This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Most primate species have relatively large brains with surfaces marked by pronounced bulges and furrows. This is not the case with common marmosets (Callithrix jacchus).
The brains of these small monkeys are smooth and virtually unfolded. Researchers at the German Primate Center (DPZ)—the Leibniz Institute for Primate Research in Göttingen—investigated which cellular processes during embryonic development cause the marmoset brain to develop differently from a certain stage onward. In experiments with brain organoids, they were able to show that certain neural progenitor cells—from which neurons arise—develop differently in marmosets, both morphologically and temporally.
Several processes occurring at different levels and involving various types of progenitor cells govern this phenomenon, which ultimately leads to a reduction in the size and folding of the marmoset brain. The study, published in Science Advances, sheds new light on the evolutionary development of the primate brain and could help improve our understanding of developmental disorders in the human brain in the future. Its size and degree of folding are the defining characteristics of the brains of many primates.
In particular, the walnut-like grooves and ridges of the human brain vastly increase its surface area and provide space for billions of nerve cells. This enables complex thought processes and makes the human brain exceptionally powerful. Researchers now believe that even the common ancestor of all primates had a medium-sized and at least partially folded brain.
However, this is not the case for some primate species living today. Common marmosets (Callithrix jacchus), a South American primate species increasingly used in biomedical research, have a smooth and nearly unfolded brain surface. Researchers at the German Primate Center have investigated how this comes about.
"We wanted to understand which changes at the cellular level cause the marmoset brain to grow less and form fewer folds," explains Lidiia Tynianskaia, one of the study's two first authors and a Ph.D. student in the Junior Research Group Brain Development and Evolution at the DPZ. "At the beginning of development, the common marmoset brain exhibits the typical structure and composition of a large, folded primate brain. As development progresses, processes must therefore occur that effectively slow down the production of nerve cells." In comparative experiments using brain organoids from common marmosets and humans, the scientists focused in particular on the brain's progenitor cells, as these are responsible for the production of neurons.
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