Stimulus Generation

Stimulus Section of the main g-PRIME scope window

2.1 Generating a Stimulus

The stimulus generation portion of the interface is found at the bottom of the main scope window. Two channels of stimulation information are generated. The first two output channels available on the selected interface are activated for stimulus generation. The first channel (Left for sound card and 0 for a NIDAQ board) contains the generated signal and the second channel contains a trigger signal that is a 5ms square pulse with 5V amplitude (depending on interface output range). The trigger signal’s rising edge is in sync with the first sample of the generated stimulus. A signal may be output by the manual “Trigger” button in single stimulus mode. The output may be repeated at a fixed interval (set in the repeat interface box in the stimulus panel) and activated using the “Start” button when the Continuous option is selected.

There are 4 modes for stimulus generation. Timing parameters are illustrated in pulse generation mode by colored bars overlaying the signal with colors corresponding to those seen in the interface option boxes.

1. One Pulse – In this mode, a single pulse is generated with pulse width set by “pulse dur” interface option and pulse delay (relative to the second channel trigger signal) set by delay 1 interface option.
2. Two Pulse – Two pulses may be generated the output is identical to the one pulse mode. The delay 2 interface option sets the time between the rising edges of two pulses.
3. Tetanic – A series of multiple pulsed stimuli may be generated. The tetanus is spanned by the two pulses. Delay 3 controls the time after the last tetanus pulse of the rising edge of the final pulse. Tetanus duration indicates the length of time to present the repeated pulse stimulus and the time between tetanic pulses is indicated by the tetanic interval. An example of an application of tetanic stimulus on a study of synaptic potentiation is illustrated in figure 6.
4. Arbitrary Stimulus Presentation – An arbitrary signal may be loaded into the interface from a variety of file types including .wav, .daq, .mat, and raw text. Only the first channel of any file type is loaded as an output signal.

The sample rate and pulse amplitude of the stimulus interface may be modified. You must activate them as interface inputs from the advanced drop down menu in the main scope program window.

2.3 Pulse Stimulus Scripting

Under Construction. A future goal includes the ability to write a script file containing pulses of various amplitudes and time spacings that could be loaded to create an arbitrary length stimulus waveform. This would be exceptionally useful in voltage clamp recordings where multiple steps of voltage amplitude pulses could be used to drive varying amplitude current injections into a cell.