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At least 397 records · Page 22Linked to original sources
PubMed2002

Crossmodal spatial influences of touch on extrastriate visual areas take current gaze direction into account.

Recent results indicate that crossmodal interactions can affect activity in cortical regions traditionally regarded as "unimodal." Previously we found that combining touch on one hand with visual stimulation in the anatomically corresponding hemifield could boost responses in contralateral visual cortex. Here we manipulated which visual hemifield corresponded to the location of the stimulated hand, by changing gaze direction such that right-hand touch could now arise in either the left or right visual field. Crossmodal effects on visual cortex switched from one hemisphere to the other, depending on gaze direction, regardless of whether the hand was seen. This indicates that crossmodal influences of touch upon visual cortex depend on spatial alignment for the multimodal stimuli, with gaze posture taken into account.

Adult↗
PubMed2003

Encoding of vibrissal active touch.

Mammals acquire much of their sensory information by actively moving their sensory organs. Yet, the principles of encoding by active sensing are not known. Here we investigated the encoding principles of active touch by rat whiskers (vibrissae). We induced artificial whisking in anesthetized rats and recorded from first-order neurons in the trigeminal ganglion. During active touch, first-order trigeminal neurons presented a rich repertoire of responses, which could not be inferred from their responses to passive deflection stimuli. Individual neurons encoded four specific events: whisking, contact with object, pressure against object, and detachment from object. Whisking-responsive neurons fired at specific deflection angles, reporting the actual whiskers' position with high precision. Touch-responsive neurons encoded the horizontal coordinate of objects' position by spike timing. These findings suggest two specific encoding-decoding schemes for horizontal object position in the vibrissal system.

Action Potentials↗
PubMed2002

Multisensory fusion: simultaneous re-weighting of vision and touch for the control of human posture.

We examined the generally held belief that the postural control system is able to re-weight its available sensory inputs in order to optimize stance control in altered sensory environments. Our view is that previous accounts of sensory re-weighting provide only indirect evidence, which is subject to alternative explanations. The present results provide strong evidence for sensory re-weighting as the primary mechanism for changes observed in postural sway between conditions. Subjects were presented with small-amplitude, oscillatory visual and somatosensory stimuli at 0.20 and 0.28 Hz, respectively, in five conditions that manipulated the amplitudes of stimulus motion. Gain calculated in each trial with respect to each of the two stimuli was found to change systematically as stimulus motion amplitudes changed across condition. The observed pattern of gain rules out a constant-weight, linear account of posture and is consistent with the re-weighting hypothesis. Parameter fits of a third-order, linear stochastic model to postural sway trajectories in each condition showed that changes in gain across condition were primarily due to changes in coupling coefficients rather than changes in parameters that characterize the stability of the postural system. Visual gain was found to depend upon visual motion amplitude and touch gain was found to depend upon touch motion amplitude, indicating intra-modality dependencies. Visual gain also depended upon touch motion amplitude, indicating an inter-modality dependence. To our knowledge, simultaneous re-weighting of more than one sensory input has never been rigorously demonstrated. These techniques may be able to resolve the source of balance control deficits across populations with far more certainty than currently possible.

Adult↗
PubMedDate not supplied

Force-feedback grasper helps restore sense of touch in minimally invasive surgery.

The age of minimally invasive surgery has brought forth astounding changes in the health care field. Less pain and quicker patient recovery have been demonstrated with several types of operations that were once performed by an open technique. With these changes have come reports of complications. The decreased sense of touch is just one of several limitations inherent to current techniques of minimally invasive surgery that limit detection of subtle or unapparent lesions on palpation, such as common duct stones and liver lesions. The purpose of this study is to demonstrate the ability of a force-feedback-equipped grasper to restore some of the sense of touch that is lost in minimally invasive surgery. To demonstrate this ability, we created six silicone phantoms of identical dimensions but graded compliance, and asked 10 subjects to place them in increasing/decreasing order of compliance. They used three tools (their dominant gloved hand, a standard laparoscopic Babcock grasper, and our force-feedback device fitted with the identical Babcock grasper) to rate the compliance of the samples in a blinded fashion. These conditions thus approximated the conditions of open surgery, minimally invasive surgery, and minimally invasive surgery fitted with a force-sensing device, in terms of palpating tissues. Five surgeons skilled in minimally invasive surgery and five nonsurgeons participated in the study. The results indicate that the force-feedback device is significantly (P <0.05) better than a standard Babcock grasper at rating tissue compliance, but was not as successful as a gloved hand (mean of squared errors = 1.06, 3. 15, and 0.25, respectively). There was no significant difference between surgeons and nonsurgeons in rating compliance. We conclude that this force-feedback instrument is able to partially restore the sense of touch in minimally invasive surgery. This restored ability may thus potentially result in more efficient operations with improved diagnostic capabilities and fewer complications during minimally invasive surgery.

