Behavior and Circuitry of Directed Orofacial Exploration

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Abstract - Research Project 2 Behavior and circuitry of directed orofacial exploration (Martin Deschênes, lead; David Kleinfeld) This Research Project considers perceptual issues along with reverse engineering of circuits for the control of vibrissa set-point, i.e., the mean position of the vibrissae. Control may occur on a multitude of levels. We focus on circuits at two levels. One level of circuitry comprises pathways within the brainstem and midbrain. Preliminary data suggests involvement of the Kölliker-Fuse nucleus and the superior colliculus as candidate premotor regions. A second level of circuitry is comprised of descending sensory and motor cortical pathways. The role of these two levels of circuitry will also be studied in relation to deflection and rhythmic motion of the nose. The top-down input from motor cortex to the vibrissa motor, and possibly nose motor, areas of brainstem may be homologous to motor cortex control of the tongue (Project 3). These data bear on the "Wiring diagram" and "Signal pathways" for premotor and pre2motor pathways. We further consider the coordination of orofacial actions in an open arena. Mice explore a novel environment using an assay in which the animal slowly increases both the coverage and dimensionality of its search. Indwelling sensors and logging electronics will allow us to monitor coordination across motor actions concurrent with the animals foraging. These data provide a set of connections that constrain models for the activation and operation of orofacial exploratory circuitry. They give insight into the operational tradeoffs that nature has made in network design. These data, along with complementary anatomy and electrophysiology data from Research Projects 1 and 3, analyzed as part of Research Project 5, provide input for a theoretical analysis of orofacial circuitry exploration (Project 4).