Cap Fitting & Electrode Placement

Measurements:

• Ear-to-ear (cm) with a tape measure.
• Nasion to inion (brow bone center to skull bump); Cz electrode must be centered.

Cap Positioning:

• Part participant’s hair down the middle.
• Fabric should start two fingers above the brow bone.
• Central line must be aligned with the center of the head.
• Secure amplifier casing onto the cap before putting it on the head.
• Strap the chin strap securely.

Electrode Placement:

• Total: 34 electrodes, 32 recording electrodes plus ground and reference.
• Ground (white) & Reference (blue) are most important.
• Start filling reference electrodes first, then all measuring electrodes.
• Recommended: 2-3 tubes of gel per session.
• Apply gel sparingly first, then exfoliate scalp by moving the syringe tip (e.g, think of filling it to look like 1 perfect scoop of ice cream in a small bowl).
• Tip: Work in pairs (one person on each side of the head).
• NOTE: Each gel syringe costs about $5. These costs add up rapidly. Please use as many gel syringes as you need to get a good signal. BUT also please be cautious to try to not unnecessarily waste. For participants with thinner or less hair, you may need 1-2 syringes. For participants with thick hair, or a lot of hair, you may need 3+ syringes. Data quality must come first. So use what you need to. Just, try to not waste.

Electrode Impedance Check:

• Click "Impedance Measurement" > "Impedance on Reference" first.
• Hit the stream button on the bottom left.
• Good impedance: Below 10kΩ (green), but up to 30kΩ (yellow) is acceptable if stable.
• If the impedance is high, move the gel rather than adding more.
• Now switch "Impedance Measurement" > "All Electrodes" and fill the rest of the electrodes.
• Electrode display: can change between name, number, impedance value (use numbers for gel filling if wanted as it matches the labels on the cap). To do that, from the main window, under "Electrodes display:" select "Electrode number"
• If electrodes wont turn color go to “Settings” > “Impedance measurement OFF” > “Signals” > “Full screen” to check if the electrode is flatlining (you can change the scale closer to 50 to see closer on the signal lines.
• Don't monitor the impedance while recording (it won't tell you anything the signal itself won't tell you); it will take too much power; and, MOST IMPORTANTLY, it will add noise to your data.

Software Setup & Recording

Connecting the Amplifier:

• Ensure Bluetooth is functioning (check Device Manager for conflicts).
• Click "Disconnected" toggle in the top left corner > "Connect".
• Blue blinking light = Connected.
• Red blinking light = Battery < 10% (do not use).

Settings Tab:

• Sampling frequency: Choose Hz as required.
• Keyboard markers: Record keyboard activities.
• Motion sensors: Enable 3D head tracking.
• Test signal: Keep OFF.
• Impedance Measurement: Turn OFF when recording to prevent noise.
• Advanced settings are for custom caps, etc. (not for us for now).

Signals Tab:

• View brain waves in real-time.
• 3D head tracking: Click the "3D" button for movement visualization.
• Common signal characteristics:

• Eye blinks: Fp1 & Fp2 (small bumps).
• Alpha waves: P3, P4, O1, O2 (eyes closed).
• Muscle noise: T7, T8 (shoulders need relaxation).
• Keyboard events: Purple line indicates key presses.

Recording Data:

• PC Recording (Bluetooth) & Device Recording (SD Card) recommended for backup.
• PC Recording: Records EEG, keyboard markers, motion tracking, and PsychoPy streams.
• Device Recording: Captures only raw EEG/motion.
• File Naming: Ensure PC & Device recordings have the same file name.

Recording Process:

• Click "Record".
• Observe data streams in real-time in the signals tab.
• Tip: Ask participants to blink and press a key to confirm artifacts during setup.
• Click "Stop Recording" when finished.
• If software crashes: Restart the stream and reconnect.
• Bluetooth recording limitation: If the participant moves too far, PC recording may stop, but the amplifier continues recording.

Data Preprocessing

ASR Algorithm (Adaptive Signal Reconstruction):

• Uses Principal Component Analysis (PCA) to remove artifacts.
• Set cutoff to 15 (higher than 5 to avoid excessive data loss).
• Provides both raw and corrected data.
• Mix Function:

• Blue = Removed data (artifacts).
• Orange = Retained data (brain signals).

