Mark Hollins - US grants

9514432 HOLLINS This research will investigate humans' sense of touch, and in particular, the ability of people to determine, by touch, what the surface of an object is like. People can often determine, by drawing a finger across a surface, whether it is cloth, styrofoam, leather etc.; it is not known, however, on what specific aspects of the stimulus event these perceptions are based. The hypothesis to be explored in this research is that small vibrations, set up in the skin when the finger moves across a textured surface, contain the information needed to make many of these judgments, and that sensory processing of the vibrations in fact contributes to texture perception. The research will test this notion in a number of ways. First, the vibrations themselves will be recorded and analyzed. The information they contain will be evaluated and compared with the performance of experimental participants. Second, higher-order features of the vibration, such as the way it waxes and wanes over time, will be manipulated to determine if perception reflects the encoding of such temporal patterns. Third, some textures will be presented repeatedly, to learn how adaptation influences the precision of texture judgments; the resulting perceptual changes will yield information about underlying sensory processes. Fourth, textures will be touched indirectly, with a small rod, thus eliminating all cues except vibration. If subjects' judgments are still accurate, the importance of vibration in texture perception will be established. Fifth, pre-recorded vibrations will be played back to the finger, to determine whether participants can recognize the original texture. These five sets of experiments will provide a thorough test of the hypothesis that vibrations contribute to tactile texture perception, an idea that has important implications for remote and prosthetic sensing, and for the possibility of sensory enhancement in persons with somesthetic impairments. In additi on, the research will contribute basic knowledge about an important aspect of tactile perception. ***

The psychophysical research proposed in this subproject will examine three types of sensory interactions involving pain -- touch gating, pain gating, and diffuse noxious inhibitory controls (DNIC) -- in normal subjects, and in patients with fibromyalgia (FM) and temporomandibular disorders (TMD). The etiology of these two chronic-pain conditions is obscure, but their symptomatology includes evidence of a centrally mediated enhancement of sensitivity to noxious stimuli. The proposed research explores the possibility that disturbances of pain gate and DNIC contribute to the magnitude of this enhancement, and that touch gate can serve as an index of its severity. Major goals of the research are to analyze the ways in which these sensory interactions vary as a function of clinical status, the extent to which their strengths are statistically related across individuals, and their degree of association with hypervigilance, as indexed by detail of pain report and other measures. Forced-choice measurement of detection and discrimination thresholds will be used to explore impairments of vibrotaction produced by pain (usually attributed to a "touch gate"): These experiments will reveal whether experimental and clinical pain have comparable effects on the touch gate, and whether, in FM as in TMD, frequency discrimination is impaired more than other measures of vibrotaction. Visual analog scaling will be used to examine the effects of vibratory stimulation on pain intensity (pain gating), and the way in which this form of interaction depends on vibration frequency. DNIC will be studied both in the context of its ability to suppress slowly increasing (C-fiber mediated) pain, and to block the temporal summation associated with wind-up.

The psychophysical research proposed in this subproject will examine three types of sensory interactions involving pain -- touch gating, pain gating, and diffuse noxious inhibitory controls (DNIC) -- in normal subjects, and in patients with fibromyalgia (FM) and temporomandibular disorders (TMD). The etiology of these two chronic-pain conditions is obscure, but their symptomatology includes evidence of a centrally mediated enhancement of sensitivity to noxious stimuli. The proposed research explores the possibility that disturbances of pain gate and DNIC contribute to the magnitude of this enhancement, and that touch gate can serve as an index of its severity. Major goals of the research are to analyze the ways in which these sensory interactions vary as a function of clinical status, the extent to which their strengths are statistically related across individuals, and their degree of association with hypervigilance, as indexed by detail of pain report and other measures. Forced-choice measurement of detection and discrimination thresholds will be used to explore impairments of vibrotaction produced by pain (usually attributed to a "touch gate"): These experiments will reveal whether experimental and clinical pain have comparable effects on the touch gate, and whether, in FM as in TMD, frequency discrimination is impaired more than other measures of vibrotaction. Visual analog scaling will be used to examine the effects of vibratory stimulation on pain intensity (pain gating), and the way in which this form of interaction depends on vibration frequency. DNIC will be studied both in the context of its ability to suppress slowly increasing (C-fiber mediated) pain, and to block the temporal summation associated with wind-up.

[unreadable] DESCRIPTION (provided by applicant): Sickle cell disease (SCD) is a major health problem, affecting approximately 1 in 600 African Americans. Although newborn screening and improvements in care have resulted in more favorable long-term prognosis, most people with this disease still encounter frequent unpredictable episodes of pain over their life span. The aim of this project is to evaluate perceptual and cognitive aspects of the SCD pain experience by capitalizing on recent advances in knowledge of both typical and altered pain processing. The approach is holistic in that multiple processes, ranging from sensory to cognitive, will be examined. The episodic nature of SCD pain will enable reversible and irreversible components of altered processing to be distinguished. Four pain processes will be studied: (1) temporal summation, a gradual increase in the intensity of pain from a continuing stimulus; (2) intensity discrimination, the clinically valuable ability to detect changes in the level of pain; (3) diffuse noxious inhibitory controls (DNIC), a process in which one pain is reduced in the presence of another, generally more intense, pain; and (4) hypervigilance, a perceptual tendency to attend excessively to, and perceptually amplify, pain and other unpleasant sensations. Taken together, experiments on these processes will begin to give a vertically-integrated picture of SCD pain processing. Pain processing will be assessed in 40 individuals with SCD, and 40 pain-free controls. Experimental pain will be produced with pressure applied to a finger-a safe, effective method used in our prior SCD research. The robustness of each process in SCD patients will be assessed (a) relative to controls, and (b) during different clinical pain states. Auditory stimuli, and social/behavioral psychometric instruments, will be used in other aspects of the study. Partially-reversible alterations of pain processing (increased temporal summation and hypervigilance; decreased pain discrimination and DNIC) are expected to be found in SCD, based on a two-stage model of SCD pain episodes that is proposed here. The long-term goals of this project are: (1) to obtain experimental evidence that will contribute to a holistic understanding of pain processing in SCD; (2) to develop and validate novel biobehavioral approaches that will permit quantitative assessment of perceptual and cognitive factors in pain processing; and (3) to provide a scientific basis for behavioral and cognitive interventions that will contribute to the alleviation of SCD pain. The intense and unpredictable pain caused by sickle cell disease is a major public health problem. This research will increase understanding of biological and psychological processes that affect the severity of this pain, laying a foundation for new behavioral and cognitive strategies to alleviate it. [unreadable] [unreadable] [unreadable]