Inflammation of the brain gray matter decreases nerve-cell activity in mouse model Damage to the brain gray matter plays an important role in the progression of multiple sclerosis. This study now shows that such damage can be caused by inflammatory reactions that lead to loss of synapses, which impairs neural activity. Multiple sclerosis (MS) is a chronic inflammatory disease that affects the central nervous system, in which nerve cells are attacked by the patient's own immune system. In many cases, the disease develops into a progressive form, which is characterized by a shift of pathology from the white matter to the gray matter, for instance to the cerebral cortex.