An R-CaMP1.07 reporter mouse for cell-type-specific expression of a sensitive red fluorescent calcium indicator
A, Left: Cell body of an R-CaMP1.07-expressing L2/3 neuron and recording pipette. Right: Simultaneous fluorescence measurement and juxtacellular AP recording from this neuron. The number of spikes per burst is indicated below the voltage trace. B, Average ΔF/F calcium transient for R-CaMP1.07 in response to a single AP in red (± S.E.M as grey traces; n = 63 transients from 8 cells, 3 mice). C, Peak amplitudes of ΔF/F calcium transients (red data points) as a function of the number of APs within short AP bursts (300-ms time window; mean ± S.E.M.). For comparison R-CaMP1.07 performance for AAV-mediated expression (same as Fig 1E) is overlaid (grey data points). D, Efficiency of AP detection in vivo was determined by estimating the distribution of the signal-to-noise ratio (SNR) under noise conditions and fitting with a Gaussian. From the fit, we determined the SNR cutoff at which less than 5% of baseline traces would be classified as false positives (SNR = 2.28). Using this threshold, 60% (38/63) of single APs, 97% of doublets (38/39) and 100% of triplets (30/30) were correctly detected (see ref. ).