Functional MRI documents neural compensation in AD patients
Researchers at the University of Pennsylvania have found that the brains of patients with Alzheimer's disease compensate in a manner similar to the brains of stroke patients: by reordering functions to relatively unaffected areas.
Alzheimer's disease does not affect the entire brain at one time in an undifferentiated manner. Instead there are regions of relative preservation of neural functioning that can take up functions from affected areas, said Dr. Murray Grossman, an associate professor of neurology at Penn.
Using functional MRI to document neural changes in 11 patients with AD and 16 healthy seniors, Grossman and colleagues employed the knowledge categories of animals and implements to evaluate the effect of Alzheimer's disease on semantic memory.
The fMRI scans indicated reduced activation in the left posterolateral temporal inferior parietal cortex as well as increased activation in left temporal cortex in the AD patients compared with healthy seniors, for both knowledge categories.
"We interpret our observations as suggesting that some of the activations are important for processing this long-term knowledge in semantic memory; that is, helping to organize the feature knowledge represented in long-term memory into a coherent concept," Grossman said.
The group also reported category-specific brain changes in AD patients. Their findings indicate that semantic memory involves category-neutral processes acting on category-specific knowledge. The study appeared in the February issue of Brain: a Journal of Neurology.
"Word meaning is extraordinarily important to humans, and our brains are able to adapt to the unfortunate circumstances of AD and optimize brain functioning so that we can maintain word comprehension as much as possible," Grossman said.
The study results suggest that alternate behavioral strategies could maintain and possibly improve behavior in AD, he said.
"Rather than restricting ourselves to medication intervention, we can also think about therapies that 'exercise' and make use of the novel brain regions activated in AD to help support communication," Grossman said.
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