In particular, the homolog of the mammalian brain, thought to be unique to our own family of apes, cats, whales and other mammals, turns out to have an avian parallel according to new research coming out of the University of Chicago. Rooted in a fifty year old hypothesis, the theory was finally confirmed with a report published in Proceedings of the National Academy of Sciences.
The reason it took so long to find the bird version of the neocortex was the sheer difference in anatomical structure and appearance. The neocortex is quite distinctive and looks and functions in a nearly identical fashion across all breeds of mammal, while the bird’s dorsal ventricular ridge (DVR) functions about the same but looks quite different. It’s only close inspection that it becomes quite clear that the DVR makes use of the same pathways traveling to and from the mammalian neocortex.
The discovery was made with chickens and zebra finch, both expressing the same multi-level brain functions as one would see in the neocortex.
Jennifer Dugas-Ford, PhD points to the sophisticated approach to finding similarities, making use of multilevel markers to show brain activity. The study showed all markers “exactly” where they would be in the DVR when compared to the neocortex, presenting a mirror image of brain activity between bird and mammal brains in this area.
Anyone who’s raised chickens may doubt the complexity of their brains, but this research makes quite clear that we’re more closely related with our cold-blooded cousins than we might like to believe.
Similar findings have been made in turtles, while failures to make the confirmation in the past seem to center around a simpler “connection” based model of study. When the hypothesis was first introduced to the science community in the 1960’s by neuroscientist Harvey Karten, all he had to provide for evidence were similarities and connections which the community found easy to dismiss as trivial or superficial. Now, some fifty years later, Karten’s hypothesis has finally been confirmed and the findings may provide a whole new territory for neuroscientists to explore in regards to how our own brains work.
One of the most interesting parts of this discovery has to do with bird vocalization and a significant difference between a mammalian and avian brain. Where the mammalian Broca’s area is relatively simple, the bird’s brain is so well tuned for complex singing and language and even tool-use that it may actually have some advantages over the mammal brain, as it communicates with itself using a series of short and long-term electrical currents thanks to special nuclei that are not found in mammalian brains. Clifton Ragsdale, PhD suggests the possibility of “specialized nuclear processing centers” in the bird’s brain where the same would be impossible in a human being.
Knowing that birds carry homologous cells and an equivalent of a neocortex will allow neuroscientists to conduct a whole new range of experiments and research in the area of restoring sight and helping people to recover from paralysis. The DVR may seem like a small discovery, but it’s one with big implications.