What a Subpopulation Tells About an Odor

EZEQUIEL M. ARNEODO; KRISTINA PENIKIS; NEIL RABINOWITZ; THOMAS BOZZA; DMITRY RINBERG

Vieques, Puerto Rico

Encuentro; PEW annual meeting; 2016

Pew Charitable Trusts

Coffee still smells like coffee whether the cup is far or close and that is an example of how sensory systems form robust neural representations to identify stimuli despite their variability. Olfaction is an ideal system to explore how this is achieved. One of the reasons is that the sensory neurons are only two synapses away from the cortex.An odor activates a set of sensory neurons with different sensitivities, determined by the type of receptor they carry. Axons of sensory neurons with the same receptor type form glomeruli on the surface of the bulb, each giving excitatory input to a set of second order cells. These cells are embedded in a network of interneurons that shape their activities before they send output downstream. We want to know how these activities are shaped: what is the transfer function of the olfactory bulb (OB).We use optogenetics to dissect the system and relate output to input in awake mice. We can Identify second order cells connected to one particular glomerulus and record their responses to odors. We know how strongly the receptor responds because that can be recorded, too.The glomeruli activate in a sequence as the odorant gradually enters the nose, because the more sensitive receptors will activate at lower concentration, which is reached earlier in the sniff cycle.We think that the activities of the second order cells carry information about the order of their parent glomerulus in the sequence, and that this sequence can represent the identity of an odor (say, coffee) regardless of its concentration.