General Information


To generate random stimuli of different types (auditory, mechanical and/or thermal) using the Richard Gracely Multiple Random Staircase (MRS) method.

Block Diagram. Click any area of the diagram for more details.

Multiple Stimuli Block Diagram
The electrical stimulator is no longer supported: it requires a dedicated isolation unit as used by the Psycho Physiology Experiment.


Command Communication (Plain Text File) Code.

File Layout.

Command Code.

Each command must start with the identification of the stimulus type to be generated: Followed by at least one space.

Followed by the command code: Followed by at least one space.

Followed by a quantity or identification, if required: Auditory Stimulus Special Considerations.

The auditory stimuli can be delivered in two different modes:
  1. Volume Controlled Mode. The same relatively large wav file is played for all the stimuli and:
    • The Amplitude is controlled by software direct speakers/head phones volume control.
    • The Duration is controlled by interrupting the playing of the file by playing a short "No Sound" wav file. This file (NoSound.wav) must be present in the application folder.
  2. Custom Generated Wav files. The Auditory stimuli are delivered through pre-generated sound (wav) files (link to UNC sound generating software page). Their amplitude and duration are not changed by this VB interface and will be played "as is" no matter the duration command setting.
    However, a scheme was developed to display the "actual" amplitude and duration of the sound:
    • The beginning of the sound file name is used as amplitude. For instance, the file name: "50-00-400-250-3000.wav" will result in a displayed amplitude equal to 50.00 % of full volume.
    • The end of the sound file name can be used as duration. For instance, the file name: "50-00-400-250-3000.wav" will result in a displayed duration equal to 3.000 sec.
    The idea is to follow this scheme to name the sound files:

    Sound file name example
Auditory Mode Selection.
  1. Volume Controlled Mode can be entered by sending "A Wav <filename>" where <filename> is the name of the sound file to be used by all stimuli.
    e.g. "A wav 3001.wav ; A dur 1 ; A amp 25 " will set the "Volume Control" mode using "3001.wav" for basic sound at a volume 25% of the hardware volume current setting. For a duration of 1 second.
  2. Custom Wav File Mode is the default mode that can be re-entered by sending "A Wav " as command without a file name.
    e.g. "A wav ; A amp 2226-2239-3001-3113.wav" will set the "Custom Wav File" mode playing the file: "2226-2239-3001-3113.wav" as is (amplitude and duration included).
Auditory Modulation feature. New August 2010

Code Examples.

Basic initialization of all the categories-
Sets the maximum, minimum, baseline and the current amplitude commands.
turns on the auditory, mechanical and thermal interfaces; turns off the electrical interface:
A MAX 101 ; M MAX 45 ; T MAX 50 
A MIN 0 ; M MIN 0 ; T MIN 20     
A BAS 0 ; M BAS 0 ; T BAS 32
A AMP 0 ; M AMP 0 ; T AMP 32
A on ; M on; T on

Timed commands-
Sets the mechanical stimulus amplitude to 32.5 for a duration of 5 seconds,
Sets the thermal stimulus amplitude to 42 for a duration of 6 seconds,
Sets the auditory stimulus to play the "wav" file: "50-00-400-250-3000.wav"
The first two numbers will be displayed as the amplitude, and the last number will be used as a duration in milliseconds, whether or not they represent the actual amplitude and duration of the sound wave.
m amp 32.5 ; m dur 5
t amp 42 ; t dur 6
a amp 50-00-400-250-3000


Multiple Stimuli Interface application program: Old version of "MultiStimuli.exe".
Quad Stimuli Interface application program (November 2011): Old version of "QuadStimuli.exe".

Quad Stimuli Interface application program for MRI TTL pulse counting: "QuadStimuli_MRI.exe".
Quad Stimuli Interface application program for fibromyalgia and other studies: "QuadStimuli_Psychophys.exe".

A NEW version of the QuadStimuli software for WINDOWS 7, that as of the 22nd of March 2012 still needs to be tested, can be downloaded at: "QuadStimuli_W7.exe".
A NEW DLL for the Win7 version of the QuadStimuli can be placed in the same folder as the application: "LJDotNet.dll".

Text File samples (Extensions to be changed to ".txt" to affect the MultiStimuli program when running): Sound Generator application program: "SoundProject.exe".

Sound File Samples: All the files, except for the sound generator, must be in the same folder.



The "Auditory" stimuli are delivered by means of the available computer sound system.
  1. First, sound "wav" files must be generated ahead of time by means of a "Sound Generator" application program such as: the UNC pakage that can be downloaded from the "Sound Experiment Help" web page.
  2. For convenience, the sound wave files should be named as indicated above, under the title : "Auditory Stimulus Special Considerations"
  3. The computer sound volume should be set (probably to its maximum) and left in the same position for the duration of the experiment.
  4. The sound files used during the test should be played at the same volume level, on the same computer, and analyzed by means of a sound level meter, for calibration purpose.


