Dog wins tally of nerve cells in the outer wrinkles of the brain

Author: Laura Sanders / Source: Science News for Students

animal brains — A new study tallied nerve cells in the brains of carnivores. Despite being relatively large, a brown bear’s brain was lacking in these cells. Meanwhile, a raccoon’s cat-sized brain was packed full.

If more nerve cells mean more smarts, then dogs beat cats, paws down, a new study finds.

That harsh reality may shock some friends of felines. However, scientists say the real surprises came from the brains of less popular carnivores. Raccoon brains are packed with nerve cells, for instance. But brown bear brains are sorely lacking.

The researchers tallied the numbers of nerve cells, or neurons, in eight species. The ferret, banded mongoose, raccoon, cat, dog, hyena, lion and brown bear are all carnivores. Comparing how many neurons each hosted in their brains gave the scientists a better understanding of how different-sized brains are built. This neural tally appears in a December 12 Frontiers in Neuroanatomy paper. Ultimately, such data may also help reveal how brain features relate to intelligence.

For now, the multispecies nerve-cell count raises more questions than it answers, says Sarah Benson-Amram. She’s a zoologist at the University of Wyoming in Laramie. “It shows us that there’s a lot more out there that we need to study to really be able to understand the evolution of brain size and how it relates to cognition,” she says.

Suzana Herculano-Houzel is a neuroscientist at Vanderbilt University in Nashville, Tenn. She and her colleagues gathered brains from the different species. For each animal, they then whipped up batches of “brain soup.” This was brain tissue dissolved in a detergent. To this they added a molecule in this slurry that attaches only to neurons. This let the researchers count the neurons in each bit of brainy real estate.