Which of the following is the RECOMMENDED impedance level for EEG electrodes?

Which of the following is the RECOMMENDED impedance level for EEG electrodes?

• A. Less than 5Ω
• B. Less than 10kΩ
• C. At least 10Ω
• D. Less than 5kΩ

Answer: (A)

Lower impedance at the electrode-skin interface is essential for high-quality EEG signals. When impedance is very low, the electrical path from the brain through the electrode to the amplifier is more efficient, so the signal is transmitted with less loss and less introduction of noise. This improves the signal-to-noise ratio and helps the amplifier reject stray common-mode noise, which is particularly important for the small amplitude EEG rhythms you’re trying to measure. Achieving a very low impedance also makes channel-to-channel comparisons more reliable and reduces the likelihood that contact issues will masquerade as true brain activity. To reach this goal in practice, the skin sites are prepared and a conductive gel or paste is used so each electrode makes good, stable contact. Impedance is checked and, if needed, adjustments are made (recleaning, reapplying gel, or re-positioning) to keep the level consistently low across all channels. Compared with looser targets, such as under 10 kΩ or even under 5 kΩ, aiming for under 5 ohms represents the strict standard that emphasizes maximizing signal integrity. The other options describe higher impedance thresholds that would permit more noise and poorer signal quality.

Lower impedance at the electrode-skin interface is essential for high-quality EEG signals. When impedance is very low, the electrical path from the brain through the electrode to the amplifier is more efficient, so the signal is transmitted with less loss and less introduction of noise. This improves the signal-to-noise ratio and helps the amplifier reject stray common-mode noise, which is particularly important for the small amplitude EEG rhythms you’re trying to measure. Achieving a very low impedance also makes channel-to-channel comparisons more reliable and reduces the likelihood that contact issues will masquerade as true brain activity.

To reach this goal in practice, the skin sites are prepared and a conductive gel or paste is used so each electrode makes good, stable contact. Impedance is checked and, if needed, adjustments are made (recleaning, reapplying gel, or re-positioning) to keep the level consistently low across all channels.

Compared with looser targets, such as under 10 kΩ or even under 5 kΩ, aiming for under 5 ohms represents the strict standard that emphasizes maximizing signal integrity. The other options describe higher impedance thresholds that would permit more noise and poorer signal quality.