MSGID: 1:317/3 648007ee   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    When pigeons dream    
      
     Date:   
         June 6, 2023   
     Source:   
         Ruhr-University Bochum   
     Summary:   
         Dreams have been considered a hallmark of human sleep for a   
         long time.   
      
         Latest findings, however, suggest that when pigeons sleep, they   
         might experience visions of flight. Researchers studied brain   
         activation patterns in sleeping pigeons, using functional magnetic   
         resonance imaging. The study revealed that similar to mammals,   
         most of the brain is highly active during REM sleep. However, this   
         wake-like state might come at a cost of reduced waste removal from   
         the brain.   
      
      
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   FULL STORY   
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   During sleep, our brain undergoes a complex set of processes to ensure   
   we wake up feeling refreshed. In humans, the different phases of sleep,   
   rapid eye movement (REM) and non-REM sleep, are associated with distinct   
   changes in physiology, brain activity, and cognition. For instance,   
   during REM sleep, our brain is very active and we experience our most   
   vivid, bizarre, and emotional dreams. During non-REM sleep, the brain   
   is metabolically less active and clears out waste products by flushing   
   cerebral spinal fluid through the brain's ventricles -- the interconnected   
   chambers that surround the structures of the brain -- and then through the   
   brain. This process supposedly helps the body to remove harmful protein   
   deposits from the brain, like those associated with the development of   
   Alzheimer's disease.   
      
   What happens in a pigeon's brain during sleep?  The question of whether   
   similar processes also take place in birds has remained unresolved until   
   now. "The last common evolutionary ancestor of birds and mammals dates   
   back about 315 million years, to the early days of land vertebrates,"   
   says Professor Onur Gu"ntu"rku"n, head of the Biopsychology Department at   
   Ruhr University Bochum. "Yet the sleep patterns in birds are remarkably   
   similar to those in mammals, including both REM and non-REM phases."   
   To find out what exactly happens when birds sleep, the researchers used   
   infrared video cameras and functional magnetic resonance imaging (fMRI)   
   to observe and record the sleeping and wakeful states of 15 pigeons   
   specially trained to sleep under these experimental conditions.   
      
   The video recordings shed light on the sleep phases in the birds. "We   
   were able to observe whether one or both eyes were open or closed, and   
   to track eye movements and changes in pupil size through the pigeons'   
   transparent eyelids during sleep," explains Mehdi Behroozi from the Bochum   
   team. Simultaneously, the fMRI recordings provided information about   
   brain activation and the flow of cerebral spinal fluid in the ventricles.   
      
   Dreams of flying "During REM sleep, we observed strong activity in brain   
   regions responsible for visual processing, including in those areas that   
   analyze the movement of a pigeon's surroundings during flight," says Mehdi   
   Behroozi. The team also noticed activity in the areas that process signals   
   from the body, especially from the wings. "Based on these observations,   
   we think that birds, just like humans, dream during REM sleep, and might   
   be experiencing flight in their dreams," adds Mehdi Behroozi.   
      
   Additionally, the scientists noticed activation of a particular brain area   
   known as the amygdala during these phases. "This suggests that if birds   
   experience something similar to our human dreams, pigeons' dreams might   
   include emotions as well," says Gianina Ungurean from the Avian Sleep   
   Group at the Max Planck Institute for Biological Intelligence. This   
   hypothesis is supported by the fact that the birds' pupils contract   
   rapidly during REM sleep, like they do during courtship or aggressive   
   behaviors while awake, as recently demonstrated by Gianina Ungurean   
   and colleagues.   
      
   Washing out the day's dust Like in humans, the flow of cerebral   
   spinal fluid through ventricles increases during non-REM sleep in   
   pigeons. However, the team discovered for the first time, in any animal,   
   that the flow diminished dramatically during REM sleep.   
      
   "We think that the increased flood of blood into the brain during REM   
   sleep, which supports the elevated brain activity, might block the   
   cerebral spinal fluid from moving from the ventricles into the brain,"   
   explains Niels Rattenborg, head of the Avian Sleep Group. "This suggests   
   that REM sleep and its functions might come at the expense of waste   
   removal from the brain."  However, the scientists are also entertaining   
   the possibility that REM sleep contributes to waste removal in unexpected   
   ways. "At the onset of REM sleep, the influx of blood increases vessel   
   diameter. This might force cerebral spinal fluid that entered the space   
   during non-REM sleep to flow into the brain tissue, and enhance the   
   outflow of fluids carrying waste products," says Gianina Ungurean.   
      
   The researchers speculate that the process of cleaning the brain during   
   sleep may be especially crucial for birds. Since their brains have a   
   higher density of neurons in comparison to mammals, the removal of waste   
   products may require more efficient -- or more frequent -- flushing   
   cycles. As birds experience more and shorter REM phases during sleep   
   than mammals, the associated frequent surge of blood might help to keep   
   their densely packed brains free of harmful waste products.   
      
   Tell us about your dreams!  In the future, the team plans to explore REM   
   sleep's potential role in waste removal. In addition, they are thinking   
   about ways to learn about the content of a pigeon's dream. "We hope to   
   train birds to report if and what they just saw upon awakened from REM   
   sleep. That would be an essential step towards establishing whether they   
   dream," explains Gianina Ungurean. But even without a detailed dream   
   analysis, the new findings already help us to better understand the role   
   of sleep, in birds as well as in humans. They highlight the importance of   
   sleep in maintaining a healthy brain and preventing cognitive decline --   
   and they also imply that dreaming has a very long history.   
      
   The study was conducted by the Bochum Biopsychology team as well as   
   researchers from the Max Planck Institute for Biological Intelligence, the   
   Max Planck Institute for Neurobiology of Behaviour, the Neurophysiology   
   Department at Ruhr University Bochum and the Universite' Claude Bernard   
   Lyon.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Animal_Learning_and_Intelligence # Birds # Biology   
                   # Mice   
             o Earth_&_Climate   
                   # Hazardous_Waste # Oil_Spills # Recycling_and_Waste #   
                   Environmental_Science   
       * RELATED_TERMS   
             o Sleep o Sleep_disorder o Pigeon_intelligence o   
             Circadian_rhythm o Brain o Neurobiology o Brain_tumor o   
             Neocortex_(brain)   
      
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   Story Source: Materials provided by Ruhr-University_Bochum. Original   
   written by Meike Driessen. Note: Content may be edited for style and   
   length.   
      
      
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   Journal Reference:   
      1. Gianina Ungurean, Mehdi Behroozi, Leonard Bo"ger, Xavier Helluy,   
      Paul-   
         Antoine Libourel, Onur Gu"ntu"rku"n, Niels   
         C. Rattenborg. Wide-spread brain activation and reduced CSF flow   
         during avian REM sleep. Nature Communications, 2023; 14 (1) DOI:   
         10.1038/s41467-023-38669-1   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230606111728.htm   
      
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