Alzheimer's Disease (AD) is a brain condition that gets worse over time. Here are some important processes that happen in the brain of someone with AD:

1. Amyloid Precursor Protein (APP) Pathway:

   • A protein called APP gets changed by two enzymes, β-secretase and γ-secretase.
   • This process causes a sticky substance known as amyloid-beta (Aβ) to build up, forming plaques in the brain.
   • About 70% of people with AD have a lot of these amyloid plaques.

2. Tau Pathway:

   • Another protein called tau can become overly modified, which leads to tangled clumps in the brain known as neurofibrillary tangles.
   • More than 95% of AD patients show these tangles when their brains are examined after they pass away.

3. Neuroinflammation:

   • Certain brain cells, called microglia and astrocytes, become activated and release chemicals that can cause inflammation.
   • This inflammation makes brain cells hurt even more.
   • In AD patients, the levels of these inflammatory markers are about 30% higher than in older people without AD.

4. Oxidative Stress:

   • AD causes the brain to create too many harmful molecules called reactive oxygen species. These can kill brain cells.
   • Damage from these harmful molecules is linked to more than 50% of the problems seen in AD.

Understanding these pathways helps scientists learn more about Alzheimer's Disease and how to treat it.