Faster Scanning Divulges New Differences Between Active and Resting Brain

Researchers used a quicker scan method and tracked brain activity in volunteers at rest and while they watched a movie to gain new insights into how brain regions work with each other in cooperative groups called networks.

Scientists are aware of several resting-state brain networks, groups of different brain regions whose activity levels rise and fall in sync when the brain is at rest. They previously used fMRI to locate and characterize these networks, but the relative slowness of this method limited the observations to activity that changes every 10 seconds or so.

A surprising result from fMRI was that the spatial pattern of activity, or topography, of these brain networks is similar at rest and during tasks.

“Brain activity occurs in waves that repeat as slowly as once every 10 seconds or as rapidly as once every 50 milliseconds,” said senior researcher Maurizio Corbetta, MD. “This is our first look at these networks where we could sample activity every 50 milliseconds, as well as track slower activity fluctuations that are more similar to those observed with functional magnetic resonance imaging (fMRI). This analysis performed at rest and while watching a movie provides some interesting and novel insights into how these networks are configured in resting and active brains.”

Understanding of how brain networks function is important for better diagnosis and treatment of brain injuries, says Corbetta.

Magnetoencephalography vs. Functional Magnetic Resonance Imaging

In contrast to fMRI, magnetoencephalography (MEG) can detect activity at the millisecond level, letting scientists examine waves of activity in frequencies from slow, 0.1-4 cycles per second, to greater than 50 cycles per second.

“Interestingly, even when we looked at much higher temporal resolution, brain networks appear to fluctuate on a relatively slow time scale,” said first author Viviana Betti, PhD, of University of Chieti, Italy,. “However, when the subjects went from resting to watching a movie, the networks appeared to shift the frequency channels in which they operate, suggesting that the brain uses different frequencies for rest and task, much like a radio.”

The study “gives us a hint of how cognitive activity dynamically changes the resting-state networks,” Corbetta said. “Activity locks and unlocks in these networks depending on how the task unfolds. Future studies will need to track resting-state networks in different tasks to see how correlated activity is dynamically coordinated across the brain.”

Reference:

Viviana Betti, Stefania Della Penna, Francesco de Pasquale, Dante Mantini, Laura Marzetti, Gian Luca Romani, Maurizio Corbetta.
Natural Scenes Viewing Alters the Dynamics of Functional Connectivity in the Human Brain.
Neuron, 2013; DOI: 10.1016/j.neuron.2013.06.022