Computational modeling indicates that surface pressure can be reliably conveyed to tactile receptors even amidst changes in skin mechanics.
Distinct patterns in neuronal firing are observed between classes of cutaneous afferents. Such differences may be attributed to end-organ morphology, distinct ion-channel complements, and skin microstructure, among other factors. Even for just the slowly adapting type I afferent, the skin's mechanics for a particular specimen might impact the afferent's firing properties, especially given the thickness and elasticity of skin can change dramatically over just days. Here, we show computationally that the skin can reliably convey indentation magnitude, rate, and spatial geometry to the locations of tactile receptors even amid changes in skin's structure. Using finite element analysis and neural dynamics models, we considered the skin properties of six mice that span a representative cohort. Modeling the propagation of the surface stimulus to the interior of the skin demonstrated that there can be large variance in stresses and strains near the locations of tactile receptors, which can lead to large variance in static firing rate. However, variance is significantly reduced when the stimulus tip is controlled by surface pressure and compressive stress is measured near the end organs. This particular transformation affords the least variability in predicted firing rates compared with others derived from displacement, force, strain energy density, or compressive strain. Amid changing skin mechanics, stimulus control by surface pressure may be more naturalistic and optimal and underlie how animals actively explore the tactile environment.
Department of Systems and Information Engineering, University of Virginia, Charlottesville, Virginia; Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia;
Yuxiang
Y
Wang
Department of Dermatology, Columbia University College of Physicians & Surgeons, New York, New York; and.
Yoshichika
Y
Baba
Department of Dermatology, Columbia University College of Physicians & Surgeons, New York, New York; and Department of Physiology & Cellular Biophysics, Columbia University College of Physicians & Surgeons, New York, New York.
Ellen A
EA
Lumpkin
Department of Systems and Information Engineering, University of Virginia, Charlottesville, Virginia; Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia; gg7h@virginia.edu.
Gregory J
GJ
Gerling
D000200:Action Potentials; D000818:Animals; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D005260:Female; D020342:Finite Element Analysis; D008465:Mechanoreceptors / Q000502:physiology*; D008822:Mice, Transgenic; D008954:Models, Biological; D011312:Pressure; D012867:Skin / Q000294:innervation*; D012879:Skin Physiological Phenomena; D046509:Tissue Culture Techniques
biomechanics; electrophysiology; finite element analysis; mechanotransduction; slowly adapting type I afferent; tactile; touch