Pigeons can dream and experience human-like emotions, biologists have found. The researchers used infrared video cameras and functional magnetic resonance imaging (fMRI) to observe and record the sleeping and waking states of 15 pigeons specially trained to sleep under experimental conditions.
During rapid sleep, the birds exhibited strong activity in brain areas responsible for processing visual data, including those areas that analyze the pigeon’s movement around during flight. This led the authors to believe that the birds are dreaming during the REM phase and may be experiencing flight in their sleep.
In addition, the scientists noticed an activation of a certain area of the brain known as the amygdala body during the REM phase. “This suggests that if birds experience something similar to our human dreams, then pigeon dreams may also include emotions,” says Janina Ungurean of the Max Planck Institute for Biological Intelligence. This hypothesis is supported by the fact that birds’ pupils rapidly contract during rapid sleep.
In addition, in pigeons, as well as in humans, the flow of the spinal cord increases during fast sleep. It is this that removes the “debris” accumulated during the day. Researchers suggest that the process of cleaning the brain during sleep may be especially important for birds. Because their brains have a higher density of neurons than mammalian brains, the removal of waste products may require more efficient “flushing” cycles.
The question of whether similar processes occur in birds has remained unresolved until now. Birds seem to fly even in their sleep! To find out exactly what happens when birds sleep, researchers used infrared video cameras and functional magnetic resonance imaging (fMRI) to observe and record the sleeping and waking states of 15 pigeons specially trained to sleep in these experimental conditions.
The video recordings shed light on the birds’ sleep phases. Scientists tracked eye movements and changes in pupil size through the pigeons’ transparent eyelids during sleep. And fMRI recordings provided information about brain activation and cerebrospinal fluid flow.
The study showed that birds experience human-like sleep phases. In pigeons, as in humans, complex processes related to information processing and emotional experiences take place during rapid sleep.