Static Touch Research Articles

A study to compare the effects of therapeutic massage and static touch on experimentally‐induced pain in healthy volunteers

A study to compare the effects of therapeutic massage and static touch on experimentally‐induced pain in healthy volunteers

Documentation of brachial plexus compression (in the thoracic inlet) utilizing provocative neurosensory and muscular testing.

Diagnosis and documentation of brachial plexus compression in the thoracic inlet, "thoracic outlet syndrome", remains difficult because the syndrome complex overlaps that of patients with cervical disc disease, intrinsic shoulder pathology, and peripheral nerve compression. While traditional electrodiagnostic testing can identify cervical radiculopathy and the rare isolated lower trunk compression, it cannot identify brachial plexus compression in the thoracic inlet. In 2000, neurosensory testing with the Pressure-Specified Sensory Device (PSSD) was applied to this diagnostic dilemma, demonstrating a significant increase in the one-point static touch cutaneous pressure threshold between controls and patients, when the index finger (upper trunk) and little finger (lower trunk) were tested with the hands at rest and after provoking the plexus by elevating the hands above the head. In the present study, this approach has been extended to include two-point static touch thresholds with the PSSD, and pinch and grip strength (Digit-Grip). Sixteen controls (mean: 34.2, range: 11 to 48 years) were tested and the 99 percent upper confidence limit calculated for percent change after elevation of the hands for 3 min. Forty-one patients symptomatic for brachial plexus compression (mean: 41.0, range: 21 to 62 years) were tested. The clinical severity of the plexus compression was dichotomized as either "severe" or "not severe" judged by the Roos and Tinel sign. Results demonstrated that when five or more of the eight possible neurosensory and motor test results were > 99 percent normal confidence limit for change, this testing has a sensitivity of 82 percent, a specificity of 100 percent, and a positive predictive value of 100 percent for the diagnosis of clinically severe brachial plexus compression. Seventeen patients who were in the "severe" category prior to surgery, were tested before and after plexus neurolysis and anterior scalenectomy. All 17 patients were clinically improved and in 16 of these patients, postoperative neurosensory and motor testing returned to a normal pattern (no significant increase in thresholds with hand elevation). It is concluded that neurosensory (PSSD) and motor testing (Digit-Grip) can help in the diagnosis and documentation of brachial plexus compression.

Evaluation of Pressure Threshold Prior to Foot Ulceration

A prospective study of 29 patients with diabetic neuropathy and 47 nondiabetic patients with tarsal tunnel syndrome were evaluated with computer-assisted neurosensory testing at three sites on the foot. The sensitivity and specificity of one-point static touch thresholds for identifying the presence of large fiber axonal loss was done using the calculated thresholds for monofilaments derived from their markings. The sensitivity for one-point static touch in identifying axonal loss was 33% for the 5.07, 38% for the 4.93, 50% for the 4.17, and 60% for the 4.08 monofilament-equivalent, with a specificity of 100% at each level. Therefore, one-point static touch testing, even using monofilaments thinner than 5.07, has a high percentage of false-negative results in identifying patients with axonal loss.

Thenar eminence quantitative sensory testing in the diagnosis of proximal median nerve compression

Diagnosis of proximal median nerve compression (PMNC) remains a clinical challenge. The authors hypothesized that measurement of the sensibility of the thenar eminence might identify PMNC by demonstrating abnormal function in the palmar cutaneous branch of the median nerve. This hypothesis was evaluated by means of quantitative sensory testing of the thenar eminence in 33 healthy volunteers, 14 patients with carpal tunnel syndrome, and 35 patients with PMNC. The cutaneous pressure thresholds for one-point static touch (1PS) and two-point static touch (2PS) were measured with the Pressure-specified Sensory Device (Sensory Management Services, Baltimore, Maryland). There was no significant difference in thenar eminence sensibility between the healthy volunteers and the patients with carpal tunnel syndrome. In contrast, patients with PMNC had higher cutaneous pressure thresholds for 1PS (p < 0.001), 2PS-pressure (p < 0.001), and 2PS-distance (p < 0.001) than did patients with carpal tunnel syndrome. The p values were less than 0.001 for each of these three comparisons between the healthy volunteers and the patients with PMNC. For the diagnosis of PMNC, quantitative sensory testing of the thenar eminence has a sensitivity of 90.3%, a specificity of 83.3%, and a positive predictive value of 87.5%.

