doi:10.1016/j.nlm.2007.01.001 
Copyright © 2007 Elsevier Inc. All rights reserved.
Enhanced spatial ability in aged dogs following dietary and behavioural enrichment
P.M.D. Nippaka, 
, 
, J. Mendelsona, B. Muggenburgb and N.W. Milgrama
aInstitute of Medical Science, Division of Life Sciences, University of Toronto, 1265 Military Trail, Toronto, Ont., Canada M1C 1A4
bInstitute for Brain Aging and Dementia, Basic Science Department, University of California, Irvine, 1226 Gillespie Neuroscience Research Facility Irvine, CA 92697-4540, USA
Received 18 September 2006;
revised 1 January 2007;
accepted 8 January 2007.
Available online 15 February 2007.
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Abstract
We examined the benefits of a broad spectrum antioxidant diet and enrichment comprised of physical exercise, environmental stimulants and cognitive testing, on spatial memory performance in beagle dogs. Both aged (N = 48) and young (N = 16) beagle dogs (Canus familiaris) were tested yearly on a three-component delayed non-match to position spatial task for three consecutive years. The results showed that young enriched animals acquired the task in fewer sessions, made fewer errors, responded slower and made fewer positional responses, compared to aged enriched animals. An analysis restricted to aged animals revealed that antioxidant administration and enrichment resulted in fewer errors, slower responses and decreased positional responses, particularly in Year 3. Finally, cohort differences emerged, which exemplify the significance of early environmental intervention. Aged dogs that were housed with other animals and exposed to an outdoor environment in early development displayed greater benefits from both interventions. These findings indicate that long-term dietary intervention and enrichment can buffer age-associated cognitive decline.
Keywords: Canine; Visual spatial task; Problem solving; Delayed non-matched to positive; Aging; Memory; Response latency; Anti-oxidents; Enrichment
Fig. 1. The bar graph displays the mean errors made across training for each treatment group for both young and aged dogs. Over the three years of training control aged dogs (Ag-C) made the most errors, compared to diet fed (Ag-AC), enriched only (Ag-CE) and enriched and diet fed (Ag-AE) aged animals. Both groups of young animals made significantly fewer errors (Yg-AC; Yg-AE) compared to all groups of aged animals. Standard errors are shown. Yg-AC, young antioxidant diet, control; Yg-AE, young, antioxidant diet and enrichment.
Fig. 2. A significant year × age interaction is shown. Young animals respond slower than aged animals until the third testing year. In Year 1 young animals RLs were significantly longer than their aged counterparts (p < .05), but by Year 3 they became indistinguishable from aged animals (p > .05). Standard errors are reported. * Indicates p < .05 statistical significance between young and aged animals RLs in Year 1.
Fig. 3. An age × subtest interaction is shown. Young animals responded slower across all three subtests, compared to aged animals. The most significant RL difference between young and aged animals was displayed on the CI subtest (* indicates p < .05 significance between young and aged animals RLs on the CI subtest). Standard errors are reported.
Fig. 4. A significant interaction between Diet and Enrichment in aged animals is shown. This interaction revealed that dogs who were both behaviourally enriched and on the antioxidant-enriched diet (A–E group) scored the highest average subtest scores compared to either antioxidant diet alone (A–C group: p < .005 significant difference between diet fed enriched animals and only diet fed animals is indicated by *) or behavioural enrichment alone (E–C group; p < .001 significant difference between diet fed enriched animals and only enriched animals is indicated by **).
Fig. 5. A Subtest and Enrichment interaction for aged animals in the two treatment years is shown. Enriched aged animals displayed significantly better CI subtest accuracy in Year 3 compared to non-enriched animals. Standard Errors are shown. CI = centre incorrect. The * indicates a significant difference in CI subtest accuracy of p < .001 between enriched dogs and non-enriched dogs.
Fig. 6. The significant interaction between Year and Diet is shown. The interaction indicated that antioxidant fed aged animals made fewer errors compared to control diet animals in Year 3 (p < .05). Standard errors are shown. * Indicates a significant difference of p < .05 in the number of errors made between diet fed and control animals in Year 3.
Fig. 7. A Year × Subtest × Diet interaction for the two treatment years is depicted. This graph shows that CI subtest accuracy remained at chance for both (a) diet fed aged animals and (b) control diet fed aged animals for both Year 2 and Year 3. Standard errors are reported. CNO, centre non-option; CC, centre correct; and CI, centre incorrect. * Indicates the chance performance on the CI subtest in both the control and diet fed animals for both treatment years. Performance on the CI subtest remained statistically lower by p < .001 compared to CNO and CC subtest accuracy (p < .001).
Fig. 8. The interaction between Cohort and Diet found in Year 2 is shown. Cohort I dogs maintained on the antioxidant diet displayed significantly fewer errors compared to Cohort II dogs maintained on the fortified diet when the analysis was restricted to an examination of Year 2 performance. Standard errors are reported. * Indicates a significant difference of p < .01 between the errors committed by Cohort 1 and Cohort 2 aged dogs.
Fig. 9. The main effects of Fortified Diet (a), Enrichment (b) and Cohort (c) found in Year 3 are shown. (a) Fortified diet fed aged animals outperformed control aged animals (p < .05), (b) enriched aged animals made fewer errors than non-enriched animals (p < .05), (c) aged animals in Cohort I made fewer errors than aged animals in Cohort II (p < .001). Standard errors are reported for each graph.
Table 1.
Acquisition of aged animals within each year of the study
The total number of aged animals that learned the task across each year of testing on the 3-DNMP task. The total number of animals that comprised each group for each year has been presented in brackets. C–C, control dogs; A–C, antioxidant diet/control; C–E, control diet/behavioural enrichment; and A–E, antioxidant diet/behavioural enrichment.
Table 2.
Mean age of groups from the start of spatial discrimination testing over three years
Mean ages and standard deviations of the four groups of old dogs and two groups of young dogs at the start of baseline spatial discrimination testing, after one year of treatment, and after two years of treatment.
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