The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Jean-louis Thonnard - One of the best experts on this subject based on the ideXlab platform.

  • Surface strain measurements of Fingertip skin under shearing.
    Journal of the Royal Society Interface, 2016
    Co-Authors: Benoit P. Delhaye, Allan Barrea, Benoni B. Edin, Philippe Lefèvre, Jean-louis Thonnard
    Abstract:

    The temporal evolution of surface strain, resulting from a combination of normal and tangential loading forces on the fingerpad, was calculated from high-resolution images. A customized robotic device loaded the Fingertip with varying normal force, tangential direction and tangential speed. We observed strain waves that propagated from the periphery to the centre of the contact area. Consequently, different regions of the contact area were subject to varying degrees of compression, stretch and shear. The spatial distribution of both the strains and the strain energy densities depended on the stimulus direction. Additionally, the strains varied with the normal force level and were substantial, e.g. peak strains of 50% with a normal force of 5 N, i.e. at force levels well within the range of common dexterous manipulation tasks. While these observations were consistent with some theoretical predictions from contact mechanics, we also observed substantial deviations as expected given the complex geometry and mechanics of Fingertips. Specifically, from in-depth analyses, we conclude that some of these deviations depend on local fingerprint patterns. Our data provide useful information for models of tactile afferent responses and background for the design of novel haptic interfaces.

  • texture induced vibrations in the forearm during tactile exploration
    Frontiers in Behavioral Neuroscience, 2012
    Co-Authors: Benoit P. Delhaye, Philippe Lefèvre, Vincent Hayward, Jean-louis Thonnard
    Abstract:

    Humans can detect and discriminate between fine variations of surface roughness using active touch. It is hitherto believed that roughness perception is mediated mostly by cutaneous and subcutaneous afferents located in the Fingertips. However, recent findings have shown that following abolishment of cutaneous afferences resulting from trauma or pharmacological intervention, the ability of subjects to discriminate between textures roughness was not significantly altered. These findings suggest that the somatosensory system is able to collect textural information from other sources than Fingertip afference. It follows that signals resulting of the interaction of a finger with a rough surface must be transmitted to stimulate receptor populations in regions far away from the contact. This transmission was characterized by measuring in the wrist vibrations originating at the Fingertip and thus propagating through the finger, the hand and the wrist during active exploration of textured surfaces. The spectral analysis of the vibrations taking place in the forearm tissues revealed regularities that were correlated with the scanned surface and the speed of exploration. In the case of periodic textures, the vibration signal contained a fundamental frequency component corresponding to the finger velocity divided by the spatial period of the stimulus. This regularity was found for a wide range of textural length scales and scanning velocities. For non-periodic textures, the spectrum of the vibration did not contain obvious features that would enable discrimination between the different stimuli. However, for both periodic and non-periodic stimuli, the intensity of the vibrations could be related to the microgeometry of the scanned surfaces.

Maria Samara - One of the best experts on this subject based on the ideXlab platform.

  • Successful Intravenous Regional Sympathetic Blockade (Bier’s Block) with Guanethidine and Lidocaine in a Patient with Advanced Buerger’s Disease (Thromboangiitis Obliterans)
    2016
    Co-Authors: Kosmas I Paraskevas, Aikaterini A Trigka, Maria Samara
    Abstract:

    A 65-year-old man, a heavy smoker with Buerger’s disease (thromboangiitis obliterans), presented to this department with persistent severe ischemic rest pain at the fingers of his right hand, not responding to oral treatment with vasodilators and analgesics. Critical blood flow was discovered in the middle, ring, and little finger, with ischemic ulcerations apparent in the Fingertips of these 3 fingers. The distal phalanx of the little finger had been amputated 6 months before because of gangrenous necrosis. In an attempt to avoid further disabling ampu-tations, the patient received 3 series of Bier’s block sessions with guanethidine and lidocaine according to a specific protocol. Marked increase in finger blood flow was induced even after the first series, and complete disappearance of both Fingertip ulcerations and ischemic rest pain was achieved. No side effects were observed. The above-described method in a patient with advanced Buerger’s disease resulted in excellent pain relief and full restoration of both blood flow and function of the affected fingers

  • successful intravenous regional sympathetic blockade bier s block with guanethidine and lidocaine in a patient with advanced buerger s disease thromboangiitis obliterans a case report
    Angiology, 2005
    Co-Authors: Kosmas I Paraskevas, Aikaterini A Trigka, Maria Samara
    Abstract:

