Mechanical Signals and Trigeminal Ganglion Neuron Responses During Whisking

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 DESCRIPTION (provided by applicant): The rat vibrissal-trigeminal system is an important model in the field of neuroscience for analyzing the relationship between sensory and motor signals and how the brain integrates this information to enable perception. Recent studies have explored the relationship between the neural signals recorded from the trigeminal ganglion (Vg) and kinematic variables (i.e., position, velocity, and phase) during both contact and non-contact (free-air) whisking. Although there is some evidence for correlation between the Vg responses and kinematic variables during contact whisking, the relationship during non-contact whisking is far less convincing. The objective of this proposal is to search for correlations between Vg responses in awake, behaving rats and mechanical variables (i.e., forces and moments) produced at the base of the whisker by vibrissal deflections during non-contact whisking. Our hypothesis is that the responses of Vg neurons during non-contact whisking are most directly correlated with mechanical variables at the whisker base generated by the inertial properties of the whisker deflecting in free-air. The alternative is that the neural responses are most directly correlated with geometric variables at the whisker base, but dominated by stochasticity. Testing this hypothesis will be achieved through three aims: In Aim 1, I will experimentally quantify density and damping as functions of whisker arc length to correctly estimate the dynamic parameters of vibrissae. For Aim 2, I will use the results generated in Aim 1 to construct a three-dimensional model of whisker dynamics. In this aim, I will also experimentally validate the spring and damping coefficients of the 3D model via dynamic whisking simulations. Finally in Aim 3, I will use the 3D dynamic model created in Aim 2 to correlate the responses of neurons in the trigeminal ganglion in awake, behaving rats with the mechanical and geometric variables produced at the base of the whisker during non-contact deflections. The final outcome of the proposed work has significance for understanding neurological coding of sensory information, especially within the trigeminal system, and will provide a 3D dynamic model for simulating both non-contact and contact whisking in future studies that relate neural signals along the trigeminal pathway to their mechanical output at the whisker base.