Biocompatible Materials↗
PubMed2003

Touch sensitivity in plants: be aware or beware.

A recent paper shows that touch sensing and gravity sensing interact to guide roots around obstacles. Upon encountering an object, the touch stimulus induces curvature behind the root tip and partially suppresses the gravity response, enabling the root to navigate around the obstacle while maintaining contact with it. These findings raise questions regarding the nature of touch sensing in roots, the location of the sensors, and the manner in which these sensory systems interact to accomplish obstacle avoidance.

Arabidopsis↗
PubMed1998

Perceiving the width and height of a hand-held object by dynamic touch.

The haptic perceptual sybsystem of dynamic touch is prominent in manipulating and transporting objects, providing a nonvisible awareness of their linear dimensions. The hypothesis that perceptions of object width and height by dynamic touch are different functions of the inertia tensor is addressed. In two experiments heights and widths of nonvisible wielded objects were judged separately. Experiment 1 used solid rectangular parallelepipeds of different sizes; Experiment 2 used objects of identical mass and linear dimensions but nonidentical inertia ellipsoids. Width and height perceptions of comparable reliability and accuracy were found to vary as distinct functions of the objects' inertial eigenvalues. Discussion focused on the notion of tangible shape and on the selectivity of attention within dynamic touch.

Hand↗
PubMed2000

The mammalian sodium channel BNC1 is required for normal touch sensation.

Of the vertebrate senses, touch is the least understood at the molecular level The ion channels that form the core of the mechanosensory complex and confer touch sensitivity remain unknown. However, the similarity of the brain sodium channel 1 (BNC1) to nematode proteins involved in mechanotransduction indicated that it might be a part of such a mechanosensor. Here we show that disrupting the mouse BNC1 gene markedly reduces the sensitivity of a specific component of mechanosensation: low-threshold rapidly adapting mechanoreceptors. In rodent hairy skin these mechanoreceptors are excited by hair movement. Consistent with this function, we found BNC1 in the lanceolate nerve endings that lie adjacent to and surround the hair follicle. Although BNC1 has been proposed to have a role in pH sensing, the acid-evoked current in cultured sensory neurons and the response of acid-stimulated nociceptors were normal in BNC1 null mice. These data identify the BNC1 channel as essential for the normal detection of light touch and indicate that BNC1 may be a central component of a mechanosensory complex.

Animals↗
PubMed2006

A stomatin-domain protein essential for touch sensation in the mouse.

Touch and mechanical pain are first detected at our largest sensory surface, the skin. The cell bodies of sensory neurons that detect such stimuli are located in the dorsal root ganglia, and subtypes of these neurons are specialized to detect specific modalities of mechanical stimuli. Molecules have been identified that are necessary for mechanosensation in invertebrates but so far not in mammals. In Caenorhabditis elegans, mec-2 is one of several genes identified in a screen for touch insensitivity and encodes an integral membrane protein with a stomatin homology domain. Here we show that about 35% of skin mechanoreceptors do not respond to mechanical stimuli in mice with a mutation in stomatin-like protein 3 (SLP3, also called Stoml3), a mammalian mec-2 homologue that is expressed in sensory neurons. In addition, mechanosensitive ion channels found in many sensory neurons do not function without SLP3. Tactile-driven behaviours are also impaired in SLP3 mutant mice, including touch-evoked pain caused by neuropathic injury. SLP3 is therefore indispensable for the function of a subset of cutaneous mechanoreceptors, and our data support the idea that this protein is an essential subunit of a mammalian mechanotransducer.

Acid Sensing Ion Channels↗
PubMed2004

The MEC-4 DEG/ENaC channel of Caenorhabditis elegans touch receptor neurons transduces mechanical signals.

