Sensory Coding by Ensembles of Neurons.

Child Health And Human Development

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Abstract

Using relatively simple animals, and focusing primarily on olfaction, our unit combines electrophysiological, anatomical, behavioral, and genetic techniques to examine the ways intact neural circuits, driven by sensory stimuli, process information. In the past year, our research program has addressed several questions, among them: What mechanisms underlie information coding and decoding? How are multi-modal stimuli integrated into unified perceptions? And how are innate sensory preferences determined? Our work reveals basic mechanisms by which sensory information is transformed, stabilized, and compared as it makes its way through the nervous system.[unreadable] [unreadable] Recently, we explored the neural coding of natural odor stimuli. Projection neurons (PNs) respond to odor puffs with odor identity- and concentration-specific sequences of spiking, inhibition, and quiescence. How does this spatiotemporal mechanism encode odors in rapid trains of nearly overlapping brief pulses, as could occur in a natural odor plume? Does the temporal structure of the stimulus interfere with the temporal structure of the neural representation? For most PN-odor combinations, numbers of odor pulse elicited spikes changed reliably with pulse position, as responses to one puff interfered with responses to subsequent ones. Despite the interference observed in individual PNs, the across-ensemble response of PNs could excellent classification success for any given 50ms bin, regardless of tested inter-pulse interval. No single PN reliably coded for the pulse timing of all odors. Yet, a template-based classification scheme using the ensemble response could reliably detect peaks in classification performance for each pulse in the train, thus encoding odor pulse arrival time and duration, as well as odor identity and concentration. Additionally, we found that repeated odor presentations caused multiple forms of neural plasticity, acting on different time scales. We are continuing to explore these issues. Additionally, we are investigating mechanisms underlying the innate coding of sensory information and multimodal sensory integration.