Brain appears to synchronise the activity of different regions to make it possible for a person to pay attention or concentrate on a task, scientists have found.
Researchers from Washington University School of Medicine in St Louis believe the process, roughly akin to tuning multiple walkie-talkies to the same frequency, may help establish clear channels for communication between brain areas that detect sensory stimuli.
"We think the brain not only puts regions that facilitate attention on alert but also makes sure those regions have open lines for calling each other," said first author Amy Daitch, a graduate student researcher.
People who suffer from brain injuries or strokes often have problems paying attention and concentrating.
"Attention deficits in brain injury have been thought of as a loss of the resources needed to concentrate on a task," said senior author Maurizio Corbetta, the Norman J Stupp Professor of Neurology.
"However, this study shows that temporal alignment of responses in different brain areas is also a very important mechanism that contributes to attention and could be impaired by brain injury," Corbetta said.
Attention lets people ignore irrelevant sensory stimuli, like a driver disregarding a ringing cell phone, and pay attention to important stimuli, like a deer stepping onto the road in front of the car.
To analyse brain changes linked to attention, the scientists used grids of electrodes temporarily implanted onto the brains of patients with epilepsy.
Before grid implantation, the scientists scanned the brains of seven epilepsy patients, using MRI to map regions known to contribute to attention.
With the grids in place, the researchers monitored brain cells as the patients watched for visual targets, directing their attention to different locations on a computer screen without moving their eyes.
When patients saw the targets, they pressed a button to let the scientists know they had seen them.
"We analysed brain oscillations that reflect fluctuations in excitability of a local brain region; in other words, how difficult or easy it is for a neuron to respond to an input," Daitch said.
"If areas of the brain involved in detecting a stimulus are at maximum excitability, you would be much more likely to notice the stimulus," she said.
The researchers' results showed that as patients directed their attention, the brain regions most important for paying attention to visual stimuli adjusted their excitability cycles, causing them to start hitting the peaks of their cycles at the same time.
In regions not involved in attention, the excitability cycles did not change.
The study is published in the Proceedings of the National Academy of Sciences.
