Small bandwidth frequency ranges are disclosed for frequency transformation and processing of EEG signals for determining sleeping staging with a sleep staging index (SF) in which a frequency transformation of a time domain EEG signal from an EEG measuring device is supplied in a plurality of sub-band frequency ranges a, b, and c. Processing of the frequency domain transformed data is performed which ascertains values A, B, and C representative of the frequency range a from 4.75 to 6.75 Hz, the frequency range b from 12.75 to 18.5 Hz, and the frequency range c from 18.75 to 35.0 Hz or representative of least two of said frequency ranges and determines therefrom a sleep staging index SF.
Apparatus for determining sleep staging