Simulators and response devices

Auditory stimulators

NOTE! Be careful when using the auditory stimulation devices in the lab! They have enough power to permanently damage hearing! Always first bring down the volume control, then turn on the stimuli, and only then carefully put on the earpieces or let a person into the shielded room.

Using the Lo-Fi system
In Presentation check that you are using the SoundBlaster sound card (under Devices).
On top of the Presentation computer there is a black audiobox (photo1).
Check the cables at the back of the box: for Lo-Fi system use the larger ones with L and R labels (photo2)
• Check the volume level setting: first turn it left to lower the sound volume before testing the sound levels to avoid damage to your hearing
If no sounds are coming from the Lo-Fi system, check that
• the volume setting on the black audiobox
• the volume settings on the computer and sound card software
• sound tubes are connected to the audio output on the side of the gantry
If you are using the Lo-Fi system, check that there are earpieces of the correct size for the participant in the MSR.
When using the Lo-Fi system use two silicon tubes going to the ear after the small sound transducer boxes (photo5). This way you get more distance between the devices that produce artifacts in the MEG and the participant. Also place the devices in such a way that they will not move during the experiment (e.g. tape them to the table).
After experiment be careful when removing the ear pieces from the silicon tubes: leave the small black adaptor pieces on the silicon tubes, and do not accidentally put them in the rubbish with the ear pieces.

Using the flat panel speakers
In Presentation check that you are using the SoundBlaster sound card (under Devices).
On top of the Presentation computer there is a black audiobox (photo1).
• Check the cables at the back of the box: for the panel speakers use the smaller ones (photo3).
• Check the volume level setting: first turn it left to lower the sound volume before testing the sound levels to avoid damage to your hearing
If no sounds are coming from the speakers, check that
• the volume setting on the black audiobox
• the volume settings on the computer and sound card software
• the power and volume are turned on in the amplifiers in the stimulation cabinet (two small metal boxes; photo4)
• the cords in the MSR are fully connected

Using the Hi-Fi system
In Presentation check that you are using the SoundBlaster sound card (under Devices).
On top of the Presentation computer there is a grey Rotel device. Turn that on. Windows computer automatically recognizes the device, when it is connected.
• Check the cables at the back of the box: for Hi-Fi ???
• Check the volume level setting: The Rotel shows volume level on it's display.
If no sounds are coming from the Hi-Fi system, check that
• the volume setting on the Rotel display
• the volume settings on the computer and sound card software
• sound tubes are connected to the speaker boxes in the stimulation cabinet
Also, check that there are earpieces of the correct size for the participant in the MSR.
When using the Hi-Fi system use two silicon tubes going to the ear. After the experiment, be careful when removing the ear pieces from the silicon tubes: leave the small black (or white) plastic adapter pieces on the silicon tubes, and do not accidentally put them in the rubbish with the ear pieces.
If the Hi-Fi system is under continuous heavy load, it might heat up. To prevent damage, there is a fuse (a circuit-breaker) inside the speaker boxes that might go off. If this happens, the stimulation ends. The only way to recover the fuse is to wait until the box cools down, and use a bit lighter stimulation next time.

Checking the delay of your auditory stimulation
Use the electret microphone for the delay test. The microphone can be found in the MEG storage room’s cabinet.
Attach the microphone cable to an Analog Input Interface socket.
Attach the microphone to the sound source, e.g. the rubber tubes, in the MSR. Turn the device on.
In the Data Acquisition software, turn on the MISC channel which is connected to the microphone for reading in the microphone signal.
Record MEG with the microphone in the MSR, while playing your experiment. You should see the audio signal on the screen in the MISC channel while recording. Make sure that the triggers are working correctly and recorded as well.
After saving the data, you can check the timing of your sound onset in relation to your trigger signals by using your favourite data processing tools. The trigger onsets can be read from channel STI101, and the stimulus onsets from the MISC channel into which you connected the microphone. If the trigger-to-stimulus delay is constant across trials, it is straightforward to compensate for it and everything is fine. However, if there is considerable jitter (several ms) between the two, you have to check and optimize your stimulus setup.

