HHSIM: AN OPEN SOURCE, REALTIME, GRAPHICAL HODGKINHUXLEY SIMULATOR

D.S. Touretzky^{1}; A. Ladsariya^{1}; M.V. Albert^{1}; J.W. Johnson^{2}; N.D. Daw^{1}

1. Computer Science Dept., Carnegie Mellon Univ, Pittsburgh, PA, USA 2. Dept. of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA

HHsim is a free, open source HodgkinHuxley simulator for teaching
introductory neurophysiology. The simulation is
"transparent", meaning all parameters of the HodgkinHuxley
equations are viewable and modifiable. It is also
"realtime": variables are plotted in a scrolling
stripchart display and stimuli are applied by clicking buttons as the
simulation progresses. The third design principle of HHsim is
extensive use of graphics, not only to display the simulator's output,
but also to help the user understand the meanings of parameters. For
example, the HodgkinHuxley variables m, h, and n
are each calculated by integrating a differential equation written in
terms of associated rate constants, e.g., alpha_{m}(V)
and beta_{m}(V). The rate constants' voltage
dependencies, which are described by exponential equations in three
parameters, are displayed graphically by HHsim so that the effect of
altering a parameter can be immediately observed. Other simulator
features include the ability to observe concentrationdependent
effects of channel blockers TTX and TEA, removal of inactivation with
pronase, plotting membrane currents in voltage clamp mode, precise
measurement of plot values via a cursor control, and exporting
simulation data to a file for use by other programs.
HHsim is written in Matlab. The source code is released under the GNU
GPL (General Public License), which permits free use and
redistribution. But HHsim is also available as a binary executable
file for users without a Matlab license. We currently provide
executables for Windows, Linux, and MacOS X. Sample exercises using
the simulator are also provided. The web site is http://www.cs.cmu.edu/~dst/HHsim . Both
undergraduate and graduate neurophysiology students have found the
simulator helpful for understanding the complexities of excitable
membranes.Support Contributed By: NSF DGE9987588 and
NIMH

