1. The need or desire together with environmental stimuli that causes an individual to act.
   MRI (Magnetic Resonance Imaging) - A high tech diagnostic tool to display tissues unseen in
   X-rays or by other techniques.
   MULTIPLE SCLEROSIS (MS) - A chronic disease of the central nervous system where myelin, the insulation on nerve fibers, is lost. MS is thought to be an autoimmune dysfunction in which the body turns on itself for some unknown reason.
   MYELIN - A white, fatty insulating material for axons which produced in the peripheral nervous system by Schwann cells, and in the central nervous system by oligodendrocytes. Myelin is
   necessary for rapid signal transmission along nerve fibers, ten to one hundred times faster than in bare fibers lacking its insulation properties. Loss of myelin accompanies many central nervous system injuries and is the principal cause of multiple sclerosis. The process of remyelination is very important in spinal cord injury research. If this is possible in the body, as many researchers believe, it may be possible to return function to intact nerve fibers. Oligodendrocytes are apparently unable to provide myelin in the mature central nervous system.
   MYELOGRAM - A diagnostic test in which an opaque liquid is injected into the spinal canal, producing an outline of it on X-rays or fluoroscope. Now somewhat outdated by modern imaging diagnostics. Some dyes are suspected of causing additional neurological problems.
   NASOGASTRIC TUBE (NG Tube) - tube that passes through the person's nose and throat and ends in the person's stomach. This tube allows for direct "tube feeding" to maintain the nutritional status of the person or removal of stomach acids.
   NEOLOGISM - Nonsense or made-up word used when speaking. The person often does not realize that the word makes no sense. NEOLOGISM - Nonsense or made-up word used when speaking. The person often does not realize that the word makes no sense.
   NERVE GROWTH FACTOR (NGF) - A "vitamin" for nerve cells. NGF, a protein, supports survival of embryonic neurons, and regulates neurotransmitters. NGF is one of several growth factors that have been identified in the central nervous system. It is theorized that these factors, including the much rarer BDNF (brain derived neurotrophic factor) and CNTF (ciliary neurotrophic factor) have important roles in regeneration. Exact knowledge of the role of growth factors continues to be a major area of neuroscience, and may lead to drugs that enhance growth of nerve tissue.
   NEUROGENIC BLADDER - Any bladder disturbance due to an injury of the nervous system.

This definition is in context to Brain Injury. See more contextual defintions for Motivation.