Sleep depth measures

Comparing visual scoring with computer EEG analysis

Three different sleep depth measures including the hypnogram

The hypnogram (on top) ist the traditional expression of sleep depth. Originally it is based on a set of visual sleep stage scoring rules which classify the sleep to wakefulness, rapid eye movement (REM) sleep, non-REM sleep stages S1 (lightest sleep) to S4 (deepest sleep) and movement time (MT).

The other two curves are sleep depth measures based on the computer analysis of the electrical activity of the brain (EEG). These curves plot the mean frequency of the EEG using two different calculation paramenter settings. Computers are able to calculate these in seconds whereas it takes 2-3 hours to produce the hypnogram carefully visually of the same sleep recording.

More information about this topic can be found in our article "Systematic performance evaluation of a continuous-scale sleep depth measure" by Antti Saastamoinen, Eero Huupponen, Alpo Värri, Joel Hasan and Sari-Leena Himanen in Medical Engineering & Physics, Vol. 29,  (2007) pp. 1119–1131.