General Information


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

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

Multiple Stimuli Block Diagram

Detailed Block Diagram.

System map with links.

EEG Room Photos

with identifiers and links

Room Photo with component identification and links.

with identifiers only

Psycho Physiology instruments - Photo with component identification.
Instrument Rack Photo with component identification.
EEG computer trigger connections Photo with component identification.

2010 EEG Room Reorganization

Proposed Mobile Rack

Psycho Physiology instruments - Mobile rack photo with component identification.


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 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 of the sound (the duration being controled by the "CNSD Stimulus Timing Unit"):
The idea is to follow this scheme to name the sound files:

Sound file name example

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 ; E MAX 20 ; M MAX 45 ; T MAX 50 ;V MAX 100  
A MIN 0 ; E MIN 0 ; M MIN 0 ; T MIN 20 ; V MIN 0     
A BAS 0 ; E BAS 0 ; M BAS 0 ; T BAS 32 ; V BAS 0
A AMP 0 ; E AMP 0 ; M AMP 0 ; T AMP 32 ; V AMP 0
A on ; E off ; M on; T on ; V on

Timed commands-
Sets the electrical stimulus amplitude to 5.7 for a duration of 4 seconds,
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.
e amp 5.7 ; e dur 4
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: "MultiStimuli.exe".

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.


Stimulus Timing Unit

The Auditory, the Electrial and the Visual stimuli timings are controlled by the Stimulus Timing Unit.
The Mechanical and Thermal stimuli Timings are controlled by software: VB "millisecond" timers that depend on the system tick(see WINDOWS Timing Investigation for details).


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".

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).


The "Visual" stimuli will be delivered by means of a "UNC Luminescence Unit".

System Check

The following software can be used to check the Mechanical and Thermal stimulation hardware, but it was designed for the Quad Stimuli system used by the "Mechanisms of Sensory Processing in Fibromyalgia" project, and will most probably not work properly for the auditory system used by the Psycho Physiology project. Tcl package to check out the system

2008 September 24
Last updated 2009 November 6