Newly Discovered Brain Structure May Grant Birds Impressive Intelligence
By Ross Pomeroy for Real Clear Science
September 25, 2020 -- Birds are capable
of some extraordinary cognitive feats. New Caledonian crows can make and use
tools. Grey parrots can learn various human words and complete certain tests of
intelligence at the level of four to six-year-old human children. Pigeons can
remember large numbers of images for several years. But how birds accomplish
these tasks despite having brains the size of walnuts has long eluded our own
comprehension.
Now, in two tandem studies, researchers
in Germany have imaged a structure in the avian brain that might just endow
birds with their impressive abilities, and maybe even grant them rudimentary
consciousness.
In the first study, scientists used 3D-Polarized
Light Imaging, a rising technique that came to prominence in the past decade or
so, to map the nerve fibers of barn owls' and pigeons' forebrains, specifically
the pallium, layers of grey and white matter that cover the upper surface.
They found that the structure and
circuitry of both bird species' pallia are strikingly similar to the pallia of
mice, monkeys, and humans.
"If the bird pallium as a whole is
organized just like the mammalian pallium, then it follows that the part of the
bird pallium that is demonstrably functionally connected like the mammalian
prefrontal pallium should also function like it," Vanderbilt neuroscientist
Suzana Herculano-Houzel wrote of the studies.
"Corvids and parrots have upwards
of half a billion neurons in their pallia and can have as many as 1 or 2
billion—like monkeys," she added. "So far, it appears that the more
neurons there are in the pallium as a whole... the more cognitive capacity is
exhibited by the animal."
In the second study, scientists at
the University of Tübingen observed the neuronal response in trained crows
as they pecked a screen in response to visual stimuli. The experiment suggested
that the pallium of crows functioned similarly to the prefrontal cortex in
primates, exhibiting neural activity that seemingly corresponds to the animal’s
perception about what it has seen. Scientists have described the prefrontal
cortex as a "mental sketch pad", representing knowledge and
information not in the immediate physical environment.
"Concluding that birds do have what
it takes to display consciousness— patterns of neuronal activity that represent
mental content that drives behavior—now appears inevitable,"
Herculano-Houzel wrote of the second study.
The broader, speculative implication of
the research is that the last common ancestor of birds and mammals, which
existed 320 million years ago, may also have had the same cognitive machinery
and thus been similarly capable of formidable thinking abilities.
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