Traces show the fluorescence and spiking activity for the neuron in vivo. (a) A layer 2/3 PV interneuron expresses the redshifted calcium indicator jRCaMP1a and the soma-targeted opsin GtACR2. Somatic calcium signals can report a decrease in firing rate. Reproduced with permission, courtesy of Elsevier. (d) Mean fluorescence versus number of action potentials for excitatory, PV, and SST neurons. (c) Mean spike-triggered fluorescence for excitatory ( n = 16), PV ( n = 10), and SST neurons ( n = 8). (b) Fluorescence versus number of action potentials was determined using the filtered spike train. The filtered spike train was smoothed with a Gaussian filter (s.d. The right panel shows fluorescence and electrophysiological traces from an example cell. The middle panel shows images including a recorded neuron. The left panel shows the mean normalized spike waveforms of 10 cells. Spiking activity was recorded under cell-attached condition. Neurons were loaded with the synthetic calcium dye Oregon Green BAPTA-1 (OGB-1). Cell type was identified based on tdTomato expression. (a) Somatic calcium transients from a parvalbumin-expressing (PV) interneuron in layer 2/3 of the mouse visual cortex, imaged using a two-photon microscope. Somatic calcium transients correlate with firing rates of cortical GABAergic neurons. We address commonly asked questions such as: Can calcium imaging be used to characterize neurons with high firing rates? Can the fluorescent signal report a decrease in spiking activity? What is the evidence that calcium transients in subcellular compartments correspond to distinct presynaptic axonal and postsynaptic dendritic events? By reviewing the empirical evidence and limitations, we suggest that, despite some caveats, calcium imaging is a versatile method to characterize a variety of neuronal events in vivo.Ĭalcium imaging calibration fluorescence neuron two-photon microscopy. We highlight experiments that have directly calibrated in vivo calcium signals recorded using fluorescent indicators against electrophysiological events. However, calcium transients have complex spatiotemporal dynamics, and since most optical methods visualize only one of the somatic, axonal, and dendritic compartments, a straightforward inference of the underlying electrical event is typically challenging.

For example, calcium influx in the soma and axonal boutons accompanies spiking activity, whereas elevations in dendrites and dendritic spines are associated with synaptic inputs and local regenerative events. A major reason is that intracellular calcium transients are reflections of electrical events in neurons. Calcium imaging is emerging as a popular technique in neuroscience.

Calcium entry in neurons dendrite