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Séminaire impromptu - Detlev SchildActivity Correlation Imaging reveals first-spike-latency coding of odor quality in the olfactory bulb

Abstract :

The first two stages of odor coding in the tadpole of Xenopus laevis will be presented, i.e. the sensory olfactory neurons in the olfactory epithelium, which then project to the first central stage of the system, the olfactory bulb. The crucial interface between sensory cells and olfactory bulb are the so-called glomerula, which relay the sensory signals and convert it into an image. Contrary to general assumptions, however, this image pixels corresponding to a particular stimulus do NOT correspond to the same point in time. We used a novel technique, activity correlation imaging, set up in our laboratory, to image many mitral cells, simultaneously and in 3D. This way it can be shown that odor quality is coded primarily by a vector of relative latencies of mitral cell activities. This changed our view of odor coding, and maybe neural coding in general, markedly.

 

Selected publications

Bao G, Schild D (2014)
Fast and accurate fitting and filtering of noisy exponentials in legendre space.
PLoS ONE, 9(3), e90500.

Alevra M, Schwartz P, Schild D (2012)
Direct measurement of diffusion in olfactory cilia using a modified FRAP approach.
PLoS ONE, 7(7), e39628. [pdf for personal use only]

Junek, S, Kludt, E, Wolf, F, and Schild, D (2010).
Olfactory Coding with Patterns of Response Latencies
Neuron 67:872-884.

Junek, S, Kludt, E, Wolf, F, and Schild, D (2010).
Olfactory Coding with Patterns of Response Latencies
Neuroforum 16(4):277.

 

Scientific focus :

Major Research Interests

We are trying to understand how the sense of smell works. Olfactory systems are able to detect and distinguish thousands of molecules in our environment. Receptor neurons are endowed with hundreds of different receptor molecules to bind odorants and transduce the chemical signals into electrical ones (Fig. 1). Chemosensory information is thus represented in a rather high-dimensional space. The receptor neurons, which code the hitting probability of odor molecules binding to their molecular receptors (Fig.2), eventually generate trains of action potentials, a one-dimensional vector of stochastic processes. They convey their information onto the brain, in particular the olfactory bulb, where the receptor neuron signals are transformed into a two-dimensional neuronal image of firing activities. Glomerula, small skeins of receptor nerve fibers and synapses in the olfactory bulb appear to be the heart of olfactory coding.

Using a combination of electrophysiological techniques, single molecule detection, photochemical and high resolution imaging techniques as well as computational and modeling methods, we are studying the biophysical and physicochemical details of
- the primary coding processes,
- the synaptic transmission in glomerula
- the generation of the neuronal chemotopic map as well as
- the processes and mechanism of odor learning and memory.

Andréas Frick (andreas.frick @ inserm.fr)