The brain is able to compensate for the harmful effects of amyloid plaques

One of the biggest mysteries of Alzheimer's disease is that amyloid plaques, which are the "calling card" of the disease, are quite often found in the brains of elderly people who do not have cognitive function disorders.

Researchers from the University of California at Berkeley, working under the leadership of William Jagust, have obtained data indicating that in the early stages of Alzheimer's disease, the human brain can reorganize in a special way, which delays the appearance of symptoms of the disease.

Amyloid plaques are small accumulations of beta-amyloid protein detected in the brain tissue of patients with Alzheimer's disease. However, the theory that these formations are the cause of the development of the disease has caused a lot of controversy. One of the reasons for the existing controversy about this is the presence of amyloid plaques in the brain tissue of many elderly people who do not suffer from dementia.

Using the method of functional magnetic resonance imaging (fMRI), the authors assessed changes in blood flow activity in the brain of three groups of people without symptoms of dementia: 22 young people, 16 elderly people with beta-amyloid plaques in brain tissue, and 33 elderly people without beta-amyloid plaques in brain tissue. During the procedure (inside the tomograph), the participants had to try to remember the maximum number of details in the photographs given to them.

Analysis of the results showed that elderly people with amyloid plaques in the brain tissue had a more pronounced increase in blood flow in the regions of the brain that are usually activated in the process of memorization, compared with the brains of their peers who do not have amyloid plaques. This meant a stronger activation of the corresponding regions of the brain in the presence of amyloid plaques in it.

Images obtained using fMRI. In section A, yellow and red indicate brain areas that are activated during memorization of the "general plan" of the image in question. On section B, yellow and red zones are painted, the increased activation of which accompanies the process of memorizing details.15 minutes after the end of the procedure, participants were provided in writing with 6 details describing the images in the photos they remembered, and asked to rate them as correct or incorrect.

According to the researchers, the level of brain activity in the process of memorization usually corresponds to the number of memorized details.

The obtained results provided the authors with a clear picture: in the case of the presence of amyloid plaques in the brain, the description of the image from memory was the more accurate, the higher the activity of the brain during its examination. This pattern did not apply to participants who did not have amyloid plaques. Based on the observations made, the authors concluded that in the early stages of the disease, the brain retains the ability to increase its activity in order to obtain more information, which can be interpreted as compensatory ability or plasticity.

An image of a brain containing amyloid plaques. Yellow and orange indicate the regions that are characterized by the strongest activation associated with the memorization of small details of the image.It was also found that the more amyloid plaques in the brain, the more pronounced the increase in its activity when performing a memorization task.

However, this pattern did not apply to people with the highest density of amyloid plaques, which indicates the transient nature of the identified phenomenon.

The authors believe that in order to get a more complete picture, it is necessary to conduct a similar experiment involving patients with Alzheimer's disease. This will allow you to find out whether the brain retains such compensatory abilities after the manifestation of the disease. However, conducting such a study is quite problematic, since for patients with cognitive impairments, memorization tasks may not be feasible.

Article by Jeremy A Elman et al. Neural compensation in older people with brain amyloid-b deposition is published in the journal Nature Neuroscience.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of UC Berkeley:
Researchers find neural compensation in people with Alzheimer’s-related protein.

16.09.2014