How Does Alzheimer’s Disease Affect The Brain
Scientists continue to unravel the complex brain changes involved in Alzheimers disease. Changes in the brain may begin a decade or more before symptoms appear. During this very early stage of Alzheimers, toxic changes are taking place in the brain, including abnormal buildups of proteins that form amyloid plaques and tau tangles. Previously healthy neurons stop functioning, lose connections with other neurons, and die. Many other complex brain changes are thought to play a role in Alzheimers as well.
The damage initially appears to take place in the hippocampus and the entorhinal cortex, which are parts of the brain that are essential in forming memories. As more neurons die, additional parts of the brain are affected and begin to shrink. By the final stage of Alzheimers, damage is widespread and brain tissue has shrunk significantly.
Brain Donation: A Generous Gift
One donated brain can make a huge impact, potentially providing information for hundreds of research studies. To become a brain donor, consider joining a study that leads to brain donation, such as studies offered by the Alzheimers Disease Research Centers, or agreeing to donate to the brain banks of NIH.
Learn more about brain donation.
Causes Of Alzheimers Disease
Scientists dont yet fully understand what causes Alzheimers disease in most people. In people with early-onset Alzheimers, a genetic mutation is usually the cause. Late-onset Alzheimers arises from a complex series of brain changes that occur over decades. The causes probably include a combination of genetic, environmental, and lifestyle factors. The importance of any one of these factors in increasing or decreasing the risk of developing Alzheimers may differ from person to person.
Don’t Miss: How Do I Know If My Mom Has Dementia
A Coordinated Push For Better Diagnosis And New Treatments
We heard from Dr Jennifer Whitwell from the Mayo Clinic in the US whose research into brain imaging in FTD is identifying new ways to distinguish between the different types of FTD. On average, people with FTD can wait up to five years for an accurate diagnosis, and reports suggest that almost three quarters of people are initially misdiagnosed. So advances in this area are vital for families affected, as well as helping researchers to improve their approach to studying the disease.
Brain imaging is also a central theme in the Genetic Frontotemporal Dementia Initiative , outlined today by Dr Jonathan Rohrer from UCL. This collaborative programme is following hundreds of people whose families are affected by inherited forms of FTD. Using brain scans, the team has already identified particular networks of nerve cells in the brain that are affected differently in FTD caused by different faulty genes.
The study is now entering a second phase with the ultimate aim to map what changes happen in brain, blood and spinal fluid in FTD and when. This will be vital for helping to guide future clinical trials of new treatments in the disease.
As the Alzheimers Research UK Drug Discovery Institutes are kick-starting new drug discovery programmes and a Dementia Consortium drug discovery project already focusing on FTD, its vital these kinds of initiatives run hand-in-hand.
- Weve already funded over £11m into FTD, donate to help us fund more.
What Part Of The Brain Does Alzheimers Affect
Alzheimers disease is a progressive disorder that starts and develops gradually in older people. As it progresses, the brain undergoes several changes, affecting memory, language, and thinking skills.
Brain shrinkage to a certain extent is normal in healthy aging but, surprisingly, the neurons are not lost in substantial numbers. In Alzheimers, however, the brain shrinks significantly due to extensive damage and neuron loss. The neurons lose the connections between them, stop functioning, and die since the disease obstructs their critical processes, including communication, metabolism, and repair.
Also Check: How To Deal With Someone With Dementia
Brain Inflammation Harms Cells
Another characteristic of Alzheimers patients brains is inflammation. Many drug trials have focused on eliminating the two proteins, beta-amyloid and tau, as a possible treatment for the disease and come up short. This has led scientists to believe there may be an alternate issue at work: inflammation of the brain. It may occur because the brains immune system isnt operating correctly whether due to a virus or aging-related stress. This can cause neurons to die in large swaths.
What Happens To The Brain In Alzheimer’s Disease
The healthy human brain contains tens of billions of neuronsspecialized cells that process and transmit information via electrical and chemical signals. They send messages between different parts of the brain, and from the brain to the muscles and organs of the body. Alzheimers disease disrupts this communication among neurons, resulting in loss of function and cell death.
Also Check: How Do You Test For Dementia
Key Biological Processes In The Brain
Most neurons have three basic parts: a cell body, multiple dendrites, and an axon.
- The cell body contains the nucleus, which houses the genetic blueprint that directs and regulates the cells activities.
- Dendrites are branch-like structures that extend from the cell body and collect information from other neurons.
- The axon is a cable-like structure at the end of the cell body opposite the dendrites and transmits messages to other neurons.
The function and survival of neurons depend on several key biological processes:
Neurons are a major player in the central nervous system, but other cell types are also key to healthy brain function. In fact, glial cells are by far the most numerous cells in the brain, outnumbering neurons by about 10 to 1. These cells, which come in various formssuch as microglia, astrocytes, and oligodendrocytessurround and support the function and healthy of neurons. For example, microglia protect neurons from physical and chemical damage and are responsible for clearing foreign substances and cellular debris from the brain. To carry out these functions, glial cells often collaborate with blood vessels in the brain. Together, glial and blood vessel cells regulate the delicate balance within the brain to ensure that it functions at its best.
