Alzheimer’s Disease & the Brain: How it Affects Memory & Cognition

Introduction 

Alzheimer's disease is most associated with memory loss, but the impacts of Alzheimer's extend far beyond that. The disease causes significant changes in the brain, gradually impairing a person's ability to think, reason, and perform everyday activities. However, by understanding the brain changes involved, one can gain insight into the challenges faced by those living with Alzheimer's disease and explore potential treatment options aimed at slowing the disease's progression. 

This blog explores how Alzheimer’s disease affects the brain and how these alterations lead to the characteristic symptoms of memory and cognitive decline. 

How Does Alzheimer’s Disease Affect the Brain? 

While some shrinkage of the brain is a normal part of aging, healthy brains typically retain most of their neurons. In Alzheimer’s disease, however, the damage is extensive. Neurons throughout the brain cease to function properly, lose connections with one another, and eventually die. This disrupts essential processes for neuron and network survival, including communication, metabolism, and repair. 

Initially, Alzheimer’s disease primarily targets the connections between neurons in brain regions associated with memory, such as the entorhinal cortex and hippocampus. As the disease progresses, it spreads to areas of the cerebral cortex responsible for language, reasoning, and social behavior. Over time, widespread damage occurs in various regions of the brain, affecting their ability to function normally. As the condition advances, individuals with Alzheimer’s disease gradually lose their capacity to live independently, and the disease ultimately leads to death. 

Stages of Alzheimer’s Disease 

In normal aging, the brain may shrink slightly, but it generally retains most of its neurons. In Alzheimer’s disease, however, significant damage occurs as neurons throughout the brain stop functioning, lose connections, and eventually die. This disrupts critical processes such as communication, metabolism, and repair within neuron networks. 

In the early stages, Alzheimer’s primarily impacts the connections between neurons in areas of the brain responsible for memory, such as the entorhinal cortex and hippocampus. As the disease progresses, it extends to regions of the cerebral cortex involved in language, reasoning, and social behavior. Over time, widespread damage affects various brain regions, impairing their normal function. As the disease advances, individuals gradually lose the ability to live independently, and Alzheimer’s ultimately leads to death. 

Neurofibrillary Tangles 

Neurofibrillary tangles are abnormal accumulations of tau protein inside neurons. Tau typically stabilizes microtubules, structures that help transport nutrients and molecules within neurons. In Alzheimer’s, tau detaches from microtubules and aggregates with other tau molecules, forming tangles that block the transport system. This disruption impairs synaptic communication between neurons. 

Emerging evidence suggests that Alzheimer related brain changes are the result of complex interactions between tau, beta-amyloid, and other factors. Tau accumulation primarily occurs in memory-related brain regions, while beta-amyloid forms plaques between neurons. As beta-amyloid levels increase, tau spreads more rapidly across the brain. 

Loss of Neuronal Connections & Cell Dysfunction 

As neurons in Alzheimer’s disease become damaged, communication networks in the brain break down, leading to widespread brain shrinkage. This process, called brain atrophy, results from significant cell death and loss of brain volume, particularly in the later stages of the disease. 

Chronic Inflammation 

Chronic inflammation in Alzheimer’s may arise from malfunctioning glial cells, which are responsible for cleaning up waste and debris in the brain. A type of glial cell called microglia typically engulfs toxins and waste products. When microglia fail to clear beta-amyloid plaques and other debris, Alzheimer’s can develop. Research is ongoing to understand how and why microglia malfunction. 

One area of focus is a protein called TREM2, which plays a crucial role in microglial function. When TREM2 does not function properly, plaques accumulate between neurons. Another type of glial cell, astrocytes, attempts to help clear the buildup, but when they also malfunction, they can trigger chronic inflammation, which further damages neurons. 

Vascular Contributions to Alzheimer’s Disease 

Vascular problems, such as beta-amyloid deposits in blood vessels, atherosclerosis, and mini-strokes, are common in people with dementia and can exacerbate brain health. Conditions like high blood pressure, diabetes, and stroke damage blood vessels, impairing the flow of oxygen and nutrients to the brain and increasing the risk of vascular dementia. 

Vascular issues can reduce blood flow to the brain and disrupt the blood-brain barrier, which normally protects the brain from harmful substances while allowing essential molecules like glucose to pass through. In Alzheimer’s, problems with this barrier can prevent glucose from reaching the brain and impede the clearance of toxic proteins like beta-amyloid and tau, leading to inflammation and further brain damage. Researchers continue to explore potential treatments to address this destructive cycle. 

How Brain Changes Affect People with Alzheimer’s Disease 

The complex molecular and cellular changes in the brain due to Alzheimer’s lead to the disease’s characteristic symptoms. Memory problems are often the first sign, as the damage primarily affects brain regions involved in forming new memories. Over time, cognitive difficulties with thinking, reasoning, and memory worsen as more brain areas become affected. In the later stages, the brain damage becomes so extensive that communication becomes impossible, and individuals become entirely dependent on others for care. Alzheimer’s disease represents a profound challenge, not only for the individuals affected but also for their families and caregivers. The damage it causes to the brain is extensive, impacting memory, cognition, and even behavior. However, with ongoing research and advances in diagnostics, new treatments are being developed to address the underlying causes of Alzheimer's, including amyloid plaques, tau tangles, and brain inflammation. 

The Takeaway 

Understanding the brain changes in Alzheimer's is essential for diagnosing the disease and developing effective treatments. Ongoing research is uncovering new insights into its mechanisms, offering hope for better therapies and interventions. Although much remains to be learned, these advancements provide optimism for potential treatments that could slow or halt the progression of the disease. Continued research and increased awareness are vital in supporting those affected, helping them navigate their journey, and ultimately improving their quality of life. With sustained effort, one may unlock solutions that offer meaningful improvements for individuals with Alzheimer’s and their families.