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 appro