Directional sensibility for quantification of tactile dysfunction.
ABSTRACT Examination of tactile directional sensibility, i.e., the ability to tell the direction of an object's motion across the skin, has been recommended by several authors for examination of patients with somatosensory disorders. Recent findings about the physiological mechanisms underlying directional sensibility suggested possibilities to further improve the test. In the present investigation a test was constructed that allowed a semiquantification of the directional sensibility of six body areas within 20 min. Normal values were obtained by testing healthy subjects (n = 40), and the normal values were compared to those obtained in a group of patients with tactile symptoms (n = 20). Ten of the patients had abnormal sensory conduction in one or several nerves, and they also had abnormal directional sensibility. Hence, examination of directional sensibility, according to the present protocol, provides a semiquantitative test that appears to be as sensitive as electrophysiological measurement of conduction in detecting dysfunction in tactile nerves.
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ABSTRACT: In experiment 1, two Macaca speciosa monkeys were trained to discriminate two forms of tactile stimulation to the legs or feet. Both stimuli were delivered by perpendicular contact of bristles to the skin, but in one case the bristles were stroked across the skin as the brush was removed, and on the other trials the brush was removed as it had been applied, with minimal movement of the bristles over the skin. This test of tactile movement detection revealed only slight, transient impairment following ipsilateral section of the dorsal spinal columns. A more severe deficit was observed after ipsilateral dorsal quadrant lesions, but recovery to a high level of performance was observed. In experiment 2, three monkeys learned to discriminate proximal vs. distal movement of the bristles over the hairy skin of either leg. Dorsal column lesions in these monkeys produced an unusually enduring inability to discriminate direction of tactile stimulus motion. This result is discussed in relation to recent theoretical statements about the importance of dorsal column transmission for perception of passively received tactile stimuli.Experimental Brain Research 06/1974; 20(4):331-346. · 2.22 Impact Factor
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ABSTRACT: The capacity of 41 neurologically healthy young adults to distinguish opposing directions of brush motion across the skin innervated by the mental nerve was determined. The velocity and orientation and the length and width of skin traversed by the moving tactile stimuli were carefully controlled. Directional sensitivity, d', was found to vary curvilinearly with velocity over the range 0.5 to 32 cm/s. Because the data from most subjects were well described by a generalized gamma function, it was possible to characterize this velocity dependency quantitatively. Specifically, indices derived from these functions were found to describe the subject's peak (i.e., maximal) sensitivity, the velocity which resulted in peak sensitivity (i.e., the optimal velocity), and the degree to which stimulus velocity influenced the ability to recognize direction of motion (i.e., the velocity-tuning of d'). Peak sensitivity, optimal velocity, and the degree of global velocity-tuning were found to differ between males and females. Confidence limits (the lower and upper 2.5% points) for the normative data were determined to enable detection and characterization of deficits in orofacial tactile motion sensitivity in individuals with damaged mandibular nerves.Experimental Neurology 07/1988; 100(3):506-23. · 4.65 Impact Factor
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ABSTRACT: Classical beliefs about the functions of the dorsal columns of the spinal cord have been attacked following recent evidence that position and vibration sensations may be carried in the dorsal spinocerebellar tracts. There is evidence that the one specific function of the dorsal columns is for the transmission of information concerning the direction of tactile cutaneous movement. Thirty normal controls, 43 patients with spinal cord disorders and 10 patients with functional disorders were examined prospectively using an easily administered "direction of scratch" protocol. Interpretation of the direction of a 2 cm vertical tactile cutaneous movement over the lower limbs was found to be accurate in normal controls and grossly inaccurate in patients with functional disorders, exceeding the error rate of guessing. Detection of direction of 2 cm scratch was moderately impaired in 11 of 13 patients with spastic paraparesis and preserved sensation to all other modalities and 23 of 24 patients with spastic paraparesis and impaired proprioception and/or vibration sensations. Direction of 2 cm scratch, proprioception and vibration sensations were preserved in the three cases with anterior spinal cord syndromes. It is proposed that tactile perception of direction of 2 cm scratch over the lower limbs is a sensitive sign of posterior column function which can be usefully incorporated into the clinical sensory examination in the evaluation of spinal cord disorders.Journal of Neurology Neurosurgery & Psychiatry 04/1989; 52(3):395-8. · 4.92 Impact Factor