Bird Brains Are Packed With Neurons: Study


We may have been underestimating bird intelligence all along — and calling someone a birdbrain might as well be more a compliment rather than an insult.

A new study made the surprising discovery that while birds have notably small brain sizes, theirs are packed with far more neurons in the part of the brain linked to intelligent behavior. The walnut-sized brain of the macaw, for instance, is definitely smaller than the lemon-sized brain of the macaque monkey, but the former is likely more intelligent.

An international team of researchers studied 28 bird species ranging in size from the small zebra finch to the 6-footer emu. Songbirds and parrots emerged with especially dense neuron clusters in their forebrain: they maintain twice as many neurons as primate brains of the same size and up to four times as much as rodent brains.

The high neuron density was found to be particularly occurring in their pallium — the brain section corresponding to the cerebral cortex, which supports higher cognitive powers such as pattern-finding or planning for tomorrow.

In birds, nature leveraged neurons’ number and size as well as their distribution across various brain regions, said senior author and Vanderbilt University neuroscientist Suzana Herculano-Houzel.

The link between neuron count and intelligence is yet to be firmly established, but the data showed that birds can indeed have greater cognitive prowess per pound than that of their mammalian counterparts, and they demonstrate novel methods of building larger brains or apart from previous beliefs that growing brains need larger neurons to grow as well because they needed to connect over longer distances.

What bird brains suggest: let neurons stay small and connected locally and allow only a tiny fraction to become big enough to forge longer connections. This will keep the neurons’ average size down, Herculano-Houzel added.

The authors are determined to find out next the cost of having greater avian brainpower than we thought.

“If they really pack this many neurons in such small brains … and can only get so much food, that may be the reason birds are limited to a certain body size,” she said in a Washington Post report, pinpointing that the creatures therefore cannot obtain enough calories because of flight and their neurons in the brain.

The team will investigate next this issue of potential size limit, expanding knowledge in the puzzling complexities of birds’ behavioral and cognitive abilities.

The findings were detailed in the journal Proceedings of the National Academy of Sciences.

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