SPLTRAK Abstract Submission
Concentration Change Processing in the Mouse Olfactory Bulb
Morgan Brown, Philip Parker, Avinash Bala, Richard Taylor, Roma Shusterman , Matt Smear
University of Oregon, Eugene, OR, United States

All sensory modalities must track how stimuli change over time. To accomplish this, many neurons in sensory systems respond preferentially to dynamic stimuli, thus enhancing temporal contrast. Given the ethological importance of odor concentration change (ΔC) to tracking an odor, the olfactory system may also accentuate temporal changes. While dynamic stimulation is standard in studies of other sensory modalities, studies of mammalian olfaction have traditionally used square stimulus pulses of the same concentration. To provide dynamic odor stimuli, we developed an odor delivery system that can change odor concentration within the typical inhalation timeframe via air dilution manifold. This enables not just fast onset of the stimulus, but fast concentration changes on the timescale of individual sniffs. Importantly, these step-function stimuli reach steady state by the time the mouse begins to inhale, making them reproducible from trial to trial. Using electrophysiological recordings, we have previously shown  that neurons of the mouse olfactory bulb explicitly encode DC. To understand the spatial distribution and morphological identity of DC sensitive neurons, we have performed calcium imaging, utilizing the ability of two photon imaging to reveal the spatial arrangement of imaged neurons. Using standard intersectional viral/transgenic techniques, we express GCaMP 7f in mitral and tufted cells of the olfactory bulb. We then image these neurons through chronically implanted windows on the dorsal surface of the bulb. Thus we can visualize ΔC-sensitive neurons, a putative cell type which may contribute to odor tracking.