By Penny Stern, MD
NEW YORK, Nov 01 (Reuters Health) -- The aging brain appears to be able to reconfigure its circuitry in order to compensate for age-related deficits, a multinational research group reports in the November issue of the journal Current Biology.
Lead author Dr. A.R. McIntosh of the Rotman Research Institute of Baycrest Centre and the University of Toronto in Canada, explained to Reuters Health how his team reached its conclusions. "We used a very simple visual memory task to test what brain circuits supported memory performance. This task was chosen because there is no age difference in performance," he said.
What does differ, McIntosh continued, is the specific brain circuitry engaged to complete the memory task. "There are a collection of regions near the back and sides of the brain -- (the) occipital and temporal cortex -- that form a strong circuit in young (study) subjects," he noted. In contrast, older brains use other brain areas such as the hippocampus and the dorsal prefrontal cortex, which are usually associated with more complex memory operations, like learning lines of a play or navigating around a new place, according to McIntosh.
"It is possible," he suggested, "that the changes in more complex memory in the elderly reflect the fact that (these areas) are recruited to support more simple memory functions and are (therefore) not available to carry out the more demanding complex memory operations."
The study findings may turn a long-held belief on its ear, however, since conventional wisdom holds that "once you are over about 18 years old, your brain is hardwired and if you lose something through damage, disease or normal deterioration, you are left with a 'hole' and that's it," McIntosh told Reuters Health. "What we are seeing is that these brain circuits are not static and can change their... operation throughout life."
The practical implications of these results may include "(using) the information about how the brain adapts to change to evaluate rehab strategies and perhaps suggest new avenues to pursue," McIntosh said. He added that this type of research "is ongoing at the Rotman Research Institute... through a large international collaboration focusing on cognitive rehabilitation." Cognition encompasses brain processes involving thinking, learning, and memory.
Before these still early findings can be applied to any current rehab regimens, McIntosh explained that his group's next step "is to see when the changes in the brain circuits start... (which) means measuring brain-behavior relationships across several points in the lifespan: from children to young adults to middle-aged to old and very old individuals." He concedes that this type of research can be "extraordinarily time-consuming" and that it may be "five years before we get any reasonable results."
Nevertheless, McIntosh believes that while "people should not come away with the impression that the brain has an unlimited or untapped capacity... a cautious optimism about the resiliency of the brain is warranted at present." He concludes that "within some boundaries, there may be room for quite a bit of change in the brain."
