Focusing attention on a visual stimulus causes neurons in the visual cortex to fire in unison. The synchronous firing appears to help tune out distractions and focus our attention. A new study suggests that the prefrontal cortex may initiate this neural activity.
In the study, published May 29 in Science, neuroscientist Robert Desimone and colleagues from the McGovern Institute for Brain Research at the Massachusetts Institute of Technology used electrodes to measure the brain activity of two monkeys engaged in an attention task. They discovered synchronous firing of neurons in the frontal eye field area of the prefrontal cortex and in a part of the visual cortex called the V4 ventral stream area.
The response in the frontal eye field occurred significantly earlier than in area V4, suggesting that the activity in the visual cortex was prompted by the activity in the prefrontal cortex. Study researchers also found an increase in high-frequency gamma oscillations between the two, indicating that the two regions were communicating. Such oscillations in the prefrontal cortex have been shown to accompany a variety of cognitive processes, including attention.
The results came as a surprise. “We certainly had reasons to believe the prefrontal cortex played an important role in controlling attention in the visual cortex, but we had no idea it actually synchronized the activity there,” Desimone says.
In addition, the exact time it took the two brain areas to communicate was reflected by the time difference in the onset of neural activity in each area— another surprise. The researchers postulate that this may be a general feature of communication across brain regions. If so, the finding could open up new approaches to treating disorders that affect attention, from attention-deficit/hyperactivity disorder to schizophrenia.
*A shorter version of this item appears in the print edition of BrainWork.