Sniff invariant odor coding

Abstract

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 allows for significantly better decoding of concentration. This suggests potential schemes for sniff waveform invariant odor concentration coding.

Significance The principles underlying invariant object recognition are of broad interest. The sensory stimuli are subject to external variability, and variability imposed by animal behavior. In olfaction active sampling, sniffing, regulates stimulus intensity and temporal dynamics at the sense organ. Does this interfere with the ability to make accurate perceptual judgments about the physical stimulus? To address this question we initially established that perception of odor intensity is not affected by variations in sampling using behavioral experiments. To identify the features of neural activity that support this invariance in intensity perception, we developed a fluid dynamics model based on odor kinetics in the nose. This model allowed us to find neural representation invariant with respect to sampling thus allowing a stable percept.