You're standing at a busy intersection. You see the traffic light change colors, a shop across the street, a woman opening an umbrella and a bus picking up speed. How is it that your brain focuses its attention almost immediately on the bus, drowning out signals associated with the other stimuli in your visual field? Robert Desimone, Pascal Fries and their colleagues at the National Institute for Mental Health provide an answer in today's issue of Science. Neurons engaged in critical taskssuch as registering the presence of a speeding busbegin to fire in sync, they say, which may amplify the importance of their message to other brain areas downstream.
The researchers monitored groups of neurons in the visual processing areas of macaque monkeys as the animals paid attention to one particular stimuli and ignored others around them. They found that neurons devoted to the subject of visual attention synchronized their activity in the gamma range. In contrast, those cells tuned to the distractions showed no coordination. "Disorders of attention are common components of various mental illnesses," Desimone says. "We're beginning to appreciate that the things that go awry in the brain may have to do with the timing of neuronal signalswith the neuronal choir going out of sync." Future studies, he adds, may seek the mechanisms, or conductors, that synchronize the choir.