Sleep patterns in the Mongolian gerbil, Meriones unguiculatus.

Sleep patterns were studied in Mongolian gerbils and normative values were derived from 48 hour recordings, during a 24-hr light-dark cycle (LD 12:12). Behavioral and electrographic observations confirmed the existence of well defined sleep states: slow-wave sleep (SWS) and paradoxical sleep (PS). During the light period, sleep occupied slightly more than half of the 12 hour period, 57.13 +/- 0.002% out of which 49.64 +/- 0.007% was occupied by SWS and 8.07 +/- 0.007% by PS. There were 23 +/- 0.01 episodes of PS with a mean duration of 2.32 +/- 0.01 min. During the dark period, sleep occupied slightly less than half of the recording time (51.75 +/- 0.01%). They spent 41.62 +/- 0.006% in SWS and 10.12 +/- 0.02% in PS. The number of PS episodes was 32 +/- 0 with a mean duration of 2.28 +/- 0.01 min. Sleep cycle duration was 7.80 +/- 3.76 min. The ratio day/night sleep was 1.17 +/- 0.002 min. We found that the gerbil in captivity, unlike most rodents that are nocturnal, is a crepuscular animal, being more active at the transitions between light and dark.