Figure 2.

d-Cre modulated sparse expression strategies enable single-cell resolution functional imaging. (A) Population, but not single-cell, voltage signals are resolved with densely expressed GEVIs. (A₁) A wide-field image showing the patched cell's location and the ROI used to generate the voltage imaging trace. An extracellular stimulation electrode was located as indicated. (A₂) A train of extracellular stimulation evoked responses from many cells, leading to a clear population voltage response in the cellular ROI. (A₃) No single cell voltage signal could be resolved despite averaging of 80 repeated trials of extracellular stimulation. (B) The expression strategy used to generate sparse expression in layer 2/3 pyramidal cells. TMP stabilizes destabilized Cre recombinase enabling TRE driven GEVI expression. (C₁) A wide-field image of sparsely expressed GEVI showing the ROI used to calculate the voltage time course. (C₂) Single-cell voltage transients can be clearly resolved with sparse expression. Red time course shows an average of eight repeats, gray shows single trial response. Fluorescence traces shown on inverted y axes.