Processing a bio-physiological signal

The invention relates to an apparatus and a method for processing at least one bio-physiological signal of a sleeping object, such as a brain wave signal or electroencephalography (EEG) signal, an electro-oculogram (EOG) signal, or an electromyogram (EMG) signal. The signal is captured by at least one sensor, which may be included in a pliable device such as a pillow or headgear. A processing unit (18) processes the at least one bio-physiological signal and thereby generates an output signal (28; 38; 44) based on the at least one bio-physiological signal and based on a signal pattern stored or generated in the processing unit (18), the output signal (28; 38; 44) comprising a temporally varying output signal pattern, wherein the output signal pattern depends on a current sleep state of the sleeping object. The output signal may be reproduced in a human-perceptible form.