Old age's mental slowdown may be reversible
more on site....
The research involved monkeys of all ages from four years (left) to 26 years (right)
The slowdown of the brain with old age is due to the lack of a brain chemical which helps neurons to be selective about what they respond to, reveals
research involving the world's oldest monkeys.
Higher brain functions, such as visual recognition or understanding language, require the processing of information in the brain but decline as people
get older. This decline appears to be due to a reduction in a neurotransmitter called GABA, say researchers, which means neurons with specific tasks
become more easily fired by some other stimulus.
Macaque monkeys, with an age equivalent to 90-years in humans, were not as sharp as their younger counterparts in visual tests despite having perfect
eyesight. But when they were given drugs to increase levels of GABA in the brain they improved vastly, say the team.
Delivering GABA calms the neurons down and they become more selective, says neuroscientist Audie Leventhal, at the University of Utah School of
Medicine, who led the study. "They look the same as they did 20 years ago," he says.
Importantly, this suggests that mental decline could be easily treated, says Leventhal. "The fact is all the cells are still there and functioning,
it's a transmitter problem - it's treatable," he told New Scientist.
Tranquillise and sharpen
The study is the first to show that increasing GABA or its effects can reverse mental decline, says Leventhal. But drugs that boost GABA's effects,
such as benzodiazepines, are normally used to tranquillise brain activity not sharpen it.
"It is counterintuitive to say that in order to make Grandpa faster, slow down his brain. Nobody was really thinking about giving tranquillisers to
an 85-year-old to perk him up - which is the implication of the study," he says. But he cautions that the team has done no research in human and that
people should start taking the drugs themselves.
Peter Tyrer, a community psychiatrist at Imperial College London, thinks the findings are "very interesting and novel". He adds that doctors have
sometimes observed a paradoxical effect of benzodiazepine drugs in which rather than calming down, people had become more alert and aggressive.
The reason GABA is so important in the brain is that it works as a "gating" mechanism, explains Leventhal. By helping neurons to respond only to
specific stimuli, it enables the brain to make sense of the vast quantity of incoming information.
However, as people get older the neurons in their brains increasingly fire non-selectively. Interpreting information then becomes like listening to
"whispering in the discotheque as opposed to shouting in a quiet room," Leventhal says.
In the work with the young and old monkeys, his team examined neurons in the part of the brain's vision cortex associated with orientation and shape.
He says this is analogous to the region used for vision in humans.
[Edited on 2-5-2003 by Netchicken]