PRESERVATION OF COGNITIVE FUNCTION IN AGED CANINES: COLLABORATIVE EFFECTS OF AN ANTIOXIDANT ENRICHED DIET AND COGNITIVE EXPERIENCE
*Milgram NW, Head EH, Zicker S, Muggenberg B, Cotman, CW
Life Science Division, University of Toronto at Scarborough, Toronto Ontario Canada
Dogs show age dependent cognitive decline that correlates with beta amyloid pathology and provides a model of human cognitive aging. We have used the canine model to examine the effects of both dietary and experiential enrichment on age dependent cognitive decline. Forty eight aged beagle dogs, 9 to12 years of age, were administered a series of cognitive tests, which included object discrimination and reversal learning tasks. This baseline data was used to divide the animals to placed into four equal sized cognitively equivalent treatment groups including: (1) control; (2) dietary enrichment only; (3)cognitive enrichment only and; (4) both cognitive and dietary enrichment). The enriched diet was supplemented with a broad base of antioxidants and mitochondrial cofactors, which included vitamin E, vitamin C, alpha lipoic acid, carnitine and various fruits and vegetables. The cognitive enrichment consisted of regular cognitive testing (5 or 6 days per week) for the duration of the study, a set of toys that were rotated weekly, and extra physical exercise. One year after starting the treatment conditions, all dogs were tested on both a size discrimination learning task, and on a reversal learning task. One year later (year two of the study) all groups were tested on both a black white discrimination learning task and a reversal learning task. Young animals tested on an identical protocol showed stable performance on the discrimination and reversal learning tasks over the three year test period, and performed significantly better than the old animals overall. Performance of the old animals, by contrast, was markedly affected by both cognitive enrichment and dietary enrichment during both the year one and year two retest. The group that received both the dietary and cognitive enrichment performed better than all other groups and did not show decremental performance over the three year period. The animals in the control condition, by contrast, showed progressive and marked impairment, with a majority of the subjects failing the year two reversal learning task. These results suggest that both dietary and cognitive enrichment can delay the development of age- dependent cognitve dysfunction, with the combination being more effective than either treatment individually.
We also compared cognitive performance, which was provided as part of the cognitive enrichment, of the animals on the enriched diet with the animals on the control diet during the first treatment year. We found that the animals on the enriched diet performed significantly better than the animals on the control diet on both a landmark discrimination learning task and on an oddity discrimination learning task. Because this testing commenced within two weeks after instituting the dietary intervention, the improved performance in this situation provides evidence that the dietary intervention per se can produce at least transient improvement in cognitive performance.
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