These studies reported that IGF-2, when directly injected into brain structures or given systemically (s.c.), can enhance memory performance in normal animals.13–15 Further, IGF-2 attenuated age-related memory decline and improved cognitive function in a rodent model of autism spectrum disorder.22,23 Although we also observed that IGF-2 facilitated fear memory extinction in uninjured sham animals, our data indicated that IGF-2 was not effective at improving memory performance in CCI-injured mice when administered 4 months post-injury. Here, IGF2 is linked to autism spectrum disorder.