Do birds dream? It seems so, and they are actually flying – 03/31/2024 – Science

I once dreamed of a kiss that hadn’t happened yet. I dreamed of the angle at which our heads tilted, the fit of my fingers behind her ear, the pressure exerted on her lips by this transfer of trust and tenderness.

Sigmund Freud would have dismissed this as a mere chimera of the desirous unconscious. But what we have since discovered about the mind suggests another possibility for the adaptive function of these parallel lives in the night.

One cold morning, shortly after the kiss dream, I watched a young night heron sleeping on a branch over the lake in Brooklyn Bridge Park, New York, with its head tucked into its chest, and I found myself wondering if birds dream.

The insight that nonhuman animals dream dates back at least to the days of Aristotle, who observed a sleeping dog bark and considered it unequivocal evidence of mental life. But René Descartes reduced other animals to mere automatons, tarnishing centuries of science with the assumption that anything different from us is inherently inferior.

In the 19th century, when German naturalist Ludwig Edinger carried out the first anatomical studies of the bird brain and discovered the absence of a neocortex — the outer layer of the brain responsible for complex cognition and creative problem solving — he considered birds to be little more than than Cartesian reflex puppets.

This view was reinforced in the 20th century by the approach, led by BF Skinner, of behaviorism, a school of thought that considered behavior a Rube Goldberg machine of stimulus and response governed by reflex, ignoring internal mental states and emotional response.

In 1861, just two years after the publication of Charles Darwin’s “The Origin of Species,” a fossil was discovered in Germany featuring the tail and jaws of a reptile and the wings and wishbones of a bird, leading to the revelation of that birds had evolved from dinosaurs.

We have since learned that although birds and humans did not share a common ancestor more than 300 million years ago, a bird’s brain is much more similar to ours than a reptile’s.

The density of neurons in their forebrain — the region involved in planning, sensory processing and emotional responses, and on which REM sleep is largely dependent — is comparable to that of primates. At the cellular level, a songbird’s brain has a structure — the dorsal ventricular crest (DVR) — similar to the mammalian neocortex in function, if not form.

Still, bird brains are capable of feats unimaginable to us, especially during sleep: many birds sleep with one eye open, even during flight.

But while sleep is an externally observable physical behavior, dreaming is an inner experience as mysterious as love — a mystery to which science has brought brain imaging technology to illuminate the inner landscape of the sleeping bird’s mind.

The first electroencephalogram (EEG) of electrical activity in the human brain was recorded in 1924, but EEG was not applied to the study of avian sleep until the 21st century. Even more incipient is functional magnetic resonance imaging (fMRI), developed in the 1990s. nineteen ninety.

The two technologies complement each other. By recording the electrical activity of large populations of neurons close to the cortical surface, EEG tracks what the neurons do more directly. fMRI can more accurately pinpoint brain activity through blood oxygen levels.

Scientists have used these technologies together to study cell firing patterns during REM sleep in an attempt to deduce the content of dreams.

A study of zebra finches mapped specific notes from melodies sung during the day to neurons firing in the forebrain. Then, during REM, the neurons fired in a similar order: The birds appeared to rehearse the songs in their dreams.

An fMRI study of pigeons found that brain regions responsible for visual processing and spatial navigation were active during REM, as were regions responsible for wing action, even though the birds were immobile in sleep: they appeared to be dreaming about flying.

The amygdala —a set of nuclei responsible for emotional regulation— was also active during REM, suggesting dreams permeated by feelings. The night heron I saw was probably dreaming too — the bent neck is a classic marker of atonia, the loss of muscle tone characteristic of the REM state.

But the most astonishing thing about bird sleep research is that without birds’ dreams, we might be dreamless too.

There are two main groups of living birds: the Paleognathians, unable to fly, like the ostrich; and the Neognatas, comprising all other birds. EEG studies in sleeping ostriches have found REM-like activity in the brainstem — an older part of the brain — while in modern birds, as well as mammals, this REM-like activity occurs primarily in the more recently developed forebrain.

Several studies of sleeping monotremes—egg-laying mammals such as the platypus and echidna—also reveal REM-like activity in the brainstem, suggesting that this was the ancestral home of REM before it slowly migrated to the forebrain.

If so, the avian brain may be where evolution designed dreams — that secret chamber adjacent to our waking consciousness where we continue to work on the problems that occupy our days.

Dmitri Mendeleev, after pondering long and hard about the arrangement of atomic weights in his waking state, arrived at his periodic table in a dream. “All the elements fell into place as needed,” he reported in his diary. “When I woke up, I immediately wrote it down on a piece of paper.”

Stephon Alexander, a cosmologist now at Brown University, made a groundbreaking discovery about the role of symmetry in cosmic inflation in a dream, earning him a national award from the American Physical Society.

For Albert Einstein, the central revelation of relativity took shape in a dream of cows simultaneously jumping and moving in a wavelike motion.

As with the mind, so with the body. Studies have shown that people learning new motor tasks “practice” them while asleep and then perform better when awake. This line of research has also shown how mental visualization helps athletes improve performance.

It may be that in REM we practice what is possible until we make it real. It may be that the kiss in my dream was not a nocturnal fantasy, but, like the night heron’s dreams of flying, the practice of possibility. We may have evolved to dream ourselves into reality — a laboratory of consciousness that began in the bird brain.