Figure 2

Illustrating phase–sensitive detection of Vf2.1.Cl fluorescence responses. (A) DIC image showing a single patch clamp pipette sealed to a non−sensory cell of the lesser epithelial ridge (cell 1, zero current potential −66 mV); scale bar, 25 μm. (B) Black diamonds: normalized optical signals from a specific cell network location; green trace: unit amplitude carrier wave delivered to cell 1; blue trace: its phase–shifted counterpart used in the computation of signal amplitude (see Methods). (C) Calibrated optical responses from the five regions of interest (ROIs) shown in (A) during a typical stimulation protocol. A low order polynomial fit was subtracted to the raw traces to compensate for the effects of photobleaching (see Methods). (D) Relative amplitude signals derived by integrating traces shown in (C) over a single carrier wave cycle (N = 1). (E) The standard deviation σ of the single pixel amplitude signal A(x,y) is plotted against the number N of integration cycles (see Methods); the black solid line is a least square fit to the data with the function σ₁/N^½ where σ₁ = 1.9 mV.