Fornix and Uncinate Fasciculus Support Metacognition-Driven Cognitive Offloading

People often use external tools to offload cognitive demands in remembering future intentions. While previous research has identified the causal role of metacognition in cognitive offloading, the neural mechanisms underlying this metacognitive control process remain unclear. To address this gap, we conducted a study with 34 participants using diffusion tensor imaging (DTI) to investigate how connections between brain regions support metacognition-driven cognitive offloading. Behaviorally, we confirmed that under-confidence in using internal memory to execute delayed intentions predicts a bias towards using external reminders. At the brain level we found that the fractional anisotropy (FA) of the fornix, a memory-related white matter tract connected to the hippocampus, positively correlated with the bias in setting up reminders. Additionally, the FA of the left uncinate fasciculus, which links the hippocampus to the prefrontal cortex and is involved in memory error monitoring, negatively correlated with deviations from optimal reminder use. Furthermore, the FA of the superior longitudinal fasciculus, a tract involved in metacognitive monitoring, moderated how confidence influenced the use of reminders. Taken together, our findings reveal a temporal-frontal neural circuit underlying metacognition-driven cognitive offloading, and provide new insights into the interaction between metacognitive monitoring and control.