Scientists claim to have discovered the first piece of evidence to prove that humans have unique cortical brain networks.
Humans have at least two functional networks in their cerebral cortex not found in rhesus monkeys. This means that new brain networks were likely added in the course of evolution from primate ancestor to human, found scientists from KU Leuven in collaboration with a team of Italian and American researchers.
Human ancestors 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.
Scientists have entertained the idea that evolution gave humans unique brain structures but conclusive evidence was lacking.
By combining different research methods, scientists have the first piece of evidence that could prove that humans have unique cortical brain networks.
"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," said neurophysiologist Wim Vanduffel from KU Leuven and Harvard Medical School.
"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," Vanduffel said in a statement.
"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," Vanduffel said.
"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," Vanduffel said.
"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," Vanduffel added.
The study used fMRI (functional Magnetic Resonance Imaging) scans to visualise brain activity. 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.
