The ability to sense humidity and wetness is an important sensory attribute for many species across the animal kingdom, including humans. Although this sensory ability plays an important role in many human physiological and behavioural functions, as humans largest sensory organ i.e. the skin seems not to be provided with specific receptors for the sensation of wetness (i.e. hygroreceptors), the neurophysiological mechanisms underlying this complex sensory experience are still poorly understood. The aim of this Thesis was to investigate the neurophysiological mechanisms underpinning humans remarkable ability to sense skin wetness despite the lack of specific skin hygroreceptors. It was hypothesised that humans could learn to perceive the wetness experienced when the skin is in contact with a wet surface or when sweat is produced through a complex multisensory integration of thermal (i.e. heat transfer) and tactile (i.e. mechanical pressure and friction) inputs generated by the interaction between skin, moisture and (if donned) clothing. Hence, as both thermal and tactile skin afferents could contribute significantly to drive the perception of skin wetness, their role in the peripheral and central sensory integration of skin wetness perception was investigated, both under conditions of skin s contact with an external (dry or wet) stimulus as well as during the active production of sweat. A series of experimental studies were performed, aiming to isolate the contribution of each sensory cue (i.e. thermal and tactile) to the perception of skin wetness during rest and exercise, as well as under different environmental conditions. It was found that it is not the contact of the skin with moisture per se, but rather the integration of particular sensory inputs which drives the perception of skin wetness during both the contact with an external (dry or wet) surface, as well as during the active production of sweat. The role of thermal (cold) afferents appears to be of a primary importance in driving the perception of skin wetness during the contact with an external stimulus. However, when thermal cues (e.g. evaporative cooling) are limited, individuals seem to rely more on tactile cues (i.e. stickiness and skin friction) to characterise their perception of skin wetness. The central integration of conscious coldness and mechanosensation, as sub-served by peripheral cutaneous A-nerve fibers, seems therefore the primary neural process underpinning humans ability to sense wetness. Interestingly, these mechanisms (i.e. integration of thermal and tactile sensory cues) appear to be remarkably consistent regardless of the modality for which skin wetness is experienced, i.e. whether due to passive contact with a wet stimulus or due to active production of sweat. The novelty of the findings included in this Thesis is that, for the first time, mechanistic evidence has been provided for the neurophysiological processes which underpin humans ability to sense wetness on their skin. Based on these findings, the first neurophysiological sensory model for human skin wetness perception has been developed. This model helps explain humans remarkable ability to sense warm, neutral and cold skin wetness.

by Chan Eliza. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 183-196). / ACKNOWLEDGEMENTS / ABSTRACT --- p.i / Chapter CHAPTER ONE: --- INTRODUCTION --- p.1 / Chapter CHAPTER TWO: --- LITERATURE REVIEW / Chapter Section 1: --- History of Merkel cells --- p.3 / Chapter Section 2: --- Morphology and characteristic response of Merkel cell receptors in the skin --- p.5 / Chapter Section 3: --- Merkel cells and other mechanoreceptors in the mammalian sinus hair --- p.16 / Chapter Section 4: --- Functions of Merkel cells --- p.29 / Chapter Section 5: --- Review of technical approaches in the study of Merkel cell physiology --- p.39 / Chapter Section 6: --- Monitoring intracellular Ca2+ with the microfluorimetric technique --- p.42 / Chapter Section 7: --- Properties of voltage-gated and ligand-operated Ca2+ channels --- p.52 / Chapter CHAPTER THREE: --- METHODS / Chapter Section 1: --- Isolation of the rat vibrissal follicles --- p.60 / Chapter Section 2: --- Procedures for fluorimetric studies --- p.63 / Chapter Section 3: --- Procedures for electrophysiological study --- p.72 / Chapter Section 4: --- Chemicals --- p.82 / Chapter CHAPTER FOUR: --- RESULTS / Chapter Section 1: --- Electrophysiological studies in an isolated sinus hair preparation --- p.89 / Chapter Section 2: --- Electrophysiological studies on slowly adapting type I (SA I) mechanoreceptors in an isolated skin-nervein vitro preparation --- p.109 / Chapter Section 3: --- Microfluorimetric studies of Merkel cells in the isolated sinus hair preparation --- p.117

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.

