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It is widely said that the brain is the most complex structure in the entire universe. Of all organs in the body, it is the least understood, and the hardest to fix.
The brain is the source of our identity. The ancient Greeks believed that the heart was the source of identity, but you can swap out a heart and still be the same person. You cannot remove your brain and expect to be the same person.
The brain consists of 86,000,000,000 neurons, all connected to each other by a huge mass of wires known as axons. The neurons are all on the outer layers of the folds of the brain lobes, and the white matter inside the lobes are the wiring.
Although it is protected by a strong firewall, the "blood-brain barrier", the brain can still be affected by diseases and viruses, such as meningitis in the tissue around the brain, and encephalitis in the brain itself.
Commonly known conditions are Alzheimer's, Parkinson's, and brain cancer. Brain cancer itself most commonly originates elsewhere in the body and migrates to the brain.
Alzheimer's is the most common cause of dementia. Its cause is still unknown except for between 1-5% of cases where genetics have been shown to be the cause. Physically, it manifests as amyloid plaques (masses of sticky proteins gluing up the works) and neurofibrillary tangles. There is no known cure, but there have been some remarkable steps recently. For example, a method described in 2015 which gently vibrates amyloid plaques with ultrasound waves to shake them apart reported restoration in memory function in 75% of all test animals.
Parkinson's disease (PD) is a disease where you gradually lose motor control. you develop tremors and find it difficult to walk. In later stages of the disease, the effects go beyond motor control and you develop dementia. Exercise and caffeine has been shown to help prevent PD. Controversially, nicotine smokers are one third less likely to develop PD, but to use smoking as a preventative measure against PD is like setting yourself on fire to keep warm. The most common treatment at the moment is Levodopa, which acts as a dampener against the motor control signals. The cause is still unknown but mostly believed to be problems with mitochondria (the powerhouses inside every cell). Research in 2016 points more precisely at an over-abundance of endoplasmic reticulum (ER - tubes in the shell of cells that help fold proteins and transport them). In their tests, they were able to stop PD in its tracks by reducing the production of mitofusin, and by reducing ER stress.
Therapies for a lot of brain diseases involve drilling into the skull and then inserting electrodes to stimulate specific parts of the brain. In June 2017, a team at MIT published a paper describing a non-invasive deep-brain stimulation method, using the interference of electrical signals provided by scalp electrodes to "steer" electrical stimulation to the desired area
There is progress being made in curing diseases of the brain, but there is no escaping the fact that of all the organs in the body, the one that you can least do without is the brain itself. You can lose a finger and carry on. You can lose a kidney and function normally. You can lose your heart and live with a replacement. But there is currently no way to recover from losing the brain itself.
But, that may soon change, as this chapter will discuss.