Dreaming Birds

Maria Popova, Do Birds Dream? NYTimes, March 26, 2024.

A study of zebra finches — songbirds whose repertoire is learned, not hard-wired — mapped particular notes of melodies sung in the daytime to neurons firing in the forebrain. Then, during REM, the neurons fired in a similar order: The birds appeared to be rehearsing the songs in their dreams.

An fM.R.I. study of pigeons found that brain regions tasked with visual processing and spatial navigation were active during REM, as were regions responsible for wing action, even though the birds were stilled with sleep: They appeared to be dreaming of flying. The amygdala — a cluster of nuclei responsible for emotional regulation — was also active during REM, hinting at dreams laced with feeling. My night heron was probably dreaming, too — the folded neck is a classic marker of atonia, the loss of muscle tone characteristic of the REM state.

But the most haunting intimation of the research on avian sleep is that without the dreams of birds, we too might be dreamless. No heron, no kiss.

There are two primary groups of living birds: the flightless Palaeognathae, including the ostrich and the kiwi, which have retained certain ancestral reptilian traits, and Neognathae, comprising all other birds. EEG studies of sleeping ostriches have found REM-like activity in the brainstem — a more ancient part of the brain — while in modern birds, as in mammals, this REM-like activity takes place primarily in the more recently developed forebrain.

Several studies of sleeping monotremes — egg-laying mammals like the platypus and the echidna, the evolutionary link between us and birds — also reveal REM-like activity in the brainstem, suggesting that this was the ancestral crucible of REM before it slowly migrated toward the forebrain.

If so, the bird brain might 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. [...]

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

There's more at the link.