A default-control network cortical gradient differentiates the imagination of social and solitary experiences

Understanding the neural basis of spontaneous thought - when attention shifts from external tasks to internally generated content such as reminiscing or planning - remains a central challenge in cognitive neuroscience. Progress in this area has lagged studies of externally driven cognition, in part because self-generated thought is difficult to control and measure. Recent work suggests that transitions between externally and internally focused cognitive states follow a continuous neural activation gradient that reflects opposing patterns of engagement of the frontoparietal control network versus the default mode network. To characterize internally focused cognitive states that prospectively engage the default mode network, we used functional Magnetic Resonance Imaging (fMRI) to measure brain activity while participants imagined a range of personal scenarios prompted by generic text cues (e.g., party, housework) to mimic natural thought. Before scanning, participants described each scenario verbally and rated its experiential feature content. Gradient-space analysis revealed a cognitive transition within imagined states: solitary activities (e.g., housework) preferentially recruited the frontoparietal network relative to the default mode network, whereas social activities (e.g., a party) showed the opposite pattern. Because all cognitive states were internally focused (imagined) and elicited via the same non-interactive task, these results refine interpretations of the frontoparietal-default mode gradient. They show that this gradient does not simply differentiate external task-positive from internal task-negative states but also tracks semantic differences between internal cognitive states.