Candace J Ikeda-Douglas, Steven C Zicker, Jimena Estrada, Dennis E Jewell, and Norton W Milgram (2004)
Prior experience, antioxidants, and mitochondrial cofactors improve cognitive function in aged beagles
Vet Ther, 5(1):5-16.
Results of this study support the free-radical theory of aging and demonstrated that providing higher levels of vitamin E in food resulted in higher serum vitamin E concentrations and improved performance on landmark-discrimination tasks in aged dogs. Factors other than vitamin E also contributed to the response but remain undefined.
Link to PubMed entry