Processing of mechanical information in the rat whisker-trigeminal system

The rat vibrissal (whisker) system provides an excellent model to study the neural processing of sensorimotor information. In particular, the rat moves its whiskers in order to sense, i.e. movement is used for sensing. The system has been investigated intensely, including whisking behavior, neuro-anatomical pathways, developmental biology and physiology.;A limitation of past investigations has been that the mechanics of whisking has not been quantified rigorously in physical terms. In particular, there has not been a systematic attempt to quantify the relationship between whisking behavior, whisker mechanics induced by whisking behavior and the neural response to the mechanics. In this thesis, I build on some recently published work, by applying concepts from information theory to quantify the relationship between movement and sensory variables and the associated neural response. I present evidence that the responses of neurons at the first stage of the vibrissal pathway can be formulated as representing the mechanical state of the whisker. This provides a foundation for investigators in this field to develop theories of higher order information processing and perception.;Vibrissal information processing is divided into several stages. The first stage, or the trigeminal ganglion, projects to the trigeminal nuclear complex. The spinal trigeminal nucleus itnerpolaris performs important integrative functions, which are currently not well understood. I describe novel experimental and analytical methods to develop a systems level understanding of this question. My data indicates that stimulation of the entire whisker array is encoded robustly in the responses of neurons, as measured by single unit, multi-unit and local field potential. Further, this response is strongly modulated by the speed and direction of whisker array traversal.;In summary, this thesis describes two important contributions to the field of neurophysiology and mathematical modeling of neural responses in the rat whisker-trigeminal sensory-motor system. The first proposes a novel scheme for representation of mechanical information at the first stage of the system and a novel experimental scheme to probe the integration of mechanical information at the second stage of the system.