Avian Sleep and its Resemblance with Mammals

Sleep, a ubiquitous behavior reported in animal kingdom spreads out from cnidarians to mammals. Evolutionarily it is linked with the development of nervous system which was first time reported in phylum Cnidaria. Thus, this information satisfies a basic function of sleep which is memory processing and information storage. Besides this, cellular restoration and synaptic scaling also encompass as the core function of sleep. Sleep is broadly characterized by the oscillation of NREM (Non-rapid eye movement) and REM (Rapid eye movement) sleep cycles in mammals. Interestingly its distant relative birds also show the same stages while sleeping. Therefore, avian sleep can act as window to understand the mechanisms associated with generation and function of mammalian sleep. Avian sleep shares many similarities with that of mammals, for instance, presence of REM/NREM sleep states which in turn are under circadian and homeostatic control. Likewise minor differences also exist between the two groups for example, the thalamocortical spindles and the ripple complex which are missing from bird sleep. Thus, avian model system can help in understanding the complicacies associated with mammalian sleep (with reference to human) during health and illness.