Distinct spatiotemporal activity in principal neurons of the mouse olfactory bulb in anesthetized and awake states

Abstract

The acquisition of olfactory information and its early processing in mammals are modulated by brain states through sniffing behavior and neural feedback. We imaged the spatiotemporal pattern of odor-evoked activity in a population of output neurons (mitral/tufted cells, MTCs) in the olfactory bulb (OB) of head-restrained mice expressing a genetically-encoded calcium indicator. The temporal dynamics of MTC population activity were relatively simple in anesthetized animals, but were highly variable in awake animals. However, the apparently irregular activity in awake animals could be predicted well using sniff timing measured externally, or inferred through fluctuations in the global responses of MTC population even without explicit knowledge of sniff times. The overall spatial pattern of activity was conserved across states, but odor responses had a diffuse spatial component in anesthetized mice that was less prominent during wakefulness. Multi-photon microscopy indicated that MTC lateral dendrites were the likely source of spatially disperse responses in the anesthetized animal. Our data demonstrate that the temporal and spatial dynamics of MTCs can be significantly modulated by behavioral state, and that the ensemble activity of MTCs can provide information about sniff timing to downstream circuits to help decode odor responses.

Reading Out Olfactory Receptors: Feedforward Circuits Detect Odors in Mixtures without Demixing

“…However, much of the variability was correlated across glomeruli, probably reflecting causes that are either irrelevant to behaving mice (e.g. anesthesia level and breathing parameters; Blauvelt et al, 2013) or could be easily factored out by neural operations such as normalization. This correlated variability is evident when the responses of all glomeruli to each trial of a specific odor were plotted against the mean response to that odor across trials (Fig.…”

“…Our analysis suggests that correlated trial-to-trial variability probably reflect slow changes due to anesthesia (Ecker et al, 2014) and breathing. Breathing induced covariation could be easily removed by lateral interactions, which is why we neglected them here (Olsen et al, 2010, Blauvelt et al, 2013, Friedrich and Wiechert, 2014). Our measurements as well as those of others (Duchamp-Viret et al, 2005) indicate that noise levels at the glomeruli and overlap of glomerular patterns are not high enough to require an additional processing stage.…”

Construction of functional neuronal circuitry in the olfactory bulb

“…Sniff speed and frequency affect sensitivity and temporal patterns of representations, respectively [105][106][107]. Odor representation is sparser in awake animals, likely because inhibitory neurons are more active [57,108,109].…”

Cellular Level Brain Imaging in Behaving Mammals: An Engineering Approach

“…Behavioral assays have since progressed, making use of the head-fixed preparation’s suitability for controlled delivery of sensory stimuli (Andermann et al, 2011; Blauvelt et al, 2013; Carey et al, 2009; Miller et al, 2014; Patterson et al, 2013; Verhagen et al, 2007). The addition of a trained behavioral response enabled studies of perceptual discrimination tasks (Andermann et al, 2010; Komiyama et al, 2010; O’Connor et al, 2010).…”