Distinct Characteristics of Odor-evoked Calcium and Electrophysiological Signals in Mitral/Tufted Cells in the Mouse Olfactory Bulb

Abstract

Fiber photometry is a recently-developed method that indirectly measures neural activity by monitoring Ca2+ signals in genetically-identified neuronal populations. Although fiber photometry is widely used in neuroscience research, the relationship between the recorded Ca2+ signals and direct electrophysiological measurements of neural activity remains elusive. Here, we simultaneously recorded odor-evoked Ca2+ and electrophysiological signals [single-unit spikes and local field potentials (LFPs)] from mitral/tufted cells in the olfactory bulb of awake, head-fixed mice. Odors evoked responses in all types of signal but the response characteristics (e.g., type of response and time course) differed. The Ca2+ signal was correlated most closely with power in the β-band of the LFP. The Ca2+ signal performed slightly better at odor classification than high-γ oscillations, worse than single-unit spikes, and similarly to β oscillations. These results provide new information to help researchers select an appropriate method for monitoring neural activity under specific conditions.

A novel odor stimulation system in freely moving, behaving animals

“…4d). The overall discrimination rate was comparable to that found in studies with traditional odor stimulation systems in head‐fixed animals (Xu & Geng 2021).…”

Value-related learning in the olfactory bulb occurs through pathway-dependent perisomatic inhibition of mitral cells

“…Note that we refer to a reduction in the GCaMP6f fluorescence relative to the baseline as “inhibition.” While such a fluorescence reduction is known to correlate with hyperpolarisation in the membrane potential [ 57 ] or a reduction in extracellularly recorded spike numbers [ 58 ], electrophysiology would be needed in a future experiment to confirm if indeed a reduction in the mitral cells’ output is widespread in the late-phase responses to reward-predictive odours.…”

Learning of probabilistic punishment as a model of anxiety produces changes in action but not punishment encoding in the dmPFC and VTA

“…This work provides a substantial expansion of our prior paper by utilizing fiber photometry to understanding neural activity during learning because it allowed us to measure neural responses during footshock punishment. While fiber photometry signals are not a direct measure of spiking seen in single unit recording, and additional studies investigating its exact relation to single-unit approaches are nascent (see Legaria et al, 2021; Sych et al, 2019; H. Xu et al, 2021), our observations that dmPFC action-related activity was most sensitive to risk of punishment and the VTA developed phasic increases at the time of action execution is consistent with unit recordings measured in Park and Moghaddam, 2017. Similarly, we observed a large reward response in the VTA consistent with previous electrophysiology findings (Park & Moghaddam, 2017; Watabe-Uchida et al, 2017).…”