In vivocalcium imaging of CA3 pyramidal neuron populations in adult mouse hippocampus

Abstract

Neuronal population activity in the hippocampal CA3 subfield is implicated in cognitive brain functions such as memory processing and spatial navigation. However, because of its deep location in the brain, the CA3 area has been difficult to target with modern calcium imaging approaches. Here, we achieved chronic two-photon calcium imaging of CA3 pyramidal neurons with the red fluorescent calcium indicator R-CaMP1.07 in anesthetized and awake mice. We characterize CA3 neuronal activity at both the single-cell and population level and assess its stability across multiple imaging days. During both anesthesia and wakefulness, nearly all CA3 pyramidal neurons displayed calcium transients. Most of the calcium transients were consistent with a high incidence of bursts of action potentials, based on calibration measurements using simultaneous juxtacellular recordings and calcium imaging. In awake mice, we found state-dependent differences with striking large and prolonged calcium transients during locomotion. We estimate that trains of >30 action potentials over 3 s underlie these salient events. Their abundance in particular subsets of neurons was relatively stable across days. At the population level, we found that coactivity within the CA3 network was above chance level and that co-active neuron pairs maintained their correlated activity over days. Our results corroborate the notion of state-dependent spatiotemporal activity patterns in the recurrent network of CA3 and demonstrate that at least some features of population activity, namely coactivity of cell pairs and likelihood to engage in prolonged high activity, are maintained over days.

A database and deep learning toolbox for noise-optimized, generalized spike inference from calcium imaging

“…In zebrafish, a total of 47 neurons in different telencephalic regions were recorded in the juxtacellular configuration in an explant preparation of the whole adult brain 24 using the synthetic calcium indicators Oregon Green BAPTA-1 (OGB-1) and Cal-520 as well as the genetically encoded calcium indicator GCaMP6f. In head-fixed mice, ground truth recordings were performed under anaesthesia in hippocampal area CA3 using the genetically encoded indicator R-CaMP1.07 25 . Furthermore, we extracted ground truth from published studies of neurons in mouse primary somatosensory cortex (S1), using Cal-520 and R-CaMP1.07, respectively (total of 21 neurons) 26 , 27 , and of inhibitory neurons in mouse primary visual cortex (V1), using OGB-1 in vivo and GCaMP6f in slices, respectively (total of 69 neurons) 28 , 29 .…”

Effective and efficient neural networks for spike inference from in vivo calcium imaging

“…In this study, we used the publicly available datasets containing both calcium imaging signals and simultaneously recorded electrophysiological signals from excitatory neurons 13 , 14 , 15 , 16 , 17 , 35 , 38 , 66 , 67 , 68 and inhibitory neurons. 38 , 67 , 69 For benchmarking and algorithm development purposes, they were recently compiled by 38 into an extensive database with 27 datasets.…”

Effective and Efficient Neural Networks for Spike Inference fromIn VivoCalcium Imaging

“…In this study, we used the publicly available datasets containing both calcium imaging signals and simultaneously recorded electrophysiological signals from excitatory neurons (Akerboom et al ., 2012; Bethge et al ., 2017; Chen et al ., 2013; Dana et al ., 2016; Huang et al, 2020; Khan et al, 2018; Rupprecht et al ., 2021; Schoenfeld et al, 2021; Tada et al ., 2014; Theis et al ., 2016) and inhibitory neurons (Khan et al ., 2018; Kwan and Dan, 2012; Rupprecht et al ., 2021). For benchmarking and algorithm development purposes, they were recently compiled by (Rupprecht et al ., 2021) into an extensive database with 27 datasets.…”

“…In this study, we used the publicly available datasets containing both calcium imaging signals and simultaneously recorded electrophysiological signals from excitatory neurons [13][14][15][16][17]35,38,[51][52][53] . For benchmarking and algorithm development purposes, they were recently compiled by 38 into an extensive database with 21 datasets.…”