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At least 721 records · Page 40Linked to original sources
PubMed2001

Arthropod touch reception: stimulus transformation and finite element model of spider tactile hairs.

Striving towards an in depth understanding of stimulus transformation in arthropod tactile hairs, we studied the mechanical events associated with tactile stimulation. A finite element model was developed taking a tarsal tactile hair of the spider Cupiennius salei as an example. Considering hair diameter, wall thickness, and curvature, the hair is subdivided into six regions each with its specific mechanical properties. When the hair is touched from above with a flat surface oriented parallel to the tarsus the point of stimulus contact moves towards the hair base with increasing load and hair deflection. Thereby the effective lever arm is reduced protecting the hair against breaking near its base. At the same time the mechanical working range of the hair increases implying higher mechanical sensitivity for small deflections (about 5x10(-5) N/degrees) than for large deflections (about 1x10(-4) N/degrees). The major stresses within the hair shaft are axial stresses due to bending. The position of stress maxima moves along the shaft with the movement of the stimulus contact point. Remarkably, the amplitude of this maximum (about 1x10(5) N/m2) hardly changes with increasing loading force due to the way the hair shaft is deflected by the stimulus.

Animals↗
PubMed1975

The subfrontal lobe and touch learning in the octopus.

Octopuses with the supraoesophageal lobes of the brain divided longitudinally can be taught to discriminate using the arms on either side. If there is no further lesion the two sides behave alike. Lesions limited to one side did not affect the performance of the contralateral, "control" side. Lesions made in the vertical (n=7) lobes led to a slight drop in the quality of performance in training to take a smooth sphere, in discrimination training (rough vs. smooth spheres) and in subsequent extinction and transfer tests. After removal of the median inferior frontal lobe (n = 10) there were somewhat greater effects in the same direction. Much larger effects followed interference with the subfrontal lobe (n = 20). Removal of parts from this always led to a marked loss of capacity for touch learning, broadly dependent on the amount of tissue removed. Removal of the whole of the subfrontal lobe (n = 6) produced animals that showed, at best, only very slight signs of learning. Such animals can adjust their overall level of response as a result of training but they seem incapable of adjusting response levels to two objects independently. These results are discussed in relation to the function of the subfrontal lobe as a memory store.

Animals↗
PubMed1977

Absolute and differential sensitivities to touch stimuli after spinal cord lesions in monkeys.

Concurrent two-choice and go--no-go procedures were used to measure difference thresholds (DLs) for discrimination of touch intensities and absolute thresholds (RLs) for detection of light tactile stimuli by Macaca speciosa monkeys. Consistent with the classical proposition that the spinothalamic tracts of primates contain sufficient tactile input to support simple recognition of light skin contact, RLs were not affected by lesions of the ipsilateral dorsal column or by subsequent section of the ipsilateral dorsolateral column. There was, however, a clear dissociation of the effects of the spinal lesions on the absolute and difference thresholds. DLs were elevated ipsilaterally by lesions of the dorsal column and, after long periods of postoperative testing (more than 6 months), the DLs returned to postoperative levels. Subsequent interruption of the dorsolateral column again elevated DLs ipsilaterally and with extensive testing DLs again returned to preoperative levels.

Animals↗
PubMed1994

Spatially modulated touch responses in parietal cortex.

Cortical neurons with low-threshold, cutaneous receptive fields on the fingers were recorded in areas 5 and 7b of the parietal lobe in two awake monkeys, trained in a visually guided reach task. 72% (81/113) of the cells responded when targets displayed on a videomonitor were actively touched. Of these, 20 neurons discharged preferentially when target contact was made on one side of the screen compared with the other. This spatial modulation of the cutaneous modality may have originated in neighboring joint-related neurons which were directionally selective.

Animals↗
PubMed1984

Touch dome properties as a function of age.

