An international team of researchers has developed a model simulating the evolution of the brain of patients with Alzheimer's disease. By comparing it to that of people spared from the disease, scientists were able to identify very precisely two key pathology biomarkers: early atrophy of the amygdala and hippocampus, which began in their forties.
Alzheimer’s disease is revealing little by little its fatal tactics. It is most likely a dysfunction of the mechanism which rids the brain cells of defective organelles, the disease is also linked to the atrophy of two specific brain structures: the amygdala and the hippocampus. This is what researchers revealed in a study just published in Scientific Reports.
‘Alzheimer's disease is characterised by changes in the brain, some of which can be measured during the life of the patient, thanks to biomarkers, such as the size of areas of the brain. The study of these biomarkers has shown in particular a decrease in the size of certain brain structures in the case of Alzheimer's, well before the appearance of the first cognitive disorders,’ is explained in a statement published by the CNRS. An observation which however needs to be clarified.
A model simulating the evolution of the brain
The two main questions on which the researchers focused are, on the one hand, the moment at which these famous ‘biomarkers’ begin to evolve differently in a patient with Alzheimer's disease; but also, on the other hand, the way this evolution occurs. To answer them, scientists developed a computer model to simulate the evolution and dynamics of the structures that make up the brain; and this, throughout their life. This is a major step forward, thanks to the analysis of a considerable amount of data.
It is indeed no less than 4,000 brain MRIs, of sick subjects, but also of people spared by the pathology, that the researchers obtained and were thus able to study, thanks to a community platform called volBrain. ‘This free platform allows researchers from all over the world to file structural MRI files and to obtain automated analysis of the volume of scanned brain structures in record time,’ the CNRS statement said.
A model that fills a lack of data
Based on this data, the team of researchers from the Bordeaux Laboratory for Computer Research (CNRS / Bordeaux INP / University of Bordeaux), the Institute of Cognitive and Integrative Neuroscience of Aquitaine (CNRS / University of Bordeaux / EPHE) and the University of Valencia, Spain were able to develop this model. A predictive model, making it possible to compensate for the grey areas in the data. ‘The scientific community does not indeed have images of all periods of life for patients with Alzheimer’s,' said the CNRS.
By comparing the ‘sick’ and ‘healthy’ version of their model, the researchers were able to distinguish the main differences in the evolution of the organ: ‘The study shows an early divergence of the pathological models compared to the normal trajectory of the organ. Ageing before 40 years for the hippocampus, then around 40 years for the amygdala, these two structures atrophy in case of Alzheimer’s,’ the statement said.
Among other dissimilarities, the researchers also noted in patients with Alzheimer's disease ‘an early enlargement of the lateral ventricles, cavities inside the brain,’ the statement said. An enlargement which is certainly early, but also appears in people spared by the disease as they age. ‘[This limits] the interest of this measure at advanced ages, hence the interest of studying the dynamics of biomarkers over a lifetime,’ the statement said. A particularly promising track, then, to finally manage to stop the fatal tactics of this terrible disease.