New research has found that humans possess at least two unique networks in their cerebral cortex that are not seen in rhesus monkeys. The rhesus monkeys, though, do have one network that seems to be unique to them that humans do not have. The researchers theorize that these networks were probably ‘added’ sometime in the last few million years. The discoveries were made by analyzing the functional brain scans of humans and of rhesus monkeys, and comparing the two during different activities.

According to currently accepted theory, the ancestors of modern humans “evolutionarily split from those of rhesus monkeys about 25 million years ago. Since then, brain areas have been added, have disappeared or have changed in function. This raises the question, ‘Has evolution given humans unique brain structures?’.” The idea has been popular amongst many scientists, but until now there there hasn’t been any evidence. (Author’s note: Focusing on the things that make humans ‘unique’ amongst other animals seems to be a very common bias amongst those in the scientific community. Previously things such as complex “language”, culture, use of tools, mathematics, empathy, etc, have been considered to be unique to humans. But now it’s known that these are present in many animals. In my opinion, this current research should be read with that in mind.)

Professor Vanduffel explains: “We did functional brain scans in humans and rhesus monkeys at rest and while watching a movie to compare both the place and the function of cortical brain networks. Even at rest, the brain is very active. Different brain areas that are active simultaneously during rest form so-called ‘resting state’ networks. For the most part, these resting state networks in humans and monkeys are surprisingly similar, but we found two networks unique to humans and one unique network in the monkey.”





“When watching a movie, the cortex processes an enormous amount of visual and auditory information. The human-specific resting state networks react to this stimulation in a totally different way than any part of the monkey brain. This means that they also have a different function than any of the resting state networks found in the monkey. In other words, brain structures that are unique in humans are anatomically absent in the monkey and there no other brain structures in the monkey that have an analogous function. Our unique brain areas are primarily located high at the back and at the front of the cortex and are probably related to specific human cognitive abilities, such as human-specific intelligence.”

The researchers utilized fMRI (functional Magnetic Resonance Imaging) scans to observe activity in the brain. “fMRI scans map functional activity in the brain by detecting changes in blood flow. The oxygen content and the amount of blood in a given brain area vary according to a particular task, thus allowing activity to be tracked.”

It’s not surprising that animals in very different environmental niches and subject to very different conditions would have brains that function differently. And it’s also worth keeping in mind, that within the controlled conditions of the lab, the behavior and brain activity of most animals, especially intelligent ones (and ones that have been raised in captivity at that), is greatly modified. Brains are relatively plastic things, regions and networks can completely change in function in response to injury, learning, and other environmental conditions.

Source: KU Leuven

Image Credits: Brain via Wikimedia Commons