Alzheimer’s disease (AD) is a chronic neurodegenerative disorder and worldwide about 47 million people are affected by this disease. The exact reasons for the occurrence of AD is not yet clearly understood. Genetic issues and deficiency of magnesium have been considered as possible reasons. In a recent study published in Brain, Thomas Cope et al., provide the first evidence that “tau” – an abnormal protein spreads between connected neurons in humans. They have used two advanced brain imaging techniques viz., positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) to identify the presence of tau and how it influences the brain connectivity. PET scan helps to identify the presence of tau and its distribution in different parts of the brain. The ability of fMRI to measure the blood flow in brain in real time helps to identify the connectivity between different regions of the brain. Besides these imaging techniques, they have also used a mathematical technique referred as graph analysis, which splits the brain in to 598 regions of equal size for a better analysis of brain connectivity. A combination of these methods provides meaningful information on the presence of tau, its distribution, the connectivity between different regions of the brain, all of which can very well be correlated to the Alzheimer’s disease.
Fig. 1 (a) Spreading of tau protein; and (b) Artist’s impression of tau spreading between connected neurons (Source: Thomas E. Cope)
Based on the inferences made in their study, Thomas Cope et al., have suggested that tau causes the neurons as well as their connections to die that prevents communication between different regions of the brain. Initially, tau affects the memory centers – entorhinal cortex and hippocampal formation while with an increase in time, difficulty in thinking and behavioral activity crops in, leading to a loss of independence. With an increase in the amount of tau, the neurons become less connected and the connections between them becomes random. The study by Thomas Cope et al., provides a clear evidence for the transneuronal spread of tau in humans. Hence, strategies to avoid the spreading of tau will be the next step towards the progress of preventing AD.
T.S.N. Sankara Narayanan
For further details, the reader may kindly refer: Thomas E Cope et al., Tau burden and the functional connectome in Alzheimer’s disease and progressive supranuclear palsy, Brain, awx347, https://doi.org/10.1093/brain/awx347
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