Voltage imaging of many neurons simultaneously at single-cell resolution is hampered by
the difficulty of detecting small voltage signals from overlapping neuronal processes in
neural tissue. Recent advances in genetically encoded voltage indicator (GEVI) imaging
have shown single-cell resolution optical voltage recordings in intact tissue through
imaging naturally sparse cell classes, sparse viral expression, soma restricted expression,
advanced optical systems, or a combination of these. Widespread sparse and strong
transgenic GEVI expression would enable straightforward optical access to a densely
occurring cell type, such as cortical pyramidal cells. Here we demonstrate that a recently
described sparse transgenic expression strategy can enable single-cell resolution voltage
imaging of cortical pyramidal cells in intact brain tissue without restricting expression to
the soma. We also quantify the functional crosstalk in brain tissue and discuss optimal
imaging rates to inform future GEVI experimental design.