and precision manipulation, seems to exist already within the peripheral nervous system. Acure impairment of tactile sensibility caused by vibrations, proved to be due to a reduced sensitivity of the mechanoreceptive afferents. A loss of manual dexterity a*vi an increased risk for accidents may therefore appear, both during and after a vibration exposure. Percussive tools, high speed drills and ultrasonic devices are known to generate mechanical energy at frequencies above 1 kHz, i.e. frequencies usually not felt. At these frequencies, it is known that most of the energy, entering the body, is absorbed by the skin. Therefore, it was investigated whether a long-term exposure to high-frequency vibration may have a detrimental effect on the cutaneous sensitivity. One group of dentists and one of therapists, professionally exposed to high-frequency vibrations, were studied with regard to vibrotactile thresholds in their hands. The study showed that deleterious effects on tactile sensibility, at local exposure to high frequency vibration, can not be excluded. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1985, härtill 6 uppsatser</p> / digitalisering@umu

Loin d’être une simple enveloppe pour notre corps, la peau constitue une frontière mécanique, physique, chimique et immunologique d’une remarquable efficacité. Cette fonction est en grande partie assurée par la couche la plus superficielle de la peau, appelée stratum corneum. Néanmoins, dans la vie de tous les jours, le frottement répété de la peau contre des surfaces textiles peut engendrer l’apparition de sensations d’inconfort et d’irritation cutanée. En particulier, en période de rhume, les frottements à répétitions des mouchoirs en papier sur le nez fragilisent la peau et peuvent provoquer des irritations parfois douloureuses. Ce travail vise à répondre aux attentes des consommateurs en termes de confort à l’usage des papiers en cellulose. Pour cela, l’étude a été décomposée en deux grands axes. Actuellement, le confort à l’usage est évalué par des panels sensoriels couteux, chronophages et surtout subjectifs. La première partie a donc été dédiée à l’objectivation des qualités tactiles des papiers en cellulose grâce au développement d’un dispositif expérimental. La seconde s’est intéressée à l’interaction entre la peau et les papiers, et au potentiel effet « irritant » lors du frottement répété. Cette étude a été menée sur un panel de volontaires in vivo et avait pour but de trouver une méthode capable de reproduire le frottement répété de papiers en cellulose en laboratoire, dans un temps limité et avec des paramètres de frottement bien contrôlés. Dans le but de quantifier la qualité sensorielle des papiers en cellulose, nous avons développé un système de doigt artificiel capable de mimer le comportement du doigt humain. Ce dispositif permet de mesurer le coefficient de frottement à l’interface doigt/papier et les vibrations générées lors du toucher. D’une part, nos résultats ont montré que les vibrations générées étaient un bon indicateur de la douceur du papier en cellulose. D’autre part, nous avons démontré que le coefficient de frottement était relié à la pilosité surfacique du papier. Ces résultats majeurs nous ont permis d’avoir une méthode quantitative de la qualité tactile des papiers. Il s’agit d’une méthode simple, rapide et reproductible qui a tout son intérêt pour l’industrie papetière qui, jusque-là utilisait des panels sensoriels onéreux et chronophage pour évaluer la qualité sensorielle de ses papiers. Dans une seconde grande partie, nous avons étudié l’irritation cutanée induite par le frottement de papiers en cellulose de différentes douceurs sur un panel de 59 volontaires. Cette partie a nécessité le développement de deux dispositifs expérimentaux. Tout d’abord, un biotribomètre rotatif a été développé pour reproduire le frottement répété de papier contre la peau. L’avantage de ce dispositif est qu’il permet de contrôler les paramètres de frottement (force normale appliquée sur la peau, vitesse de frottement et durée du test). Pour évaluer les réactions cutanées et l’endommagement du stratum corneum, nous avons développé un système d’indentation sans contact capable de mesurer les propriétés mécaniques de la peau. Les résultats ont montré que l’irritation de la peau induite par le frottement répété de papier était plus importante pour des papiers moins doux. Cette irritation est visible à travers une augmentation de la perte insensible en eau de la peau, de la rougeur et du flux sanguin et une diminution de ses propriétés mécaniques. / Far from being a mere envelope around our bodies, the skin forms a mechanical, physical, chemical and immunological barrier. This protective task falls in large part in the outermost layer, the stratum corneum. However, in our daily lives, the repeated friction of cellulose tissues against the skin surface may induce discomfort feelings and cutaneous reactions. In particular, during colds, the repeated friction of tissues could compromise the skin around the nose and induce painful irritation. This work is about meeting consumer needs in terms of softness and user comfort of cellulose tissues. To this end, the study was decomposed into two main parts. The first part was devoted to the quantification of the tactile quality of the tissues. The second one was interested in the skin/tissue