The cerebral cortex or the cortex is the area of the human brain, evolutionarily speaking, newer (it is about 500,000 years old); it is crucial for rational thinking, information processing, memory, and attention. Its thickness varies slightly between the sexes and, although not much has been revealed about the genetic foundations that influence the size of its surface, its structure has been linked to several psychiatric traits, such as schizophrenia, bipolar disorder, depression, ADHD or even autism.
Given its still manifest ignorance, it is of enormous importance that the first map of the human cerebral cortex has been made: it includes 200 regions of the genome and more than 300 specific genetic variations that could probably play a role in different psychiatric and neurological disorders.
The genetic code is information carried by cells in their nucleus, somewhat like the instruction book for a household appliance. All human beings share most of the genetic code, but each individual has genetic variants, which are the slight differences that make each and every one of us unique. It depends on genetics whether we have blonde, brown or red hair; the color of the eyes, the type of blood and, also, our predisposition to suffer certain diseases. However, many genetic variants have no known importance, they are not determinants for our traits. For this reason, identifying the genetic variants associated with the size and structure of the brain’s cortex posed a great challenge for scientists.
Method
By studying magnetic resonance images and the DNA of more than 50,000 people, the authors of this map were able to identify these gene variants, which shed light on how genetics contribute to creating differences in the cerebral cortex of individuals. . This map represents a milestone in the discipline of neuroscience; so much so that researchers consider, according to a press release from the University of North Carolina School of Medicine, that their new brain genetic roadmap is a kind of ‘Rosetta stone’ (the famous and ancient collection of Egyptian inscriptions whose decipherment led to the understanding of hieroglyphic writing), which will help translate how some genes affect physical brain structure and neurological consequences for individuals.
What new information does this map provide?
First, it has been determined that some genetic variants are associated with the surface area of the cortex ; however, other genetic variants are associated with the thickness of the cortex . Furthermore, genes that determine surface area are related to early fetal development, while thickness appears to be driven by genes active in the adult cortex.
People with a propensity for depression or insomnia are genetically more inclined to have a lower surface area of the cortex, while people with a genetic risk for Parkinson’s disease tend to have a higher surface area. In addition, the map also allowed the discovery of specific genes that drive brain development and aging in people around the world.
Reference :
The study has been published by the journal Science and directed by Jason Stein, assistant professor in the Department of Genetics, UNC School of Medicine; Sarah Medland, Principal Investigator at the QIMR Berghofer Medical Research Institute in Australia; Paul Thompson, associate director of the Institute for Neuroimaging and Informatics; and Mark and Mary Stevens of the University of Southern California.
Stein et al., ‘The genetic architecture of the human cerebral cortex’. Scicence (2020) https://doi.org/10.1126/science.aay6690
