Physiological time structure of the tibialis anterior motor activity during sleep in mice, rats and humans.

The validation of rodent models for restless legs syndrome (Willis-Ekbom disease) and periodic limb movements during sleep requires knowledge of physiological limb motor activity during sleep in rodents. This study aimed to determine the physiological time structure of tibialis anterior activity during sleep in mice and rats, and compare it with that of healthy humans. Wild-type mice (n = 9) and rats (n = 8) were instrumented with electrodes for recording the electroencephalogram and electromyogram of neck muscles and both tibialis anterior muscles. Healthy human subjects (31 ± 1 years, n = 21) underwent overnight polysomnography. An algorithm for automatic scoring of tibialis anterior electromyogram events of mice and rats during non-rapid eye movement sleep was developed and validated. Visual scoring assisted by this algorithm had inter-rater sensitivity of 92-95% and false-positive rates of 13-19% in mice and rats. The distribution of the time intervals between consecutive tibialis anterior electromyogram events during non-rapid eye movement sleep had a single peak extending up to 10 s in mice, rats and human subjects. The tibialis anterior electromyogram events separated by intervals <10 s mainly occurred in series of two-three events, their occurrence rate in humans being lower than in mice and similar to that in rats. In conclusion, this study proposes reliable rules for scoring tibialis anterior electromyogram events during non-rapid eye movement sleep in mice and rats, demonstrating that their physiological time structure is similar to that of healthy young human subjects. These results strengthen the basis for translational rodent models of periodic limb movements during sleep and restless legs syndrome/Willis-Ekbom disease.