A simple model of mechanotransduction in primate glabrous skin

Abstract

Tactile stimulation of the hand evokes highly precise and repeatable patterns of activity in mechanoreceptive afferents; the strength (i.e., firing rate) and timing of these responses have been shown to convey stimulus information. To achieve an understanding of the mechanisms underlying the representation of tactile stimuli in the nerve, we developed a two-stage computational model consisting of a nonlinear mechanical transduction stage followed by a generalized integrate-and-fire mechanism. The model improves upon a recently published counterpart in two important ways. First, complexity is dramatically reduced (at least one order of magnitude fewer parameters). Second, the model comprises a saturating nonlinearity and therefore can be applied to a much wider range of stimuli. We show that both the rate and timing of afferent responses are predicted with remarkable precision and that observed adaptation patterns and threshold behavior are well captured. We conclude that the responses of mechanoreceptive afferents can be understood using a very parsimonious mechanistic model, which can then be used to accurately simulate the responses of afferent populations.

Simulating tactile signals from the whole hand with millisecond precision

“…We fit the parameters of these models on electrophysiological recordings obtained previously (18). These models were similar to earlier ones (57,70,71), with some key differences. First, rather than simply using skin indentation depth (along with derivatives) as IF model input, we used the static and dynamic pressure as calculated from the skin mechanics model.…”

“…The kernel consists of two parts: a fast component, which decays completely within 4 ms, and a slow component, which contributes maximally 8 ms after a spike is triggered and decays within 36 ms (a similar model is shown in ref. 71). In all fitted models, the first component was weighted more heavily than the second component, leading to initially strong but lingering weak inhibition after each spike.…”

“…Second, PC fibers are known to respond to vibration far away from their locations, which requires the wave propagation (dynamic) component of the model. However, incorporating skin mechanics is not necessary to achieve high spiking precision (for stimuli located directly above the receptor location), because previous models were able to reproduce precise spiking patterns evoked by vibrating probes without implementing a skin mechanics model (70,71). Frequency selectivity of different afferent types.…”

Behavioral assessment of sensitivity to intracortical microstimulation of primate somatosensory cortex

“…However, this comparison provides an order of magnitude approximation that can be refined as more sophisticated models linking pressure and its derivatives to perceived intensity are developed. The mapping between pressure and perceived intensity could in principle be derived by combining models that characterize the relationship between perceived intensity and afferent responses (46) with models that simulate populations' responses to arbitrary spatiotemporal skin deformations (47)(48)(49)(50). In any case, ignoring the dynamical component of mechanically induced sensations, peak ICMS-evoked sensations correspond to those evoked by 200-600 kPa exerted on the skin (estimated from ref.…”

Natural scenes in tactile texture

“…Weber et al 2013). Indeed, each afferent class conveys a signal that is a nonlinear transformation of the spatio-temporal pattern of skin deformation (Dong et al 2013;Kim et al 2010;Sripati et al 2006), and it is those signals that are processed centrally to culminate in perception.…”