This invention relates to methods and compositions for treating central nervous system (CNS) disorders with cognitive impairment. In particular, it relates to the use of inhibitors of synaptic vesicle glycoprotein 2A (SV2A), alone or in combination with valproate, in treating central nervous system (CNS) disorders with cognitive impairment in a subject in need or at risk thereof, including, without limitation, subjects having or at risk for age-related cognitive impairment, Mild Cognitive Impairment (MCI), amnestic MCI (aMCI), Age-Associated Memory Impairment (AAMI), Age Related Cognitive Decline (ARCD), dementia, Alzheimer's Disease(AD), prodromal AD, post traumatic stress disorder (PTSD), schizophrenia, amyotrphic lateral sclerosis and cancer-therapy-related cognitive impairment.