A study was made of touch domes in the lumbar skin of rats of different ages. The mean density of the domes in 11- to 29-day-old rats ("pups") was 43.1 +/- 16.6/cm2 and was approximately four times higher than that in adult animals (11.6 +/- 2.8/cm2); no loss of domes appeared to have taken place in the oldest animals examined (21 months). By repeating measurements of density in the territory of a single T13 dorsal cutaneous nerve, it was shown that density decreased during body growth because no additional domes were formed to compensate for enlargement of the skin. The mechanical thresholds of the domes were lowest in the youngest rats and highest in the oldest ones (mean values, 3.21 +/- 1.96 and 9.19 +/- 5.88 microns, respectively). The sizes of the domes increased until adulthood, the mean diameters being 170 +/- 8 and 314 +/- 9 microns, respectively in pups and mature animals. The possible implications of the findings for spatial discrimination by the rat central nervous system have been considered.

Aging↗
PubMed1984

Effects of vincristine sulfate on touch dome function in the rat.

The responses of touch domes in hairy skin of the rat to mechanical stimulation were examined after single doses of vincristine sulfate. Within 24 h of drug administration, the mean thresholds of domes to brief mechanical pulses had increased threefold, from 5.2 +/- 2.0 to 14.2 +/- 8.8 microns. This elevated threshold was maintained for 2 weeks but by the 3rd week the domes had recovered normal excitability. Measurements of response latency suggested that the increase in receptor thresholds occurred without impulse propagation being impaired in the axons.

Animals↗
PubMed1984

The meaning of touch in care practice.

76 respondents were asked to categorise 28 specified examples of touching within health care. Broad agreement was found across the sample group as a whole, in its application of 8 of the 10 categories offered by the researchers. The need for alternative or additional categories and the occasional differences between responses of professional groups are discussed.

Female↗
PubMed1975

Influence on touch, vibration and cutaneous pain of dorsal column stimulation in man.

Five patients out of a group of ten who had dorsal column electrodes implanted for the relief of chronic pain were examined for the influence of the stimulation on the spontaneous pain and on the thresholds for touch, vibration and cutaneous pain induced by pinching. Stimulation producing paraesthesias resulted in an almost immediate abolishment of spontaneous pain and was accompanied by significant elevations of both tactile and vibratory thresholds. Elevation of thresholds was confined to segments below the site of implantation and occurred bilaterally also when the paraesthesias were restricted to one side. The changes of thresholds generally persisted for some time after the stimulation but these effects were short lasting in comparison with the effect on spontaneous pain. Elevation of sensory thresholds is presumably not due to blocking of the primary neurones but to central inhibitory mechanisms. The thresholds for induced cutaneous pain were not influenced by dorsal column stimulation except for one case in whom an abnormally low threshold within an hyperaestethic area became normalized.

Adult↗
PubMed1996

Basal and touch-evoked fos-like immunoreactivity during experimental inflammation in the rat.

Fos-immunoreactivity can readily be induced in spinal cord neurones by noxious, but to a much more limited extent, by innocuous peripheral stimuli. The present study has investigated whether low intensity stimuli and electrical stimulation of A beta afferents elicit greater c-fos expression during the behavioural sensory hypersensitivity generated by experimental peripheral inflammation. We have examined the time-course of c-fos expression after inflammation produced by either an intra-plantar injection of the irritant turpentine oil or of complete Freund's adjuvant (CFA). In the former case, a significant initial expression in all dorsal horn laminae was followed by a gradual decrease, whereas after CFA injection, an initial expression limited to the superficial laminae subsequently extended into the deep laminae, with a decrease at 24 h and an increase in labelling at later times. Low intensity touch stimuli repeated for 10 min, when applied at 24 h and 48 h after CFA injection, elicited a significant increase in the number of Fos-immunoreactive neurons in both the superficial and deep laminae of the dorsal horn compared to non-inflamed animals. Electrical stimulation of the sciatic nerve 24 h post-CFA injection, at a strength sufficient only to activate A beta-afferents fibres (100 microA, 50 microseconds, 10 min), also elicited a significant increase in labelling relative to the same stimuli applied in control animals, especially in laminae V-VI. The present results demonstrate that low intensity cutaneous stimuli elicit a significantly greater increase in c-fos expression in dorsal horn neurons during peripheral inflammation and that A beta-afferent input contributes to this, a finding that may relate to the allodynia experienced during inflammation.

