It has long been known that neurons in human brains fire in unison when a person pays attention. Now scientists have located the brain centre that controls this neural chorus.
MIT neuroscientists have found that neurons in the prefrontal cortex - the brain's planning centre - fire in unison and send signals to the visual cortex to do the same, generating high-frequency waves that oscillate between these distant brain regions like a vibrating spring.
The waves, also known as gamma oscillations, have long been associated with cognitive states like attention, learning, and consciousness.
"We are especially interested in gamma oscillations in the prefrontal cortex because it provides top-down influences over other parts of the brain. We know that the prefrontal cortex is affected in people with schizophrenia, ADHD and many other brain disorders, and that gamma oscillations are also altered in these conditions.
Our results suggest that altered neural synchrony in the prefrontal cortex could disrupt communication between this region and other areas of the brain, leading to altered perceptions, thoughts, and emotions," said senior author Robert Desimone.
The researchers explained this neural synchrony by using the analogy of a crowded party with people talking in different rooms-if individuals raise their voices at random, the noise just becomes louder.
But if a group of individuals in one room chant together in unison, the next room is more likely to hear the message, and if the people in the other room respond in the same way, the two rooms can communicate.
In the study, the researchers looked for patterns of neural synchrony in two "rooms" of the brain associated with attention - the frontal eye field (FEF) within the prefrontal cortex and the V4 region of the visual cortex.
By training two macaque monkeys to watch a monitor displaying multiple objects, and to concentrate on one of the objects, the researchers monitored neural activity in both the above regions of the brain.
They analysed the timing of the neural activity and found that the prefrontal cortex became engaged by attention first, followed by the visual cortex-as if the prefrontal cortex commanded the visual region to snap to attention.
The delay between neural activity in these areas during each wave cycle revealed the speed at which signals travel from one region to the other, which indicated that the two brain regions were talking to one another.
The study has been published in the journal Science.