What Happens To The Brain During Alzheimer's?

VOICE OVER: Noah Baum WRITTEN BY: Mark Sammut
Alzheimer's Disease affects up to 50 million people worldwide. It's one of the most common forms of dementia in the world today. But it's also one of the most misunderstood medical conditions out there. In this video, Unveiled uncovers how Alzheimer's takes hold of the human brain; why certain symptoms show before others; and how researchers are working toward the ultimate goal of one day finding a cure.

What Happens to the Brain During Alzheimer’s?

The brain is an incredibly complex thing. But, while it is one of the human body’s most impressive and important structures, it can also go wrong.

This is Unveiled, and today we’re answering the extraordinary question; What Happens to the Brain During Alzheimer’s?

Alzheimer’s is the sixth leading cause of death in the United States. It’s a type of dementia, a term covering various progressive disorders that impact cognitive function. Common symptoms include memory loss, absent-mindedness, mood swings, and confusion. And, although there are other types of dementia, Alzheimer’s accounts for at least 60% of cases.

According to the Alzheimer’s Association, more than 5 million Americans are living with the disease. And, according to Alzheimer’s Disease International, there are 35 to 50 million people who have Alzheimer’s worldwide. As a cure is yet to be found and the number of cases is predicted to triple during the next three decades, it’s a major concern for modern medicine.

So, how does a healthy brain operate? It’s a complicated machine made up of a network of neurons which receive, compute and relay information across the body. An average adult brain carries 100 billion interconnected neurons that are constantly firing electrical and chemical signals through branches known as dendrites and axons. Depending on whether or not the chemical neurotransmitter excites the targeted neuron, an action is either completed or blocked. In a healthy brain, neurons should be able to communicate freely, carry nutrients, and evolve depending on the needs of the body. But Alzheimer’s impedes all of these functions.

All forms of dementia are progressive. The symptoms worsen over an extensive period of time, at a rate that differs from case to case. Alzheimer’s develops through multiple ‘stages’, although traces of the disease can be found years prior to Alzheimer’s truly taking hold.

While a standard MRI doesn’t usually show anything, Molecular Imaging tests at a cellular level and, with Alzheimer’s, identifies damaging clumps of matter lodged in the spaces separating neurons. The key offender is the amyloid-beta protein. If the brain’s working as it should do, then amyloid-beta is ejected before it loses functionality. But, if it isn’t ejected, then parts of it can dislodge, harden and form a kind of ‘brain plaque’.

This plaque then blocks the transmission of signals between neurons, leading the brain to believe that cut-off cells are now disabled. The body does try to fight back, however, with the immune system staging an all-out attack. But, it doesn’t always work.

Besides neurons, the brain also carries glial cells which (among other things) protect against harmful pathogens and clutter. Microglia is the specific cell tasked with producing the chemical to eliminate the amyloid-beta protein. If the plaque resists, the microglia double down and release even more chemicals. But soon, the targeted area of the brain can get inflamed - meaning the already degenerating cells are damaged, but also healthy brain matter is destroyed. As the plaque spreads, the problem gets worse.

Researchers still aren’t sure exactly why the brain should struggle to rid itself of the Alzheimer’s-causing byproducts of this particular protein. Some studies suggest that susceptible brains produce an overabundance of amyloid-beta, while others suspect the production rate is always the same but that the clearing up process (for some reason) slows down in certain brains. Regardless, if the plaque’s allowed to form then the brain’s neurons can’t communicate or regenerate.

Dislodged protein cells aren’t the only suspected cause of Alzheimer's, though. Neurons are always sending and interpreting signals, which means the brain consumes approximately 20% of the body’s entire energy store. In order to maintain a healthy system, every part of every cell body needs nutrients - which is where microtubules and tau protein come into play.

Existing inside neurons, microtubules are responsible for transferring nutrients from the nucleus to the dendrites and axons - those branches along which brain signals are fired. Tau protein works to stabilize microtubules, keeping them firmly in place and regulating the flow of nutrients. When Alzheimer’s sets in, though, defective tau proteins disconnect and fall away, to form neurofibrillary tangles - which wind up blocking signals out of and preventing nutrients into their cell. Without fuel, the neuron gradually withers and dies.

Amyloid plaques and neurofibrillary tangles are generally accepted as the two main signals of Alzheimer’s. It’s because the brain is so incredibly flexible and adaptive that behavioral symptoms only begin to show once a substantial percentage of neurons are impacted. Which is why Alzheimer’s can be difficult to diagnose early. Once it is diagnosed, however, the way it develops can sometimes be predicted, and most of its effects can be traced back to specific cerebral regions.

The brain governs the body across four main lobes, each with a primary focus. The temporal lobe’s hippocampus is charged with storing short-term memories and is often among the first areas affected by Alzheimer’s. Since long-term memories are stored in various areas across the brain, someone with Alzheimer’s may recall a childhood experience more easily than remembering yesterday's dinner. The temporal lobe also interprets auditory data and language, though, so other early signs of Alzheimer's are forgotten plans, dropped conversations, or lapses in judgment.

The disease eventually spreads to the brain’s other lobes. Increased irritability and a lack of motivation are thought to be a byproduct of plaques and tangles influencing the frontal lobe's neurons. As this area of the brain regulates behavior and motor movement, a person can seem increasingly erratic or they might struggle to perform everyday tasks.

The parietal lobe deals with sensory information and is also key for spatial awareness. As this region shrinks through Alzheimer's, someone may struggle to recognize family members, walk without assistance, or react to any physical sensation. And, lastly, the occipital lobe interprets and transmits visual data received from the eyes. When Alzheimer’s reaches here, it breaks down this process to cause further confusion.

Although research is ongoing, a cure for Alzheimer’s has yet to be discovered. While genetics and age are predictors of the condition, doctors also recommend maintaining an active lifestyle as a potential way to reduce the risk of contracting it. Cardiovascular exercise increases the flow of blood and nutrients to the brain along with potentially reducing blood pressure by relieving stress - all of which encourages your neurons to keep firing as usual. Keeping socially and mentally active is also advised, as the links connecting neurons are strengthened through repeated stimulation.

There is no sure-fire way of staving off Alzheimer’s, but we do understand more about it today than ever before. We know which proteins to monitor, which symptoms to look out for and how best to continue living with Alzheimer’s as independently as possible. The development of dementia is an incredibly complex process, but that’s what happens to the brain during Alzheimer’s.