Reading this story requires you to willfully pay attention to the sentences and to tune out nearby conversations, the radio and other distractions. But if a fire alarm sounded, your attention would be involuntarily snatched away from the story to the blaring sound.
New research from Vanderbilt University reveals for the first time how our brains coordinate these two types of attention and why we may be temporarily blinded by surprises.
The research was published March 7, 2010, in Nature Neuroscience.
"The simple example of having your reading interrupted by a fire alarm illustrates a fundamental aspect of attention: what ultimately reaches our awareness and guides our behavior depends on the interaction between goal-directed and stimulus-driven attention. For coherent behavior to emerge, you need these two forms of attention to be coordinated," Ren- Marois, associate professor of psychology and co-author of the new study, said. "We found a brain area, the inferior frontal junction, that may play a primary role in coordinating these two forms of attention."
The researchers were also interested in what happens to us when our attention is captured by an unexpected event.
"We wanted to understand what caused limitations in our conscious perception when we are surprised," Christopher Asplund, a graduate student in the Department of Psychology and primary author of the new study, said. "We found that when shown a surprise stimulus, we are temporarily blinded to subsequent events."
In their study, the research team asked individuals to detect the letter "X" in a stream of letters appearing on a screen while their brain activity was being monitored using functional magnetic resonance imaging, or fMRI. Occasionally, an image of a face would unexpectedly interrupt the stream.
The surprise caused the subject to completely miss the "X" the first couple of times, despite the fact they were staring directly at the part of the screen on which it appeared. They were eventually able to identify it as successfully as when there was no surprise.
Using fMRI, the researchers found that the inferior frontal junction, a region of the lateral prefrontal cortex, was involved in both the original task and in the reaction to the surprise.
"What we think might be happening is that this brain area is coordinating different attention systems - it has a response both when you are controlling your attention and when you feel as though your attention is jerked away," Asplund said.