Amazing stuff! My conclusion: Smart birds need less vigilance! 😊
However, the scientists appear to have failed to document or mention where the research subjects ( were taken from or located (e.g. natural habitat, laboratory, urban area). This is quite an omission, so bad an omission that it may qualify as junk science. The researchers only mention "European jackdaws". The official news release by the Max Planck Neuroscience institute also does not mention at all where these "European jackdraws" came from.
I believe, it is critically important to mention where (in which environment) these birds were investigated. For example, I would argue that birds in urban areas may need to be less vigilant because there is an overpopulation of birds and fewer predators.
Caveat: I did read the entire article.
"Birds exhibit two types of non-REM sleep:
symmetric (both brain hemispheres sleeping deeply) and
asymmetric (one hemisphere sleeping lightly while the other stays alert).
van Hasselt et al. investigated how birds balance these sleep modes under increased sleep pressure caused by deprivation.
Using high-density EEG on European jackdaws, researchers found that during heightened sleep need, birds prioritize symmetric sleep over asymmetric sleep, sacrificing vigilance to recover from sleep loss. This trade-off highlights the constraints imposed by the need for deep, restorative sleep on the birds’ ability to remain alert for potential threats."
"Summary:
- Birds, unlike humans, can sleep deeply with both halves of their brains (symmetrically) or with one half sleeping lighter than the other (asymmetrically).
- Study of European jackdaws led by an international team of researchers shows that when sleep-deprived, jackdaws were more likely to fall into deep sleep with both brain halves at the expense of keeping one half vigilant – especially early in the night, when the need to recover is greatest.
- Observing how birds navigate the trade-off between vigilance and sleep may help scientists better understand how sleep loss affects brain function more broadly, including in us.
... When humans sleep, our brains cycle through stages, alternating between rapid eye movement (REM) sleep and non-REM sleep roughly every 90 minutes. Birds go through these same stages, but typically in much shorter bursts – and their sleep patterns are far more flexible than ours. ..."
From the highlights and abstract:
"Highlights
• High-density EEG shows local homeostatic responses to sleep loss in the avian brain
• Theta oscillations occur during non-REM sleep in non-hippocampal brain regions
• Non-REM sleep occurs symmetrically and asymmetrically between the hemispheres
• Asymmetric sleep is sacrificed for symmetric sleep when sleep pressure increases
Summary
Sleep is a dangerous part of an animal’s life. Nonetheless, following sleep loss, mammals and birds sleep longer and deeper, as reflected by increased electroencephalogram (EEG) slow-wave activity (SWA; ≈1–5 Hz spectral power) during non-rapid eye movement (NREM) sleep.
Stimulating a brain region during wakefulness also causes that region to sleep deeper afterwards, indicating that NREM sleep is a local, homeostatically regulated process.
Birds and some marine mammals can keep one eye open during NREM sleep, a behavior associated with lighter sleep or wakefulness in the hemisphere opposite the open eye—states called asymmetric and unihemispheric NREM sleep, respectively.
Closure of both eyes is associated with symmetric NREM or REM sleep.
Birds rely on asymmetric and unihemispheric sleep to stay safe. However, as sleeping deeply with only one hemisphere at a time increases the time required for both hemispheres to fulfill their need for NREM sleep, increased sleep pressure might cause birds to engage in symmetric sleep at the expense of asymmetric sleep. Using high-density EEG recordings of European jackdaws (Coloeus monedula), we investigated intra- and inter-hemispheric asymmetries during normal sleep and following sleep deprivation (SD). The proportion of asymmetric sleep was lower early in the sleep period and following SD—periods of increased sleep pressure. Our findings demonstrate a trade-off between the benefits of sleep and vigilance and indicate that a bird’s utilization of asymmetric sleep is constrained by temporal dynamics in their need for sleep."
Too tired to stay alert? A difficult trade-off between sleep and vigilance (original press release) "Sleep-deprived European jackdaws trade vigilance for deep sleep – a strategy that could carry risks in the wild."
(open access)
Graphical abstract
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