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Smear, M. C.

Publications and source records attributed to Smear, M. C..

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Sniff invariant odor coding

Sampling regulates stimulus intensity and temporal dynamics at the sense organ. Despite variations in sampling behavior, animals must make veridical perceptual judgments about external stimuli. In olfaction, odor sampling varies with respiration, which influences neural responses at the olfactory periphery. Nevertheless, rats were able to perform fine odor intensity judgments despite variations in sniff kinetics. To identify the features of neural activity supporting stable intensity perception, in awake mice we measured responses of Mitral/Tufted (MT) cells to different odors and concentrations across a range of sniff frequencies. Amplitude and latency of the MT cells responses vary with sniff duration. A fluid dynamics (FD) model based on odor concentration kinetics in the intranasal cavity can account for this variability. Eliminating sniff waveform dependence of MT cell responses using the FD model significantly improves concentration decoding. This suggests potential schemes for sniff waveform invariant odor concentration coding.\n\nHighlightsO_LIOdor concentration discrimination does not depend on sniff frequency\nC_LIO_LIAmplitude and latency of MT cell responses vary with sniff frequency\nC_LIO_LIA fluid dynamic based model accounts for sniff dependent variability in the responses\nC_LIO_LITransforming MT cell responses with this model achieves sniff invariant coding\nC_LI

neuroscience

Odor concentration change detectors in the Olfactory Bulb

Dynamical changes in the environment strongly impact our perception 1,2. Consistent with this, sensory systems preferentially represent stimulus changes, enhancing temporal contrast 3,4. In olfaction, odor concentration changes across consecutive inhalations ({Delta}Ct) can guide odor source localization. Yet the neural representation of {Delta}Ct has not been studied in vertebrates. We have found that a subset of mitral/tufted (M/T) cells in the olfactory bulb explicitly represent {Delta}Ct. These concentration change detectors are direction selective: some respond to positive {Delta}Ct, while others represent negative {Delta}Ct. This change detection enhances the contrast between different concentrations and the magnitude of contrast enhancement scales with the size of the concentration step. Further, {Delta}Ct can be read out from the total spike count per sniff, unlike odor identity and intensity, which are represented by fast temporal spike patterns. Our results demonstrate that a subset of M/T cells explicitly represents {Delta}Ct, providing a signal that may instruct navigational decisions in downstream olfactory circuits.

neuroscience