The reactive control of fingertip forces maintaining grasp stability was examined in man during a prehensile task. Blindfolded subjects used the precision grip between the tips of index finger and thumb to restrain an object that was subjected to unpredictable load forces. These were delivered tangential to the parallel grip surfaces of the object. Load forces, grip forces (perpendicular to the grip surfaces) and position of the object were recorded.Subjects automatically adjusted the grip forces to loads of various amplitudes and rates. Thereby they maintained a reliable safety margin against frictional slips without using excessive grip forces. A rapid rise in grip force lasting about 0.2 s was triggered after a short delay following the onset of a sustained ramp load increase. This 'catch-up' response caused a quick restoration of an adequate grip:load force ratio that prevented frictional slips. If the ramp load continued to increase after the catchup response, the grip force also increased in parallel with the load change in a 'tracking' manner. Consequently, during the hold phases of 'ramp-and-hold' loads, the employed grip forces were approximately proportional to the load amplitude. Sensory information about the rate of change of the load force parametrically scaled the 'catchup' and 'tracking' responses.Following anesthetic block of sensory input from the digits, the grip responses were both delayed and attenuated or even abolished. To compensate for these impairments, subjects had to voluntarily maintain exceedingly high grip forces to prevent the object from slipping. The grip control improved slightly during hand and forearm support conditions that allowed marked wrist movements to occur in response to the loading. This indicates that signals from receptors in muscles, joints or skin areas proximal to the digits can to some extent be used to adjust grip forces during impaired digital sensibility. In contrast, these signals had only minor influence on the control during normal digital sensibility.Grip responses to loads delivered in various directions revealed that the load direction, in relation to gravity and to the hand's geometry, represents intrinsic task variables in the automatic processes that maintain a stable grasp. The load direction influenced both the response latencies and the magnitudes of the grip responses. The response latencies were shortest for loads in directions that were the most critical with regard to the consequences of frictional slippage, i.e., loads directed away from the palm or in the direction of gravity. Recordings of signals in cutaneous afferents innervating the finger tips demonstrated that these effects on the response latencies depended on differences in the time needed by the central nervous system to implement the motor responses. The short latencies in the most ‘criticar load directions may reflect the preparation of a default response, while additional central processing would be needed to execute the response to loads in other directions. Adjustments to local frictional anisotropies at the digit-object interface largely explained the magnitude effects.In conclusion, grip responses are automatically adjusted to the current loading condition during unpredictable loading of a hand held object. Subjects call up a previously acquired sensorimotor transform that supports grasp stability by preventing both object slippage and excessive grip forces. Cutaneous sensory information about tangential forces and frictional conditions at the digit-object interface is used to initiate and scale the grip responses to the current loading conditions, largely in a predictive manner. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1995, Härtill 5 uppsatser</p> / digitalisering@umu

Diss. (sammanfattning) Linköping : Univ. / Härtill 5 uppsatser.

Thesis (Ph.D.)--University of Florida, 2004. / Typescript. Title from title page of source document. Document formatted into pages; contains 127 pages. Includes Vita. Includes bibliographical references.

