Making Sense of Latency in Odor Responses in the Olfactory Bulb

EZEQUIEL M. ARNEODO

New York

Congreso; Sense2Synapse; 2014

Olfaction is an ideal sense to study how the receptors´ level representation of a stimulus is transformed before getting to the brain. We use optogenetics and electrophysiology to determine features of the transformation carried by the olfactory bulb (OB) on a single channel of information, conformed by the route of one particular receptor type. In the mammalian OB axons of each genetically identified and tractable receptor type converge into glomeruli and form synapses with second order mitral/tufted (M/T) cells. These cells receive excitatory input from only one glomerulus, and readily relay to higher brain areas. Their activity is shaped by their glomerular excitatory input and by the inhibition delivered by a vast network of inhibitory interneurons. One fundamental question is what M/T cells tell about the odor response of their parent receptor type. In order to address this, we use­­ ChR2 to identify M/T cells connected to one particular receptor type and record extracellular activity of OB neurons using Si- probes in an awake acute mouse preparation. We monitor the activity of M/T cells connected to the M72 glomerulus in response to odorants for which the dose-response relationship is well characterized. We find that the latencies of the M/T cell responses relative to the sniff cycle relate to the response profile of the receptor.