Spinning brain waves help the mind refocus after distraction

Summary: Neuroscientists have discovered that when the brain is distracted, coordinated “rotating” waves of neural activity help it refocus. Using electrical recordings in animals, the team found that neurons in the prefrontal cortex synchronize in circular patterns (like starlings in flight) to recover from cognitive interruptions.

When this rotation came full circle, performance remained excellent; when he fell short, errors came. The findings suggest that the brain uses these energy-efficient traveling waves as a natural analog computing system to restore concentration after interruptions.

Key facts

Rotational recovery: Rotating neural waves in the prefrontal cortex help the brain regain focus after a distraction. Predictive power: complete circular rotations correlated with correct task performance; incompletes predicted errors. Analog efficiency: The study suggests that the brain uses analog-type traveling waves to perform calculations efficiently.

Source: MIT Picower Institute

As sure as the brain is prone to distraction, it can also refocus on the task at hand.

A new animal study by scientists at MIT’s Picower Institute for Learning and Memory shows how that appears to happen: Coordinated neural activity in the form of a spinning brain wave brings thinking back on track.

“The spinning waves act as shepherds directing the cortex toward the correct computational path,” said the study’s senior author, Earl K. Miller, the Picower Professor in the Picower Institute and the Department of Brain and Cognitive Sciences at MIT.

Tamal Batabyal, a postdoctoral fellow at the Picower Institute, is the lead author of the study published Nov. 3 in the Journal of Cognitive Neuroscience.

mathematical ‘rotations’…

In the study, animals were given a visual working memory task, but sometimes experienced one of two different types of distractions while trying to remember an object they saw.

As expected, the distractions affected the animals’ performance on the task, sometimes causing them to make errors or at least slowing down their reaction time when the task required them to act.

Meanwhile, the researchers monitored the electrical activity of a sample of hundreds of neurons in the prefrontal cortex, a brain region responsible for higher-level cognition.

To analyze how neural activity varied as the animals performed the task over hundreds of sessions (with or without distractions and in cases where the animals performed well or not so well), the researchers employed a mathematical and visualization measure that measures their degree of coordination over time called “subspace coding.” Subspace coding shows that the activity of cortical neurons is highly coordinated.

“Like starlings murmuring in the sky,” Miller said.

After the distraction, a rotating movement occurred in subspace, as if the “birds” were gathering again in circles after an interruption in their formation. In other words, Miller said, the spinning seemed to represent the recovery of their active state after the distraction.

In fact, the rotations predicted the animal’s performance on the task. In cases where the distraction did not cause an error, the neural data showed a full circle, indicating that recovery was complete.

In cases where distractions caused the animals to make mistakes, the trajectory did not complete a circle (by an average of 30 degrees). The trajectory during the wandering sessions showed a slower speed, which could explain the lack of recovery from distraction.

A related finding was that animals recovered better if the time between distraction and the need to act was longer. The data showed that the brain needed that time to mathematically complete the circle and get back on track behaviorally.

The subspace coding data suggested that neurons function in a highly coordinated manner and that this rotational organization helps maintain their concentration. In particular, rotations only occurred if there was a distraction (both styles triggered them) that the animals tried to ignore. The rotations did not occur spontaneously.

…reflect physical rotations

Subspace coding is just an abstract mathematical representation of neural activity over time. But when the researchers looked at direct physical measurements of neural activity, they found that it actually reflected an actual traveling wave spinning through the cortex.

Multiple measurements showed that neuronal spiking activity had a spatial order with continuously changing angles, consistent with a wave of activity rotating through the cortical electrode. In fact, the real wave rotated with the same speed as that represented mathematically in the subspace encoding.

“In principle, there is no reason why a rotation in this mathematical subspace should directly correspond to a rotation on the crustal surface,” Miller said.

“But it is. That suggests to me that the brain is using these traveling waves to do calculations, analog calculations. Analog computing is much more energy efficient than digital computing, and biology favors energy efficient solutions. It’s a different, more natural way of thinking about neural computing.”

In addition to Miller and Batabyal, the paper’s other authors are Scott Brincat, Jacob Donoghue, Mikael Lundqvist, and Meredith Mahnke.

Funding: Funding for the study came from the Office of Naval Research, the Simons Center for the Social Brain, the Freedom Together Foundation, and the Picower Institute for Learning and Memory.

Key questions answered:

About this neuroscience research news

Author: David Orenstein
Source: MIT Picower Institute
Contact: David Orenstein – MIT Picower Institute
Image: Image is credited to Neuroscience News.

Original research: Open access.
“State-space trajectories and traveling waves after distraction” by Earl K. Miller et al. Journal of Cognitive Neuroscience

Abstract

State-space trajectories and traveling waves after a distraction

Cortical activity shows the ability to recover from distractions. We analyzed pFC neural activity of monkeys performing working memory tasks with buffer delay distractions (a cued gaze shift or irrelevant visual input).

After the disruption, there were rotation dynamics between states and spaces that returned to population patterns similar to those before the disruption. In fact, rotations were more complete when the task was performed correctly than when errors were made.

We find a correspondence between state space rotations and traveling waves across the pFC surface.

This suggests a role for emergent dynamics such as state-space rotations and traveling waves in recovery from distractions.