Title the Vibrissa Resonance Hypothesis the Vibrissa Resonance Hypothesis

Acknowledgements The authors would like to acknowledge Maria Neimark and Dr. Jason Ritt for collaboration on development of many of the ideas presented here, and Cheryl Cheney for assistance in preparation of the manuscript. Overview The vibrissa sensory system has recently emerged as a predominant model for investigation of mammalian sensory processing. The anatomical markers of representation throughout the system, most notably the barrels in primary somatosensory cortex (SI) [1], make this system attractive for studies of neural structure and function. Further, rats can employ their vibrissae for a wide variety of perceptual tasks, ranging from shape perception to the fine discrimination of textured surfaces. Despite the growing interest in the vibrissa sensory system, until recently the transduction of information into neural activity by the vibrissae themselves has received relatively little attention. In this chapter, we propose the vibrissa resonance hypothesis. We suggest that one of the intrinsic biomechanical properties of the vibrissae—their propensity to resonate at specific frequencies—plays an important role in information processing. Specifically, we propose that the amplification of high frequency inputs by vibrissa resonance should enhance the detection of small amplitude high frequency stimuli (e.g., of sound or of surface roughness) and that the frequency tuning within single vibrissae and the orderly organization of these properties across multiple vibrissae facilitates the discrimination of frequency specific stimuli. Vibrissa resonance may also be crucial to the temporal coding of sensory input on broad and fine time scales. In the first section of this chapter, we provide an overview of the importance of frequency encoding in somatosensory processing. We then provide a review of other sensory systems in 3 which resonance is proposed to play a role in signal transduction, most notably the auditory system. We conclude this section with a description of the vibrissa resonance hypothesis. In the second section of this chapter, we review recent findings demonstrating that vibrissae resonate in response to sinusoidal and naturalistic stimuli, including sound pressure waves. We then describe the neural correlates of vibrissa resonance. Vibrissa resonance is translated into an increase in the rate of action potential activity demonstrated by peripheral and SI neurons. Because vibrissa resonance properties vary systematically across the face, with lower frequencies represented more posterior and higher frequencies represented more anterior, a map of frequencies is observed across SI with a system of isofrequency columns extending along arcs of vibrissae. These findings support the hypothesis that a …