The present invention relates to compositions comprising a combination of PKC activators and PKC inhibitors and methods to modulate &alpha；-secretase activity； improve or enhance cognitive ability； and/or reduce neurodegeneration in individuals suffering from diseases that impair cognitive ability, particularly Alzheimer's Disease. The invention also relates to methods for improving or enhancing cognitive ability. The present invention also provides methods for increasing the generation of non-amyloidogenic soluble APP (sAPP) comprising the activation of protein kinase C (PKC) in the brain and inhibiting PKC in peripheral tissues. Macrocyclic lactones (i.e. bryostatin class and neristatin class) are preferred PKC activators and Vitamin E is a preferred PKC inhibitor for use in the inventive composition.
