Learn Your Lobes: An Introduction to the Brain
For the last year, I have blogged about Alzheimer’s disease. I have discussed the diagnosis, the treatment, driving issues and many related topics. One thing I have not done is put Alzheimer’s disease in the context of the body part that is failing in this disease, the brain. For many people this topic may sound intimidating or perhaps unrelated to the disease. However, I will attempt to make this discussion relevant and interesting.
First some background information. One could argue that the brain of a human is the most complex of all organs. It hears, sees, feels, tastes, commands the limbs, talks, reads, writes, makes decisions and accomplishes numerous other functions. Most importantly for our interests, it is the organ of memory. Your ears may hear the concert; your eyes may see the famous painting; your fingers may feel the silk nightgown; your nose may smell that skunk that you just ran over with your car and your mouth may taste that delicious chocolate, but only your brain remembers what the experience was like, where it happened and the numerous other details involved. So, although the sensory abilities described above are not typically affected by Alzheimer’s disease, the memory of these experiences and perhaps the appreciation of them can be markedly affected.
Let’s briefly discuss some of the impairments that occur in Alzheimer’s disease.
In one of my former blogs, I listed and discussed amnesia, agnosia, apraxia, spatial impairment, and impairment judgment as cognitive functions that could be disturbed in Alzheimer’s disease.
Not every person is affected equally and some of these dysfunctions may be more disruptive than others, depending on the person affected.
For example, severe apraxia which is a disorder of learned motor function, might have an impact on a carpenter greater than it would on a banker.
Let’s start our brain discussion with amnesia. Amnesia is loss of memory ability. Our brains rely on many different areas of the brain, but the most important one affected in Alzheimer’s disease is the hippocampus. It is called the hippocampus because viewed in cross-section, it looks a little like a sea horse. There are two hippocampi, one on each of the brain. They are located deep in the temporal lobes. The temporal lobes are large structures on each side of the brain beneath the skull. They are shaped a little like very fat sausages and lie beneath that region of the skull named the temporal bone. They extend for about the length of a short hand from behind the eyes to behind the ears. These lobes, especially the hippocampal areas in them, are affected early in Alzheimer’s disease. They become smaller (atrophied) and begin to fail in their function of memory.
The temporal lobes are one of four sets of left and right brain lobes. The others are the frontal, which in case you can’t guess, are in the front of the brain, the occipital, which are in the back of the brain and the parietal, which are behind the frontal, above the parietal and in front of the occipital.
The parietal lobes are also commonly affected early in Alzheimer’s disease. These regions of the brain are important for integrating information. As such, it is damage to these lobes that can produce, apraxia (trouble with complex movements), agraphia (trouble with writing and spelling), agnosia (trouble with knowing what things are), aphasia (trouble with coming up with words and other features of speech), acalculia (trouble with calculations) and spatial disorientation (tendency to get lost). It is some of these impairments that can be very disruptive to patients’ activities of daily living.
The frontal lobes are important for decision making and have a major role in personality. They may also be affected in Alzheimer’s disease and when disordered the patients may begin to seem very unlike themselves. Personality changes may occur early or late in Alzheimer’s disease, but when they occur, can be as equally devastating as memory loss. Judgment and insight may also be affected by damage to the frontal lobes.
In summary, Alzheimer’s disease may be viewed as a "multi-focal" disorder as it affects the frontal, parietal and temporal lobes of the brain and causes multiple types of brain, and therefore cognitive dysfunction.
Dr. David Roeltgen is a neurologist who wrote about Alzheimer’s for HealthCentral. He is an Associate Professor of Neurology at Cooper University Hospital, in Camden, New Jersey. He has experience in both private practice and academic neurology. He has continued or developed interests and done research on disorders of cognition, including Alzheimer’s, dementia, headache and Parkinson’s disease.