The cerebellum – a part of the brain once recognized primarily for its role in coordinating movement – has undergone evolutionary changes that may have contributed to the use of human culture, language, and tools. This new finding appears in a study by Elaine Guevara of Duke University and her colleagues, published on May 6 in the journal PLOS Genetics.
Scientists studying how humans developed their remarkable ability to think and learn have frequently focused on the prefrontal cortex, a part of the brain vital for executive functions, such as moral reasoning and decision making. But recently, the cerebellum has started to receive more attention for its role in human cognition. Guevara and his team studied the evolution of the cerebellum and prefrontal cortex by looking for molecular differences between humans, chimpanzees and rhesus macaque monkeys. Specifically, they examined the genomes of two types of brain tissue from the three species for epigenetic differences. These are modifications that do not change the DNA sequence but can affect which genes are turned on and off and can be inherited by future generations.
Compared to chimpanzees and rhesus macaques, humans have shown greater epigenetic differences in the cerebellum than in the prefrontal cortex, underscoring the importance of the cerebellum in the evolution of the human brain. Epigenetic differences were particularly apparent on genes involved in brain development, brain inflammation, fat metabolism, and synaptic plasticity – the strengthening or weakening of connections between neurons depending on how often they are used.
The epigenetic differences identified in the new study are relevant to understanding how the human brain works and its ability to adapt and make new connections. These epigenetic differences can also be involved in aging and disease. Previous studies have shown that epigenetic differences between humans and chimpanzees in the prefrontal cortex are associated with genes involved in psychiatric conditions and neurodegeneration. Overall, the new study affirms the importance of including the cerebellum when studying the evolution of the human brain.
Guevara adds: “Our results support an important role for the cerebellum in the evolution of the human brain and suggest that the previously identified epigenetic features that distinguish the human neocortex are not unique to the neocortex.”
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