Transformation of mechanical energy into ionic currents is essential for touch, hearing and nociception. Although DEG/ENaC proteins are believed to form sensory mechanotransduction channels, the evidence for this role remains indirect. By recording from C. elegans touch receptor neurons in vivo, we found that external force evokes rapidly activating mechanoreceptor currents (MRCs) carried mostly by Na(+) and blocked by amiloride-characteristics consistent with direct mechanical gating of a DEG/ENaC channel. Like mammalian Pacinian corpuscles, these neurons depolarized with both positive and negative changes in external force but not with sustained force. Null mutations in the DEG/ENaC gene mec-4 and in the accessory ion channel subunit genes mec-2 and mec-6 eliminated MRCs. In contrast, the genetic elimination of touch neuron-specific microtubules reduced, but did not abolish, MRCs. Our findings link the application of external force to the activation of a molecularly defined metazoan sensory transduction channel.

Amiloride↗
PubMed2002

Unmyelinated tactile afferents signal touch and project to insular cortex.

There is dual tactile innervation of the human hairy skin: in addition to fast-conducting myelinated afferent fibers, there is a system of slow-conducting unmyelinated (C) afferents that respond to light touch. In a unique patient lacking large myelinated afferents, we found that activation of C tactile (CT) afferents produced a faint sensation of pleasant touch. Functional magnetic resonance imaging (fMRI) analysis during CT stimulation showed activation of the insular region, but not of somatosensory areas S1 and S2. These findings identify CT as a system for limbic touch that may underlie emotional, hormonal and affiliative responses to caress-like, skin-to-skin contact between individuals.

Adult↗
PubMed1992

Open-set word identification by an adult with profound hearing impairment: integration of touch, aided hearing, and speechreading.

The ability of an adult with profound hearing impairment to integrate speech information from touch, aided hearing, and speechreading in identification of open-set words was investigated. A list was obtained of 735 words that the subject failed to identify using any single modality: touch, with either the Tacticon 1600, a multichannel electrocutaneous vocoder (TV), or the Tactaid II, a 2-channel vibrotactile aid (TA); aided hearing (H); or speechreading (S). To test integration, observed word identification performance in combined-modality conditions was compared with predicted performance calculated from single-modality scores. Words were randomly assigned to seven conditions: (a) S+H, (b) H+TV, (c) H+TA, (d) S+TV, (e) S+TV+H, and (f) S+TA+H. Results indicated that the subject integrated speech information across modalities, with highest performance in the S+TV+H and S+TA+H conditions. Integration also occurred when both speechreading and touch were used and when both speechreading and aided hearing were used.

Adult↗
PubMed1999

Modes of relating in a caring conversation: a research synthesis on presence, touch and listening.

The purpose of this qualitative research synthesis was to develop an ontological and theoretical understanding of presence, touch and listening in a caring conversation. The material consisted of 28 articles published between 1989 and 1997 in caring and nursing journals. The examination was based on a qualitative research synthesis approach applied to each concept separately. The synthesis was summed up in a model encompassing two modes of relating in a caring conversation: a connection with high intersubjectivity and a contact with limited intersubjectivity. In a connection the nurse is listening, using caring and connective touch and is present as 'being with' the patient. In a contact, the nurse is hearing, using task orientated touch and is present as 'being there' for the patient. A connection is grounded in a mutual receiving which allows a high degree of intersubjectivity. The nurse and the patient are not only present to each other as roles but also as unique persons. Contact is grounded in the attentive attitude of the nurse and in the fact that the nurse and the patient are relying on roles which allow a limited intersubjectivity. The model provides a point of departure for clinical discussions among nurses as well as areas for further research in the field of nurse-patient communication.

Caregivers↗
PubMed2000

Phantom limb pain treated with therapeutic touch: a case report.

Phantom limb pain is a widespread condition that responds poorly to conventional medical and surgical treatments. A case report is presented of the successful treatment of phantom leg pain in a 62-year-old man with peripheral vascular disease using the complementary medical technique of Therapeutic Touch. The clinical and research literature of Therapeutic Touch is briefly reviewed, with regard to subjective outcome measures like pain and anxiety, as well as to several objective measures of physiologic function. The possible role of nonspecific factors like placebo responsiveness or hypnotic dissociation in this case are considered, as are the applicability of complementary and alternative medicine to phantom limb pain, the neurologic mechanisms that generate phantom sensations, and the possible mechanism of action of Therapeutic Touch.

