Distribution of the intensity-characteristic parameters of cat rapidly adapting mechanoreceptive fibers

Abstract

Modeling population responses of nerve fibers requires statistical characterization of fiber-response properties. The rate/intensity characteristics of cat rapidly adapting (RA) fibers were fitted by four-parameter, piece-wise linear functions using nonlinear regression (n = 14; R² > 0.958). The parameters were tested against the null hypothesis that they are lognormally distributed. The test fails to reject this hypothesis (Kolmogorov-Smirnov; p > 0.477). However, a significant statistical difference was found between the specific lognormal distributions obtained from monkey (Johnson, J Neurophysiol37: 48-72, 1974) and cat for all four parameters (Kolmogorov-Smirnov; p < 0.0075, p < 0.05, p < 0.0001, p < 0.00007). Although the stimulus contactor size was not the same in monkey and cat studies, the differences between monkey and cat fibers are attributed to anatomical differences in the glabrous skin of both species. Modeling studies suggest that the absolute firing thresholds of RA fibers have a right-skewed distribution because of the anatomical constraints present in both species' skin. Meissner corpuscles, which are the sensory end-organs of RA fibers, are likely to be found deeper in the skin within dermal papilla, therefore, the thresholds can be elevated. However, the thresholds are bounded at the lower end, probably due to the epidermal junction that acts as a superficial mechanical barrier for these corpuscles.

• Rapidly Adapting Fiber
• Mechanoreceptor
• Intensity Characteristic
• Lognormal Distribution