Afferent Pathways↗
PubMed1994

Touch and visualisation to facilitate a therapeutic relationship in an intensive care unit--a personal experience.

This paper describes how the nature of touch was explored and utilised in nursing practice to promote a therapeutic relationship between nurse and client in an intensive care setting. It explains how this, and other complementary therapies such as visualisation and relaxation techniques, were used to facilitate a counselling situation, and also to effect the resolution of acute anxiety as an alternative to the traditional allopathic approach.

Adolescent↗
PubMed2004

On the inability to ignore touch when responding to vision in the crossmodal congruency task.

We investigated the extent to which people can selectively ignore distracting vibrotactile information when performing a visual task. In Experiment 1, participants made speeded elevation discrimination responses (up vs. down) to a series of visual targets presented from one of two eccentricities on either side of central fixation, while simultaneously trying to ignore task-irrelevant vibrotactile distractors presented independently to the finger (up) vs. thumb (down) of either hand. Participants responded significantly more slowly, and somewhat less accurately, when the elevation of the vibrotactile distractor was incongruent with that of the visual target than when they were presented from the same (i.e., congruent) elevation. This crossmodal congruency effect was significantly larger when the visual and tactile stimuli appeared on the same side of space than when they appeared on different sides, although the relative eccentricity of the two stimuli within the hemifield (i.e., same vs. different) had little effect on performance. In Experiment 2, participants who crossed their hands over the midline showed a very different pattern of crossmodal congruency effects to participants who adopted an uncrossed hands posture. Our results suggest that both the relative external location and the initial hemispheric projection of the target and distractor stimuli contribute jointly to determining the magnitude of the crossmodal congruency effect when participants have to respond to vision and ignore touch.

Adult↗
PubMed2006

Spatial limits on referred touch to an alien limb may reflect boundaries of visuo-tactile peripersonal space surrounding the hand.

In this study, the spatial limits of referred touch to a rubber hand were investigated. Participants rated the strength of the perceived illusion when the rubber hand was placed in one of six different spatial positions (at a distance of 17.5-67.5cm horizontal from the participant's own hand). The results revealed a significant nonlinear relationship in the strength of the illusion, with the strongest ratings given when the two hands were closest; decaying significantly after a distance of 30cm. The time taken to elicit the illusion followed a similar trend. These results may reflect the response properties of bimodal visuo-tactile cells encoding peripersonal space around the hand.

Adult↗
PubMed2004

The attentional selection of spatial and non-spatial attributes in touch: ERP evidence for parallel and independent processes.

To investigate the functional relationship between spatial and non-spatial attentional selectivity in somatosensory processing, event-related potentials (ERPs) were recorded to mechanical tactile stimuli, which were delivered to the right or left hand, and were low or high in frequency (Experiment 1), or soft or strong in intensity (Experiment 2). Participants' task was to attend to a specific combination of one stimulus location and one non-spatial attribute. Spatial attention was reflected in enhanced N140 components followed by a sustained attentional negativity. ERP effects of non-spatial attention (enhanced negativities to the attended frequency or intensity) were observed in the same latency range, suggesting that the attentional selection of relevant spatial and non-spatial attributes occurs in parallel. Most importantly, ERP correlates of attention directed to stimulus frequency and intensity were unaffected by the current focus of spatial attention. In contrast to vision, where the selective processing of non-spatial attributes is hierarchically dependent on selection by location, but similar to auditory attention, spatial and non-spatial attentional selectivity appear to operate independently in touch.

Adult↗
PubMed2006

Integration of force and position cues for shape perception through active touch.

This article systematically explores cue integration within active touch. Our research builds upon a recently made distinction between position and force cues for haptic shape perception: when sliding a finger across a bumpy surface, the finger follows the surface geometry (position cue). At the same time, the finger is exposed to forces related to the slope of the surface (force cue). Experiment 1 independently varied force and position cues to the curvature of 3D arches. Perceived curvature could be well described as a weighted average of the two cues. Experiment 2 found more weight of the position cue for more convex high arches and higher weight of the force cue for less convex shallow arches--probably mediated through a change in relative cue reliability. Both findings are in good agreement with the maximum-likelihood estimation (MLE) model for cue integration and, thus, carry this model over to the domain of active haptic perception.