Orientador: Wagner Cotroni Valenti / Banca: Laura Satiko Okada Nakaghi / Banca: Irene Bastos Franceschini Vicentini / Banca: Helenice Pereira de barros / Banca: Roberto Munehisa Shimizy / Resumo: Os crustáceos dispõem de estruturas sensitivas que permitem receber estímulos do meio. Estes são usados para localizar e capturar o alimento. As estruturas de quimiorrecepção e mecanorrecepção são reconhecidas como os principais sentidos usados pelos crustáceos decápodas para identificação de partículas alimentares. O Macrobrachium rosenbergii é uma espécie que passa por uma fase planctônica e outra bentônica, faz grandes migrações a favor ou contra a corrente conforme a fase do ciclo de vida ou estágio fisiológico e muda o hábito alimentar de carnívoro à onívoro. Portanto, deve apresentar mecanismos de percepção dos estímulos do meio, que se modificam ao longo do desenvolvimento. Assim, a hipótese levantada nessa pesquisa foi que M. rosenbergii apresenta estruturas sensitivas na superfície do corpo e apêndices, que se modificam desde a eclosão da larva até a fase adulta. O objetivo deste trabalho foi pesquisar a ocorrência de estruturas sensitivas ao longo do desenvolvimento ontogenético de M. rosenbergii. A pesquisa ocorreu no setor de carcinicultura do CAUNESP. As larvas e pós-larvas foram coletadas de larvicultura sob sistema fechado dinâmico segundo Valenti (1998) e os juvenis e adultos dos sistemas de cultivo do setor. Os animais foram fixados com Karnovsky e dissecados. De cada animal, retiraram-se as antênulas, as antenas, as maxilas, as placas mandibulares, os três maxilípedes e os olhos para possibilitar a observação dos apêndices e as estruturas sensitivas. Os apêndices e olhos foram metalizados e fotodocumentados em microscópio eletrônico de varredura. Os olhos também foram analisados com técnicas de microscopia eletrônica de transmissão e técnica de rotina para análises histológicas segundo Behmer (2003). Identificaram-se setas sensitivas em todos os estágios larvais, pós-larva, juvenil e adulto. Elas distribuem-se em todos... (resumo completo, clicar acesso eletrônico abaixo) / Abstract: The crustaceans dispose of sensitive structures that allow them to receiive stimuli from environment. These are used to locate and capture food. Chemoreceprion and mechanoreption are known as the main senses used by the decapod crustaceans to indentify food particles. The Macrobrachium rosenbergii is a species that goes through a planktonic and a benthonic phase performs great migrations against or within the current depending on the life cycle phase or physiological stage and changes its feeding haits from carnivorous to omnivorous. Thus, it should present perception mechanisms of environment stimuli that are modified during development. Therefore, the hypotheisis brought up in this research was that the M. rosenbergii presents sensitive structures on the surface of the body and appendices that change from since the hatching of the larva up to the adult phase. The object of this paper was to research the occurrence of the sensitive structures during the entogenetic development of the M. rosenbergii. The research was performed at the carciniculture sector of the CAUNESP. The larvae and post larvae were collected from larvae culture under a closed dynamic system according to Valenti (1998) and the yong and adult larvae from the cultivating systems of the sector. The animals were set with Karnovsky and dissected. From each animal the antennules, the antennas, the maxillas, the mouthpiece plates, the three maxilipedes and the sensitve structures. The appendices and eyes were metalized and photo documented by way of electronic transmission techniques and rotine techniques for histological analysis according to Behmer (2003). Sencitive setae were identified in all larval stages, post larval, young and adult. They are distributed in all of the dissected appendices with Intense morphological variantions. They present. They present typical morphological pattern of the sensitive setae, with basal... (Complete abstract click electronic access below) / Doutor