The "Electrical" stimuli will be delivered by means of a UNC Electrical Stimulator "Basic" model.

Precaution when using the electrical, mechanical and visual stimulators for the first time.
These three stimulators use LabJack U12 USB DAQ cards. Their ID/serial numbers are kept in the initialization file:
"MultiStrimuliOGM.ini". When their recorded ID is incorrect, the software performs an auto detection routine that may modify the settings on the other unit(s) which may cause unexpected results. In order to avoid any problem, it is recommended to disconnect all the units with a LabJack except for the one being used for the first time until it has successfully been placed "On Line".


The "Mechanical" stimuli are delivered to the thumb nail by means of a "Thumb Nail Stimulator".

Two small additions were made to the original schematics
(encircled in red on the schematics) :
  1. To permit detecting the presence of the Thumb Nail device among the units equipped with a LabJack U12 DAQ that are attached to the computer.
  2. To detect whether the 15vdc power is turned on, without which the Thumb Nail Stimulator is non-functional.
Precaution when using the electrical and mechanical stimulators for the first time.
See the statement for the "Electrical" stimulator above.


The "Thermal" stimuli are delivered by means of a Medoc TSA-II thermode.

TSA II Hardware particularities.

The TSA II Hardware driver is a Visual Basic 2008 (VB.NET) program based on a Medoc Visual Basic(vb6) package. This package requires a few files to be present in the same folder in order to run. A list of these files can be found at the "Medoc TSA II & Pathway Thermal Stimulators" help page.
The TSA II power should be on at least 20 seconds before a "Thermal" stimulator "On" command is sent to the "Multiple Stimuli Software", which causes "SHOVAL.EXE" to initialize the hardware. This initialization normally takes approximately 10 seconds if every thing goes well, and sometime closer to 30 seconds.

Recommended steps to perform the first time the TSA is used:
  1. Ascertain that all the Medoc files required to run the TSA are present in the main "Multiple Stimuli" package folder:
  2. Test run a Medoc package such as "WINTSA.EXE" or "Covas.exe" to make sure the TSA II is running properly.
    Open the "Utility" ==> "Setup" (See picture) and check:
    • That the Thermode type/size (16x16 or 30x30) is correct.
    • The RS232 communication port (COM) number associated with the thermode.
  3. Open the TSAII initialization file "Options.ini" and check the entries for the thermode type and the COM port:

    Maximal Temperature=50

    Edit the file if incorrect (make sure not to add any spaces).
    If the thermode has a size of 16x16, the line should read: "Thermode=1"
    If the thermode has a size of 30x30, the line should read: "Thermode=0"
    Edit the "port=COM5" if the thermode is connected to a different port.
    You can also change the maximum temperature to a different value if you desire.
Remarks about every day use of the TSA:

Shortly after sending a "Thermal" "On" command to the "Multiple Stimuli" software, the Medoc "TSA initialization" starts. It is best to patiently wait for its completion.
When all is well, the TSA II starts its water pump with its distinctive chatter, and the initialization window automatically hides behind the main window.
When things do not go so well the software may send an alarming series of error messages which means things just did not go as expected, and a review of the steps mentioned above for the first time the TSAII is used may be necessary.

TSA II Calibration.

Hardware Calibration:

Sorry, but the Medoc company does not provide a hardware calibration for its TSAII.

Software Calibration:

A software calibration procedure was implemented. It uses a Medoc supplied YSI 4600 precision thermometer and a thermode holder jig similar to the one supplied with their Pathway system (Drawing of Pathway Calibration Check Jig).

Thermal Gradient & Subject Response Time.

  1. To measure the Medoc TSAII temperature gradient.
  2. To measure the subject response time.
Subject Response Panel When the "Subject response ON" check box is checked, the small panel below it appears.
  • Both measurements (the temperature gradient or "Ramp" and the "Subject response") start when the thermode temperature reaches the "From" temperature that must be entered by the user and must have a value between the starting temperature (the baseline) and the final temperature (the stimulus amplitude).
  • The "Ramp" measurement stops when the "To" temperature is reached. The user must also enter the "To" temperature that must have a value between the "From" temperature and the final temperature.
  • The "Subject response" measurement stops when the subject presses one of the TSAII "Subject Response Device" buttons (modified computer mouse)
  • Pressing a "Subject Response Device" button also aborts the stimulus: the thermode temperature returns to baseline.
  • Notice that if the subject responds before the "To" temperature has been reached no temperature gradient measurement can be performed.
  • The "Direct_Quad_Stimuli" Tcl program originally designed to debug this Multi Stimuli system is a simple way to control the execution of these measurements.
  1. The "Ramp" in C/sec
  2. Its duration in milliseconds
  3. And the subject response time in milliseconds, from the beginning of the ramp ("From" time).

System Check

Tcl package to check out the system

2008 September 24
Last updated 2012 March 24