Evidence for the duplex theory of tactile texture perception.

Three experiments are reported bearing on Katz's hypothesis that tactile texture perception is mediated by vibrational cues in the case of fine textures and by spatial cues in the case of coarse textures. Psychophysical responses when abrasive surfaces moved across the skin were compared with those obtained during static touch, which does not provide vibrational cues. Experiment 1 used two-interval forced-choice procedures to measure discrimination of surfaces. Fine surfaces that were readily discriminated when moved across the skin became indistinguishable in the absence of movement; coarse surfaces, however, were equally discriminable in moving and stationary conditions. This was shown not to result from any inherently greater difficulty of fine-texture discrimination. Experiments 2 and 3 used free magnitude estimation to obtain a more comprehensive picture of the effect of movement on texture (roughness) perception. Without movement, perception was seriously degraded (the psychophysical magnitude function was flattened) for textures with element sizes below 100 microns; above this point, however, the elimination of movement produced an overall decrease in roughness, but not in the slope of the magnitude function. Thus, two components of stimulation (presumably vibrational and spatial) contribute to texture perception, as Katz maintained; mechanisms for responding to the latter appear to be engaged at texture element sizes down to 100 microns, a surprisingly small value.

Influence of shape on haptic curvature perception

Curvature discrimination of hand-sized doubly curved surfaces by means of static touch was investigated. Stimuli consisted of hyperbolical, cylindrical, elliptical and spherical surfaces of various curvatures. In the first experiment subjects had to discriminate the curvature along a specified orientation (the discrimination orientation) of a doubly curved surface from a flat surface. The curvature to be discriminated was oriented either along the middle finger or across the middle finger of the right hand. Independent of the shape of the surface, thresholds were found to be about 1.6 times smaller along the middle finger than across the middle finger. Discrimination biases were found to be strongly influenced by the shape of the surface; subjects judged a curvature to be more convex when the perpendicular curvature was convex than when this curvature was concave. With the results of the second experiment it could be ruled out that the influence of shape on curvature perception was simply due to a systematic error made by the subject regarding the discrimination orientation.

Endothelial damage caused by uncoated and fluorocarbon-coated poly(methyl methacrylate) intraocular lenses

Purpose: To assess endothelial damage induced by poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) coated with a fluorocarbon polymer, Teflon™ AF to make them highly hydrophobic.Setting: Department of Ophthalmology, Hôtel-Dieu Hospital, Paris, France.Methods: Ten Teflon-coated and 10 uncoated PMMA IOLs were used in an in vitro static touch model. The corneal endothelium was placed in direct contact with the IOL for 15 seconds and then stained with trypan blue and alizarin red. The endothelial damage produced by each IOL in the area of contact was assessed semiquantitatively and quantitatively.Results: Teflon-coated IOLs produced significantly less endothelial damage than uncoated PMMA IOLs (P < .0001). Endothelial cells in contact with Teflon-coated IOLs did not usually adhere to the IOL surface. In contrast, the uncoated IOLs produced large areas of endothelial cell loss.Conclusion: Teflon-coated PMMA IOLs have an antiadhesive effect that reduced endothelial damage after IOL insertion in an in vitro model.