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A microscopia permite o conhecimento dos tecidos e possibilita avaliar a morfologia de vÃrias estruturas biolÃgicas. Os mecanorreceptores e terminaÃÃes nervosas livres sÃo as unidades elementares funcionais do sistema nervoso perifÃrico. Elas transmitem ao sistema nervoso central informaÃÃes fisiolÃgicas em forma de potencial de aÃÃo, quando os constituintes articulares, cÃpsulas, ligamentos e mÃsculos sÃo submetidos aos estresses do movimento e da dor. Foram avaliadas a presenÃa, localizaÃÃo e densidade dos mecanorreceptores e terminaÃÃes nervosas livres nos ligamentos laterais do tornozelo: talofibular anterior, calcaneofibular e talofibular posterior, em 24 tornozelos, de 13 cadÃveres masculinos, nÃo formalizados. A idade presumida variou de 18 a 65 anos com a mÃdia de 41,6 anos. Cada ligamento foi dividido em 3 partes ou regiÃes: proximal, central e distal para coloraÃÃo com o cloreto de ouro a 1%. Em seguida obtiveram-se cortes seriados de 20 micrÃmetros de espessura para estudos na microscopia de luz. Foram identificados 3 tipos de mecanorreceptores, Rufini, Pacini e Golgi alÃm das terminaÃÃes nervosas livres. Utilizou-se tambÃm a classificaÃÃo de Freeman e Wike, 1967. Realizou-se a contagem individual de cada terminaÃÃo neural atravÃs da histomorfometria por sistema de teste. Este mÃtodo permitiu relacionar a contagem com a Ãrea e encontrar a densidade de cada receptor por regiÃo em milÃmetro quadrado. Concluiu-se que houve predomÃnio das terminaÃÃes neurais, tipo Pacini em relaÃÃo Ãs demais (p < 0,001). Por outro lado, nÃo houve diferenÃa significante quando comparada a densidade total entre as 3 partes ou regiÃes e a densidade total entre os 3 ligamentos (p>0,05). / Microscopic examination of different tissues is widely used to evaluate the morphology of biological structures. When joint components such as capsules, ligaments and muscles are submitted to mechanic stress and pain, free nerves endings and mechanoreceptors located within these anatomical structures detect and relay this physiological information to the central nervous system. Ankle lateral ligaments (anterior talofibular, talocalcaneal and posterior talofibular) obtained from 24 ankles of 13 masculine non-formolized unclaimed cadavers were used in the study. Age ranged from 18 to 65 years (mean age: 41,6 years). Ligaments samples were divided into 3 equal parts (proximal, central and distal segments). Following tissue impregnation with gold chloride 1% solution, serial cuts (20Â thickness) were studied under light microscopy. Mechanoreceptors (Rufini, Pacini and Golgi) and free nervous endings were identified, according to Freeman and Wikeâs classification. Counting of individual mechanoreceptors and free nerves endings (histomorphometry) and evaluation of mechanoreceptor density in squared millimeter areas was carried out in all samples. There was a significant prevalence of Pacini (p<0.001) compared with Rufini and Golgi mechanoreceptors types. However, there was no significant difference in mechanoreceptors density in the different tendon segments analyzed (p>0.05).

