There’s a lot going on inside the average brain. And to help manage all the sensory input and though processes, signals, brain networks communicate at different frequencies to avoid traffic jams at busy intersections, a new study suggests.
"We found that different brain networks ticked at different frequencies, like clocks ticking at different speeds," said lead author Joerg Hipp of the University Medical Center at Hamburg-Eppendorf and the University of Tübingen, both in Germany.
Brain studies are commonly done using magnetic resonance imaging, which tracks blood flow. But it can’t measure frequency. "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, said study team member Maurizio Corbetta, a neurologist at Washington University. “We know that some signals in the brain can cycle as high as 500 hertz, or 500 times per second."
The new study used magnetoencephalography (MEG) to analyze brain activity in 43 healthy volunteers. MEG detects very small changes in magnetic fields in the brain that are caused by many cells being active at once. It can detect these signals at rates up to 100 hertz.
"Many neurological and psychiatric conditions are likely to involve problems with signaling in brain networks," Corbetta explained. "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."
The study showed that networks that included the hippocampus, a brain area critical for memory formation, tended to be active at frequencies around 5 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 32 hertz.
These "time-dependent" networks resemble different airline route maps, the researchers explained. They overlap but each ticks at a different rate.
"There have been a number of fMRI studies of depression and schizophrenia showing 'spatial' changes in the organization of brain networks," Corbettta said. "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."
The research will be published May 6 in Nature Neuroscience.