Multiple channels help brain avoid traffic overload

Washington: Multiple signalling channels within the brain ensure that they don’t overload the organ with too much traffic at their busiest roundabouts and keep it healthy and fit, say researchers.

“Many neurological and psychiatric conditions are likely to involve problems with signalling in brain networks,” says study co-author Maurizio Corbetta, professor of neurology at Washington University.“

Examining the temporal structure of brain activity from this perspective may be especially helpful in understanding psychiatric conditions like depression and schizophrenia, where structural markers are scarce,” adds Corbetta, the journal Nature Neuroscience reports.

Scientists usually study brain networks – areas of the brain that regularly work together – using magnetic resonance imaging, which tracks blood flow.
They assume that an increase in blood flow to part of the brain indicates increased activity in the brain cells of that region, according to a Washington University statement.

“Magnetic resonance imaging is a useful tool, but it does have limitations,” Corbetta says. “It only allows us to track brain cell activity indirectly, and it is unable to track activity that occurs at frequencies greater than 0.1 hertz, or once every 10 seconds. We know that some signals in the brain can cycle as high as 500 hertz, or 500 times per second.”

For the new study, conducted at the University Medical Centre (UMC) at Hamburg-Eppendorf, Germany, researchers used a technique called magnetoencephalography (MEG) to analyse brain activity in 43 healthy volunteers.

MEG detects miniscule changes in the brain’s magnetic fields caused by the simultaneous activity of many cells. It can detect these signals at rates up to 100 hertz.

“We found that different brain networks ticked at different frequencies, like clocks ticking at different speeds,” says Joerg Hipp of the UMC at Hamburg-Eppendorf.

For example, networks that included the hippocampus, a brain area critical for memory formation, tended to be active at frequencies around five hertz. Networks constituting areas involved in the senses and movement were active between 32 hertz and 45 hertz.

Many other brain networks were active at frequencies between eight and 2 hertz. These “time-dependent” networks resemble different airline route maps, overlapping but each ticking at a different rate.

“MEG studies provide a window into a much richer ‘temporal’ structure. In the future, this might offer new diagnostic tests or ways to monitor the efficacy of interventions in these debilitating mental conditions,” Corbetta adds.


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