Stimulus dependent diversity and stereotypy in the output of an olfactory functional unit

Olfactory inputs are organized in an array of parallel functional units (glomeruli), each relaying information from sensory neurons that express a given odorant receptor to a small population of output neurons, mitral/tufted (MT) cells. MT cells have complex temporal responses to odorants, but how these diverse responses relate to stimulus features is not known. We recorded in awake mice responses from “sister” MT cells that receive input from a functionally-characterized, genetically identified glomerulus, corresponding to a specific receptor (M72). Despite receiving similar inputs, sister MT cells exhibited temporally diverse, concentration variant, excitatory and inhibitory responses to most M72 ligands. In contrast, the strongest known ligand for M72 elicited temporally-stereotyped, early excitatory responses in all sister MT cells that persisted across all odor concentrations. Our data demonstrate that information about ligand affinity is encoded in the collective stereotypy or diversity of activity among sister MT cells within a glomerular functional unit in concentration-independent manner.