What may cause extremely low voltage due to phase cancellation in EEG recordings?

Phase cancellation in EEG recordings occurs when signals from different electrodes that are out of phase with each other cancel each other out, resulting in extremely low voltage readings. The concept of phase cancellation is linked to how the electrode potentials interact.

When there is a salt bridge, it can create a pathway that conducts electrical activity between electrodes connected at different potentials. This can lead to an interference pattern where the signals being recorded have opposing phases, subsequently leading to cancellation of those signals in the differential recording, causing low voltage readings. Thus, a salt bridge can indeed produce phase cancellation effects, particularly if it connects areas of varying electrical potential.

In contrast, a short circuit might not lead to low voltage due to phase cancellation but rather could potentially eliminate the signal altogether or produce erratic readings. High-frequency noise generally disrupts the clarity of the signal but does not inherently cause cancellation effects. Likewise, while electrode misplacement can lead to inaccurate readings, it typically results in more signal distortion rather than specific phase cancellation.