The relationships between skin hardness, pressure perception and two-point discrimination in the fingertip

With the recent introduction of computer-assisted sensibility testing devices, it is possible to investigate the hypothesis that the neurological mechanisms responsible for perception of pressure and two-point discrimination are influenced by skin hardness. This study examined the relationships between the skin hardness of the human index and little finger pulp and the perception of pressure in 25 adults. Skin hardness was measured using the Derma-Durometer. Pressure perception was measured with the Pressure-Specified Sensory Device for both static and moving touch stimuli and for two-point discrimination. The mean hardness of the fingertip pulp was 12.5 +/- 0.6 gm/mm2. There was no statistically significant difference in hardness between the dominant and non-dominant, right and left, index and little, or male and female fingertips. Skin hardness was independent of age for this population. The highest correlation, which was r = 0.46, was found between the cutaneous pressure threshold for one-point static touch and skin hardness. While this degree of correlation is significant at the P < 0.02 level, the r2 = 21%, demonstrating that this degree of correlation leaves 79% of the variability unexplained. These results suggest a physical interaction between mechanoreceptors and dermis that is only partially explained by the hardness of the skin.

Tactile sensing data interpretation for object manipulation

Abstract This paper describes work that has been done in extracting and interpreting tactile sensing data. A flat, 16 by 16 tactile sensor array, with conductive rubber as transducing element, is used. The work aims at investigating appropriate methods to determine contact force, centre of gravity and orientation of the object from a single static touch. Measurement accuracy is enhanced with respect to traditional 2D methods by using ‘3D’ tactile information. A new method, based on tactile data, for estimating the diameter of a cylindrical object is explored with satisfactory results. A multi-fingered robot hand equipped with tactile sensors will use this method to perform rolling manipulations.

Neural mechanisms of tactual form and texture perception.

In the last decade or so, there has been rapid movement toward the use of more complex stimuli in the study of perceptual function related to the hand. This review has focused on the neural mechanisms of form and texture perception. Evidence from neurophysiological and psychophysical studies in which static touch, scanning touch, and the Optacon were used indicate that the spatial acuity of the RA system may be as much as three times poorer than the SAI system, evidence that suggests that form perception is dominated by the SAI system. Pattern recognition behavior in a tactual letter recognition task appears to be directly related to the response properties of SAI afferent fibers. Psychophysical studies of roughness perception show that roughness magnitude is related to surface structure in an orderly manner. Because roughness varies along an intensive continuum, mean impulse rate in one or more of the afferent systems is the most obvious coding possibility. No satisfactory relationship between mean impulse rate and roughness has been observed, however. The strongest hypothesis is that tactual roughness perception is based on spatial variation in the SAI population response. The combined evidence from studies reviewed here suggests complementary roles for each of the afferent systems, which are presented as working hypotheses: The SAI system is the primary spatial system and is responsible for tactual form and roughness perception when the fingers contact a surface directly and for the perception of external events through the distribution of forces across the skin surface. The PC system is responsible for the perception of external events that are manifested through transmitted high-frequency vibrations of the kind that are critical in the use of objects as tools. The RA system is responsible for the detection and representation of localized movement between skin and a surface as well as for surface form and texture when surface variation is too small to activate the SAI afferents effectively.

Quantitative static light touch and nociceptive examination: A prerequisite to microneurosurgery

Quantitative static light touch and nociceptive examination: A prerequisite to microneurosurgery

Tactile recognition of raised characters: A parametric study

The accuracy of tactile recognition of raised characters was studied as a function of five variables: (1) height of the upper surfaces of the characters relative to the surrounding base, (2) character set (uppercase roman and braille), (3) spatial extent of the characters (two sizes), (4) mode of touch (static and moving), (5) contact force (two values). All stimuli were felt with the distal pad of the right index finger. The experiment was a repeated-measures design with six subjects. There were significant main effects of all variables except contact force. Of the tests for interaction, only height × mode was significant; the indication is that, whereas moving the finger permits a considerable improvement in performance over static touch for very shallow characters, moving the finger improves performance only slightly over static touch for characters of much greater height.