The dorsal and ventral default mode networks are dissociably modulated by the valence and vividness of imagined events

Recent work has shown that the brain’s default mode network (DMN) is active when people imagine the future. Here we test whether future imagination can be decomposed into two dissociable psychological processes linked to different subcomponents of the DMN. While measuring brain activity with fMRI as subjects imagine future events, we manipulate the vividness of these events to modulate the demands for scene construction, and we manipulate the valence of these events to modulate the demands for evaluation. We found that one subcomponent of the DMN, the ventral DMN or medial temporal lobe subsystem, responds to the vividness but not the valence of imagined events. In contrast, another subcomponent, the dorsal or core DMN, responds to the valence but not the vividness of imagined events. This separate modifiability of different subcomponents of the DMN by vividness and valence provides strong evidence for a neurocognitive dissociation between (1) the construction of novel, imagined scenes from individual components from memory and (2) the evaluation of these constructed events as desirable or undesirable. Significance Statement Previous work has suggested that imagination may depend on separate neural networks involved in the construction and evaluation of imagined future events. This study provides strong neural evidence for this dissociation by demonstrating that two components of the brain’s default mode network (DMN) uniquely and specifically respond to different aspects of imagination. The vividness of imagined events modulates the ventral DMN, but not the dorsal DMN, while the valence of imagined events modulates the dorsal DMN, but not the ventral DMN. This supports the dissociable engagement of these sub-networks in constructing and evaluating imagined future events.