Study Reveals Possible New Key to Human Evolution

By | February 10, 2012

Structural and functional brain imaging analyses, combined with computational analyses, reveal highly connected, centrally located regions of the human cortex (front part of the brain) that form a “structural core” of the brain.  Liza Gross, Wikimedia Commons 

For the first five years of life, human cognition slowly comes to fruition, receiving and storing information and experience from the environment and enabling humans to advance beyond the capabilities of their primate cousins, according to a study published online in Genome Research. An international team of researchers have identified extended synaptic development in the prefrontal cortex of the human brain that sheds new light on the evolution of human cognition and suggests another reason why the human family diverged from other primates 4-6 million years ago.

“Why can we absorb environmental information during infancy and childhood and develop intellectual skills that chimpanzees cannot?” asks study author Dr. Philipp Khaitovich of the Chinese Academy of Sciences and the Max Planck Institute for Evolutionary Anthropology. “What makes the human brain so special?”

To find answers to these questions, Khaitovich and his colleagues applied microarray and RNA-sequencing technology to explore the changes in how genes are expressed as the postnatal brain develops during the first years of life for humans, chimps, and the more distantly related macaques. The group found that the time duration of these changes in humans differed markedly from that of other primates. By sampling the prefrontal cortex, the part of the brain that scientists have long thought was much more highly developed in humans, and the cerebellum, a more ancient and basic brain region related to motor control, they found that the synaptic genes of the prefrontal cortex reached their peak expression after the first five years, in contrast to first-year-of-life peak expression for the other sampled primates. This was not observed in the cerebellum.

“Among all developmental changes specific to the human brain, one process – synaptogenesis – clearly stood out,” said Khaitovich. “Our findings suggest that the human brain remains extremely plastic and susceptible to environmental input during the first five years of life.”

Synaptogenesis is critical for learning and memory in the developing brain, a process that involves the formation, strengthening, and elimination of certain synaptic connections, providing the foundation for the more advanced cognitive (thinking) skills characteristic of humans. A synapse is a structure in the nervous system that permits a neuron to pass an electrical or chemical signal to another cell in the brain. …

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