interaction and the potential irritant effect during the repeated friction. In order to quantify the sensorial quality of tissues, we developed an artificial finger that mimics the human touch. This device enables the measurement of the friction coefficient of the tissue against the skin surface, and the evaluation of the generated vibrations. On one hand, the results showed that the vibrations were a good indicator of the softness of a tissue. In another hand, we showed that the friction coefficient was related to the surface texture of the tissue. These key results allowed us to have a rapid, simple and reproducible method to evaluate the tactile quality of a tissue. This method is very useful for the paper industry which was previously using expensive and time-consuming sensorial panels. In the second part of the thesis, we studied the cutaneous reactions induced by the repeated friction of tissues with different softnesses. This study was performed in vivo, on 59 volunteers of the laboratory. Two innovative devices were developed. First, an in vivo rotary tribometer was developed to reproduce the repeated friction of the tissue onto the skin. The advantage of this device is the full control of the friction parameters such as the applied normal force, the sliding velocity and the duration of the test. In order to evaluate the cutaneous reactions, we developed a contactless indentation device which is able to measure the mechanical properties of the skin. The results showed that the cutaneous reactions were higher when the paper was unsoft. The cutaneous irritation was visible through the increase of the trans-epidermal water loss, the redness and the blood flow of the skin and through the decrease of its mechanical properties. Beyond the findings, during the thesis, we developed new innovative and effective methods to characterise the tactile quality of tissues and evaluate the cutaneous reactions induced by the repeated friction of them on the skin.

Les rongeurs utilisent leurs vibrisses pour sonder tactilement leur environnement. Tout contact induit des contraintes mécaniques lentes quasi-statiques et rapides vibratoires, qui se propagent jusqu'en base de vibrisse où des mécanorécepteurs dédiés les détectent. C'est cette étape de transduction mécanique de l'information tactile opérée par les vibrisses, avant tout codage neuronal,que nous avons étudiée.En combinant expériences biomimétiques et modélisations, nous avons cherché à isoler les contributions relatives des composantes lentes et rapides pour la détection etlocalisation d'objets, et la perception de textures. Un des enjeuxétait de comprendre ce qui d'un point de vue mécanique confère aux rongeurs leur rapidité et acuité remarquables. Pour cela, nous avons d’abord étudié la dynamique de choc vibrisse-objet, et montré que la position radiale de l’objet pouvait être encodée à la fois dans le taux de variation de la composante quasi-statique du moment en base et dans l’amplitude et la fréquence des vibrations induites. En mimant le mouvement de whisking, nous avons de plus montré qu’utiliser la composante vibratoire permet aux rongeurs une détection des contacts plus rapide et plus robuste. Nous avons ensuite étudié la perception de textures élémentaires, et montré que la variation maximale du moment en base dépendait de manière univoque de leur taille. Des expériences sur rats anesthésiés combinant suivi des vibrisses et mesures d’activité neuronale dans le cortex nous ont enfin permis de proposer un mécanisme d’encodage des textures où la topographie de la surface est modulée par les propriétés de vibrations de la vibrisse et démodulée au niveau neuronal. / Rodents use their facial whiskers to probe their environment by touch. Any contact induces both slow quasi-static and fast vibratory mechanical stresses that propagate down to the base of vibrissae where dedicated mechanoreceptors detect them. It is this phase of mechanical transduction of the tactile information operated by the whiskers, prior to any neural coding, that we have studied here. By combining biomimetic experiments and theoretical modeling, we have sought to separate the relative contributions of both slow and fast components, for the detection and localization of objects, as well as the perception of textures. One of the challenges of this work was to understand what determines from a mechanical point of view, rodents remarkable temporal and spatial precision.For this, we have first studied the shock dynamic between a whisker and an object and shown that the radial position of the object could be encoded both in the rate of change of the quasi-static component of the base torque as well as in the amplitude and frequency of the induced vibrations. In addition, by mimicking the whisking mode adopted by rodents, we have shown that using the vibratory component allows rodents to detect contacts faster and more robustly.We then studied the perception of elementary textures and showed that the maximum variation of the base torque depends univocally on their size. Experiments on anesthetized rats, combining whisker optical tracking and cortical neural activity measurements, led us to propose an encoding mechanism of texture perception where the surface topography is modulated by the vibration properties of the whiskers and demodulation occurs at a neuronal level.

