Scientists at Washington University School of Medicine in St. Louis, MO, have found that, to allow us to concentrate, we synchronize different regions of our brains in a process that the researchers describe as "roughly akin to tuning multiple walkie-talkies to the same frequency."
Normally, people are able to filter out information from their senses that are not relevant to the immediate task at hand.
The scientists behind this new study - published in the journal Proceedings of the National Academy of Sciences - use the example of a person driving a car, who is able to ignore a ringing cell phone while paying intention to important sights or sounds, such as a deer stepping in front of the car.
But people who have experienced a brain injury or stroke often find it difficult to concentrate on things.
One of the study's authors, Dr. Maurizio Corbetto, says that previously scientists thought that these concentration problems were "thought of as a loss of the resources needed to concentrate on a task."
Dr. Corbetto's team wanted to see how changes within the brain were linked to attention. To investigate this, they first used magnetic resonance imagery (MRI) to scan the brains of volunteers who have epilepsy, mapping areas of the brain that scientists know influence attention.
A grid of electrodes allowed scientists to measure very fast changes within their patients' brains.
The brains of the volunteers were then temporarily implanted with a grid of electrodes. These electrodes allowed the scientists to measure very fast changes in the brain that occur within milliseconds.
The patients were then asked to watch for visual targets on a computer screen. As soon as they saw the targets, the patients would press a button so the scientists would know they had seen them.
Comparing the data from the grid of electrodes with the information on when the patients saw their targets, the scientists noticed that volunteers were more likely to see a target if oscillations within the brain were aligned.
Oscillations from different brain regions are not normally aligned, but when these different areas of the brain synchronized, and became "excited" at the same time, it was easier for the patients to pay attention to visual stimuli.
Another of the study's authors, graduate student researcher Amy Daitch, explains:
"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. If areas of the brain involved in detecting a stimulus are at maximum excitability, you would be much more likely to notice the stimulus."
Brain regions that are not associated with attention would not synchronize or change in excitability during the task. The scientists think that if two regions of the brain responsible for attention are not aligned then it makes it difficult from a brain signal to travel from one region to another.
Using the researchers' metaphor of the brain like multiple walkie talkies, we can imagine how, in people who have experienced brain damage, that these walkie talkies are "out of tune." This lack of consistency in "tuning" prevents one brain region from communicating information to another.
"This study shows that temporal alignment of responses in different brain areas is a very important mechanism that contributes to attention and could be impaired by brain injury," says Dr. Corbetta.
The next step for this research is to investigate methods for bringing the excitement of these brain regions into alignment more rapidly.