A bipolar derivation utilizes how many electrodes that overlie an electrically active area?

A bipolar derivation utilizes how many electrodes that overlie an electrically active area?

• 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)

In a bipolar EEG derivation, you record the difference between two electrodes that are each placed over regions of cortex that are actively generating electrical activity. This differential setup captures a local voltage gradient produced by nearby neural sources, while helping suppress shared noise through common‑mode rejection. If one electrode were over an inactive area, the potential difference would be weak and less representative of localized activity, because you’d be pairing an active site with a poor reference. So the best setup uses two electrodes that overlie an electrically active area.

In a bipolar EEG derivation, you record the difference between two electrodes that are each placed over regions of cortex that are actively generating electrical activity. This differential setup captures a local voltage gradient produced by nearby neural sources, while helping suppress shared noise through common‑mode rejection. If one electrode were over an inactive area, the potential difference would be weak and less representative of localized activity, because you’d be pairing an active site with a poor reference. So the best setup uses two electrodes that overlie an electrically active area.