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How the brain copes with ageing

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How the brain copes with ageing

New York, Sep 16 (IANS) As the brain begins to shrink with age, it increases communication between the two brain hemispheres to help older people compensate for the negative aspects of ageing, new research has found.

“This study provides an explicit test of some controversial ideas about how the brain reorganises as we age,” said lead author Simon Davis, assistant professor at Duke University, Durham, North Carolina.

“These results suggest that the ageing brain maintains healthy cognitive function by increasing bilateral communication,” Davis added.

For the study published in the journal Human Brain Mapping, the researchers used a brain stimulation technique known as transcranial magnetic stimulation (TMS) to modulate brain activity of healthy older adults while they performed a memory task.

When researchers applied TMS at a frequency that depressed activity in one memory region in the left hemisphere, communication increased with the same region in the right hemisphere, suggesting the right hemisphere was compensating to help with the task.

In contrast, when the same prefrontal site was excited, communication was increased only in the local network of regions in the left hemisphere.

This suggested that communication between the hemispheres is a deliberate process that occurs on an “as needed” basis.

Furthermore, when the authors examined the white matter pathways between these bilateral regions, participants with stronger white matter fibres connecting left and right hemispheres demonstrated greater bilateral communication, strong evidence that structural neuroplasticity keeps the brain working efficiently in later life.

“Good roads make for efficient travel, and the brain is no different. By taking advantage of available pathways, ageing brains may find an alternate route to complete the neural computations necessary for functioning,” Davis said.

These results suggest that greater bilaterality in the prefrontal cortex might be the result of the ageing brain adapting to the damage endured over the lifespan, in an effort to maintain normal function.

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Human brains not as exceptional as thought: Study

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Brain
Human brains not as exceptional as thought: Study

NewYork, November 1,2017: When it comes to brainpower, humans may not be as exceptional as we like to think as researchers have found that some animals including the world’s smallest monkeys devote a large proportion of their body energy to the brain, just as we do.

Even the ring-tailed lemur and the tiny quarter-pound pygmy marmoset, the world’s smallest monkey, devote as much of their body energy to their brains as humans do, said the study published in the Journal of Human Evolution.

 “We don’t have a uniquely expensive brain,” said study author Doug Boyer, Assistant Professor at Duke University in Durham, North Carolina, US.

“This challenges a major dogma in human evolution studies,” Boyer added.

The study compared the relative brain costs of 22 species.

The results suggest that the ability to grow a relatively more expensive brain evolved not at the dawn of humans, but millions of years before, when our primate ancestors and their close relatives split from the branch of the mammal family tree that includes rodents and rabbits, said Arianna Harrington from Duke University.

Previous studies calculated the amount of energy needed to fuel a brain based on neuron counts.

But because the current study’s method for estimating energy use relies on measurements of bone, rather than soft tissue such as neurons, it is now possible to estimate brain energy demand from the fossilised remains of animals that are extinct too, including early human ancestors, according to the researchers.

“All you would need to take the measurements is an intact skull and some of the neck vertebrae,” Harrington said.(IANS)