Sleep spindles, a hallmark of mammalian NREM, have not been observed during avian sleep 5, 6, 10. For example, many birds remain vigilant during sleep, opening one or both eyes during SWS, and only closing both eyes during REM sleep 7, 8, 9. Additionally, birds show an intermediate stage (IS) of sleep, which has been compared to the early stages of mammalian non-REM (NREM) sleep and which can be considered a transitional stage of sleep 5, 6.ĭespite these similarities, clear differences do exist between mammals and birds. In birds, SWS is characterized by delta activity (1–4 Hz) with some tonic muscle tone, and REM sleep is generally characterized by low amplitude brain activity and conjugate and occasional non-conjugate eye movements. Pigeons were one of the first non-mammalian animals whose sleep was investigated 3, 4, and it is now generally accepted that birds undergo behavioral sleep and show signs of both SWS and REM sleep. Reconstructing the evolution of sleep across groups of amniotes has been a major thrust of comparative sleep research, and these investigations have usually provided (1) a description of the presence or absence of behavioral sleep, (2) a search for electrophysiological evidence of SWS and REM sleep, and (3) a final interpretation about what the presence or absence of certain features of sleep in an animal means to the evolution of sleep within amniotes.Īs major features of sleep were first defined in mammals, the search for electrophysiological features of sleep in both avian and non-avian reptiles was heavily influenced by mammalian-like indicators of sleep, i.e., the presence of slow waves or delta power, (indicative of SWS in the mammalian cortex), and non-SWS characterized, by low amplitude brain activity, concomitant eye movement, and decreased muscle tone (measured using electromyogramy (EMG) and indicative of mammalian REM sleep). Sleep-or a sleep-like state-has been observed across animal taxa, including early animals without a centralized nervous system, such as the cnidarian 1, 2. Sleep is a reversible state characterized by a reduced level of behavioral activity and responsiveness to the environment. Overall, our results reveal that significant changes occur in the neural signatures of sleep during maturation in an avian brain. A graph theory analysis revealed that in adults, highly correlated EEG activity tended to be distributed across fewer networks that were spread across a wider area of the brain, whereas in juveniles, highly correlated EEG activity was distributed across more numerous, albeit smaller, networks in the brain. Synchronous activity during sleep was larger for recording sites in the left hemisphere for both juveniles and adults, and generally intra-hemispheric synchrony was larger than inter-hemispheric synchrony during sleep. In addition, we observed that functional connectivity increased rapidly during maturation of young juveniles, and was stable or declined at older ages.
The amount of IS was significantly larger in male juveniles engaged in vocal learning compared to female juveniles, which suggests that IS could be important for vocal learning. Whereas adults spent more time in SWS and REM sleep, juveniles spent more time in intermediate sleep (IS).
Do these age-dependent variations in sleep patterns also occur in the avian brain? Does vocal learning have an effect on sleep patterns in birds? To answer these questions, we recorded multi-channel sleep EEG from juvenile and adult zebra finches for several nights. Studies in human and a limited number of other mammalian species show that this organization of sleep into interleaving stages undergoes radical changes during lifetime. Here we will look at pictures of homes of different animals, birds, and insects and what are they called in English.Despite their phylogenetic differences and distinct pallial structures, mammals and birds show similar electroencephalography (EEG) traces during sleep, consisting of distinct rapid eye movement (REM) sleep and slow wave sleep (SWS) stages. Some animals will even build homes to hide from predators. Similarly, animals need a home where they can feel safe and secure from outside dangers, where they can lay their eggs, raise their young, and sleep at night for protection from the cold and hot, and harsh weather conditions.
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