While some areas of the brain activate, or turn on their activity, when a person tries to remember something, other areas deactivate, or suppress their activity. Results from this study showed that along the spectrum from healthy people at low risk, to people with mild memory problems, to patients with Alzheimers disease, there was increasingly impaired activation in the MTL, an area of the brain associated with episodic memory that normally turns on during a memory task. More surprising, however, was increasingly impaired deactivation in the posteromedial cortices (PMC), an area recently implicated with personal memory that normally suppresses its activity during a memory task. The magnitude of deactivation in the PMC was closely related to the level of memory impairment in the patients and significantly correlated with their neuropsychological testing scores.
While previous studies have suggested that MTL activation may be a possible marker of Alzheimers, based on the findings, Dr. Petrella and colleagues concluded that, compared to activation in the MTL, deactivation in the PMC may represent a more sensitive marker of early Alzheimers disease.
In other words, the brain not only loses its ability to turn on in certain regions, but also loses its ability to turn off in other regions, and the latter may be a more sensitive marker. These findings give us insight into how the brains memory networks break down, remodel and finally fail as memory impairment ensues, Dr. Petrella said.
The researchers hope that fMRI will eventually help to identify patients at risk for developing Alzheimers disease.
The next step is to conduct a large, multicenter study to see if fMRI can be combined with other imaging and genetic tests to scan for future disease, said study co-author P. Murali Doraiswamy, M.D., chief of the Division of Biological Psychiatry and Alzhe
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Radiological Society of North America