Discovery Of New Dementias With Symptoms Like Alzheimers
Sometimes what looks like Alzheimers disease is not, as findings from both the ROSMAP and 90+ studies show. Peter T. Nelson, M.D., Ph.D., professor of pathology and laboratory medicine at the University of Kentucky , and neuropathology core leader at the UK Sanders Brown Center and Alzheimers Research Disease Center, is conducting NIA-funded research to identify and understand how these other brain pathologies contribute to dementia.
Over multiple years, neuropathologists noticed, during autopsy, that the brains of many older adults had tau tangles like those seen in Alzheimers. However, unlike Alzheimers disease, these brains lacked amyloid plaques. In 2014, Nelson, in collaboration with NIA and a team of top Alzheimers researchers, named this pathology PART, or primary age-related tauopathy.
Continuing research indicates that PART is a relatively common pathology that develops as people age. Alone, PART leads to mild cognitive decline that occurs at a slower rate than Alzheimers disease. However, when combined with other pathologies, such as Lewy bodies, PART can increase the severity of memory and thinking problems. While the tau tangles of PART pathology are like what is seen in Alzheimers, PART pathology is found in different parts of the brain. Researchers are actively studying these differences to both understand how PART affects cognition and to identify biomarkers that could distinguish PART from early Alzheimers.
Also Check: What Can You Do To Help Prevent Dementia
Tangles And Cell Death
In normal brain tissue, a protein called tau stabilizes microtubules. Microtubules are key parts of cell structure.
In a diseased brain, protein strands, or threads, become tangled. As a result, the brain system of transporting cell nutrients along parallel structures which can be compared to railroad tracks falls apart.
Without these critical nutrients, brain cells die.
Memory and thinking depend on the transmission of signals across 100 billion neurons in the brain.
AD interferes with this cell signal transmission. It also affects the activity of brain chemicals called neurotransmitters.
The scrambled chemistry produces flawed signaling, so the brains messages are lost. This impacts the ability to learn, remember, and communicate.
Microglia are a type of cell that initiate immune responses in the brain and spinal cord. When AD is present, microglia interpret the beta-amyloid plaque as cell injury.
The microglia go into overdrive, stimulating inflammation that further damages brain cells.
Some AD research focuses on how this inflammatory response can be reduced or controlled.
Final Stages Of Alzheimer’s
In the final stages, people may lose the ability to feed themselves, speak, recognize people and control bodily functions. Memory worsens and may become almost non-existent. Constant care is typically necessary. On average, those with Alzheimer’s live for 8 to 10 years after diagnosis, but this terminal disease can last for as long as 20 years.
Also Check: How Do Social Workers Help Alzheimer’s Patients
The Effects Of Alzheimer’s On The Brain
Heather Mercer is native to Northwest Ohio and graduated from Loma Linda University with two doctorate degrees . She is currently a professor at Owens Community College, as well as a fact-checker for Verywell Health. She has gained experience in a variety of settings, ranging from corporate wellness and preventive medicine, to mental health, chronic disease, and end-of-life care.
Alzheimer’s disease is a degenerative disease of the brain. Understanding how the anatomy of the Alzheimer’s brain differs from a normal brain gives us insight. It can help us cope better with the changes that happen to our loved ones as a result of this debilitating disease.
In Alzheimer’s disease, the appearance of the Alzheimer’s affected brain is very different to a normal brain. The cerebral cortex atrophies. That means that this area of the brain shrinks and this shrinkage is dramatically different from the cerebral cortex of a normal brain. The cerebral cortex is the outer surface of the brain. It is responsible for all intellectual functioning. There are two major changes that can be observed in the brain using magnetic resonance imaging :
- The amount of brain substance in the folds of the brain is decreased
- The spaces in the folds of the brain are grossly enlarged.
Brain Changes In Early Alzheimers
The very first evidence of Alzheimers may be seen in the brain as much as twenty years before diagnosis. Abnormal patches and tangles of proteins start to form in the areas of the brain that control thought, planning and memory. These affect the connections between the brain cells, eventually causing the destruction of the cells.
One of the first areas damaged is the part of the brain called the hippocampus. This is the area important for learning things and making new memories. This is why people with early dementia may struggle to retain new information. It is common for someone to clearly recall all the details of a childhood party but be unable to remember what they had for lunch, or a phone-call they received that morning.
Damage to the left hemisphere of the brain can cause problems with language, meaning that many people, at this stage, may struggle to find the right word for something.
Read Also: What To Put On Alzheimer’s Medical Bracelet
Distribution Of Amyloid Plaques
In AD, senile plaque and neurofibrillary tangle formation tend to form neuroanatomically in stereotypic patterns, which has led to several staging schemes . One of the first attempts to stage amyloid plaques in AD was proposed by Heiko and Eva Braak. A three stage scheme was proposed, with the basal frontal and temporal lobes affected in Stage A, extension into the association neocortices and hippocampus in Stage B, and finally reaching primary cortices, subcortical nuclei and cerebellum in Stage C . Within the cortical layers, layers III and Va are most affected, layers IV and Vb were affected less, and other layers were relatively spared . More recently, the Braak plaque staging has been modified by his research associate, Dietmar Thal, and this scheme of amyloid phases using highly sensitive silver staining or A antibodies has been adopted by NIA-AA and BrainNet Europe . In Thal Phase 1 the neocortex is involved, expanding to the allocortex in Phase 2, subcortical nuclei, including the striatum, in Phase 3, with involvement of brainstem in Phase 4 and cerebellum in Phase 5 . For practical work, phases 14 can be determined by amyloid deposition in the medial temporal lobe . It is not unusual for neurologically normal patients to have Thal 13 amyloid phase as shown in Table .
