Which theory specifies the minimum sampling rate used in relation to the highest frequency signal recorded?

The Nyquist theory, formulated by Harry Nyquist, specifies that in order to accurately reconstruct a signal without aliasing, the sampling rate must be at least twice the frequency of the highest frequency component of the signal being recorded. This principle is crucial in fields such as signal processing and digitization of analog signals, including EEG recordings. When the sampling rate meets this minimum requirement, it ensures that all the necessary information from the signal is captured accurately, allowing for precise analysis and interpretation of the data. This underpins the importance of choosing an appropriate sampling rate when conducting electroencephalographic measurements.