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This episode of SciShow is brought to you in partnership with Gates Notes. Head to to learn more about some of the latest breakthroughs in creating reliable, affordable, and accessible Alzheimer’s Diagnostics.

To learn more about Alzheimer's head to: To find a clinical trial, head to:

Alzheimer’s is a devastating form of dementia, but we maybe one step closer to finding a way to catching it earlier.

Hosted by: Hank Green

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PTIONS:. This episode of SciShow is brought to  you in partnership with Gates Notes. Head to to learn more  about some of the latest breakthroughs in creating reliable, affordable, and  accessible Alzheimer’s Diagnostics. [♪ INTRO]. Detecting Alzheimer’s Disease  early on can be a huge challenge.

But it’s crucial to helping patients maintain a higher quality of life for  a longer period of time. You might already know that Alzheimer’s  is a devastating form of dementia, it causes cognitive decline and memory loss  that interferes with a person's daily life. But there’s a small group of brain  cells that starts changing an average of 25 years before that cognitive decline starts.

And it could be a key to catching  Alzheimer’s decades earlier. One of the hallmarks of Alzheimer’s Disease is the accumulation of tau proteins in the brain. Tau proteins help healthy brains  develop their cellular structure.

But in Alzheimer’s brains, they seem to change in a way that makes them harmful rather than helpful. There’s a strong correlation  between tau accumulation in the brain and cognitive impairment. While we don’t exactly know how, tau  sometimes clumps up within neurons to make a toxic tangle that can damage  connections and destroy brain cells.

Tangles got their name because  they literally look like something is tangled around your brain cells. And they’re found in the memory center,  or hippocampus, of many aging brains. But previous studies have only found  them widespread outside the hippocampus in the brains of patients with dementia.

Scientists have compared the post-mortem  brains of people who were diagnosed with Alzheimer’s and people who  weren’t and found that the brains of those with Alzheimer’s have fewer  cells and are smaller overall. The tangles kill off more and more  brain cells as Alzheimer’s progresses. So these tangles across the brain are bad news.

But if we find them early, it’s possible that  people could start preventative treatment before cognitive decline, rather than  after it’s too late to be effective. One of the first places that tangles  form outside of the hippocampus is a small group of cells called the locus  coeruleus, located in the brainstem, at the back of the brain where it meets the spine. Tangles can start accumulating  there about 25 years before cognitive decline starts.

And the locus coeruleus is connected  to pretty much the entire brain. It’s involved in regulating arousal and  memory, among other things, by transporting the chemical norepinephrine to parts of  the brain that control those behaviors. These are all processes that people  with Alzheimer’s have difficulty with.

As Alzheimer’s continues progressing, the  locus coeruleus starts getting smaller by both volume and cell number. And this also affects the amount of norepinephrine in the brain and the central nervous system. In a 2017 study, scientists compared the  brains of individuals with no symptoms and those with mild cognitive  impairment and found that, in the group with mild cognitive impairment,  the locus coeruleus was 30% smaller.

Then stepping that up from mild  cognitive impairment to moderate. Alzheimer’s symptoms, the locus  coeruleus was an additional 25% smaller. But importantly, the locus coeruleus  appears to start to get smaller even before a person usually  gets an Alzheimer’s diagnosis.

This means that the locus coeruleus  might be a good place to keep an eye on if someone is at higher risk  for developing Alzheimer’s. So using brain imaging technologies,  it could be possible to give people regular check-ups to monitor locus coeruleus size or norepinephrine concentration in the brain. One technology that makes this possible is an MRI.

The locus coeruleus is a  very small part of the brain, so it can be hard to see in an MRI. But MRIs that highlight the chemicals the locus coeruleus makes would show where it is. Another option is to get a PET scan.

This technology can highlight cells  with a lot of something called NET, which is the norepinephrine transporter  and it’s found in high amounts where there’s a lot of norepinephrine. So a PET searching for NET could  also monitor the locus coeruleus. A sample of norepinephrine levels  can also be taken from your plasma.

A 2020 study found that low  levels of plasma norepinephrine correlated with lower levels of tau in the brain. They also found that these  plasma levels correlated with the mental state of the  sampled Alzheimer’s patients. This is just one study, and there’s  definitely a lot more research that needs to be done, but it’s  a promising starting point.

If a professional sees a noticeable  change in these characteristics, it could be a flag to look deeper and  consider starting treatments before the tangles spread to other parts of  the brain and cognition deteriorates. Preventative medicine is so important  in many aspects of human health. And the earlier we are able to detect Alzheimer’s, the better care we can provide for patients.

Learning more about the complex ways it changes different parts of the brain can help  get us closer to doing just that. Thank you for watching! And thank you to Gates Notes for  sponsoring this episode of SciShow.

If you’re interested in learning  more about the latest advancements in Alzheimer’s Diagnostics testing,  from a simple blood test being developed in Sweden to highly sophisticated  apps you might one day have access to on your smartphone, head to  or click the link in the description. [♪ OUTRO].