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Duke University Medical Center
Left Frontal & Left Temporal Atrophy in Early Alzheimer's, July 7, 2006
Memory loss associated with early Alzheimer's disease (AD) may be linked to altered activity in several areas of the brain, according to a study in the July issue of Radiology.
For the first time, researchers at Duke University Medical Center in Durham, N.C., used a special, high-field- strength, functional magnetic resonance imaging (fMRI) scanner to study the brain activity of people with amnestic mild cognitive impairment (MCI), a precursor to AD, and found altered functionality in both the frontal and temporal lobes of the brain.
Previous studies looking at structural changes alone have shown evidence that brain atrophy in the earliest stages of AD tends to be restricted to the temporal lobe, a region critical to long-term memory formation. "Involvement of both the frontal and temporal lobes in the earliest stages of AD suggests the possibility of a breakdown in the communication pathway between these two regions, which partipcate in the formation of short-term and long-term memories, respectively," said lead author Jeffrey R. Petrella, M.D., associate professor of radiology and director of Alzheimer's Disease Imaging Research Laboratory at Duke. "So in many ways the AD brain may be like a computer that is having problems with both its temporary files and its hard-drive files." MCI affects an estimated 15 percent of the elderly population in the United States. Ten to 15 percent of people with MCI develop AD every year compared to one percent of the normal elderly population. Amnestic MCI is characterized by mild memory impairment and is often confused with ordinary age-related forgetfulness. The researchers used 4-Tesla fMRI, which has a very strong magnetic field, to observe the brain activity of 20 elderly patients with amnestic MCI and 20 age-matched controls with no memory impairment during a memory task that tested memory formation and retrieval. "It's like doing a treadmill test for heart patients, except this test puts your brain on a treadmill," Dr. Petrella said. The test required 40 patients to recall names of familiar faces and to learn and recall unfamiliar face-name associations. All patients showed brain activation in several brain regions during the task, but, compared with the controls, the patients with MCI showed a lower level of activation in the prefrontal cortex (during formation and retrieval), left hippocampus (during retrieval) and left cerebellum (during formation) and an increased level of activation in the posterior frontal lobes (during retrieval).