A presente pesquisa tem como objetivo tratar das relações que se estabelecem entre usuário e produto, exploradas através de uma análise de seus elementos compositivos: sentidos, percepção e significação, considerando o viés humano, e materiais, acabamentos e superfície, considerando o objeto. A intenção é contribuir com uma metodologia que possa auxiliar no projeto de produtos e interfaces com parâmetros mais objetivos, respaldando a escolha do designer na transposição do abstrato ao material. Através do estudo de técnicas empregadas na Análise Sensorial de alimentos foi possível derivar uma aplicação customizável para a análise do sentido do tato, fazendo uma referência à importância de comprovar as possibilidades de exploração dentro do aprofundamento em um dos sentidos. Esta metodologia, apresentada ao término da pesquisa, foi esquematizada e aplicada em todas as suas etapas. Com este objetivo, utilizaram-se equipamentos de medição, uma equipe de julgadores treinados e pessoas aleatórias para obter medidas objetivas, subjetivas e afetivas. Mostra-se com este estudo que há maneiras de transitar com mais fluência entre o que se deseja projetar e como isso deve ser feito para que a mensagem seja transmitida. Exploram-se as possibilidades decorrentes do uso de equipamentos tecnológicos, do treinamento científico de julgadores e a interface mais subjetiva, do afeto, que faz voltar ao usuário o foco do design. Tal encontro evidencia caminhos possíveis para uma projetação mais abrangente, mais coerente com o que se deseja transmitir e quem se deseja alcançar. / This research aims to address the relations that can be established between user and product, explored through an analysis of its composing elements: senses, perception and meaning, considering the human approach, and materials, surface and finishing, considering the object. The intention is to contribute with a methodology that can assist in designing products and interfaces with more objective parameters, supporting the designer`s choice when transposing from abstract to material. Through the study of techniques employed in the Sensory Analysis of food it was possible to derive a customizable application for the analysis of the sense of touch, making a reference to the importance to demonstrate the possibilities of exploring deeper one of the senses. This methodology, presented at the end of the research, was outlined and applied at all stages. For this purpose were used measurement equipments, a team of trained assessors and people at random to obtain objective, subjective and emotional measures. It is showed with this study that there are ways to move more fluently between what is the project intention and how this should be executed in order to transmit the right message. The possibilities arising from the use of technological equipment, the scientific training of assessors and a more subjective interface of affection are explored, which puts the user back in the design focus. This meeting shows possible ways to a broader projecting, more consistent with what is being transmitted and who is the target.

A presente pesquisa tem como objetivo tratar das relações que se estabelecem entre usuário e produto, exploradas através de uma análise de seus elementos compositivos: sentidos, percepção e significação, considerando o viés humano, e materiais, acabamentos e superfície, considerando o objeto. A intenção é contribuir com uma metodologia que possa auxiliar no projeto de produtos e interfaces com parâmetros mais objetivos, respaldando a escolha do designer na transposição do abstrato ao material. Através do estudo de técnicas empregadas na Análise Sensorial de alimentos foi possível derivar uma aplicação customizável para a análise do sentido do tato, fazendo uma referência à importância de comprovar as possibilidades de exploração dentro do aprofundamento em um dos sentidos. Esta metodologia, apresentada ao término da pesquisa, foi esquematizada e aplicada em todas as suas etapas. Com este objetivo, utilizaram-se equipamentos de medição, uma equipe de julgadores treinados e pessoas aleatórias para obter medidas objetivas, subjetivas e afetivas. Mostra-se com este estudo que há maneiras de transitar com mais fluência entre o que se deseja projetar e como isso deve ser feito para que a mensagem seja transmitida. Exploram-se as possibilidades decorrentes do uso de equipamentos tecnológicos, do treinamento científico de julgadores e a interface mais subjetiva, do afeto, que faz voltar ao usuário o foco do design. Tal encontro evidencia caminhos possíveis para uma projetação mais abrangente, mais coerente com o que se deseja transmitir e quem se deseja alcançar. / This research aims to address the relations that can be established between user and product, explored through an analysis of its composing elements: senses, perception and meaning, considering the human approach, and materials, surface and finishing, considering the object. The intention is to contribute with a methodology that can assist in designing products and interfaces with more objective parameters, supporting the designer`s choice when transposing from abstract to material. Through the study of techniques employed in the Sensory Analysis of food it was possible to derive a customizable application for the analysis of the sense of touch, making a reference to the importance to demonstrate the possibilities of exploring deeper one of the senses. This methodology, presented at the end of the research, was outlined and applied at all stages. For this purpose were used measurement equipments, a team of trained assessors and people at random to obtain objective, subjective and emotional measures. It is showed with this study that there are ways to move more fluently between what is the project intention and how this should be executed in order to transmit the right message. The possibilities arising from the use of technological equipment, the scientific training of assessors and a more subjective interface of affection are explored, which puts the user back in the design focus. This meeting shows possible ways to a broader projecting, more consistent with what is being transmitted and who is the target.