Alzheimers Disease Is An Irreversible Progressive Brain Disorder That Slowly Destroys Memory And Thinking Skills And Eventually The Ability To Carry Out The Simplest Tasks In Most People With Alzheimers Symptoms First Appear In Their Mid
Alzheimers disease is currently ranked as the sixth leading cause of death in the United States, but recent estimates indicate that the disorder may rank third, just behind heart disease and cancer, as a cause of death for older people.
Alzheimers is the most common cause of dementia among older adults. Dementia is the loss of cognitive functioningthinking, remembering, and reasoningand behavioral abilities to such an extent that it interferes with a persons daily life and activities. Dementia ranges in severity from the mildest stage, when it is just beginning to affect a persons functioning, to the most severe stage, when the person must depend completely on others for basic activities of daily living.
The causes of dementia can vary, depending on the types of brain changes that may be taking place. Other dementias include Lewy body dementia, frontotemporal disorders, and vascular dementia. It is common for people to have mixed dementiaa combination of two or more disorders, at least one of which is dementia. For example, some people have both Alzheimers disease and vascular dementia.
Alzheimers disease is named after Dr. Alois Alzheimer. In 1906, Dr. Alzheimer noticed changes in the brain tissue of a woman who had died of an unusual mental illness. Her symptoms included memory loss, language problems, and unpredictable behavior. After she died, he examined her brain and found many abnormal clumps and tangled bundles of fibers .
Changes in the Brain
Genetics
Read Also: How To Convince Someone To Get Tested For Dementia
What Are The Symptoms Of Alzheimers Disease
AD is a type of dementia, a term used to describe a condition that involves memory loss and other cognitive difficulties. There are a number of different types of dementia, howevereach with its own causes and specific symptom profile. AD is just one variation.
The best-recognized sign of mental decline in AD is problems with memory. In the early stages of the disease, this often manifests as difficulties creating new memories, and problems are especially noticeable with , or memories about information and events . Early on, patients are typically able to maintain older memories and non-declarative memories. Over time, however, all memory can be affected, and even the most enduring memories may deteriorate.
But memory deficits are just one aspect of AD symptomatology. Patients can also experience problems with communication, and the ability to read and write may be impaired. Unpredictable mood disturbances, ranging from apathy and depression to angry outbursts, can occur. Thinking often becomes delusional, and a substantial subset of patients even experience visual hallucinations.
Its not just cognition thats affected, though. Movement is hindered, causing patients to begin to lose mobility and have trouble performing even the simplest acts of self-care. Basic motor functions like chewing and swallowing become faulty, and incontinence eventually occurs.
Why Do Protein Deposits Form In The First Place
Researchers want to know why these protein aggregates form in the first place, how they distribute in the brain, how their signalling works, and how they and their precursors cause neurodegeneration.
A range of theories have been put forward to explain what kickstarts damaging protein aggregation. In the case of Alzheimers, this includes problems with the way oxygen is metabolised in brain cells and the movement of internal cell contents. The brains response to inflammation, and its systems for clearing waste could also play a role.
One main theory is that once amyloid-ß begins to accumulate, it then promotes the build-up of tau. But the relationship is not simple, because tau also has a role in influencing the toxic effects of amyloid-ß.
Although some genetic risk factors for dementias have been identified, particularly for Alzheimers disease , we still dont know how these act to influence protein aggregation and cause degeneration. This is a key area of research focus, and knowing the answers to these questions is crucial to the prevention and treatment of dementia.
Don’t Miss: Why Is It Called Alzheimer’s
Other Types Of Dementia
Alzheimers is not the only type of dementia. Other types of dementia affect the brain in slightly different ways.
For example, fronto-temporal dementia affects the frontal or temporal lobes of the brain. This initially affects behavior, speech, or both. As the disease progresses, it may look more like Alzheimers, causing memory loss and other forms of brain dysfunction.
To differentiate Alzheimers from other dementias, a doctor may look at a combination of symptoms and brain changes.
Dementia Symptoms And Areas Of The Brain Dementia Symptoms And Areas Of The Brain
Knowing how different types of dementia affect the brain helps explain why someone with dementia might behave in a certain way.
Dementia and the brain
Until recently, seeing changes in the brain relied on studying the brain after the person had died. But modern brain scans may show areas of reduced activity or loss of brain tissue while the person is alive. Doctors can study these brain scans while also looking at the symptoms that the person is experiencing.
The most common types of dementia each start with shrinkage of brain tissue that may be restricted to certain parts of the brain.
Don’t Miss: What Type Of Doctor Deals With Alzheimer’s