White Matter Matters

Summary:
For decades scientist focused on the gray matter of the brain and not that white matter. Gray matter is the site of mental computation and memory storage. It is composed of neuronal cell bodies or neurons. White mater is underneath this gray matter and takes up nearly one-half of the human brain. This white matter is composed of millions of communication cables with long wires called axons. These axons connect neurons in different brain regions and are covered by a white fatty substance called myelin. The functioning of this white matter is just as critical to mental and social skills as gray matter and appears is different amounts in people with different experiences of with mental dysfunctions. The extent of the white matter in the human brain also changes throughout one's life.
Not every axon is insulated or coated by myelin. On those which are gaps occusr in the insulation at about every millimeter. These gaps are named nodes of Ranvier after Louis-Antone Ranvier. Myelin is wrapped up to 150 times between each of these nodes, and the white substance allows nerve impulses to travel 100 times faster through the axons according to modern investigation. Te extensive wrapping of myelin id done by two types of glial cells: an octopus-shaped oligodendrocyte cell and a sausage-shaped Schwann cell, the latter working outside the brain and spinal cord. However, the formation of myelin by these cells is not completely random. Strict proportions excist between the insulation thickness and the diameter of the axon. The ration 0.6 of bare axon diameter divided by total fiber diameter is optimal for maximum conduction velocity. The Schwann cell, as discovered by Klaus-Armin Nave in Gottingen, Germany, is able to detect neuregulin, a protein coating axons, and respond to the amount of this protein by wrapping more or fewer myelin sheets.
As the formation of myelin occurs, it moves from the back to the front of the cerebral cortex. The last sites of myelination are the frontal lobes which are responsible for higher-level reasoning, planning and judgment. The myelination process begins in early life and may not be completed until ager twenty-five or thirty partly because axons continue to grow and change in response to experience. Studies by colleagues at the Stockholm Brain Institute in Sweden show that changes occur in the white matter when and individual is learning a complex skill. For example, one investigation of these colleagues shows that regions connecting parts of the cerebral cortex, which help coordinate movement of the fingers with other cognitive processes, are more highly developed in profession pianists than non-musicians. Myelin can also change in response to the environment. Some reports show that 17% less white matter is in the corpus callosum of children who suffer sever neglect.
The conclusion that experience can influence myelination is plausible for several reasons. When the brain responds to experiences and neurons send electical impulses through the axons, the impulses can regulate specific genes in neurons. One of these genes produces L1-CAM which is a sticky protein essential for putting the first layer of membrane around the axon so that myelination can occur. One type of glial cell can also sense the movement of impulses. .This cell is called an astrocyte and can release chemicals which cause oligodendorcytes tot make more myelin. A mutation of the astrocyte gene causes Alexander disease which can bring about mental retardation and abnormal myelin.
The information sent through the axons must arrive at the right areas of the brain at the right time. Because neurons exist both far and near the final destination of the information being sent, the information must be delayed in some situations. This delaying can occur because myelin exists in greater amounts on some axons and because the nodes of Ranvier are more frequent and abundant on some axons than others. The more myelin insulating the axon, the quicker the information a nd impulses are transferred. Likewise, the greater amount of nodes allows the signal to be generated and regulated at a quicker pace. The precise timing of various impulses and signals strengthens certain neuronal circuits and, therefore, facilitates learning skills. Among learning skills affected by white matter is Dyslexia which is t he result of disrupted timing of information transmission in circuits required for reading. Tone deafness is the result of defects in processing in the cerebral cortex, the site of sound analysis. Schizophrenia is now believed to be the result of abnormal white matter with a less than ideal number of oligodendrocytes and of mutated genes involved in the formation of myelin. Other abnormalities linked to the white matter or to myelination are ADHD, bipolar disorder, language disorders, autism, cognitive decline in aging and Alzheimer's disease.
Myelination has a great deal to do with a person's extended ability to obtain new skills at a young age. The insulation of nerve fibers dictates when learning can best occur. Young children can better learn a foreign language because the brain circuits detecting speech rewire in accordance to sounds of a person's childhood. Certain skills, like piano-playing and tennis, which require much practice and repetition, are best learned during childhood because a child's brain is involved in myelinataion more than that of an adult. Because this process mainly occurs during childhood and adolescence, the environment of one's childhood greatly affects one's brain and neural connections. It is probable that the firing of neurons can stimulate myelination as a result of intensive training at any age. However, treatments have yet tot be made to alter the white matter in order for this to occur.


Opinion:
This article concerning the intricate, complex and fascinating control center of the human body brings to light for me many of the brain's complexities, functions and influences. Man is just beginning to touch upon the details and design of the body. Within the simple discovery of the importance of white matter are more discoveries about the functions and mechanisms of this group of cells. I find it fascinating and awe-inspiring that along with the great diversity of each part of the body from organs to individual proteins, God has created a specific functions for each of these parts. For example, the astrocyte cell which senses impulses plays a big roll in stimulating other cells to form myelin essential for the body's health. One mutation in the astrocyte gene can bring about Alexander disease. This possible result does not, however, show me that God makes mistakes . Rather it shows me that even the smallest part of God's creation has huge importance to the body. The design and creation of the human body and all its components is also a testimony to the incredible ability of God to work everything in perfect timing. If He can orchestrate the timing of two different signals from different neurons to arrive simultaneously at the same brain region, how much more can He control the timing of events in our daily lives.