• Alzheimer's disease is characterized by loss of neurons and synapsesin the brain.• Firstly, AD affects the hippocampus and severely before other partsof the cortex . So memory is usually the first thing to start to falter inAlzheimer's disease.• Later, the frontal lobes, cerebral cortex and certain subcorticalregions.• Finally, this loss results in gross atrophy of the affected regions,including degeneration in the temporal lobe and parietal lobe, and themost parts of the frontal cortex.