Exploring the past and impending future in the here and now: Mind-wandering in the default state

Although mind-wandering is a ubiquitous psychological phenomenon, little is known about the neural operations that support this core feature of human cognition. Using a combination of behavioral and functional brain imaging (fMRI) methods, the current investigation demonstrates that recruitment of circumscribed regions of the default network – cortical areas that are active during unconstrained cognitive periods – depends on people's proclivity for reflecting on events from the distant past or impending future while mindwandering. The present results reveal that whereas medial temporal regions (e.g., parahippocampal cortex) are recruited when the mind wanders to memories of past episodes, areas involved in propsection (e.g., frontal polar and hippocampal) are active when mind-wandering centers on future events. Consistent with recent findings, there is some overlap between the cortical regions involved in thinking about the past and the future. The significance of spontaneous self-projection in time is considered.