Movie of propagating nerve impulses traversing morphology changes, simulated using the Hodgkin-Huxley equations.
Over four decades ago Dick FitzHugh published (1968) an instructional motion picture of nerve impulse propagation along an axon using the NIH computer for simulations of his BvP model
(now called the FitzHugh-Nagumo equations, an idealization of the HH equations). John Rinzel recently had this 20 min 16mm movie, complete with a sound track, converted to digital form and posted it
for viewing.
A full decade after FitzHugh's movie the movie from my lab at Duke (now converted to a 7.5 min QuickTime movie) showed computer simulations of the HH equations for morphological changes as well as changes in channel densities. Both movies were made well before the appearance of desktop computers that could run QuickTime and other associated software tools; making such a movie then was a tedious process and both groups used similar methods. Ours required a computer, a storage CRT display, a movie camera, and a program that sent a signal to the camera to take a single shot and advance to the next frame. Four steps were required for our movie:
A voltage-vs-space trace was was computed on a Digital Equipment Corporation (DEC) PDP/8e;
The output of the PDP/8e was displayed on a large Tektronix 4002 storage CRT;
The camera was triggered to photograph the display and then was advanced by a single frame;
The time was incremented (by about 25µsec) and the voltage-vs-space integration repeated.
We repeated each of these four steps until the transient voltage had nearly returned to its initial value. We then varied the channel densities or the morphology and repeated whole the process. We photographed an image of each set of channel densities and morphological values as well as titles and credits.
Ronald Joyner developed the implicit integration method for solving the partial differential equation. Norman Stockbridge adapted the code for advancing and displaying the voltage trace, then triggering the movie camera. Carmen Williams programmed the displays and ran the simulations. Keith Nye edited and developed the final version of the movie.