A presente pesquisa tem como objetivo tratar das relações que se estabelecem entre usuário e produto, exploradas através de uma análise de seus elementos compositivos: sentidos, percepção e significação, considerando o viés humano, e materiais, acabamentos e superfície, considerando o objeto. A intenção é contribuir com uma metodologia que possa auxiliar no projeto de produtos e interfaces com parâmetros mais objetivos, respaldando a escolha do designer na transposição do abstrato ao material. Através do estudo de técnicas empregadas na Análise Sensorial de alimentos foi possível derivar uma aplicação customizável para a análise do sentido do tato, fazendo uma referência à importância de comprovar as possibilidades de exploração dentro do aprofundamento em um dos sentidos. Esta metodologia, apresentada ao término da pesquisa, foi esquematizada e aplicada em todas as suas etapas. Com este objetivo, utilizaram-se equipamentos de medição, uma equipe de julgadores treinados e pessoas aleatórias para obter medidas objetivas, subjetivas e afetivas. Mostra-se com este estudo que há maneiras de transitar com mais fluência entre o que se deseja projetar e como isso deve ser feito para que a mensagem seja transmitida. Exploram-se as possibilidades decorrentes do uso de equipamentos tecnológicos, do treinamento científico de julgadores e a interface mais subjetiva, do afeto, que faz voltar ao usuário o foco do design. Tal encontro evidencia caminhos possíveis para uma projetação mais abrangente, mais coerente com o que se deseja transmitir e quem se deseja alcançar. / This research aims to address the relations that can be established between user and product, explored through an analysis of its composing elements: senses, perception and meaning, considering the human approach, and materials, surface and finishing, considering the object. The intention is to contribute with a methodology that can assist in designing products and interfaces with more objective parameters, supporting the designer`s choice when transposing from abstract to material. Through the study of techniques employed in the Sensory Analysis of food it was possible to derive a customizable application for the analysis of the sense of touch, making a reference to the importance to demonstrate the possibilities of exploring deeper one of the senses. This methodology, presented at the end of the research, was outlined and applied at all stages. For this purpose were used measurement equipments, a team of trained assessors and people at random to obtain objective, subjective and emotional measures. It is showed with this study that there are ways to move more fluently between what is the project intention and how this should be executed in order to transmit the right message. The possibilities arising from the use of technological equipment, the scientific training of assessors and a more subjective interface of affection are explored, which puts the user back in the design focus. This meeting shows possible ways to a broader projecting, more consistent with what is being transmitted and who is the target.

We still struggle to deliver autonomous robots that perform manipulation tasks as simple for a human as picking up items. A portion of the difficulty of this task lays on the fact that such operation requires a robot that can deal with uncertainty in an unstructured environment. We propose in this thesis the use of visual and tactile perception for providing solutions that can improve the robustness of a robotic manipulator in such environment. In this thesis, we approach robotic grasping using a single 3D point cloud with a partial view of the objects present in the scene. Moreover, the objects are unknown: they have not been previously recognised and we do not have a 3D model to compute candidate grasping points. In experimentation, we prove that our solution is fast and robust, taking in average 17 ms to find a grasp which is stable 85% of the time. Tactile sensors provide a rich source of information regarding the contact experienced by a robotic hand during the manipulation of an object. In this thesis, we exploit with deep learning this type of data for approaching the prediction of the stability of a grasp and the detection of the direction of slip of a contacted object. We prove that our solutions could correctly predict stability 76% of the time with a single tactile reading. We also demonstrate that learning temporal and spatial patterns leads to detections of the direction of slip which are correct up to 82% of the time and are only delayed 50 ms after the actual slip event begins. Despite the good results achieved on the previous two tactile tasks, this data modality has a serious flaw: it can only be registered during contact. In contrast, humans can estimate the feeling of grasping an object just by looking at it. Inspired by this, we present in this thesis our contributions for learning to generate tactile responses from vision. We propose a supervised solution based on training a deep neural network that models the behaviour of a tactile sensor, given 3D visual information of the target object and grasp data as an input. As a result, our system has to learn to link vision to touch. We prove in experimentation that our system learns to generate tactile responses on a set of 12 items, being off by only 0.06 relative error points. Furthermore, we also experiment with a semi-supervised solution for learning this task with a reduced need of labelled data. In experimentation, we show that it learns our tactile data generation task with 50% less data than the supervised solution, incrementing only 17% the error. Last, we introduce our work in the generation of candidate grasps which are improved through simulation of the tactile responses they would generate. This work unifies the contributions presented in this thesis, as it applies modules on calculating grasps, stability prediction and tactile data generation. In early experimentation, it finds grasps which are more stable than the original ones produced by our method based on 3D point clouds. / This doctoral thesis has been carried out with the support of the Spanish Ministry of Economy, Industry and Competitiveness through the grant BES-2016-078290.