What is the difference between grey and white matter in the brain?

Alzheimer’s is a grey matter disease, and white matter has a central role in how the disease develops and progresses.

The central nervous system of the brain is made up of two kinds of tissue: grey matter and white matter.

The grey matter contains the cell bodies, dendrites and the axon terminals, where all synapses are. The white matter is made up of axons, which connect different parts of grey matter to each other. It is the white matter that allows communication to and from grey matter areas and controls the functions the body is unaware of, such as temperature, blood pressure and heart rate. Additional functions of white matter include the intake of water, dispensing of hormones, food and emotions.

Grey matter takes up about 40 percent of the brain. The senses of the body — speech, hearing, feelings, seeing and memory — and control of the muscles are all part of the grey matter’s functions.

In early or younger onset Alzheimer’s disease and atypical Alzheimer’s disease, the deterioration of white matter could be an early marker that precedes grey matter atrophy. White matter lesions from damaged white matter in the brains of elderly individuals can be seen on MRI testing. The cause of these white matter lesions are generally linked to diseases affecting the blood vessels in the brain, and identifying the specific disease leads to a particular treatment. Usually, these white matter lesions lead to the diagnosis of vascular dementia. That being said, white matter lesions indicating blood vessel disease can also lead to the wrong diagnosis and/or treatment.

According to a study by Dr. Daryl Gress in the American Journal of Neuroradiology, normal aging was associated with declines in gray matter volume that were observed specifically in the hippocampus area of the brain in Alzheimer’s cases. This research suggests that these findings support Alzheimer’s disease as a specific pathologic disease rather than an extension of the normal aging process.

Researchers say more data will be needed to establish the association of chronic vascular disease to gray matter loss.