Spikes Initiate in the Axon Initial Segment in Purkinje Neurons
Figure 3. Example comparison of a recorded action potential versus voltage sensitive dye imaging. The dye responds quickly to changes in membrane potential (within 5 microseconds), so follows the kinetics of action potentials faithfully (although there may be noise in the signal). Example here is from squid giant axon (Ross et al. J. Membrane Biol. 33: 141-183; 1977).