    A 65-year-old man, a heavy smoker with Buerger's disease (thromboangiitis obliterans), presented to this department with persistent severe ischemic rest pain at the fingers of his right hand, not responding to oral treatment with vasodilators and analgesics. Critical blood flow was discovered in the middle, ring, and little finger, with ischemic ulcerations apparent in the Fingertips of these 3 fingers. The distal phalanx of the little finger had been amputated 6 months before because of gangrenous necrosis. In an attempt to avoid further disabling amputations, the patient received 3 series of Bier's block sessions with guanethidine and lidocaine according to a specific protocol. Marked increase in finger blood flow was induced even after the first series, and complete disappearance of both Fingertip ulcerations and ischemic rest pain was achieved. No side effects were observed. The above-described method in a patient with advanced Buerger's disease resulted in excellent pain relief and full restoration of both blood flow and function of the affected fingers.

Na Jin Seo - One of the best experts on this subject based on the ideXlab platform.

  • application of vibration to wrist and hand skin affects Fingertip tactile sensation
    Physiological Reports, 2015
    Co-Authors: Kishor Lakshminarayanan, Abigail Lauer, Viswanathan Ramakrishnan, John G Webster, Na Jin Seo
    Abstract:

    A recent study showed that Fingertip pads' tactile sensation can improve by applying imperceptible white-noise vibration to the skin at the wrist or dorsum of the hand in stroke patients. This study further examined this behavior by investigating the effect of both imperceptible and perceptible white-noise vibration applied to different locations within the distal upper extremity on the Fingertip pads' tactile sensation in healthy adults. In 12 healthy adults, white-noise vibration was applied to one of four locations (dorsum hand by the second knuckle, thenar and hypothenar areas, and volar wrist) at one of four intensities (zero, 60%, 80%, and 120% of the sensory threshold for each vibration location), while the Fingertip sensation, the smallest vibratory signal that could be perceived on the thumb and index Fingertip pads, was assessed. Vibration intensities significantly affected the Fingertip sensation (P   0.01), all compared with the zero vibration condition. This effect with vibration intensity conforms to the stochastic resonance behavior. Nonspecificity to the vibration location suggests the white-noise vibration affects higher level neuronal processing for Fingertip sensing. Further studies are needed to elucidate the neural pathways for distal upper extremity vibration to impact Fingertip pad tactile sensation.

  • remote vibrotactile noise improves light touch sensation in stroke survivors Fingertips via stochastic resonance
    Journal of Neuroengineering and Rehabilitation, 2013
    Co-Authors: Leah R Enders, Pilwon Hur, Michelle J Johnson, Na Jin Seo
    Abstract:

    Stroke rehabilitation does not often integrate both sensory and motor recovery. While subthreshold noise was shown to enhance sensory signal detection at the site of noise application, having a noise-generating device at the Fingertip to enhance Fingertip sensation and potentially enhance dexterity for stroke survivors is impractical, since the device would interfere with object manipulation. This study determined if remote application of subthreshold vibrotactile noise (away from the Fingertips) improves Fingertip tactile sensation with potential to enhance dexterity for stroke survivors. Index finger and thumb pad sensation was measured for ten stroke survivors with Fingertip sensory deficit using the Semmes-Weinstein Monofilament and Two-Point Discrimination Tests. Sensation scores were measured with noise applied at one of three intensities (40%, 60%, 80% of the sensory threshold) to one of four locations of the paretic upper extremity (dorsal hand proximal to the index finger knuckle, dorsal hand proximal to the thumb knuckle, dorsal wrist, volar wrist) in a random order, as well as without noise at beginning (Pre) and end (Post) of the testing session. Vibrotactile noise of all intensities and locations instantaneously and significantly improved Monofilament scores of the index Fingertip and thumb tip (p < .01). No significant effect of the noise was seen for the Two-Point Discrimination Test scores. Remote application of subthreshold (imperceptible) vibrotactile noise at the wrist and dorsal hand instantaneously improved stroke survivors’ light touch sensation, independent of noise location and intensity. Vibrotactile noise at the wrist and dorsal hand may have enhanced the Fingertips’ light touch sensation via stochastic resonance and interneuronal connections. While long-term benefits of noise in stroke patients warrants further investigation, this result demonstrates potential that a wearable device applying vibrotactile noise at the wrist could enhance sensation and grip ability without interfering with object manipulation in everyday tasks.

