Deconstructing and Reconstructing Olfactory Circuits


April 2, 2015 - 3:00pm
NW 243
About the Speaker
Rainer Friedrich (Friedrich Miescher Institute for Biomedical Research)

We exploit advantages of zebrafish to study neuronal computations in the olfactory system and the underlying mechanisms. We found that the olfactory bulb, the first olfactory processing center in the vertebrate brain, performs at least two important computations: pattern equalization and pattern decorrelation. Equalization involves a population of interneurons (short axon cells) that are coupled to principal neurons (mitral cells) by gap junctions and GABAergic synapses. This circuit boosts weak input and attenuates strong input to mitral cells, thereby stabilizing the mean and variance of odor-encoding activity patterns against variations in stimulus intensity. Theoretical models and some experimental evidence indicate that decorrelation may be a generic consequence of sparse inhibitory feedback onto mitral cells. To understand these and other distributed neuronal computations in more detail we imaged the olfactory bulb at ultrastructural resolution by serial block face electron microscopy (SBEM). Using an efficient manual pipeline for neuron tracing, we densely reconstructed the neuronal circuitry in the olfactory bulb with high accuracy. The results reveal novel features of olfactory circuits and are beginning to provide detailed insights into the structural basis of distributed neuronal computations underlying pattern processing in the olfactory system.