Information Preservation in Neural Codes

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PROJECT SUMMARY Many things happen at once - there are always abundant stimuli to be perceived, items to be remembered, and courses of action to be planned. While considerable research has explored how our brains screen out the onslaught, we know less about how information about multiple stimuli is preserved despite limitations in neural processing capacity. This proposal explores potential brain mechanisms that may play a role in such information preservation. We recently found evidence that neural populations contain fluctuating activity patterns: some neurons alternate between encoding one stimulus and encoding another on a sub-second to second time scale. We now seek to understand the organizing principles through which such fluctuating activity patterns serve to preserve and/or select information. Specifically, we will test how such fluctuating activity patterns are coordinated with other neurons across sensory and motor representations, and whether/how they contribute to performance of information- preserving vs. information-selecting (attention) tasks. We will focus on one structure previously implicated in information preservation - the inferior colliculus, which is an essential node of the auditory processing stream through which nearly all ascending auditory information must pass, and one structure previously implicated in information selection - the superior colliculus, a multimodal brain area that has been shown to play a role in controlling eye movements and spatial attention. We will specifically focus on (a) how fluctuations depend on the overlap in the population of neurons potentially driven by each stimulus; (b) how fluctuations are coordinated across neurons; and (c) whether and how these properties are affected by neural and behavioral contexts taxing either the ability to preserve multiple stimuli or select individual stimuli to guide a behavioral response. Recordings will be conducted with multiple electrodes, allowing the assessment of coordinated fluctuation patterns via novel statistical approaches. These experiments will yield important insights into how neural representations operate when challenged with multiple stimuli. The ability to keep multiple items in mind is central to communication, working memory, attention, and sensory-motor skills, and it may be adversely affected in disorders such as attention-deficit disorder, autism, central auditory processing disorder, and age-related hearing loss.