Adult↗
PubMed2006

Touching on somatosensory specializations in mammals.

Specialized species often reveal general principles of brain organization and provide systems for analysis of sensory function. Subterranean species dependent on touch have particularly large somatosensory areas with modular cortical representations of sensory surfaces. Some species have added cortical areas to processing networks, have developed tactile foveas and have superior colliculi primarily devoted to somatosensation rather than vision. Recent studies reveal surprisingly large cortical representations of oral structures in primates and mole-rats. Cortical modules represent a range of different sensory surfaces in rodents, star-nosed moles and primates, indicating that similar developmental mechanisms operate in diverse species. Finally, manipulation of patterning genes in mice suggests evolutionary mechanisms for producing the specialized corticies of subterranean species.

Afferent Pathways↗
PubMed2004

Evaluation of healing by gentle touch in 35 clients with cancer.

An uncontrolled, preliminary evaluation of healing by gentle touch in clients with cancer was carried out at The Centre for Complementary Care in Eskdale, Cumbria. All clients attending The Centre between 1995 and 2001 were invited to participate. Data were collected from 35 clients with cancer. Outcome measures included pre- to post-treatment changes in physical and psychological functioning. Assessments were made using a questionnaire with visual analogue scales for subjective rating of symptoms and the EuroQoL (EQ-5D), a generic state of health measure. Wilcoxon Signed Ranks tests showed statistically significant improvements in psychological and physical functioning, with positive effects on quality of life. The most pronounced improvements were seen in ratings for stress and relaxation, severe pain/discomfort, and depression/anxiety, particularly in those with the most severe symptoms on entry. The study found no adverse effects resulting from the treatment. These findings indicate that healing is a safe and effective adjunct to conventional medical treatment with the potential to ameliorate some of the more stressful aspects of cancer, including those inherent in current cancer treatment strategies. Rigorous evaluation of this modality by prospective, randomised, controlled trial is strongly warranted, as are investigations into its potential for use in palliative care.

Adult↗
PubMedDate not supplied

Pilot study to test the effectiveness of Healing Touch on agitation in people with dementia.

A pilot study was conducted to investigate the effects of Healing Touch (HT) on agitation in persons with dementia. Because of the restricted availability of patients, the main purpose of the study was to investigate the effectiveness of HT on dementia patients who demonstrated similar high levels of agitation as measured by the Cohen-Mansfield Agitation Inventory. Results indicated that agitation levels were significantly lowered and that HT is worthy of further study.

Activities of Daily Living↗
PubMed2006

Touch activates human auditory cortex.

Vibrotactile stimuli can facilitate hearing, both in hearing-impaired and in normally hearing people. Accordingly, the sounds of hands exploring a surface contribute to the explorer's haptic percepts. As a possible brain basis of such phenomena, functional brain imaging has identified activations specific to audiotactile interaction in secondary somatosensory cortex, auditory belt area, and posterior parietal cortex, depending on the quality and relative salience of the stimuli. We studied 13 subjects with non-invasive functional magnetic resonance imaging (fMRI) to search for auditory brain areas that would be activated by touch. Vibration bursts of 200 Hz were delivered to the subjects' fingers and palm and tactile pressure pulses to their fingertips. Noise bursts served to identify auditory cortex. Vibrotactile-auditory co-activation, addressed with minimal smoothing to obtain a conservative estimate, was found in an 85-mm3 region in the posterior auditory belt area. This co-activation could be related to facilitated hearing at the behavioral level, reflecting the analysis of sound-like temporal patterns in vibration. However, even tactile pulses (without any vibration) activated parts of the posterior auditory belt area, which therefore might subserve processing of audiotactile events that arise during dynamic contact between hands and environment.

Adult↗