Alzheimer's ultimately affects all parts of the brain but each person is affected differently as the disease progresses. In part, this is due to the nature and extent of the damage being caused to different areas of the brain.
Each section of the brain is known as a lobe. Here, we examine the effects of damage to the four lobes of the brain: frontal, occipital, parietal, and temporal. Alzheimer's is characterized by predominant damage to the temporal lobe of the brain, and often the extent of damage extends to other areas.
Frontal Lobe Damage
As the name suggests, the frontal lobe of the brain is towards the front. Damage to the frontal lobe can have a number of effects in terms of type and severity. For example, damage might result in a loss of motivation, with the person becoming tired, lethargic, and struggling to get out of bed.
Because the frontal lobes are important for planning and organizing our actions any damage can result in people having to re-learn even the simplest of tasks, which is not really an option in dementia. In Alzheimer's disease, a sign of frontal lobe damage might be seeing someone do the same thing over and over again such as folding a cloth, putting a shoe on and off, or repeatedly picking or touching something with no purpose.
The frontal lobes also have a role in regulating behavior and help prevent us from saying or doing things that might be viewed as threatening, bizarre or generally inappropriate. Damage can result in a range of behaviors such as swearing, undressing, urinating in public, eating and drinking non-food items, and so on.1
Temporal Lobe Damage
The temporal lobes of the brain are essential for memory. Our memory for events is known as episodic memory. Episodic memory helps us to remember things such as where we left the car keys. For this type of memory to work, we need to be able to take in new knowledge and hold on to it, a process known as encoding. Properly encoded information makes the next stage of episodic memory, known as retrieval, a little easier (I left the car keys in the kitchen).
Damage to the temporal lobes and parts of the frontal lobes means that while certain objects might be recognized there is little or no ability to capture new information and remember it later. Because there are different types of memory each is affected differently according to the severity of damage. In such circumstances a person with early memory problems can be helped to recall information with cues such as photographs, or reminding the person of other people who were at a particular event, and so on.
Occipital Lobe Damage
The occipital lobes of the brain are mainly involved in processing information from the eyes. The ability to see objects is achieved by the eyes but the ability to make sense of what we see is the job of the occipital lobe. Sometimes damage or stimulation of the occipital lobes can result in visual hallucinations. For reasons yet to be determined, this area of the brain seems relatively unaffected in Alzheimer's disease.
If damage to the occipital lobes does occur, it may lead to an inability to recognize objects. This, coupled with degenerative processes in other parts of the brain, could explain why clothing, baths, toilets, etc are not perceived for what they are – or their purpose understood.2
Parietal Lobe Damage
The parietal lobes have an important role in integrating our senses. In most people, the left side parietal lobe is thought of as dominant because of the way it structures information to allow us to read and write, make calculations, perceive objects normally, and produce language. Damage to the dominant parietal lobe can lead to difficulty writing and understanding arithmetic and being unable to tell left from right or to point to named fingers.
Damage to the non-dominant lobe, usually the right side of the brain, will result in different problems. This non-dominant lobe receives information from the occipital lobe and helps provide us with a 'picture' of the world around us. Damage may result in an inability to recognize faces, surroundings, or objects (visual agnosia).2 So someone may recognize your voice, but not your appearance (you sound like my daughter, but you're not her).
Also, because this lobe also has a role in helping us locate objects in our personal space, any damage can lead to problems in skilled movements (constructional apraxia) leading to difficulties in drawing or picking objects up.
A Word From Verywell
The symptoms of Alzheimer's disease can be explained by the area of the brain that is damaged. By understanding the pathology or the science behind why your loved one behaves a certain way, forgets things, or has difficulty performing tasks of everyday living, you may be able to cope with their disease better.