Brain Function and Myelin Biology
Brain White Matter development
The majority of neuronal circuits are established during prenatal brain development, and inaccuracies in this process can cause severe and/or lethal malformations. In contrast, in the postnatal brain, and to a lesser extent during adulthood, the development/maturation of the brain White Matter (WM) is the dominant process, so that WM keeps growing for about 50 years in humans and occupies close to 50% of the brain volume. Compromised WM integrity is associated with diverse neurological issues in children and adults.
In addition to neuronal plasticity, structural changes in the brain WM were reported in classical studies of learning. More recently, MRI studies in humans support the notion that remodeling of the WM is necessary for learning. Moreover, experimental research in animals suggests that production of myelin, a main component of the WM, is required for learning.
Brain White Matter, myelin, and learning
Oligodendrocytes make myelin
The WM is densely populated by oligodendrocytes (OLs), the cell type producing the myelin that wraps up neuronal axons. Myelination of axons represents an evolutionary advantage, as it allows rapid nerve conduction, and better data processing. Therefore, understanding the mechanisms regulating myelination by OLs during development, learning, and after injury, implies great potential to benefit human well-being.
When myelin or myelination go wrong
Multiple Sclerosis (MS) is a disease in which myelin integrity is compromised. As WM/myelin is widely distributed along the adult brain, myelin damage potentially affects diverse brain regions, and thus, diverse brain functions. This is reflected by a plethora of symptoms in MS, including diverse motor skills and cognitive issues.
In a group of diseases named RASopathies, which includes Neurofibromatosis Type 1 (NF1) and Costello Syndrome (CS), WM abnormalities are also common, suggesting that abnormal myelin is related to the disease. In fact, most RASopathy patients also present with neurological issues, from learning and motor disabilities to mental retardation. This further supports the important roles of WM/myelin in cognitive functions.