Old age's mental slowdown may be reversible

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Although this article is from 2003, some may find it of interest regarding the

recent posts on Depression & GABA

 

19:00 01 May 2003

http://www.newscientist.com/article.ns?id=dn3686

 

a.. NewScientist.com news service

a.. Shaoni Bhattacharya

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 humans and that people

should not 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.

 

Making sense

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.

 

The researchers measured the neuronal responses in monkeys watching computer

screens displaying various stimuli, such as moving horizontal lines or flashing

dots. Certain neurons should only have been activated in response to specific

stimuli - but this was not the case in the oldest monkeys.

 

When GABA and a GABA-enhancing drug were delivered to the brain cells, the team

saw an improvement in the selectivity of neurons in the older animals within a

couple of minutes.

 

Leventhal believes a lack of GABA as people age will not just affect vision but

all higher brain functions. The team is now exploring the effects of GABA

further and has filed patent applications for this new role of GABA-enhancing

drugs in humans.

 

Journal reference: Science: (vol 300, p 812)

 

 

 

 

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