Fig. 2.

Somatic calcium transients correlate with firing rates of cortical GABAergic neurons. (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. Cell type was identified based on tdTomato expression. Neurons were loaded with the synthetic calcium dye Oregon Green BAPTA-1 (OGB-1). Spiking activity was recorded under cell-attached condition. The left panel shows the mean normalized spike waveforms of 10 cells. The middle panel shows images including a recorded neuron. The right panel shows fluorescence and electrophysiological traces from an example cell. The filtered spike train was smoothed with a Gaussian filter (s.d. = 0.5 s). (b) Fluorescence versus number of action potentials was determined using the filtered spike train. Gray lines, individual cells. Black line, mean ± s.e.m. (c) Mean spike-triggered fluorescence for excitatory ($n=16$), PV ($n=10$), and SST neurons ($n=8$). (d) Mean fluorescence versus number of action potentials for excitatory, PV, and SST neurons. The figure is adapted from Ref. 32. Reproduced with permission, courtesy of Elsevier.