Intelligence has allowed humans to not only survive but thrive in a wide variety of environments, but new research reveals that this intellectual advantage comes at a cost: we become much more susceptible to brain decline.
Neuroscientist Sam Vickery of Heinrich Heine University and his colleagues found that the extra neural capacity humans have developed since splitting off from our closest relatives more than six million years ago makes grey matter more vulnerable to the effects of aging.
Vickery and his team applied their algorithm to MRI scans of 189 chimpanzee (Pan troglodytes) and 480 human brains to map and compare grey matter volume, and also looked for differences between the brains of chimpanzees, olive baboons (Papio anubis), and rhesus macaques (Macaca mulatta).
The team found no association between brain expansion and age-related decline in function when comparing chimpanzees and baboons, and even improved brain health with age when comparing chimpanzees and macaques, suggesting that our uniquely human cortical expansion has increased our vulnerability to age-related brain degeneration.
“The prefrontal cortex plays a key role in higher cognitive functions, including executive control, working memory, and language,” Vickery and team explain. “The massive expansion of the prefrontal cortex, which has played a key role in the evolutionary development of primate cognition, is accompanied in humans by a marked age-related decline in gray matter.”
In contrast to the human brain, which has expanded to accommodate higher cortical functions, chimpanzee brain regions are relatively larger than baboons and macaques and are typically associated with sensory information and movement.
“This may be related to the superior tool-using abilities of chimpanzees compared with Cercopithecus monkeys,” Vickery and colleagues say. Write in a paper.
The unique patterns of neurological changes that occur with age can be exacerbated by degenerative diseases such as Alzheimer’s and Parkinson’s.
The prefrontal cortex is one of the first areas to be affected by age-related changes, eerily supporting the theory that the parts of the brain that mature last during development are the first to experience age-related decline. These parts of the brain also appear to have a lower density of neurons than other parts of the brain, which researchers believe may contribute to their cellular vulnerability.
Chimpanzees lose some grey matter as they age, but to a much lesser extent than humans.
Vickery and his team caution that most of the chimpanzee MRI samples were female, which could skew the results, so further studies with balanced sex ratios across all species compared are needed to confirm the findings.
If the team’s results prove accurate, it certainly puts a personal spin on the saying “with great power comes great responsibility,” because if we want our superhuman thinking abilities to last, we will need to spend more time and effort caring for the human mind in order to maintain its incredible capabilities.
This study Scientific advances.
