Calcium Imaging in Neuroscience

Abstract

Calcium imaging uses fluorescent indicator molecules to monitor changes of intracellular free calcium concentrations. Calcium imaging is employed to examine electrically excitable tissues such as muscle and neuronal tissue (including glia) where membraneā€related electrical activity is tightly coupled to significant calcium movements into or within cells. In the context of neuroscience research, calcium imaging can be applied at many scales, ranging from a single part of a single neuron to populations of many interconnected neurons. The ability to move between different scales of resolution is a major advantage of calcium imaging, making this technique an important tool for enhancing our understanding of the brain.

Key concepts

  • Brain researchers use calcium imaging to monitor electrical activity in neurons.

  • Calcium can be imaged at many scales: from the subcellular to entire brain regions.

  • Calcium imaging can use different dyes and optical methods.

Keywords: neuroscience; neurophysiology; optical calcium imaging; calcium indicator; calcium dye

Figure 1.

Calcium imaging is used to detect brain activity both on the scale of neuronal compartments and on the scale of networks of synaptically interconnected neurons. This figure shows an example of each scale from in vitro experiments using two photon laser scanning microscopy. Top left: Detail of a dendrite of a single neuron in the cerebral cortex which was filled with the calcium indicator dye Fura‐2. Top right: time course of the intensity of the fluorescent light emitted by a small area of the dendritic shaft which is indicated by the red rectangle on the left. The downward deflection of the signal shown corresponds to an intradendritic calcium increase following an artificial electrical stimulation of the dendrite. Note that here the ratiometric calcium dye Fura‐2 reports increased intracellular calcium concentration with decreased fluorescence emission. This is due to a shift in the optimum excitation wavelength while the excitation wavelength stays constant. Also note the slow drift of the fluorescence baseline over time which is a result of photobleaching of the dye. Bottom left: A population of neurons and glial cells in the cerebral cortex, stained with the calcium indicator dye Oregon Green BAPTA‐1pseudo‐coloured. Bottom right, traces: Intensity of emitted fluorescence over time collected from four example cells. Different cells are engaged differently in two events of spontaneous activity. Oregon Green BAPTA‐1is a non‐ratiometric dye and the increase of fluorescence emission indicates an increase of intracellular calcium concentration following action potential generation. Bottom right, population activity map: The calcium signals of 160 neurons which could be detected in the fluorescence image were thresholded and plotted over time, resulting in a binary ON‐OFF map. The red colour indicates active periods when a cell exhibits a significantly increased concentration of intracellular calcium. Green indicates activity on the level of the whole population.

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How to Cite close
Neubauer, Florian B, and MacLean, Jason N(Jan 2010) Calcium Imaging in Neuroscience. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0021391]