Jun Ueda - One of the best experts on this subject based on the ideXlab platform.

  • wearable sensorimotor enhancer for Fingertip based on stochastic resonance effect
    IEEE Transactions on Human-Machine Systems, 2013
    Co-Authors: Yuichi Kurita, Minoru Shinohara, Jun Ueda
    Abstract:

    This paper reports on the results of an experiment involving a wearable sensorimotor enhancer intended to improve tactile sensitivity in human Fingertips. As briefly exposing tactile receptors to subsensory vibration is known to enhance tactile sensitivity thanks to a phenomenon called stochastic resonance in the somatosensory system, applying white-noise vibration to a Fingertip is expected to improve the sense of touch and associated motor skills. Against such a background, a prototype of a wearable device called a sensorimotor enhancer is proposed here. The device is attached to the radial side of the Fingertip and stimulates tactile receptors by applying vibration from a lead zirconate titanate piezoelectric stack actuator. This design keeps the palmar region free, thereby helping to maintain the wearer's manipulative ability. Sensory and motor tests involving 11 human subjects were conducted to determine the efficacy of the device, and the results confirmed its usefulness.

Miguel A L Nicolelis - One of the best experts on this subject based on the ideXlab platform.

  • creating a neuroprosthesis for active tactile exploration of textures
    Proceedings of the National Academy of Sciences of the United States of America, 2019
    Co-Authors: Joseph E Odoherty, Solaiman Shokur, Leonel E Medina, Mikhail A Lebedev, Miguel A L Nicolelis
    Abstract:

    Intracortical microstimulation (ICMS) of the primary somatosensory cortex (S1) can produce percepts that mimic somatic sensation and, thus, has potential as an approach to sensorize prosthetic limbs. However, it is not known whether ICMS could recreate active texture exploration—the ability to infer information about object texture by using one’s Fingertips to scan a surface. Here, we show that ICMS of S1 can convey information about the spatial frequencies of invisible virtual gratings through a process of active tactile exploration. Two rhesus monkeys scanned pairs of visually identical screen objects with the Fingertip of a hand avatar—controlled first via a joystick and later via a brain–machine interface—to find the object with denser virtual gratings. The gratings consisted of evenly spaced ridges that were signaled through individual ICMS pulses generated whenever the avatar’s Fingertip crossed a ridge. The monkeys learned to interpret these ICMS patterns, evoked by the interplay of their voluntary movements and the virtual textures of each object, to perform a sensory discrimination task. Discrimination accuracy followed Weber’s law of just-noticeable differences (JND) across a range of grating densities; a finding that matches normal cutaneous sensation. Moreover, 1 monkey developed an active scanning strategy where avatar velocity was integrated with the ICMS pulses to interpret the texture information. We propose that this approach could equip upper-limb neuroprostheses with direct access to texture features acquired during active exploration of natural objects.

  • creating a neuroprosthesis for active tactile exploration of textures
    bioRxiv, 2019
    Co-Authors: Joseph E Odoherty, Solaiman Shokur, Leonel E Medina, Mikhail A Lebedev, Miguel A L Nicolelis
    Abstract:

    Abstract Intracortical microstimulation (ICMS) of the primary somatosensory cortex (S1) can produce percepts that mimic somatic sensation and thus has potential as an approach to sensorize prosthetic limbs. However, it is not known whether ICMS could recreate active texture exploration—the ability to infer information about object texture by using one’s Fingertips to scan a surface. Here we show that ICMS of S1 can convey information about the spatial frequencies of invisible virtual gratings through a process of active tactile exploration. Two rhesus monkeys scanned pairs of visually identical screen objects with the Fingertip of a hand avatar, controlled via a joystick and later via a brain-machine interface, to find the one with denser virtual gratings. The gratings consisted of evenly spaced ridges that were signaled through ICMS pulses generated when the avatar’s Fingertip crossed each ridge. The monkeys learned to interpret these ICMS patterns evoked by the interplay of their voluntary movements and the virtual textures of each object. Discrimination accuracy across a range of grating densities followed Weber’s law of just-noticeable differences (JND), a finding that matches normal cutaneous sensation. Moreover, one monkey developed an active scanning strategy where avatar velocity was integrated with the ICMS pulses to interpret the texture information. We propose that this approach could equip upper-limb neuroprostheses with direct access to texture features acquired during active exploration of natural objects.