Stochastic Nonlinear Dynamics of Sensory Nervous Systems

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DESCRIPTION: (provided by applicant) The long-term objective of the proposed research is to gain a better understanding of the functional roles of nonlinear and stochastic processes in neural mechanisms of information processing in the sensory nervous systems of vertebrates. We will use the electro-receptors of paddlefish as an advantageous experimental model for studying general basic mechanisms of sensory systems, especially mechanisms involving oscillations, bursting, noise, synchronization, and stochastic resonance. Paddlefish are a newly developed model system presenting unique experimental advantages for studying sensorineural integration. We discovered recently that electro-receptors have a novel bi-periodic organization: they have two distinct types of self-sustained oscillators, one cycling at 40-70 Hz in the primary afferent, together with 25-30 Hz oscillators in the electro-sensitive epithelium. The two types of oscillators are coupled uni-directionally by hair cell -to- afferent excitatory synapses. Electro-receptors therefore offer a well-defined peripheral oscillatory neural network for defining nonlinear and stochastic sensory mechanisms. This proposal includes components of experimental neurophysiology, behavioral biology, and computational neuroscience, and is based on physical theory of stochastic nonlinear systems. We will study the electro-sensory system of paddlefish on different levels, using: (i) in vitro preparations to gain information about the structural basis and cellular mechanisms of oscillations in hair cells and afferent terminals, (ii) in vivo preparations together with approaches from nonlinear dynamics to characterize the electro-receptor response dynamics, their transfer and sensory encoding properties, stochastic resonance, synchronization, and noise-induced transitions to a bursting mode of stimulus encoding, (iii) feeding behavior experiments to confirm the validity of proposed sensory encoding rules, and (iv) theoretical and computer modeling to explore numerically the functional roles of oscillatory activity in neurosensors. The proposed research is intended to lead to a better understanding of basic physiological properties of hair cell - primary afferent sensory receptors, including those mediating hearing and balance in humans, as well as general fundamental mechanisms of sensory processing in oscillatory neural networks, which include the human visual, olfactory, auditory, and somatosensory systems, as well as the disordered networks of epileptic and Parkinsonian patients.