Figure 7. Multiple site recording of spike propagation success (A) and failure (B) at the junction between axonal branches Br5 and Br2.

The recording area is indicated by multiple traces superimposed over the CCD image of the same intact neuron. Each trace represents the output of one diode for 70 ms centred around the peak of the spike. Four trials were averaged. The spatial and temporal characteristics of the propagation block are shown as a sequence of nine frames, 1 ms apart, in the colour-coded display. A, orthodromic action potential evoked by soma stimulation invaded all axonal branches. B, antidromic action potential evoked peripherally in Br5, by a current pulse delivered through a suction electrode attached to the cut end of the peripheral nerve, failed at the bifurcation. C and D, decline of the relative spike amplitude with distance from the region of full excitability in the direction of the site of propagation block. In D, the y-axis shows the relative spike amplitude.