Predicting SA-I mechanoreceptor spike times with a skin-neuron model.

Slowly adapting type I (SA-I) mechanoreceptors encode the edges and curvature of touched objects by generating neural spikes in response to indentation of the skin. Beneath this general input-output relationship, models are of great utility for understanding the sub-processes, as SA-I transduction sites are inaccessible to whole-cell recording. This work develops and validates a SA-I skin-receptor model that combines a finite element model of skin mechanics, a sigmoidal function of transduction, and a leaky integrate-and-fire model of neural dynamics. The model produced a R(2)=0.80 goodness of fit between predicted and observed firing rates for 3 and 5mm grating stimuli. In addition, modulation indices of predicted firing rates for 3 and 5mm gratings are 0.46 and 0.59, respectively, compared to the 0.71 and 0.72 found in vivo. An analysis of predicted first spikes indicates their latency may also be enhanced by edges, as edge proximity shortened first spike latencies by 26.2 and 41.8 ms for the 3 and 5mm gratings, respectively. The model described here bridges the gap between those models that transform sustained indentation to firing rates and those that transform vibration to spike times.

[1]  A. Freeman,et al.  Cutaneous mechanoreceptors in macaque monkey: temporal discharge patterns evoked by vibration, and a receptor model , 1982, The Journal of physiology.

[2]  M. Srinivasan,et al.  An investigation of the mechanics of tactile sense using two-dimensional models of the primate fingertip. , 1996, Journal of biomechanical engineering.

[3]  R. Johansson.  Tactile sensibility in the human hand: receptive field characteristics of mechanoreceptive units in the glabrous skin area. , 1978, The Journal of physiology.

[4]  G. J. Gerling,et al.  Fingerprint lines may not directly affect SA-I mechanoreceptor response , 2008, Somatosensory & motor research.

[5]  J Bell,et al.  A mechanoreceptor model for rapidly and slowly adapting afferents subjected to periodic vibratory stimuli. , 1995, Mathematical biosciences.

[6]  A. W. Schopper,et al.  A structural fingertip model for simulating of the biomechanics of tactile sensation. , 2004, Medical engineering & physics.

[7]  D P Corey,et al.  Two mechanisms for transducer adaptation in vertebrate hair cells. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[8]  Ellen A. Lumpkin,et al.  Spider toxins activate the capsaicin receptor to produce inflammatory pain , 2006, Nature.

[9]  R. Sivamani,et al.  Tribometrology of Skin , 2004 .

[10]  Kenneth O. Johnson,et al.  A continuum mechanical model of mechanoreceptive afferent responses to indented spatial patterns. , 2006, Journal of neurophysiology.

[11]  Y. Fung,et al.  Biomechanics: Mechanical Properties of Living Tissues , 1981 .

[12]  Kazumi Kobayashi,et al.  Relationship between the Structure of Human Finger Tissue and the Location of Tactile Receptors , 1998 .

[13]  A. Freeman,et al.  A model accounting for effects of vibratory amplitude on responses of cutaneous mechanoreceptors in macaque monkey , 1982, The Journal of physiology.

[14]  J. Lévêque,et al.  Mechanical properties and Young's modulus of human skin in vivo , 2004, Archives of Dermatological Research.

[15]  P. Khalsa,et al.  Encoding of compressive stress during indentation by slowly adapting type I mechanoreceptors in rat hairy skin. , 2002, Journal of neurophysiology.

[16]  A. Ugural,et al.  Advanced strength and applied elasticity , 1981 .

[17]  Eugene M. Izhikevich,et al.  Which model to use for cortical spiking neurons? , 2004, IEEE Transactions on Neural Networks.

[18]  S S Hsiao,et al.  Vibratory adaptation of cutaneous mechanoreceptive afferents. , 2005, Journal of neurophysiology.

[19]  K. O. Johnson,et al.  Tactile spatial resolution. II. Neural representation of Bars, edges, and gratings in monkey primary afferents. , 1981, Journal of neurophysiology.

[20]  K. O. Johnson,et al.  Time-course of vibratory adaptation and recovery in cutaneous mechanoreceptive afferents. , 2005, Journal of neurophysiology.

[21]  Balasundar I Raju,et al.  3-D finite-element models of human and monkey fingertips to investigate the mechanics of tactile sense. , 2003, Journal of biomechanical engineering.

[22]  R. H. Myers,et al.  Response Surface Methodology: Process and Product Optimization Using Designed Experiments , 1995 .

[23]  R. Johansson,et al.  First spikes in ensembles of human tactile afferents code complex spatial fingertip events , 2004, Nature Neuroscience.

[24]  J. Nicholls.  From neuron to brain , 1976 .

[25]  R. Johansson,et al.  Sensitivity to edges of mechanoreceptive afferent units innervating the glabrous skin of the human hand , 1982, Brain Research.

[26]  Kenneth O. Johnson,et al.  The roles and functions of cutaneous mechanoreceptors , 2001, Current Opinion in Neurobiology.

[27]  Wulfram Gerstner,et al.  Spiking Neuron Models , 2002 .

[28]  K. O. Johnson,et al.  Tactile spatial resolution. III. A continuum mechanics model of skin predicting mechanoreceptor responses to bars, edges, and gratings. , 1981, Journal of neurophysiology.