Habituation to evoked responses is obvious in waking but still controv
ersial in sleep. Single-response analysis proves short-term habituatio
n of auditory evoked potentials in stage 2 NREM sleep. The data are di
scussed referring to the two-system hypothesis of sensory processing i
n sleep and to DC instability and sleep maintenance mechanisms in stag
e 2 NREM. It is suggested that information processing might continue i
n sleep.