OPM-MEG Lab Recording Steps

1. Before participant arrives (~30 min prior)

Go to the MEG room: turn off the fan and place the "Do not disturb" sign on the door — the fan introduces noise into the recording, and the sign prevents interruptions during the session.
On stim PC: load the experiment and be ready to enter the participant ID — the experiment code should already be ready before the participant arrives, so they don't have to wait while you set things up.
Close the curtain — blocks outside light from interfering with the projector, especially important when the stimulus background is dark.
Check the microphone volume — set loud enough to clearly hear the participant from outside the MSR.
Check the display setting (duplicated vs. extended screen) and speaker setting (which speaker, volume) — confirms the stimulus presentation will behave as expected during the run.

Move the helmet to the center and close the MSR door — required baseline condition for an empty-room recording.
Run the standard steps (auto start (take ~2 mins) → degauss → zero-fielding → calibration → close loop) and record empty room for at least 1 min — establishes the noise floor and system state before the participant goes in.
Check the signal — catches sensor or system issues before the participant is in the helmet. (Rob prepared MATLAB signal-check code under /document.)

Present the consent form and have the participant sign — ethics requirement; must be done before any procedure.
Explain the experiment task (either now or later), including the time frame (number of blocks, task per block, total expected duration) — gives the participant a full picture so they can pace themselves and ask questions.

Ask whether they need the toilet or water — aim for ~1 hour comfortable inside the MSR without leaving, since leaving requires re-degaussing.
Remove all metal; ask and check again — metal disturbs the OPM signal and degaussing.
Fit the brain net with ears tucked out — the goal is to keep the hair flat against the scalp so the helmet sits as close to the scalp as possible; do not stuff all the hair into the net, as this adds bulk. The net is mainly for hygiene.
Ask participant to remove shoes — reduces metal/dirt brought into the MSR.
Move the screen back to make space for the participant to enter — keeps the entry path clear.

Enter the MSR and have the participant sit in the chair.
Ask whether they need a footrest — helps them sit relaxed for the full session.
With the participant relaxed, place the helmet centered on the head — stable, not slipped to one side. Ask if it's comfortable and adjust as needed — helmet position directly affects sensor-to-scalp distance and signal quality.

Position the screen so the participant can see it clearly (measure viewing distance if needed to set stimulus size) — ensures stimuli subtend the intended visual angle.
Instruct the participant to stay relaxed and try to keep the head still during recording — reduces movement artifacts.
Inform the participant before turning off the lights — avoids startling them in a confined space.
Inform the participant before closing the door — same reason; reduces anxiety in the MSR.

As soon as the MSR door is closed, open the video monitor window — so the participant is visible from outside throughout the session.
As soon as the door is closed, use the speaker to let the participant know you can hear them and they can speak up anytime — reassures them they are not isolated.
Standard recording-start steps: (degauss → zero-fielding → calibration → close loop).
Inform the participant once setup is complete and recording is about to start — so they can get ready and focus.
Press record — without this, no data will be saved.
Run some practice trials before the official trials — lets the participant get familiar with the task and reduces early-trial errors.
During each block break, check in with the participant and acknowledge their engagement — maintains motivation and gives you a chance to catch any issues.

As soon as the experiment ends, use the speaker to inform the participant that you'll come into the MSR to remove the helmet — prevents the participant from trying to remove it themselves, which can damage the sensors.
If the MSR was very dark during the experiment, open the door slowly — gives the participant time to adjust gradually to the brighter environment.
3D scan with helmet on: instruct the participant to close their eyes whenever the scanner's flashing light is on. Avoid flashing the light directly at the front of the face for prolonged periods — scan from the sides as well, as side angles also capture useful coverage and reduce light exposure to the eyes.
Bring the participant out of the MSR and seat them in the chair for the head-only 3D scan. Clear the area around the chair so you can move fully around it, including behind — needed to capture the complete head geometry.