Figure 3.

Dual-electrode recordings of action potentials. A, Recording from proximal electrode during sequential current injection (steps increasing by 10 pA from −30 to +70 pA; select traces are shown for clarity) into proximal (Ai) and distal (Aii) electrodes. Electrodes are spaced 110 μm apart. Thus, the proximal electrode was “active,” i.e., current was injected into the recording electrode on the left half of the trace. B, Simultaneous distal electrode recording during sequential current injection protocol as in A. Thus, the distal electrode was passive on the left side of the trace (Bi), but “active” on the right side (Bii). C, Magnified records of action potentials in proximal (black) and distal (red) electrodes during proximal current injection. The blue box is positioned similarly to those in Ai, Bi (not to scale). D, Magnified records of action potentials in proximal (black) and distal (red) electrodes during distal current injection. The green box is positioned similarly to those in Aii, Bii (not to scale). Note that the proximal action potential was larger and faster in both conditions.