REU subproject for The Vibrissotactile Natural Scene

Overview: The sensory and motor systems of an animal species co-evolve with its nervous system, and all three evolve within the context of that species’ particular ethological niche. In the fields of vision and audition, the receptive fields of central neurons have been found to be tuned to the statistics of the "natural scene," that is, the properties of the stimuli that the animal is likely to encounter in its natural environment. In the field of somatosensation it has been more challenging to quantify the natural tactile scene, in part because somatosensory signals are so tightly linked to the animal’s movements. The proposed work aims to begin to quantify the natural tactile scene for the rat vibrissal system by combining careful behavioral monitoring and simulations of rat head and whisker movements. The project has two major goals. First, to characterize the statistics of the geometry of the environments that the rat naturally inhabits. In Bayesian terms, this statistical distribution is called the "prior," because it describes the properties of the environment, unbiased by the tactile sampling choices of the animal. Second, to quantify the statistics associated with the rat’s choices of head motions and whisk cycle. In Bayesian terms, this statistical distribution is called the "posterior," because it incorporates the bias of the rat when preferentially sampling different parts of the tactile scene. Intellectual Merit: The work proposed here is one of the first attempts to quantify the statistics of active touch. The relative mechanical simplicity of the vibrissae allows for the simulation of the complete set of tactile inputs transmitted by the array, a level of description not currently feasible for the hand. The vibrissal array is thus a promising candidate system in which to make specific predictions for the receptive field properties that enable spatiotemporal integration during active touch. Equally important, the work will develop an appropriate mathematical framework for characterizing the geometry of natural scenes, a necessary step towards achieving a description of active somatosensation using information theoretic measures. The work contributes to our knowledge of haptic exploration and animal behavior by quantifying changes in the rat’s selection of Exploratory Procedures (EPs) based on cue salience and task familiarity. Finally, the proposed work specifically addresses a critical barrier to progress in the field of vibrissal research. At present, neurophysiologists often struggle with determining appropriate patterns of whisker stimulation to characterize the responses of central neurons in the trigeminal system (e.g., barrel cortex). The neuroethological approach taken here will lead to the identification of naturalistic patterns of stimulation, and thus lay the groundwork necessary to generate specific predictions for the integrative properties of these neurons. Broader Impacts: The PIs have an extensive history of involving undergraduates in research, and the proposed work budgets for four REU students each year. The PI founded Northwestern’s robotics club in spring 2014, and is presently its advisor. The club has over 70 active students, and fourteen students are presently participating in the "WildRat" project, which aims to construct a set of whisking-based robots. The club does outreach to Evanston high school and has a social media presence on Facebook, Twitter, and a regularly-maintained website. Based on their work with this robotics club, the PIs will develop a set of hardware models to descr