This 2015 German rodent study found:
“The control of sleep and memory consolidation may share common molecular mechanisms.”
Somewhat counter to the “Enhanced memory consolidation” in the study’s title, the researchers also found:
“Elevated IGF2 [insulin-related growth factor 2] signaling in the long term, however, has a negative impact on cognitive processing.”
The IGF2 finding was in genetically altered mice that had their circadian rhythm permanently disturbed, however. The study didn’t clearly determine the contribution of other factors that could have contributed to the cognitive decline.
The study traced fear memories induced by stress through the cerebrum to the anterior cingulate cortex and hippocampus parts of the limbic system.
Researchers have no problems studying emotional memories in these brain areas with rodents. In human memory experiments, however, emotional content is consistently excluded, as though our memories had nothing to do with our feelings.
http://www.pnas.org/content/112/27/E3582.full “Enhanced memory consolidation in mice lacking the circadian modulators Sharp1 and -2 caused by elevated Igf2 signaling in the cortex”