If each neuron produced random noise that is independent from what its neighbor neuron is doing, the brain cell on the receiving end could simply pool all incoming signals and average out the noise. Reynolds compares it to diversifying risk in a stock portfolio: "If you have a portfolio of stocks whose prices vary independently, you can reduce fluctuations by dividing your investment among a large pool of stocks."

Unfortunately, for neurons this option is off the table since most of the brain's background noise originates in waves of spontaneous nerve signals that undulate across a large population of brain cells. Says Mitchell, "These fluctuations can't be simply averaged out since they are shared across the neural population." To extend the investment analogy, say you put your money into a pool of real estate investments. Your portfolio is subject to fluctuations in the real estate market - the correlated fluctuations in the values of individual investments - no matter how big the pool.

But an interesting thing happened when the researchers measured the activity of a large population of visual neurons in animals trained to play a simple video game that required rapt attention to a visual stimulus on the screen. The internal fluctuations or shared noise quieted down, increasing the visibility of the incoming sensory information.

"Attention is an essential part of perception," says Reynolds. "Brain disorders in which attention fails therefore have devastating effects. Gaining insight into the neural mechanisms of attention is essential if we are to understand the causes of these perceptual deficits and find ways to treat them. By revealing a major new attentional mechanism, Jude has taken a major step toward understanding the neural mechanisms of conscious awareness."

Source: Salk Institute