Biomedical subjects

Gregory O Gibson

Publications and source records attributed to Gregory O Gibson.

3 recordsLinked to original sources

PubMed2005

The effect of force and conformance on tactile intensive and spatial sensitivity.

The effect of force on intensive and spatial processing was examined with three measures of tactile sensitivity. One of the measures based on intensive cues is the smooth-grooved (SM/GV) task, and the two other measures based on spatial cues are the grating orientation and gap detection tasks. Measures were made at two locations that vary in sensitivity and in the density of innervation of the primary afferent fibers, the right index fingerpad and the palmar surface of the proximal phalanx (fingerbase). At each location, psychometric functions were generated for each of the three measures for two forces (50 and 200 g). The results indicated that increasing force led to marked improvement on the task that relied on intensive cues; however, on the tasks that relied on spatial cues, force had no effect on performance. Biomechanical measures were made of the depth to which the skin invades the grooves of the contactors (conformance) at the two test sites, with the two forces, and with different groove widths. Conformance was found to be a joint function of force and groove width. Further, performance on the SM/GV task could be predicted by the amount of conformance. The psychophysical results are consistent with the view that increasing conformance increases neural activity in the primary afferent fibers, and that this increase in neural activity improves SM/GV performance, but has little effect on the quality of the spatial image.

Afferent Pathways↗

PubMed2005

Tactile spatial sensitivity and anisotropy.

A gap detection task was examined for its usefulness as a measure of tactile spatial sensitivity and as a measure of anisotropy. In Experiment 1, sensitivity was measured with a gap detection task both with and without a latex glove at three locations on the hand: the fingerpad, fingerbase, and palm. Results showed that sensitivity varied as a function of location and was correlated with changes in the density of innervation of the primary afferent fibers. In accord with other measures of spatial sensitivity, the glove had a moderate effect on sensitivity in the gap detection task. The results both with and without the glove were more similar to those obtained using another measure of spatial sensitivity, the grating orientation task, than to those obtained using the smooth-grooved task, which is considered an intensive measure. In Experiments 2-4, anisotropy was examined using the gap detection and grating orientation tasks, as well as the smooth-grooved task. Locations on the index finger, palm, and arm were tested. Results indicated that anisotropy was revealed only by tasks that relied on spatial cues. The differences between spatial sensitivity measured in the proximal-distal orientation as compared with the lateral-medial orientation varied by location and were as much as 2.35/1. The results are discussed in terms of what they may reveal about the underlying mechanisms responsible for tactile anisotropy.

Anisotropy↗

PubMed2002

Relative roles of spatial and intensive cues in the discrimination of spatial tactile stimuli.

Two psychophysical measures of tactile sensitivity--grating-orientation (GO) and smooth-grooved (SG) discrimination--were used to determine tactile spatial acuity with and without an intermediate surface (latex glove) interposed between the contactor and the skin. Measures were made at three locations that varied in sensitivity and in density of innervation of the primary afferent fibers: the index fingerpad (fingertip), palmar surface of the proximal phalanx (fingerbase), and the thenar eminence (palm). Neurophysiological studies have suggested that the density of innervation of SAI fibers is a limiting factor in spatial acuity. In the present study, without a glove, the GO thresholds varied as a function of location. With the glove, increases in the GO thresholds were relatively uniform and modest. Without a glove, however, the SG thresholds were well below the GO thresholds, and changing the site of stimulation had little effect on the threshold. With a glove, the SG thresholds increased by 100% to more than 300% as in comparison with those in the no-glove condition. The largest increases occurred at the less sensitive locations. The results of the GO task are consistent with the view that GO is a valid measure of spatial acuity. The results of the SG task, however, are inconsistent with previous results and suggest that both spatial and intensive factors are involved in this task.

Cues↗