Rodents have a similar decrease in circulating IGF-1 levels with age and intra-cerebroventricular (icv) IGF-1 replacement to older F344xBN rats, which increases concentrations of IGF-1 in the hippocampus to levels found in young animals, reverses these cognitive deficits (Trejo et al., 2007). Here, IGF1 is linked to Cognitive impairment.