Operating Instructions 

Introduction 

MetaNeuron is a computer program that models the basic electrical properties of neurons and axons. The program is intended for the beginning neuroscience student and requires no prior experience with computer simulations. 

Different aspects of neuronal behavior are highlighted in the five lessons presented in MetaNeuron. The first two lessons, Membrane Potential and Membrane Time Constant, illustrate the passive properties of neuronal membranes. The third and fourth lessons, Axon Action Potential and Axon Voltage Clamp, demonstrate how voltage- and time-dependent ionic conductances contribute to the generation of the action potential in the axon. The fifth lesson, Synaptic Potential and Current, illustrates how synaptic potentials are generated through the activation of ionotropic neurotransmitter receptors. 

The lessons in MetaNeuron do not attempt to model the full complexity of neuronal behavior. The simulations simplify neuronal properties, highlighting the basic principles of neuronal function. 

The Axon Action Potential and Axon Voltage Clamp simulations are based on the Hodgkin-Huxley equations. MetaNeuron represents 1 cm² of neuronal membrane and has a capacitance of 1 μF. 

Operation of MetaNeuron 

MetaNeuron simulations run automatically when the program is opened. A lesson is selected from the "Lesson" pull-down menu or from the function keys. The five lessons in MetaNeuron run independently of each other. If the parameters in one lesson are changed, the changes will not affect the operation of the other lessons. 

Changing Parameter Values 

Experiments are run in MetaNeuron by changing the values of the parameters displayed in the top portion of the screen. Parameter values can be changed in two ways: 

1. Select the number in a parameter value box by clicking on it, type a new value, and hit "Enter". 

2. Click on the gray button to the right of a parameter value box and drag the mouse. Moving the mouse up or to the right increases the value in increments of 1. Moving the mouse down or to the left decreases the value by 1. If the "Shift" or Ctrl" keys are depressed while moving the mouse, the parameter values change in increments of 10 or 0.1, respectively. 

Parameters in boxes that are grayed out cannot be changed. The values of these parameters are determined by other parameters on the screen or are not currently activated. 

All parameters in a lesson can be reset to their default values by selecting "Restore Lesson to Default" (Ctrl+D) in the "File" pull-down menu. 

Graphs of Parameter Values 

Some of the parameters in a lesson are plotted in the graph in the lower portion of the screen. The traces are color coded and corresponding trace labels are shown to the right of the graph. Traces in the graph are updated as a parameter value is changed. 

The sweep duration, the total time displayed on the X-axis of the graph, is controlled by the "Sweep duration" parameter above the graph. 

Family of Traces 

A family of traces can be generated in a graph by selecting the check box to the right of a parameter value box. For instance, to generate a family of traces for a range of stimulus amplitude values, select the "Stimulus 1" "Amplitude" check box. Then enter the desired "Start value", "End value" and "Increment" In the "Range" window above the graph. To return to the single trace mode, click the "Single Value" button in the "Range" window. 

3D Display 

A family of traces can be displayed in three dimensions by clicking the "3D Graph" button above the graph. The display can be rotated by clicking on the window and dragging the mouse. 

Measuring Traces with the Cursor 

The X and Y values of any point on a graph can be determined by moving the mouse over the graph and clicking. The X and Y values, in units appropriate for the yellow trace, are displayed in the "Cursor" window to the right of the graph. The Y value where the mouse is clicked is shown in white. The Y value of the yellow trace is shown in yellow. If multiple yellow traces are displayed (range option), the Y value of the yellow trace closest to the cursor is shown.