Which principles do EEG amplifiers operate on?

EEG amplifiers primarily operate on the principles of both differential measurements and amplification. The differential measurement aspect is crucial because EEG signals are typically very small and can be easily contaminated by noise. By using a differential approach, the EEG amplifier can effectively compare the electrical activity between two electrodes placed on the scalp, which helps in isolating the brain’s electrical signals from other noise sources, such as muscle activity or environmental interference.

Amplification is also a key function of these devices. Given that the electrical signals generated by neuronal activity are in the microvolt range, amplification is necessary to bring these signals to a level suitable for processing and interpretation. This allows for more accurate readings and effective visualization of the brain's activity.

While some options focus solely on one of these principles, the combined operation of both differential and amplification makes the first choice the most comprehensive and correct answer.