Instruction manual

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6 Input and Output 86
Holding Potential: This is a voltage between ±10V that can be programmed to shift the
resting voltage of an excitable tissue (like a nerve). It is also known as a holding voltage
because it can be used to hyper polarize the membrane potential of an excitable tissue and
prevent it from depolarizing or “firing.”
Building Output
Protocols in Train
Mode
Connect the stimulus outputs to one of its own BNC inputs as described in the Building
Output Protocols in Pulse Mode section of this chapter.
Note: Never connect both the positive (red) and the negative (black) banana outputs of a 214 unit to its
own inputs, as this causes a short circuit that could damage the amplifier. These red and black outputs can
be connected to other devices (nerve chambers, stimulating electrodes, and more), but not to its own
inputs.
In many applications, more than one burst or train of pulses must be delivered. Before the
parameters of the trains or bursts are specified, the dimensions of the pulses that will fill the
bursts must be selected. After the pulse is designed, the frequency, duration, and number of
trains can be programmed.
An Example of
Pulse Trains
1 To construct and record an example of pulse trains, select Preferences from the Edit menu. On the
Channels page of the Preferences dialog window set a channel that has a BNC input to record at
10,000 samples/second and display 0.5 second on the screen (Figure 6-2 on page 83).
2 Go to the Stimulator page of the Preferences dialog window; select Trains from the box in
the upper left corner of the page.
3 Enter the following values into the appropriate boxes on the Stimulator page:
Delay 100msec (an arbitrary value)
Amplitude 1V
Number of Pulses 10 (10 pulses at 100 Hz = 0.1 sec)
Pulse Width 5ms
Pulse Frequency 100 Hz
Number of Trains 25
InterTrain Duration 900ms
These settings will create a protocol that delivers: a train of pulses every second; 10 pulses in
each train with a frequency of 100 Hz; and, all pulses with an amplitude of 1V and a width of
5msec. Since a train occurs every second and is 100msec long, the time between trains, the
InterTrain Duration, needs to be 900msec.
4 Press the Record button. The DAC will wait 100 milliseconds (the delay value entered) and begin to
deliver ten 5ms pulses in a tenth of second. Each pulse will be 1V high. After 900 milliseconds, a
second burst of ten pulses with the same parameters will occur. These bursts will appear in this manner
until a total of 25 bursts have occurred.
5 If you only wanted the train or burst to repeat four times, the number four should be entered in the
Number of Trains box. The completed output protocol should look something like Figure 6-5 on page
87.