The attention that’s required to listen to someone in a loud, crowded room or suddenly avoid an obstacle when driving and listening to a program at the same time involves many parts of our brain being on the same page. This neuronal orchestration is almost too complicated to decipher, but thanks to the use of electrodes implanted into the brains of patients, researchers at Washington University School of Medicine were able to study attention deficits by gaining a detailed glimpse into the process of how the brain lets us shift our attention and focus on a task.
This rare, intimate access to a person’s brain activity led the authors to propose that when we attend to a certain type of stimulus, activity in the brain’s sensory areas align themselves much like numerous walkie-talkies dialing into the same radio frequency to maintain clear channels of communication.
“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,” first author, Amy Daitch, explained in a news release. In the journal, Proceedings of the National Academy of Sciences, the authors concluded that this open line of communication is based on synchrony, or as senior author, Maurizio Corbetta, explained, “temporal alignment of responses in different brain areas.” It is possible that this synchrony is temporarily lost when someone injures his or her brain, which would explain the difficulty that concussed athletes have in maintaining attention as well as people with attention deficit disorder.
The study team, which included co-senior author, Eric Leuthardt, took advantage of a grid of electrodes that were implanted in the brains of seven epileptic patients who were about to undergo surgery. As opposed to magnetic resonance imaging (MRI) that detects change in the brain every two to three seconds, electrodes can pick up alterations in activity in a matter of milliseconds. Once the scientists gauged which parts of the patients’ brain were involved with attention, they had the patients direct their attention to specific targets on a screen while their brain activity was monitored.
The researchers focused on how specific brain areas would fluctuate in excitability when the patients suddenly focused on a task. Gauging how easily a brain area responded to an input indicated the likelihood of noticing what was being presented on the screen. Interestingly, they found that when patients focused on a target, the cycles of excitability of various brain regions that are involved with attention would sync up despite acting as if they had nothing to do with each other otherwise. Conversely, the excitability of regions not involved in attention did not change. “If the cycles of two brain regions are out of alignment, the chances that a signal from one region will get through to another region are reduced,” Corbetta explained.
Furthermore, the study authors were able to distinguish different types of concentration — holding versus shifting attention, for example — by finding that they required unique frequencies of synchronized brain activity. They explained that this could “minimize unnecessary cross-talk” when the brain must deal with different types of attention demands.
Source: Daitch A L, Sharma M, Roland J L, et al. Frequency-specific mechanism links human brain networks for spatial attention. PNAS. 2013.