Circadian modulation of human reward function: Is there an evidentiary signal in existing neuroimaging studies?

•A systematic review identified 15 relevant fMRI studies, of which 13 found evidence of moderation of neural reward function by a circadian proxy measure.•Specific reward-related regions/networks subserving the effect included the medial prefrontal cortex, ventral striatum, putamen, and default mode network.•Circadian moderation was observed in measures of both reward anticipation and reward receipt, with more consistent evidence for the latter.•Consistent with neurobiological findings in animals, and behavioural evidence in humans, these findings motivate future research to better characterise circadian moderation of reward functioning.