RT Journal Article
SR Electronic
T1 The Echidna <strong><em>Tachyglossus aculeatus</em></strong> Combines REM and Non-REM Aspects in a Single Sleep State: Implications for the  Evolution of Sleep
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 3500
OP 3506
DO 10.1523/JNEUROSCI.16-10-03500.1996
VO 16
IS 10
A1 Siegel, J. M.
A1 Manger, P. R.
A1 Nienhuis, R.
A1 Fahringer, H. M.
A1 Pettigrew, J. D.
YR 1996
UL http://www.jneurosci.org/content/16/10/3500.abstract
AB Placental and marsupial mammals exist in three states of consciousness: waking, non-REM sleep, and REM sleep. We now report that the echidna Tachyglossus aculeatus, a representative of the earliest branch of mammalian evolution (the monotremes), does not have the pattern of neuronal activity of either of the sleep states seen in nonmonotreme mammals. Echidna sleep was characterized by increased brainstem unit discharge variability, as in REM sleep. However, the discharge rate decreased and the EEG was synchronized, as in nonREM sleep. Our results suggest that REM and non-REM sleep evolved as a differentiation of a single, phylogenetically older sleep state. We hypothesize that the physiological changes that occur during postnatal sleep development parallel certain aspects of the changes that have occurred during the evolution of sleep–waking states in mammals.