4.2 EEG recording systems and electrode placement

EEG recording systems are crucial for capturing brain activity. They consist of electrodes, amplifiers, filters, and digital converters that work together to collect and process neural signals. Understanding these components is key to obtaining high-quality EEG data for brain-computer interfaces.

Proper electrode placement and skin preparation are essential for accurate EEG recordings. The International 10-20 system standardizes electrode positions, while careful skin prep and impedance checks ensure good signal quality. These practices form the foundation for reliable BCI data collection.

EEG Recording System Components and Setup

Components of EEG recording systems

Top images from around the web for Components of EEG recording systems

• 

  10-20 system (EEG) - Wikipedia View original

  Is this image relevant?

• 

  Frontiers | Amplitude of Sensorimotor Mu Rhythm Is Correlated with BOLD from Multiple Brain ... View original

  Is this image relevant?

• 

  10-20 system (EEG) - Wikipedia View original

  Is this image relevant?

• 

  Frontiers | Amplitude of Sensorimotor Mu Rhythm Is Correlated with BOLD from Multiple Brain ... View original

  Is this image relevant?

1 of 2

Top images from around the web for Components of EEG recording systems

• 

  10-20 system (EEG) - Wikipedia View original

  Is this image relevant?

• 

  Frontiers | Amplitude of Sensorimotor Mu Rhythm Is Correlated with BOLD from Multiple Brain ... View original

  Is this image relevant?

• 

  10-20 system (EEG) - Wikipedia View original

  Is this image relevant?

• 

  Frontiers | Amplitude of Sensorimotor Mu Rhythm Is Correlated with BOLD from Multiple Brain ... View original

  Is this image relevant?

1 of 2

• Electrodes capture brain's electrical activity from scalp (non-invasive) or directly from brain tissue (subdural or depth electrodes)
• Amplifiers boost weak EEG signals differential amplifiers with high input impedance reduce noise and interference
• Filters remove unwanted frequencies high-pass filter eliminates slow drifts, low-pass filter removes high-frequency noise, notch filter reduces power line interference (50 or 60 Hz)
• Analog-to-Digital Converter (ADC) transforms analog EEG signals into digital data sampling rate determines temporal resolution (typically 250-1000 Hz), bit depth affects amplitude resolution (commonly 16-24 bits)
• Recording device (computer) stores and processes digitized EEG data
• Display system enables real-time waveform visualization and topographic mapping of brain activity
• Impedance checker ensures proper electrode-skin contact (target < 5 kΩ)
• Calibration unit verifies system accuracy and consistency
• Electrode cap or net holds multiple electrodes in standardized positions
• Conductive gel or paste improves electrical conductivity between electrodes and scalp

International 10-20 electrode placement

• Standardized method ensures reproducibility across subjects and studies
• Naming convention uses letters for brain regions (F: Frontal, T: Temporal, C: Central, P: Parietal, O: Occipital) even numbers for right hemisphere, odd for left, "z" for midline
• Measurement technique based on skull landmarks (nasion, inion, preauricular points) distances between electrodes are 10% or 20% of total front-back or left-right distance
• Key electrode positions include Fp1/Fp2 (frontopolar), F3/F4/Fz (frontal), C3/C4/Cz (central), P3/P4/Pz (parietal), O1/O2 (occipital), T3/T4/T5/T6 (temporal)
• Extended 10-20 system adds electrodes for higher density recordings (128 or 256 channels)

Electrode Application and Recording Considerations

Skin preparation for EEG

• Gentle abrasion removes dead skin cells reduces impedance (NuPrep gel, exfoliating scrub)
• Cleaning with alcohol removes oils further lowers impedance
• Reducing skin impedance improves signal quality and reduces artifacts
• Electrode application requires conductive gel or paste (Ten20 conductive paste, Elefix)
• Apply proper amount of gel to avoid bridging between electrodes
• Secure electrodes with adhesive tape or electrode cap
• Perform impedance check target levels typically < 5 kΩ
• Troubleshoot high impedance by reapplying gel or adjusting electrode position
• Consider participant comfort proper electrode pressure to avoid skin irritation

Reference and ground electrodes

• Reference electrode provides common reference point for all other electrodes
• Common reference locations include earlobes, mastoids, or Cz
• Average reference uses mean of all electrodes as reference point
• Ground electrode reduces common-mode interference typically placed on forehead or mastoid
• Reference choice influences waveform appearance crucial for inter-electrode comparisons
• Re-referencing in offline analysis allows changing reference post-recording for different analyses
• Active electrodes incorporate built-in amplifiers reduce noise and reference electrode dependence