UBE3A and Down syndrome: The present findings in the Ts65Dn trisomy mouse model of Down syndrome and the Ube3a maternally-derived mutant mouse model of Angelman syndrome, along with our previous parallel findings in the Fmr1 mutant mouse model of Fragile X syndrome38, support the strategy of therapeutic behavioral interventions using spaced sessions of distributed learning opportunities, to enhance cognitive abilities in neurodevelopmental disorders characterized by intellectual disabilities.