Alzheimer's patients can't hide the unimportant
The brain of Alzheimer's patients hardly ignores irrelevant sensory stimuli when solving a visual task. In addition, the neurons in higher brain areas that enable associations are hardly active. This was determined by Alexander Drzezga from the Technical University of Munich in he althy subjects, Alzheimer's patients and people with a mild cognitive disorder (LKS), which often precedes Alzheimer's disease.
The scientists had their subjects solve a visual orientation task, which Alzheimer's patients find difficult even in the early stages of their disease. A positron emission tomograph recorded the brain activity of the participants. The Alzheimer's and LKS patients showed a very high activation of the brain regions responsible for processing sensory stimuli; in higher cortex areas, however, the neurons remained largely silent.
According to the researchers, this reflects the difficulties of Alzheimer's patients in linking perceptions with information stored in the brain. For example, they see a certain face, but cannot form the association "daughter" with it. In he althy subjects, on the other hand, the highest activity was observed in these areas during the processing of the task.
In addition, the Alzheimer's and LKS patients could not block out irrelevant sensory stimuli: during their attempt to solve the visual task, the auditory cortex was activated to an unexpected extent. The more pronounced the symptoms of the disease were, the more intensely the neurons fired there. In the he althy controls, on the other hand, hardly any activity was observed in this brain region - this allowed them to focus their attention on the task without being distracted by unimportant information.
Drzezga concludes from the results that even before the onset of the disease, the ability to ignore irrelevant things is decreasing. With his results, he hopes to enable earlier diagnosis and better research into the effect of new drugs on thought disorders.
