A bipolar derivation utilizes which of the following?

A bipolar derivation utilizes which of the following?

• A. One electrode that overlies an electrically active area
• B. Two electrodes that overlie an electrically active area
• C. One electrode over an active and one over an inactive area
• D. Two electrodes that overlie an electrically inactive area

Answer: (B)

A bipolar derivation is a differential recording that uses two electrodes to measure the voltage difference between two sites on the scalp. The goal is to capture local cortical activity while suppressing broad, nonlocal noise that both electrodes pick up. That’s why the best choice is two electrodes that overlie electrically active areas. With both electrodes placed over active cortex, the difference reflects true regional activity and reduces common noise, giving a clearer picture of local EEG rhythms. If one electrode were over an inactive area or if both were over inactive areas, the recorded difference would be weak or dominated by noise and would not represent localized brain activity. Using a single active electrode with a distant reference would be a monopolar setup, not a bipolar one, and would not emphasize the local differential signal.

A bipolar derivation is a differential recording that uses two electrodes to measure the voltage difference between two sites on the scalp. The goal is to capture local cortical activity while suppressing broad, nonlocal noise that both electrodes pick up.

That’s why the best choice is two electrodes that overlie electrically active areas. With both electrodes placed over active cortex, the difference reflects true regional activity and reduces common noise, giving a clearer picture of local EEG rhythms. If one electrode were over an inactive area or if both were over inactive areas, the recorded difference would be weak or dominated by noise and would not represent localized brain activity. Using a single active electrode with a distant reference would be a monopolar setup, not a bipolar one, and would not emphasize the local differential signal.