Figure 6.

Consequence of internal fluorescence when imaging population of cells. (A) Schematic of a neuron under high magnification with plasma membrane and internal fluorescence in green. The cell is projected onto multiple pixels enabling the experimenter to choose pixels with optical activity. In this example the red, highlighted pixels labeled 1–4 have a large ΔF/F while pixels highlighted in blue, labeled 5–8, exhibit low or no change in fluorescence upon depolarization of the plasma membrane. (B) Same cell under low magnification now only projects onto a few pixels. The pixel highlighted in black, labeled 9, is a summation of pixels 1–8 in (A). The experimenter is no longer able to avoid the non-responsive, internal fluorescence.