People with early-stage Alzheimer's disease can utilize additional areas in the brain to perform successfully on memory tests, according to a study reported in the Feb. 1 issue of the Journal of Neuroscience.

Previous studies have confirmed that individuals in the early stages of the disease show increased activity in the brain's prefrontal regions when performing cognitive tests. This is the first time that researchers have found a direct link between this compensatory brain activity and successful performance on semantic and episodic memory tests.

People with early-stage Alzheimer's begin to experience problems with their episodic and semantic memory. Semantic refers to the accumulation of general knowledge such as names of countries, famous people and historic events. Episodic refers to events that one experiences throughout life like a visit to the dentist or graduation.

"We found that patients who were able to recruit the prefrontal cortex of the brain to a greater degree than other patients, performed more accurately on memory tests," said lead researcher Dr. Cheryl Grady, senior scientist with the Rotman Research Institute at Baycrest Centre for Geriatric Care in Toronto.

While she cautioned that this compensatory effect does not last forever and diminishes as the disease progresses, Grady said the findings would inspire further research with could foster more effective treatments to extend this compensatory effect and delay the degenerative effects of Alzheimer's for longer periods.

In the study, 12 healthy older adults and 11 older patients with probable early-stage Alzheimer's participated in a series of semantic and episodic memory tasks that were flashed on a computer screen.

Overall, Alzheimer's patients performed less accurately on the semantic and episodic tasks compared to the normal, healthy controls. However, the range of scores was quite large in the Alzheimer group, with some performing poorly and others performing within the normal range.

For Alzheimer's patients who did better on the memory tasks, researchers found that their prefrontal network activity was more expansive. This additional activity occurred in the right frontal and temporoparietal areas and was unique to the Alzheimer's group, according to the researchers.

Other sources: Baycrest Centre for Geriatric Care