The results advance our understanding of how externally and internally focused neural networks interact to facilitate complex thought, researchers said.
"The prevailing view is that activating brain regions referred to as the default network impairs performance on attention-demanding tasks because this network is associated with behaviours such as mind-wandering," said Nathan Spreng from the Cornell University.
"Our study is the first to demonstrate the opposite that engaging the default network can also improve performance," said Spreng, who led the study.    

There are plenty of neuroimaging studies showing that default network activation interferes with complex mental tasks but in most, Spreng said, the mental processes associated with default network conflict with task goals.
If you start thinking about what you did last weekend while taking notes during a lecture, for example, your note-taking and ability to keep up will suffer.     

Spreng and his team developed a new approach in which off-task processes such as reminiscing can support rather than conflict with the aims of the experimental task.
Their novel task, 'famous faces n-back,' tests whether accessing long-term memory about famous people, which typically engages default network brain regions, can support short-term memory performance, which typically engages executive control regions.
While undergoing brain scanning, 36 young adults viewed sets of famous and anonymous faces in sequence and were asked to identify whether the current face matched the one presented two faces back.
The team found participants were faster and more accurate when matching famous faces than when matching anonymous faces and that this better short-term memory performance was associated with greater activity in the default network.
The results show that activity in the default brain regions can support performance on goal-directed tasks when task demands align with processes supported by the default network, the authors said.
The study was published in the Journal of Neuroscience.