Proactive by default

The discovery of the brain's extensive "default network" has taken the world of cognition and neuroscience by storm. A flood of exciting findings started to pour in, demarcating and characterizing this network. With it came a slew of ideas striving to ascribe a function to this substantial, omnipresent and vigorous activity: daydreaming, planning, episodic memory, mental simulations, creativity, theory of mind, self-projection, imagining, and so on, yielding a corresponding number of debates. Most, if not all, of these functional attributions seem sound, yet often too remote from each other to believe they are all mediated by the same network. To bridge the different accounts of the function of the default network, we have argued that the most logical conclusion is that the default network carries a more foundational process, which is the common denominator and the platform for all those other processes. We propose that this basic process is the activation of context-based associations. Associative activations serve as the building-blocks and the vehicle that is essential for all those other functions with which the default network has been implicated. Therefore, we do not suggest that any previous account is incorrect, but rather that the level on which the default operation needs to be explained has to be parsimoneous, on the more elementary process on which all others build. This proposal has emanated from a striking overlap we had initially noticed between activations obtained during context-based associative processing and the default network, and it has been supported by multiple converging findings since, as reviewed here. Following this fundamental link, we further address the question of how spontaneous and how resource-demanding is the default extraction of contextual information, and we conclude by discussing the involvement of contextual associations in creative thought as well as in mental health.