Grey Matter

What is grey matter?

Grey matter is a type of tissue in your brain and spinal cord (central nervous system) that plays a crucial role in allowing you to function normally from day to day. It consists of high concentrations of neuronal bodies, axon terminals (endings) and dendrites.

A nerve cell (neuron) consists of:

• A large cell body (neuronal body), which contains a nucleus. The nucleus controls the cell’s activities and contains the cell’s genetic material.
• One elongated extension (axon) for sending electrical signals.
• Many branches (dendrites) for receiving signals from other cells.

Grey matter forms early in fetal development. Once a baby is born, the volume of grey matter increases until around the age of 8. After this, the density of grey matter increases until about the age of 20. This increase in density allows for high processing and further mental development. Neurons don’t renew or regenerate, however. So, if a neuron is damaged or dies, it doesn’t get replaced.

The nervous systems of all mammals (rats, dolphins, humans, etc.) are similar. However, the human brain has many structural differences. Human brains have many convolutions on the surface. The “grooves” are called sulci, and the “bumps” are called gyri. This thin sheet of sulci and gyri contains neurons that lie on the surface of your brain. This is called grey matter.

The sulci and gyri that form grey matter allow tremendous expansion of the surface area of your brain during development when your brain must fold and “wrinkle” on itself to fit within your skull. This allows humans to have significantly more grey matter than other mammals. For example, a human brain has approximately 1,000 times more grey matter on the surface than a mouse.

What’s the difference between grey matter and white matter?

White matter and grey matter are both essential parts of your brain and spinal cord. Approximately 40% of your brain consists of grey matter and 60% is made of white matter.

Grey matter consists of neuronal cell bodies and their dendrites. The dendrites are short protrusions (like little fingers) that communicate with neurons close by. In contrast, your white matter consists of the long axons of neurons that transmit impulses to more distant regions of your brain and spinal cord.

Because grey matter has a large number of neuronal bodies (which contain the nucleus of the cell), this is where information processing happens. The grey matter is the seat of a human’s unique ability to think and reason. The grey matter is the place where the processing of sensation, perception, voluntary movement, learning, speech and cognition takes place.

White matter’s role is to provide communication between different grey matter areas and between grey matter and the rest of your body.

Grey matter gets its color from a high concentration of cell bodies of neurons. White matter gets its color from a protective covering over the axons called the myelin sheath.

What does grey matter do?

Grey matter throughout your central nervous system is essential for controlling movement, memory and emotions. Different areas of your brain are responsible for various functions. Grey matter plays a significant role in all aspects of human functioning.

Where is grey matter located?

Grey matter forms the surface of your brain. It’s also present in parts inside your brain and spinal cord.

Brain

The surface and deep areas of your brain contain grey matter. The ridges and grooves of your brain — gyri and sulci — are made of grey matter. These structures increase surface area to allow for more neurons and allow humans to have a higher level of brain functioning than other mammals.

The highest concentrations of grey matter are in your:

• Cerebellum. This part of your brain has more neuronal cells than the rest of your brain combined.
• Cerebrum.
• Brainstem.

Spinal cord

Grey matter creates a hornlike structure throughout the inside of your spinal cord (with white matter on the outside). It splits into specific sections in your spinal cord:

• The anterior grey column.
• The posterior grey column.
• The lateral grey column.

What causes the loss of grey matter?

Grey matter decreases (atrophies) when its nerve cells die. A common cause of grey matter nerve cell death is a lack of blood flow to the cells. As these cells are constantly working, they require a large supply of oxygen (through your blood) to function efficiently. If there’s a lack of oxygen and blood flow, such as from a stroke or brain hemorrhage (bleed), they can die or become damaged.

Grey matter neurons also die naturally with age, but they’re the longest-living cells in your body.

Other conditions related to grey matter damage include:

• Alzheimer’s disease: An abnormal buildup of proteins in your brain causes Alzheimer’s disease. The buildup of these proteins — amyloid protein and tau protein — causes nerve cells in your grey matter to die.
• Parkinson’s disease: Parkinson’s disease is caused by a loss of nerve cells in the part of your brain called the substantia nigra, which consists of grey matter.
• Multiple sclerosis (MS): MS is commonly known as a disease that affects your white matter — it’s a demyelinating disease. However, recent research shows that it also results in the loss of grey matter, especially deep grey matter.
• Traumatic brain injury (TBI): If you experience blunt force trauma to your head, your grey matter may become damaged due to an intracerebral hemorrhage, which can lead to grey matter cell apoptosis (“programmed” cell death).

What are common signs and symptoms of grey matter damage?

In general, grey matter damage can cause the following symptoms:

• Memory loss.
• Cognitive impairment, such as issues with language, attention, reasoning and judgment, and complex decision-making.
• Motor (movement) issues, especially fine motor skills (using your hands to complete tasks, like buttoning a shirt).

What tests check the health of grey matter?

Healthcare providers often use MRI (magnetic resonance imaging) to assess the health of your grey and white matter. They use this imaging test to help diagnose conditions like Parkinson’s disease and multiple sclerosis.

Other tests that can assess grey matter health and function include functional MRI (fMRI) and positron emission tomography (PET).

Can you treat grey matter damage?

Unfortunately, there’s no known way to treat or reverse grey matter damage. Once neurons die, they don’t regenerate. Neurons also don’t multiply like other cells in your body.

The only way to treat conditions that involve grey matter damage or loss is to manage the symptoms.

How can I keep my grey matter healthy?

Proper blood and oxygen flow are essential to the health of your grey matter. Because of this, it’s important to manage risk factors for cerebrovascular disease. Steps you can take include:

• Managing high blood pressure (hypertension).
• Exercising regularly.
• Limiting your intake of alcohol.
• Maintaining a healthy weight.
• Getting quality sleep.
• Managing your blood sugar and cholesterol levels.
• Avoiding or quitting smoking.
• Reducing stress.

While grey matter loss naturally happens with aging, studies show that people 65 years and older who exercise regularly generally have more grey matter volume than people in this age group who don’t exercise regularly. Based on this evidence, being active throughout your life may help keep your grey matter healthy and living longer.

In addition, learning new skills or information over multiple weeks (not just hours) may improve the health of your grey matter. Although this kind of mental stimulation may not grow new neurons, it can grow new connections between neurons, called brain plasticity (neuroplasticity).

A note from Cleveland Clinic

Grey matter is essential tissue in your brain and spinal cord that allows you to interact with the world around you. It’s the root of all mental functioning. A range of conditions can affect your grey matter. You can support your brain health by making healthy lifestyle choices, such as exercising regularly and maintaining a healthy weight for you. If you suspect that you or a loved one has symptoms related to a brain condition, talk to a healthcare provider.