Oscillations in the brain, spanning several orders of magnitude in frequency range, may form a system that provides a syntactical framework for packaging information into `neuronal letters, words and sentences' (4). Olfaction is arguably at the forefront of understanding the role of oscillations in sensory perception (6-18). Indeed, studies in awake behaving animals show efficient odor quality coding by tiling of the response on the sniff phase (21-24). However, as indicated by Uchida and co-workers (14), whether tiling in the oscillatory phase does code for odor quality, or intensity at a certain frequency of firing, is still open to question. Interestingly, oscillations likely play a role in conveying information on odor valence. Indeed, it has been proposed that OB ? oscillations are associated with higher cognitive processes, such as making choices or initiating actions and convey information relevant for olfactory learning (16). Thus, while the olfactory system is arguably at the forefront of understanding the role of oscillations in sensory systems, there is a need to understand the precise role of these oscillations in conveying information on odorant features and valence in the OB. We have identified a major gap in understanding neural oscillations in the OB. We postulate that, phase amplitude coupling (PAC) of the ? oscillations in the ? cycle, described in the OB by Rojas-Libano and co- workers (25), likely plays a role in transfer of sensory and valence information. We will test the hypothesis that tiling of fast oscillatory response of MCs along the phase of the slower ? oscillations, conveys odor information critical for odor discrimination and learning and we will determine whether different types of information are carried at different frequency bandwidths (? vs. low or high ?).
Aim 1. Awake behaving closed loop optogenetic experiments to test the hypothesis that phase amplitude coupling facilitates olfactory discrimination.
Aim 2. Test the hypothesis that transient within-trial increase in the activity of noradrenergic axons in the olfactory bulb modulate oscillatory M/T cell responsiveness resulting in enhanced discrimination of sensory input.
Aim 3. Test the hypothesis that phase coupled stimulation of mitral cells at different bandwidths carry different types of odorant information.

Public Health Relevance

In humans, disorders of the sense of smell are encountered in diseases such as Alzheimer's, bipolar depression and schizophrenia. This grant will study olfactory coding in the olfactory bulb, a fundamental process that plays an important role in olfaction.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
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Somatosensory and Chemosensory Systems Study Section (SCS)
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Sullivan, Susan L
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University of Colorado Denver
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