What is a small fluctuating output recorded by the EEG instrument called when there is no input signal?

The small fluctuating output recorded by the EEG instrument when there is no input signal is known as noise. In the context of EEG, noise refers to unwanted electrical signals that can come from various sources and can interfere with the accurate recording of brain activity. It can arise from a range of factors, including electrical interference from devices nearby, muscle activities, or inherent electronic fluctuations within the EEG equipment itself.

Identifying noise is crucial in EEG recordings, as it helps technicians and clinicians distinguish between genuine brain signals and those that might obscure them. Effective noise management leads to cleaner data and more reliable interpretations of brain activity.

The other options represent different phenomena. Output voltage refers to the actual measurement of electrical energy that the EEG instrument produces, which can be an accurate representation of input signals. Linear distortion refers to the alteration of a signal as it passes through a system, leading to possible inaccuracies in the data. 60Hz interference specifically indicates a common form of noise that is linked to electrical power sources, but it is a subset of the broader category of noise. Understanding these distinctions helps in refining EEG measurements for better diagnostic accuracy.