Functional significance of parallel sensory pathways in the rat vibrissal system.

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DESCRIPTION (provided by applicant): Recent studies have demonstrated similarities between the rat vibrissal (trigeminal) sensory pathways and visual pathways that could expand the vibrissal system as a model for visual sensory processing. Specifically, the lemniscal and extralemniscal vibrissal pathways have been likened to the parvo-cellular and magno-cellular visual pathways and the paralemniscal vibrissal pathway shows anatomical similarity to the visual konio-cellular pathway. These results evoke the hypothesis that the trigeminal pathways are analogs of the three visual pathways, potentially separating spatial (parvo), temporal (magno) and self-movement (konio) information into three distinct pathways. However, this hypothesis arises through a controversial stimulation technique: artificial whisking, which is disputed because it activates muscles used for whisker motion in an ethologically implausible manner. Thus, there is a clear need to independently valuate the results of this stimulation technique to further test this proposal's central hypothesis that the three major trigeminal ascending pathways (lemniscal, extralemniscal and paralemniscal) encode spatial, temporal and self-movement information. In analogy to the ascending visual pathways (parvo, magno and konio), we hypothesize that the lemniscal pathway encodes high acuity spatial information, the extralemniscal pathway carries precise temporal information, and the paralemniscal pathway contains reafferent information. The central hypothesis will be tested through the completion of three specific aims. Aim 1: Train rats to discriminate between free air, a flat wall and a curved wall. Aim 2: Establish the functional significance of the para- and extra-lemniscal pathways at the level of the brainstem trigeminal nuclei based on a separation of whisker motion and whisker contact information. Aim 3: Establish the functional significance of the lemniscal pathway at the level of the brainstem trigeminal nuclei (Vnuc) based on spatiotemporal patterns of whisker motion and contact. This proposal outlines three primary innovations using the awake, behaving animal: (1) the first neural recording from the Vnuc during a controlled behavior, (2) the second chronic recording from the vibrissal portion of the Vnuc ever made, and (3) the first simultaneous measurement of all whisker contact times during unrestrained behaviors. PUBLIC HEALTH RELEVANCE Perception is based strongly on sensory and motor processing at lower levels of the nervous system. Understanding the sensorimotor basis of perception could lead to novel treatments for pathologies that distort a patient's perceptions. This proposal aims to further develop the vibrissal system as a model of the sensorimotor basis of perception, which could be instrumental for understanding of perceptual deficits in humans.