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Feb 15, 2023

Gene Expression in Neurons Solves a Brain Evolution Puzzle

Posted by in categories: biological, evolution, neuroscience

๐“๐ก๐ž ๐ง๐ž๐จ๐œ๐จ๐ซ๐ญ๐ž๐ฑ ๐ฌ๐ญ๐š๐ง๐๐ฌ ๐จ๐ฎ๐ญ ๐š๐ฌ ๐š ๐ฌ๐ญ๐ฎ๐ง๐ง๐ข๐ง๐  ๐š๐œ๐ก๐ข๐ž๐ฏ๐ž๐ฆ๐ž๐ง๐ญ ๐จ๐Ÿ ๐›๐ข๐จ๐ฅ๐จ๐ ๐ข๐œ๐š๐ฅ ๐ž๐ฏ๐จ๐ฅ๐ฎ๐ญ๐ข๐จ๐ง. ๐€๐ฅ๐ฅ ๐ฆ๐š๐ฆ๐ฆ๐š๐ฅ๐ฌ ๐ก๐š๐ฏ๐ž ๐ญ๐ก๐ข๐ฌ ๐ฌ๐ฐ๐š๐ญ๐ก ๐จ๐Ÿ ๐ญ๐ข๐ฌ๐ฌ๐ฎ๐ž ๐œ๐จ๐ฏ๐ž๐ซ๐ข๐ง๐  ๐ญ๐ก๐ž๐ข๐ซ ๐›๐ซ๐š๐ข๐ง, ๐š๐ง๐ ๐ญ๐ก๐ž ๐ฌ๐ข๐ฑ ๐ฅ๐š๐ฒ๐ž๐ซ๐ฌ ๐จ๐Ÿ ๐๐ž๐ง๐ฌ๐ž๐ฅ๐ฒ ๐ฉ๐š๐œ๐ค๐ž๐ ๐ง๐ž๐ฎ๐ซ๐จ๐ง๐ฌ ๐ฐ๐ข๐ญ๐ก๐ข๐ง ๐ข๐ญ ๐ก๐š๐ง๐๐ฅ๐ž ๐ญ๐ก๐ž ๐ฌ๐จ๐ฉ๐ก๐ข๐ฌ๐ญ๐ข๐œ๐š๐ญ๐ž๐ ๐œ๐จ๐ฆ๐ฉ๐ฎ๐ญ๐š๐ญ๐ข๐จ๐ง๐ฌ ๐š๐ง๐ ๐š๐ฌ๐ฌ๐จ๐œ๐ข๐š๐ญ๐ข๐จ๐ง๐ฌ ๐ญ๐ก๐š๐ญ ๐ฉ๐ซ๐จ๐๐ฎ๐œ๐ž ๐œ๐จ๐ ๐ง๐ข๐ญ๐ข๐ฏ๐ž ๐ฉ๐ซ๐จ๐ฐ๐ž๐ฌ๐ฌ. ๐’๐ข๐ง๐œ๐ž ๐ง๐จ ๐š๐ง๐ข๐ฆ๐š๐ฅ๐ฌ ๐จ๐ญ๐ก๐ž๐ซ ๐ญ๐ก๐š๐ง ๐ฆ๐š๐ฆ๐ฆ๐š๐ฅ๐ฌ ๐ก๐š๐ฏ๐ž ๐š ๐ง๐ž๐จ๐œ๐จ๐ซ๐ญ๐ž๐ฑ, ๐ฌ๐œ๐ข๐ž๐ง๐ญ๐ข๐ฌ๐ญ๐ฌ ๐ก๐š๐ฏ๐ž ๐ฐ๐จ๐ง๐๐ž๐ซ๐ž๐ ๐ก๐จ๐ฐ ๐ฌ๐ฎ๐œ๐ก ๐š ๐œ๐จ๐ฆ๐ฉ๐ฅ๐ž๐ฑ ๐›๐ซ๐š๐ข๐ง ๐ซ๐ž๐ ๐ข๐จ๐ง ๐ž๐ฏ๐จ๐ฅ๐ฏ๐ž๐.

The brains of reptiles seemed to offer a clue. Not only are reptiles the closest living relatives of mammals, but their brains have a three-layered structure called a dorsal ventricular ridge, or DVR, with functional similarities to the neocortex.


The neocortex stands out as a stunning achievement of biological evolution. All mammals have this swath of tissue covering their brain, and the six layers of densely packed neurons within it handle the sophisticated computations and associations that produce cognitive prowess. Since no animals other than mammals have a neocortex, scientists have wondered how such a complex brain region evolved.

Now, however, by analyzing molecular details invisible to the human eye, scientists have refuted that view. By looking at patterns of gene expression in individual brain cells, researchers at Columbia University showed that despite the anatomical similarities, the neocortex in mammals and the DVR in reptiles are unrelated. Instead, mammals seem to have evolved the neocortex as an entirely new brain region, one built without a trace of what came before it. The neocortex is composed of new types of neurons that seem to have no precedent in ancestral animals.

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