Visual stimulators

The projector (Projectiondesign FL35) is controlled by the stimulus computer (Stim-PC). Alternatively, you can play movies (Blu-Ray, DVD) using the player next to it. Available stimulus control software are Presentation, PsychoPy, and PsychToolbox (Matlab). The Stim-PC houses a powerful video card, make sure you employ it in your stimulus control software.
There are two displays on the Stim-PC. The one on the left is for controlling the computer. The one on the right is a high-performance monitor for showing the actual stimuli (mirroring the projector). You can set the refresh rate of the stimuli to 120 Hz, but please turn it back to 60 Hz after your experiment. 1920x1080p (Full HD) resolution (16:9 frame ratio) should be used.

Note! Please avoid changing the focus and other settings of the projector to not mess up other users’ experiments!

Checking the delay of your visual stimulation
There is a specific piece of equipment for measurements of visual delay in the MEG storage room cabinet. Attach the photodiode to the screen with the suction cup, and plug the other end to the data acquisition system via the Analog Input Interface. Turn the equipment on. Run at least part of your experiment as normal (without the subject), but be sure to include the plugged MISC channel into your measurement setup in the Data Acquisition software. Make sure that you can see the photodiode response to the visual stimuli in the MISC channel and that the triggers are working correctly and are recorded. Save the data. You can now use Graph, Plotter or your favourite data analysis software to check the trigger-to-stimulus delay directly from the recorded data: the trigger latency can be read from channel STI101, and the stimulus latency from the MISC channel which you connected with the photodiode. If the trigger-to-stimulus delay is constant across trials, it is straightforward to compensate for it and everything is fine. If there is considerable jitter (several ms), you have to make changes to your stimulus setup.

Somatosensory stimulators

Demetec (or in special case Digitimer) constant current stimulator. As the electrode pairs (anode+cathode) one can use ring electrodes, a spike combined with a ring, wrist strap or Ambu sticker electrode or double electrode to stimulate wrist nerves. The last one uses small, white sponges that need wetting. This induces finger movement or twitches when attached correctly.

The current stimulator needs a 5 V input trigger (behind the device). The Demetec Stimulus Current Generator has three buttons in front panel of which one is button/selector. Press it -> selection. Turn it -> switch selection. Can be set to external triggering or to some constant, internal triggering. Set the current fairly low when starting your day. The required current depends on electric conductivity of the electrodes and the participant. Read separate manual of the device to get more information.

Motor stimulation

Separate document for ankle strength sensors and ankle actuators (so called strength chair).

Finger movement with a device based on one Festo artificial muscle exists in the MEG device storage. Maximum movement is approx 2-3 cm when using the absolute maximum operating pressure of 8 bar. The device uses same electronics and pressure valves and inlets as the ankle actuator of the “strength chair”.

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Consider blocking the ears and eyes of the participant. The device makes some noise when moving. Also using tape - or something similar - are advised to use to tie the other fingers away from the moving part. The device can be placed on the table of the MEG chair or there is a separate shelf prepared. Using the separate shelf it is possible to minimize the vibration effects of the movement which might get lead to the MEG via chair.

Sports-oriented equipment

Strength measurement chair

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Ankle actuator

Static strength sensors

Stimulus settings

Switchboxes for projector and trigger signals

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Situated right below the Windows stimulus PC screen. These are simple switches only. Use these to switch for trigger and/or projector source between Windows and Linux PCs.

Note that the projector screen switch does not work, if you want to send 120 Hz frame rate images or with some screen resolutions. Always check first that your stimulus images work properly. If 120 Hz or those non-functioning screen resolutions are necessary, one has to do re-cabling in the screen system. Also on the Linux system the default screen resolution or frame rate might not work. To circumvent this one has to run a shell script which forces the output signal into a functioning one. This script is on the desktop with name "prepare_screen_for_projector.sh". Double click it to run it.

Response devices

Elekta Touchpad

 

Two, big, white pads with a lever-like switch that either blocks or unblocks a red light.

CurDes optical devices

Four color buttons. There is a 4-button and 8-button versions available. Normally the 4-button version is always connected to the MEG system. If 8-button one is needed, this will require some re-cabling in the stimulus cabin to the trigger box. Ask help if you don't know what to do. And always remember to put the 4-button version back after you are done.

Touchpad

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Connect to your stimulus PC via a long USB cable with a safety breaker to get coordinate-based responses. Has been tested in Presentation on Windows PC and also in Linux stimulus PC in one project. The frame is wooden but inside there is small amount of electronics. Will produce some noise if moved close to MEG. So don't move during experiment.

Eye-tracker

Available stimulus control software

Presentation (Windows PC)

Matlab (Linux)

Python (Linux)