Researchers at Washington University School of Medicine in St. Louis and the University of Chieti, Italy have found that when a person learns a new task, there is a measurable change in his or her spontaneous brain activity - something that was earlier believed to be "white noise".
It was also found that the degree of change reflects how well subjects have learned to perform the task.
"Recent studies have shown that in the absence of any overt behaviour, and even during sleep or anaesthesia, the brain's spontaneous activity is not random, but organized in patterns of correlated activity that occur in anatomically and functionally connected regions," says senior author Dr. Maurizio Corbetta.
"The reasons behind the spontaneous activity patterns remain mysterious, but we have now shown that learning causes small changes in those patterns, and that these changes are behaviourally important," he added.
Initially, the researchers used functional connectivity magnetic resonance imaging to scan the spontaneous brain activity of 14 volunteers as they sat quietly.
Next, researchers scanned the subjects as they spent one to two hours a day for five to seven days learning to watch a display inside the MRI scanner for the brief presence of an inverted "T" in a specific part of the screen.
The researchers found that two sets of brain areas were particularly active during the task- part of the visual cortex that corresponded to the portion of the visual field where subjects were looking for the "T", and areas in the dorsal part of the brain involved in directing attention to the location on the screen.
After the visual training, scientists again scanned the subjects' brains while they did nothing.
When the subjects rested at the start of the experiment, spontaneous activity in the two parts of the brain that are important to the visual task was either not linked or weakly correlated.
And the two regions involved in the upcoming task were only occasionally active at the same time.
However, after learning, each region was more likely to be active when the other region wasn't.
Subjects who were more successful at the task exhibited a higher degree of this "anti-correlation" between the two regions after learning.
Corbetta suggested that this learning-induced change in the brain's spontaneous activity might reflect what he calls a "memory trace" for the new skill.
The trace makes it easier to use those parts of the brain together again when the same challenge recurs.
"It's as though these two brain systems are learning to get out of each other's way. After learning, the brain can identify the targets at a glance in a way that requires less direct attention and thus less interaction between the regions involved in the task," said Corbetta.
The study has been published online this week in the Proceedings of the National Academy of Sciences.