The present invention provides methods for reducing Aβ deposition, Aβ neurotoxicity and microgliosis in an animal or human afflicted with a cerebral amyloidogenic disease, such as Alzheimer's disease (AD), by administering therapeutically effective amounts of the (R)-enantiomer of the dihydropyridine compound nilvadipine, also known as (−)-nilvadipine, to the animal or human. Further provided are methods for reducing the risk of Aβ deposition, Aβ neurotoxicity and microgliosis in animals or humans suffering from traumatic brain injury by administering (−)-nilvadipine after the traumatic brain injury and continuing treatment for a prescribed period of time thereafter.