- Tuckett, RP; Horch, KW; Burgess, PR
- Four threshold parameters of cat guard hair and field mechanoreceptors were measured: velocity threshold, ratio of retraction-to-indentation velocity threshold (linear directional sensitivity), tuning curve slope, and recovery curve duration. These measurements were made to determine the range of threshold behavior present in these receptor populations, to see if these 4 properties correlate with each other, and to determine if either the guard hair or the field-receptor population is composed of distinct receptor types. Hair receptors were studied by stimulating the skin over innervated follicles, field receptors by stimulating the skin in the central portion of the receptive field. Both hair and field receptors displayed a wide range of values for all 4 of the parameters measured. The hair receptors, as a whole, differed significantly from the field-receptor population in having less linear directional sensitivity and more steeply sloping tuning curves. Tests were made of the degree to which the parameters correlated with each other. All paired parameter correlations were significant in the hair-receptor population. The higher a receptor's velocity threshold, the greater its tendency to have: (a) a lower retraction-to-indentation velocity threshold, (b) a more negatively sloping tuning curve, and (c) a shorter recovery curve. The same trends were evident in the field-receptor population except that recovery curve duration was not significantly correlated with tuning curve slope or directional sensitivity. The reason for these correlations is unknown. These studies did not provide evidence for the presence of distinct receptor types within the hair or field groups since no clear discontinuities could be seen in the distribution of any measured parameter across either the hair- or field-receptor population. However, the range of properties was large with respect to the sample size so that the existence of distinct receptor types could not be ruled out. When guard hair receptors were classified as G1, intermediate or G2, and field receptors were classified as F1, intermediate or F2 with simple hand-held stimulators, significant differences were found between each receptor type in most of the quantitatively measured parameters. Two types of discriminant functions applied to these data showed that hair and field receptors can be divided into these subcategories with a high degree of reliability using hand-held stimulators; however, the data do not indicate whether these subcategories are distinct receptor types.
- January 1, 1978
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