The study of brain functioning in Alzheimer’s disease and normal individuals using positron emission tomography
Functional neuroradiological studies, such as those conducted with positron emission tomography (PET), are a great help in the early diagnosis of Alzheimer’s disease (AD), and provide a new dimension in the study of brain plasticity. There are a great number of studies conducted at rest that have confirmed that temporal-parietal hypometabolism is the most salient characteristic of AD. However, there are a few activation studies, which can measure the response of the brain metabolism to neuropsychological tests of increasing complexity. These studies have shown that with simple memory tests patients with AD and non-demented controls have similar response. However, as the tests became more complex, with the subsequent increase cognitive effort, the patients with AD have a greater activation of the frontal and parietal cortices, bilaterally, compared to controls. These results showed that the AD patients have a normal response (with respect to the activation of episodic memory systems) to their abnormal memory. This indicates that in early stages there is an effort of normal cerebral systems to compensate dysfunctional systems (brain plasticity). We do not know the response of normal system functioning to semantic memory deficits. This will be very important to evaluate drug therapy responses
