Nature
PUBLISHED
Having a “bird brain” is not as insulting as it sounds. Despite their puny brain size, some birds have been shown to be just as smart as apes. Perhaps a little-known type of neuron – the neocortical intratelencephalic cell – could explain why.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.A new study has looked into bird brains and their neural circuitry, only to discover that they actually possess a type of brain cell very similar to one found in primates. This might hint at why both these beasts share a similar sense of intelligence despite having such different brain structures and evolutionary pasts.
“Birds are more intelligent than you think, and they do clever things. So, the question is: What kind of brain circuitry are they using?” Clifton Ragsdale, professor of neurobiology at the University of Chicago and senior author of the study, said in a statement. “What this research shows is that they’re using the same cell types with the same kinds of connections we see in the neocortex, but with a very different kind of organization.”
The research, recently published in the journal Current Biology, looked at the dorsal ventricular ridge (DVR) of chickens. This area of the bird brain is believed to play a similar role to the primates' neocortex, a large chunk of the brain associated with communication, sensory perception, cognition, and high-level intelligence. However, one problem with this comparison is that the DVR and the neocortex are completely different structures.
"The structure of the avian DVR looks nothing like the mammalian neocortex, and this has historically been a huge problem in comparative neuroscience," said lead author Steven Briscoe. "Anatomists have debated how to compare the DVR and neocortex for over a century, and our identification of IT neurons in the bird DVR helps to explain how such different brain structures can give rise to similar behaviors."
Now, scientists have discovered that birds and primates both have very similar neocortical intratelencephalic cells, also known as IT neurons, within their DVR and neocortex.
Weirdly enough, birds and primates also share this similarity with another animal, not so associated with high-level intelligence: alligators. Crocodilians are the closest living relatives of birds, but these groups diverged more than 240 million years ago. While it's unclear why alligators don't have the sharp wits of an ape, it does pose the idea that birds and primates evolved higher cognitive abilities independently from one another millions of years ago.
“[The cells are] not just found in mammals, which we knew, but in non-avian reptiles like alligators and avian reptiles, or birds," Ragsdale said. "It begins to clarify where and how in evolution we got this fantastic structure, the neocortex."
