Explorations into the default network of the human brain
The default network, an assembly of functionally connected regions, has been one of the most robustly observed features of the brain and is implicated in a vast array of cognitive abilities, neurological and psychiatric disorders, as well as typical and atypical development. Yet the specific functional role of the default network has remained controversial. Long-held perceptions of the default network has suggested that it is “task-negative,” or behaviorally relevant only in its deactivation. My work has argued that, far from being ‘task negative’, these brain regions are active and necessary for flexible goal pursuit, allowing past knowledge and experience to guide ongoing thought and action. In this talk I will outline a series of studies demonstrating that the default network of the brain supports spontaneous and stimulus-independent thought, including episodic simulation, autobiographical planning, social cognition, and mind-wandering. Next, I review recent work suggesting that the default network is not solely internally-focused, but rather interacts with other large-scale brain systems to support externally-directed cognitive control abilities when prior knowledge is goal relevant. I will then shift towards a more translational focus, demonstrating how the architecture of the default network changes across the lifespan,, and how these changes predict individual differences in the trajectory of cognitive aging. To conclude, I look forward from these explorations of default network function to formulate a broader conceptualization of the shifting architectures of brain and cognitive function across the lifespan, and suggest that drawing these parallels can help redefine our perceptions of human aging.