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Figure 5 Schematic drawings illustrating how double component action potentials may arise. An activation front (arrows) that passes a discontinuity, being a high resistance gap (panel a), or a site with impedance mismatch (panel b) generates double component action potentials at sites before (1) and after (2) the discontinuity (panel c). Because this process is active, at least one of the components has a large (suprathreshold) amplitude. When activation blocks at the discontinuity, only one deflection remains (panel d). A weak coupling between bundles (panel e) or summation of activation in branching structures (panel f) also gives rise to double component action potentials. When the wave fronts (arrows) are propagating in these structures, the configuration of the generated action potentials is similar to those that arise at high resistance gaps or sites with a load mismatch. When, however, wave fronts are dying, double component action potentials with subthreshold amplitudes may arise (panel h). 1 and 2 indicate recording sites.
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