Speaker: Upinder Bhalla, Ph.D., Professor, National Center for Biological Sciences, India
Date: Thursday, November 12, 2015
Time: 10:00 am – 11:00 am
Location: 46-3310
Host: Matt Wilson, Ph.D.

Title: What, where and how much: the code in your nose

Abstract: Odors are an extraordinarily rich but misunderstood window into the chemical world. Consider the dimensions of chemical stimuli: odor identity, odor intensity, and odor timing. It has long been known that identity and intensity of odorants is encoded, at least in part, by the timing of the activity of cells in the olfactory pathway. This introduces a confound when we recognize that odors are discriminated with < 50 ms precision, in order to achieve localization. How does the olfactory system encode time itself, when identity and intensity encoding also use timing? We used recordings, behavior and computer models to explore these questions. We delivered very precise odor stimuli in patterned pulses, in mixtures, and at different concentrations to dissect odor coding. We find that essentially all combinations of odor mixtures and timings can be predicted from a linear convolution of odor input with impulse responses of individual neurons. We also find that laterality is strictly preserved in the olfactory system, as a basis for odor directionality. Taking this into the behavioural arena, we find that a sophisticated combination of stereo localization with a range of near-optimal tracking strategies keep rats on track in odor guided tasks. To keep our own understanding on track in each of these domains, we have made models of bulbar computation as well as of high-level odor tracking strategies. These models give some unexpected insights into how odor information shapes behavior.