Amputation, Surgical↗
PubMedDate not supplied

Outcomes of comfort touch in institutionalized elderly female residents.

Comfort touch as a holistic nursing intervention has gained considerable attention in the past decade. The purpose of this experimental study was to examine whether comfort touch improved the perceptions of self-esteem, well-being and social processes, health status, life satisfaction and self-actualization, and faith or belief and self-responsibility in 45 institutionalized elderly female residents. Results revealed that comfort touch significantly improved the perceptions of all elements. This article offers recommendations for practice, research, and education.

Aged↗
PubMed2000

Vertical and bisection bias in active touch.

We investigated the conditions that underlie the vertical and bisection illusion in touch, in order to understand the basis of their similarity to visual illusions, and the means of reducing the biases in length perception by active touch. Movement, speed, and spatial reference cues were tested. Movements in scanning L-shapes in ipsilateral and contralateral (across the body midline) table-top space produced significant underestimation of the vertical line with the right hand, but not with the left hand. Right-handed scanning of L-shapes showed no significant bias when the vertical line in the figure was aligned to the body midline, suggesting that spatial cues were involved. The vertical line was overestimated in inverted T-shapes, but underestimated in rotated T-shapes, implicating line bisection. Holding scanning latencies constant reduced the vertical error for inverted T-shapes, but could not explain the bisection bias. Sectioning biases were predicted by the location of junctions on sectioned lines, showing that junction points act as misleading anchor cues for movement extents. The illusion was significantly reduced when reference information was added by instructing subjects to relate two-handed scanning of the figure to an external frame and to body-centred cues. It is argued that disparities in spatial reference (anchor) cues for movement extents are involved in vertical and bisection biases in active touch. The hypothesis that length illusions depend on disparities in spatial reference information can also account for the similarity of the tactile to the visual horizontal-vertical illusion.

Adolescent↗
PubMed2000

Affectionate same-sex touch: the influence of homophobia on observers' perceptions.

The author extended the proposition (V. J. Derlega, R. J. Lewis, S. Harrison, B. A. Winstead, & R. Costanza, 1989) that the fear of being seen as homosexual accounts for the common finding that U.S. women engage in more same-sex touch than do U.S. men. The author proposed a theoretic model positing that the magnitude of homophobia's influence on behavior and on reactions to behavior is proportional to the likelihood that the behavior is sexual in nature. An experiment involving reactions to same-sex embraces demonstrated that, although homophobia was negatively related to evaluations of same-sex affectionate touch, the magnitude of the relationship covaried with the probability that the touch was sexual. The implications of these findings for longer range theory development are discussed.

Adolescent↗
PubMed1995

Interpersonal distance, body orientation, and touch: effects of culture, gender, and age.

Video recordings of naturally occurring interactions in England, France, the Netherlands, Italy, Greece, Scotland, and Ireland were coded and analyzed to examine the effects of culture, gender, and age on interpersonal distance, body orientation, and touch. Results partially supported expected differences between contact cultures of southern Europe and noncontact cultures of northern Europe with respect to touch. More touch was observed among Italian and Greek dyads than among English, French, and Dutch dyads. In addition, an interaction effect between age and gender for body orientation suggested opposite development trends for mixed-sex dyads and male dyads. Whereas mixed dyads tended to maintain less direct orientations as they aged, male dyads maintained more direct orientations.

Adult↗
PubMed2003

Intra- and interactive touch on the face.

Experiments were performed in which the subjective size of steel balls was judged by the method of absolute magnitude estimation (AME). The balls were rolled actively ("scripting") by the right index finger pad of the subject over the passively receiving areas of the face, namely the forehead, cheek and the vermilion border of the lower lip. These areas were stimulated on the subject's own person (intra-active touch), on another person's face (interactive touch) and by another person upon the face of the subject (interactive touch). Results indicate that size perception appears to be governed primarily by the mechanical characteristics of the stimuli, including the balls and the sites on the face. When the subject's finger was used to script upon another's face, there were significant differences among or between the sites. When another person scripted upon the subject's face there were no significant differences among any of the sites. The results are discussed considering mode of stimulation and tissue mechanics.

Cheek↗