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The human brain can concentrate on externally focused tasks, such as answering a question or solving a puzzle, or internally focused tasks, such as daydreaming. Until recently, these activities were believed to be mutually exclusive. That is, activating one suppressed the other. But now, evidence suggests that engaging the internally focused brain network actually improves performance of the externally focused network.
A recent study, published in the Journal of Neuroscience, reports that the default network – the one responsible for internal focus such as mind-wandering and reminiscing – supports task performance of executive control regions of the brain.
The researchers conducted functional neuroimaging of 36 adults who were shown a series of pictures of famous and non-famous faces. The participants were asked to identify and match faces that that appeared earlier in the sequence. This activity engaged the default network, since it involved reminiscing, but also involved a goal-oriented task. The authors concluded that better performance on the cognitive task was associated with increased activation of the default network.
This conclusion is only applied to tasks that support each other – recognizing faces about which a participant was reminiscing. It remains unclear if internally directed thought that is contextually irrelevant to the task at hand will improve externally focused cognition.
Neuroscientists have long believed that the dorsal attention network (the network that directs externally directed cognition) and the default network are competitive. The dorsal attention network controls task-based cognitive performance, and the default network that controls internally focused thought, such as spontaneous thought, stimulus-independent thought, mind-wandering and autobiographical planning, is thought to be active when the brain is at rest. Scientists hypothesized that the default network needed to be suppressed when the attention network was active in order to prevent interference.
Now, neuroscientists are realizing that the networks may not be entirely independent or competitive. They likely work together more than previously believed, and their respective performances are modulated by other brain networks.
The human mind likes to wander, and undirected thought forms a large part of our mental experience. Likely, our brain integrates external information and cognition with internal focus to determine personal meaning, such as knowledge about past experiences, motivations, future plans, and social context. According to the authors of the recent study, the default network and the attention network (and, probably, other networks) continuously interact to reconcile external goals with internal meaning.
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