PSGM Parameters

Some experiments in visual neuroscience measure the behavioral and neuronal response to electrical stimulation of a specific neural region. One way to do this in Maestro is to use a marker pulse to trigger an external electrical pulse stimulator, like those available from Grass-Telefactor.

Such a setup does not give the experimenter trial-by-trial control of the amplitude, pulse width, and other characteristics of the the pulse train delivered. Alternatively, Maestro's Pulse Stimulus Generator Module (PSGM) can deliver a wide variety of pulse train stimuli and is available for use in Trial mode.You can set up a trial to deliver a single PSGM stimulus sequence, starting at a particular segment during the trial. The Pulse Stimulus Generator control group, on the Perturbations/PSGM tab pane at the top of the Trial Editor, sets the parameters for the pulse generator:

    • Operational mode. The combo box selects the PSGM sequence type: Single (a single pulse of specified duration and amplitude), Two Pulses (two independent pulses separated by an interpulse interval), Biphasic (a single two-phase pulse), Train (one or more trains, each consisting of one or more identical pulses, and Biphasic Train (similar to Train, except the pulses are biphasic). If Not In Use is selected, then the PSGM is disabled.

    • Starting segment. This spinner control selects the trial segment during which the PSGM sequence is started. Exactly when it starts depends on whether or not the external trigger is enabled.

    • External trigger? If this check box is left unchecked, then the PSGM sequence is "software-started" during the first millisecond of the specified trial segment. If you need to synchronize the sequence with some external event, check this box and ensure that the external trigger signal fires during the specified trial segment (for example, you could use one of Maestro's own digital outputs as the trigger!). If the trigger signal does not arrive before the segment ends, then the PSGM sequence will not occur at all.

    • Pulse amplitudes. Use these numeric text fields to set the first (left-hand field) and second (right-hand field) pulse amplitudes, in millivolts. The second pulse amplitude only applies in the Two Pulses, Biphasic, and Biphasic Train modes. Allowed range is [-10240..10160] in 80mV increments. Bad values are auto-corrected.

    • Pulse widths. Use these numeric text fields to set the durations of the first (left-hand field) and second pulses, in microseconds. The second pulse width only applies in the Two Pulses, Biphasic, and Biphasic Train modes. Allowed range is [50..2500] in 10µs increments. Bad values are auto-corrected.

    • Interpulse interval (IPI). This numeric text field sets the "start-to-start" interval between successive pulses in the Two Pulses, Train, and Biphasic Train modes. Allowed range is [1..250] in 1ms increments. Note that Maestro will auto-correct the IPI if it is less than or equal to the width of pulse #1 (or the sum of the two pulse widths in the biphasic modes).

    • Intertrain interval (ITI). This numeric text field sets the "start-to-start" interval between successive pulse trains in either of the two train modes. Allowed range is [10..2500] in 10ms increments. Note that ITI must always be greater than IPI × #Pulses. Maestro will auto-correct the ITI (and possibly the #Pulses) if this is not the case.

    • #Pulses, #Trains. These numeric fields specify, respectively, the number of pulses per train and the number of trains in the PSGM stimulus sequence. They are applicable only to the two train modes. Allowed range is [1..250].