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O interesse de pesquisadores pelo estudo do sistema proprioceptivo vem crescendo nas Ãltimas dÃcadas. Isto à decorrente da importÃncia da integridade deste sistema no tratamento das enfermidades ortopÃdicas. Os mecanorreceptores e as terminaÃÃes nervosas livres sÃo as unidades microscÃpicas fundamentais da propriocepÃÃo e do sistema nervoso aferente. Eles transmitem ao sistema nervoso central informaÃÃes fisiolÃgicas em forma de potencial de aÃÃo, quando as estruturas articulares, cÃpsula, ligamentos e mÃsculos, sÃo submetidas ao estresse do movimento. Foram avaliadas a presenÃa e a densidade dos mecanorreceptores na cÃpsula, ligamento da cabeÃa femoral e labrum acetabular de 45 quadris masculinos. Destes, 30 foram obtidos de pacientes do sexo masculino com artrose secundÃria (grupo I) durante artroplastia e 15 de cadÃveres frescos com articulaÃÃo do quadril normal (grupo II). A idade mÃdia do grupo I foi de 56,5 e do grupo II foi de 35,6 anos. Os fragmentos obtidos foram mensurados em 2mm e corados com cloreto de ouro a 1%. ApÃs fixaÃÃo os fragmentos foram seccionados com criostato, em sÃrie de 6 micrÃmetros de espessura e submetidos à microscopia de luz. Foram identificados trÃs tipos de mecanorreceptores: Ruffini, Pacini e Golgi, alÃm das terminaÃÃes nervosas livres de acordo com a classificaÃÃo de Freeman e Wike (1967). Em cada grupo foi determinado o nÃmero e a densidade de mecanorreceptores e em seguida foram comparados os resultados. Concluiu-se que o predomÃnio das terminaÃÃes tipo Pacini no gurpo controle foi significante quando comparado com os corpÃsculos tipo Rufini (p < 0,01) e Golgi (p < 0,001).Enquanto que no grupo artrose a densidade do tipo Golgi foi menor que o tipo Pacini(p < 0,001) e terminaÃÃes nervosas livres( p < 0,01).Por outro lado, quando comparados a densidade total das terminaÃÃes nervosas nos dois grupos observou-se uma reduÃÃo significante nos quadris artrÃsicos (p = 0.008). Isto sugere fortemente que a integridade do sistema proprioceptivo parece sofrer modificaÃÃes em quadris artrÃsicos, como conseqÃÃncia da reduÃÃo do nÃmero de terminaÃÃes nervosas. Estudos eletrofisiolÃgicos futuros serÃo necessÃrios para definir o papel das terminaÃÃes nervosas e o padrÃo proprioceptivo do quadril normal do quadril artrÃsico. / Proprioceptive studies have reported growing interest in investigators in the last few decades. This is result of relevant integrity of this system in the treatment of orthopedic diseases. Mechanoreceptors and free nerve endings are the microscopy basic units from proprioception and peripheral nervous system. They transmit to the central nervous system physiological information with detection threshold when the joint are submitted to mechanical stress. The presence and density of mechanoreceptors were investigated in the capsule, teres ligament and acetabulum labrum from 45 hips joint. Of these 30 were obtained from male patients (Group I) with secondary arthrosis at open arthoplasty and 15 of fresh cadaver with normal hip joint (Group II). The mean age of group I was 56,6 and the group II was 36,5 years. The fragments obtained were measured up to 2mm and stained with gold chloride 1%. After fixation the fragments were sectioned with cryostat at serial sections of 6Âm thickness and examined using light microscopy. We identified 3 types of mechanoreceptors: Ruffini, Pacini and Golgi corpuscles, as well free nerve endings according of Freeman and Wike classified 1967. Each group was determined the number and density of mechanoreceptors and then it was compared. We conclude that the number of Pacini type was significative when it was compared with Rufini ( p < 0,01 ) and Golgi types (p< 0,001), in the normal group. However, the denstity of the Golgi type was minor compared to the Pacini ( p < 0,001) and free nerve ending ( p < 0,01 ) in the arthrosis group. Therefore, when the density total of nerve endings in normal hips were compared with arthosis hips we founded that the number decreased (p = 0.008). This is suggests strongly that the integrity of proprioceptive system seems to be modified by arthosis in consequence of nerve endings numbers. In the future, electrophysiological studies will be necessary to determine the rule of nerve endings and proprioceptive system in the normal and arthosis hip.

Individuals constantly modulate their exploratory movements and adapt their internal hypotheses to incoming sensory information to achieve a thorough and realistic percept. Perception depends on the exploratory movements as well as influencing them. While this seems to be common sense, scientifically we know very little about the temporal dynamics during haptic exploration. To address this, we investigated the exploratory force modulations of two groups of healthy young adults during the exploration of grated surfaces with differing detection difficulty during successive (n = 20) and random stimulus presentation (n = 20). Results showed that exploratory force depended on stimulus properties and increased with increasing detection difficulty. Both experiments yielded the same direction of results with slightly smaller effects in the random stimulus presentation group. Across exploration time average fingertip force also increased. The biggest increase occurred systematically at the beginning (within the first 40 percent) of exploration time per stimulus indicating that most critical information is received during the initial contact phase and is directly transformed into the exploration procedure and force application. Furthermore, video-analyses and comparisons to our high temporal resolution data revealed strong dynamic changes in pressure application during test stimulus exploration with differences in the force dynamics and exploration strategies of simple and difficult stimuli.