Cholesterol is in every cell in our body and becomes concentrated in our brain. Our brain is 60 percent fat, with over 25 percent of that being cholesterol. Most of the cholesterol in the brain is produced in the hypothalamus itself, establishing cholesterol as an integral part of our brain.
One of the most dramatic difference between young and old brains is the reduced myelination—fat sheathing—around nerves, which might explain why aging brains shrink at one percent a year. Myelin is a sheet of lipid, or fat, with the highest cholesterol content of any brain tissue. Even neurotransmitters, the chemical words used in the language that the brain communicates in, are made of cholesterol. George Bartzokis, with UCLA, and his colleagues, found a correlation between diminishing speed of performing tasks and diminishing level of myelination. The older we get, the less myelination we have. And in older age we can destroy this protective layer much faster through excessive alcohol intake and some non-/prescription drugs.
Myelination seems to be important in how we learn. Although grey matter—on the outside of the cortex made up of neurons—carry messages and does the “thinking”—white matter—the myelinated part of the brain—controls the strength of signals. Myelination is how we learn, strengthening some signals above others. Myelination develops at different ages. Starting from the back of the brain as children, and finishing off at the front of the brain in adulthood. This explains why certain tasks are easier when you are a child then at older ages (learning to speak without an accent.)