A complementary relationship between wake and REM sleep in the auditory system: a pre-sleep increase of middle-ear muscle activity (MEMA) causes a decrease of MEMA during sleep

Since some evidence has supported a complementary relationship between waki ng and REM-sleep eye movement (variations in frequency, amplitude, or direc tion of waking saccades have been found to inversely affect the correspondi ng parameters of rapid eye movements), the present study assessed whether t his relationship can also be shown for other phasic components of REM sleep , such as middle-ear muscle activity (MEMA), as a consequence of an increas e of middle-ear reflex frequency during pre-sleep wake. Ten subjects were s tudied in three consecutive nights (one adaptation, one baseline, one exper imental). In the experimental night, subjects underwent a 2-h pure-tone (10 00 Hz, 90 dB SPL) auditory stimulation and MEMA was monitored every 15 min; noise exposure during daytime was also controlled. Results show that MEMA frequency during REM sleep significantly decreased during the experimental nights compared with baseline nights, while each sleep variable as well as mean daily auditory input did not present any significant difference betwee n baseline and experimental nights. Results suggest that the complementary relationship between wake and REM sleep is not bounded to oculomotor activi ty, but it may also be extended at least to middle-ear muscle phasic activi ty.