Fluctuation of the human limbic functional connectivity along the time of day

Motivation: Human behaviors and mental states are closely modulated by the circadian rhythm, whose genetic basis has been studied. However, the neural correlates remain elusive. Goal(s): We studied how functional connectivity within the limbic system changes throughout the day. Approach: Using resting-state fMRI data from the Human Connectome Project, we analyzed the functional connectivity to limbic regions, including the amygdala, hippocampus, and hypothalamus. Results: The anterior-inferior hypothalamus maintained stable connectivity across time of day.The hippocampus connectivity to the medial prefrontal cortex and precuneus increased over the course of the day, whereas the amygdala connectivity to the postcentral gyrus and temporal poles showed a decline. Impact: Functional connectivity in the limbic system can be moderately but significantly increased or decreased over 24 h, suggesting that complex coordination between the limbic system and the cortex can change over the course of a day.