Alzheimer's disease and schizophrenia appear to modern medicine as radically different disorders, but new research suggests they each affect the same areas of the brain.
Oxford University researchers examined 484 healthy subjects, aged 8 to 85, utilizing Magnetic resonance imaging (MRI) scans, studying how human brains change as aging takes place. They found regions of the brain that developed last were also the first to deteriorate with advanced age. These areas help to direct high-level processing of visual, auditory and other sensory information, and are associated with long-term memory and intellectual ability. This part of the brain does not develop until adolescence or early adulthood.
"These complex regions, which combine information coming from various senses, seem to be more vulnerable than the rest of the brain to both schizophrenia and Alzheimer's, even though these two diseases have different origins and appear at very different, almost opposite, times of life," Gwenaëlle Douaud of Oxford University said.
Schizophrenia was once labeled as "premature dementia." Some current-day researchers believed the two conditions were, somehow, linked. However, there was no proof of that until now. When investigators on the study examined MRI scans taken of patients suffering from both conditions, they found the same regions of the brain were affected.
"This large-scale and detailed study provides an important, and previously missing, link between development, aging and disease processes in the brain. It raises important issues about possible genetic and environmental factors that may occur in early life and then have lifelong consequences," Hugh Perry of the Medical Research Council, stated in a press release.
Physicians have few tools available to determine which patients could develop schizophrenia or Alzheimer's.
A scientific idea known as the retrogenesis became popular in the 1880's. This theory postulated that mental abilities decline in the opposite order to which they develop in humans, or during evolution. A healthy adult, the hypothesis argued, could regress to mental abilities of a child, then a baby, and finally, a chimpanzee. This new study could lend credence to that idea from long ago.
Although the idea of brain decline in seniors is not new, this study was the first to recognize a specific network in the organ, dedicated to higher functions, that shows a clear record of damage with advancing years.
Chimpanzees and other primates do not have the same neural center identified in the study, and the animals are free of schizophrenia and Alzheimer's disease. This suggests the longer lifespans and higher brain functioning among humans could play an important role in the presence of the diseases.
The connection between Alzheimer's disease and schizophrenia was detailed in the Proceedings of the National Academy of Sciences (PNAS).
