Wide-Field Calcium Imaging of Neuronal Network Dynamics In Vivo

Abstract

A central tenet of neuroscience is that sensory, motor, and cognitive behaviors are generated by the communications and interactions among neurons, distributed within and across anatomically and functionally distinct brain regions. Therefore, to decipher how the brain plans, learns, and executes behaviors requires characterizing neuronal activity at multiple spatial and temporal scales. This includes simultaneously recording neuronal dynamics at the mesoscale level to understand the interactions among brain regions during different behavioral and brain states. Wide-field Ca2+ imaging, which uses single photon excitation and improved genetically encoded Ca2+ indicators, allows for simultaneous recordings of large brain areas and is proving to be a powerful tool to study neuronal activity at the mesoscopic scale in behaving animals. This review details the techniques used for wide-field Ca2+ imaging and the various approaches employed for the analyses of the rich neuronal-behavioral data sets obtained. Also discussed is how wide-field Ca2+ imaging is providing novel insights into both normal and altered neural processing in disease. Finally, we examine the limitations of the approach and new developments in wide-field Ca2+ imaging that are bringing new capabilities to this important technique for investigating large-scale neuronal dynamics.

Enteric Nervous System: Identification of a Novel Neuronal Sensory Network in the Duodenal Epithelium

“…Changes in fluorescence reflect fluctuations in intracellular calcium ( in [Ca 2+ ]), an indirect indicator of neural activity. 38 Action potentials increase in [Ca 2+ ], causing the fluorescent probes to bind more calcium, resulting in augmented fluorescence emission. 39 Isolated villous-crypt units were seeded on polyl-lysine-coated coverslips, incubated with Fluo-4 AM (10 µM) for 30 min at 4C, and washed (two times) with Dulbecco medium.…”

“…Changes in fluorescence reflect fluctuations in intracellular calcium ( in [Ca 2+ ]), an indirect indicator of neural activity. 38 Action potentials increase in [Ca 2+ ], causing the fluorescent probes to bind more calcium, resulting in augmented fluorescence emission. 39…”

Convolutional neural network classifies visual stimuli from cortical response recorded with wide-field imaging in mice

“…Some of these indicators, called genetically encoded calcium indicators (GECIs), are sensitive to fluctuations in intracellular calcium, an indirect indicator of neural activity [14]. Improvements in technology allowed in vivo imaging of neural activity and, among GECIs, the GCamP family is the most used in neuroscience applications [15]. Imaging is performed after the head fixation of the animal.…”

“…Imaging is performed after the head fixation of the animal. The images can be captured with a closed skull by thinning the bone or using glass coverslips achieving partial transparency, or an open skull by replacing the bone flap with transparent materials [15]. The images are obtained by exploiting a light source, usually provided by LEDs, combined with a light-sensing device, usually attached to a microscope, to capture emission fluorescence [14,15].…”

“…The images can be captured with a closed skull by thinning the bone or using glass coverslips achieving partial transparency, or an open skull by replacing the bone flap with transparent materials [15]. The images are obtained by exploiting a light source, usually provided by LEDs, combined with a light-sensing device, usually attached to a microscope, to capture emission fluorescence [14,15]. Often performed in mice, wide-field calcium imaging has been widely used in the literature to evaluate neural dynamics across broad brain areas, especially to explore the interaction between them, thanks to its high signal-to-noise ratio (SNR) and spatiotemporal resolution.…”