If grey matter is a computer, white matter is the cable. When neurons and brain matter work together, it's called "cognition".

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Grey Matter vs White Matter

Grey matter is where your brain neurons are located. Grey matter is found in the outer areas of your brain. Neurons are the key players in brain activities like thinking, remembering, feeling, and doing. All these functions working together are called “cognition”. Loss of cognition – cognitive decline – is what happens when you start losing neurons and grey matter. The human brain has better cognition than any other animal brain. The outside of the huma brain, called the cerebral cortex, is overdeveloped in humans compared to other animals. It makes up over 80 percent of the brain mass and contains about 100 billion neurons.

Each neuron communicates with other neurons through nerve fiber extensions, called axons. Like the cable coming off a computer, axons need to be wrapped with a protective coating to effectively carry nerve signals. This wrapping is called myelin. Because myelin is white, areas thick with axons bundles are called white matter. White matter is found in the inner areas of the brain and the outside of the spinal cord. If white matter is lost, it may regrow as long as axons are connected to healthy neurons. Unlike skin cells or bone cells, once neurons are lost, they are usually gone forever.

Is It Possible to Replace Grey Matter?

Grey matter decreases when neurons die. A common cause is a stroke or brain hemorrhage. Neurons also die naturally with age, although they are the longest living cells in the body. Unnatural causes of neuronal death include Parkinson’s disease, Alzheimer’s disease, and traumatic brain injury. Until recently, brain researchers believed you are born with all the neurons you will ever have. Some newer research suggests that some areas of the brain can make new neurons, called neurogenesis, but this is still an unproven theory. For now, there is no known way for you to replace lost grey matter.

What Happens to Grey Matter as You Age?

As you age, and you naturally lose neurons. Messages passing through white matter begin to slow down. Part of aging is also a decreased blood supply to your neurons, caused by aging of your heart and blood vessels. Waste products and other chemicals also begin to build up in the aging brain causing plaques and tangles to form, which can break down neurons. That is why some gradual slowing of thought, memory, and thinking – cognitive decline – is a normal part of aging. These changes do not usually cause severe memory loss or dementia unless you have a disease like Alzheimer’s.

Tips for Brain Health

Grey Matter Supplements

You probably can’t prevent loss of grey matter that comes with age, but you may be able to slow it down. You have probably seen adds for brain supplements that can increase cognitive function, reduce your risk of dementia, or prevent Alzheimer’s disease. According to the National Center for Complementary and Integrative Health (NCCIH), this is what the science says about supplements and their effect on brain matter:

• Ginkgo biloba. A review of studies on Gingko biloba for brain health that included over 2,500 people found that it may slow down cognitive decline, especially in people who already have some cognitive impairment.
• Omega-3 fatty acids. There has been research supporting the use of this supplement for reducing cognitive decline, but most studies have found it has no effect on cognition in older people.
• Vitamin E. There is some evidence that this vitamin may slow cognitive decline in Alzheimer’s disease. However, most studies do not find any benefit.
• In laboratory and animal studies, this supplement shows promise for decreasing the plaques and tangles that occur in aging and Alzheimer’s disease, however, human studies have been few and inconsistent.

NCCIH says that other supplements including vitamin B, vitamin D, multivitamins, coconut oil, and melatonin do not have enough research to support their use for brain health.

Brain Maintenance

According to Harvard University’s Harvard Health and the Alzheimer’s Association, the best way to maintain the health of your grey matter is with a healthy lifestyle. These are their tips for brain health:

• Get regular aerobic exercise. This will keep your neurons supplies with blood and oxygen and reduce cognitive decline.
• Stimulate your brain. Although stimulation may not grow new neurons it can grow new connections between neurons, called brain plasticity. Examples include doing mental gymnastics like puzzles or learning something new through reading or taking a class.
• Switch to a Mediterranean style diet. People who eat lots of fish, fruits, vegetables, nuts, and olive oil have less cognitive decline and dementia. A diet for brain health also includes less animal fat and less salt.
• Don’t smoke. Smoking increases cognitive decline.
• Work with your doctor to control your blood pressure, blood sugar, and to maintain a healthy weight.
• Get enough sleep. Poor sleep has been linked to increased problems with memory and thinking.
• Watch out for depression. Untreated depression has been linked to cognitive decline. Get help if you are struggling with depression, stress, or anxiety.
• Don’t be a loner. Studies show that people who have more healthy and active relationships have better brain health.
• If you drink alcohol, don’t abuse it. Excessive drinking is a big risk factor for dementia.
• Prevent head injuries. Traumatic brain injuries kill neurons. Wear a helmet when riding a bike or plying a contact sport, and wear your seatbelt.