Filters & Preprocessing:

• Default filter spreads signals out in the software.
• In MATLAB, signals appear compressed and require additional processing.
• Software we will use for analysis: ERPLab & MNE.

Cleaning & Maintenance

Post-Session Cleaning:

• Remove the amplifier before washing the cap.
• Disconnect connector box (place in a waterproof bag).
• Rinse cap in cool-to-warm water (not hot), being sure to turn the cap both inside & outside. Follow these cap washing instructions from mbt
• Use mascara brushes and or toothbrush (ONLY use soft toothbrush bristles on the cap, NOT the tongue scraper) to push gel through electrodes.
• Once gel is completely removed from the cap and electrodes:
  • Take plastic tub next to the drying cap drying rack, place in sink, and lace cap in the tub.
  • Leave EEG amplifier socket/connector outside of tub, being sure that it stays dry.
  • Apply Envirocide over the cap and electrodes.
  • The cap does NOT need to be fully submerged
  • Instead, all parts of the cap and electrodes should be wet with Envirocide.
  • Also wet the toothbrush you used to clean gel from the cap.
  • Also wet any plastic combs and or mascara brushes used during the study.
  • The cap, electrodes, toothbrushes, combs, and mascara brushes must stay wet with Envirocide for 3 minutes (this completes a full sterilization)
  • Rinse envirocide from cap, electrodes, toothbrushes, combs, and mascara brushes using the lab sink.
• Air dry cap, electrodes, toothbrushes, combs, and mascara brushes on rack, using fan or a hairdryer on cold if necessary. Be sure to support eeg amplifier wires, do not allow strain on wires.
• Do NOT use rubbing alcohol.
• ONLY clean cap and electrodes with white-listed cleaners.
• Offer to wash the participant's hair after the session.
• Clean sink using water and Clorox wipes

Important notes about Envirocide:

Each bottle costs about $45. Please use as much as you need to fully wet the entire cap, all electrodes, toothbrushs, combs, and mascara brushes. But please do not waste. Use what you need, just be mindful.

IMPORTANT Please wear gloves (provided in lab) while working with Envirocide. It is a skin irritant. If you get it on your skin, wash completely

• Review the safety sheet for working with Envirocide.

Cleaning Salon Towels

Promptly wash all towels and laundry bags after a data collection in order to prevent mold/mildew. To clean towels and laundry bags, follow these steps:

• Wash in a hot-water laundry cycle with detergent and half a cup of bleach (towels and laundry bags are bleach safe).
• Dry on a high-heat setting.

Repair & Maintenance:

• Electrodes are repairable. May require shipping the cap back for repairs.
• Amplifier can be repaired. Ship back to the manufacturer.
• Repairs are:
  • Terrible for your research. They may result in long (e.g. one month) delays.
  • Expensive. Repairs cost money, international shipping rates are high, and customs fees associated with international shipping are massive.
• **Be very careful with the equipment.(( Depending on the lab's finances, we may not be able to replace damaged equipment for a prolonged period of time.

Battery Life:

• Lasts: 4-12 hours (8 hours typical).
• Full charge time: 4.5 - 5 hours.
• Charging: Use USB-A to USB-C (DO NOT use USB-C to USB-C as it is a fast charging cable and will not work).

Troubleshooting Guide

• Bluetooth connection issues: Check Device Manager for conflicting drivers. If necessary, review install instructions found on the USB Drive associated with the Smarting Pro Amplifier (see gold box in storage closet in lab).
• Red blinking light: Battery < 10% → Charge before use.
• High impedance values: Move gel around electrodes; do not add more.
• Electrode won’t turn green: Check impedance settings, ensure amplifier is clicked in.
• Flatline signal: Remove and reinsert amplifier until it clicks.
• Software crashes: Restart software & reconnect stream.

Additional Notes

• 3D head movement tracking is not recorded but can be exported for reconstruction in external software.
• Triggers can be labeled manually or within stimulus code.
• Electrodes may stop recording (rarely). Decide whether to continue or restart recording.
• Tip: Rachael's old lab would just adjust with the syringe to see if we can fix the signal during recording (it takes a couple seconds); depends on if your experiment can spare for the slight distraction.