From single scenes to extended scenarios: The role of the ventromedial prefrontal cortex in the construction of imagery-rich events

Mental events are fundamental to daily cognition, including the recollection of past experiences, the anticipation of future scenarios, and engagement in imaginative, fictitious thought. Typically, these temporally extended mental events unfold within coherent spatial contexts, rich in naturalistic scenes and objects. However, there remains a significant gap in understanding how these events are represented in the brain. This study aimed to investigate the neural patterns involved in the construction of temporally extended mental events. Using ultra-high field functional magnetic resonance imaging, we examined brain regions previously implicated in this cognitive process, including the ventromedial prefrontal cortex (vmPFC), hippocampus, and posterior neocortex. We employed a novel experimental paradigm in which participants engaged in three forms of mental imagery: single objects (e.g., "a black espresso"), single scenes (e.g., "a busy café"), and extended scenarios (e.g., "meeting a friend for coffee"). We identified a shared neural network, comprising the vmPFC, hippocampus, and posterior neocortex, engaged across all forms of mental imagery. However, we observed a hierarchical organization in their contributions: the posterior neocortex supported the construction of objects, scenes, and scenarios, while the hippocampus primarily contributed to scenes and scenarios. The vmPFC exhibited a stepwise increase in activation, peaking during scenario construction. These findings suggest that the construction of mental events involves dynamic interactions between perceptual representations in the posterior neocortex, spatial coherence provided by the hippocampus, and integrative processes within the vmPFC. While the vmPFC may play a particularly prominent role in constructing temporally extended scenarios, it likely also contributes to the integration of elements within single scenes.