Abstract: The landmark discrimination learning test can be used to assess the ability to utilize allocentric spatial information to locate targets. The present experiments examined the role of various factors on performance of a landmark discrimination learning task in beagle dogs. Experiments 1 and 2 looked at the effects of age and food composition. Experiments 3 and 4 were aimed at characterizing the cognitive strategies used in performance on this task and in long-term retention. Cognitively equivalent groups of old and young dogs were placed into either a test group maintained on food enriched with a broad-spectrum of antioxidants and mitochondrial cofactors, or a control group maintained on a complete and balanced food formulated for adult dogs. Following a wash-in period, the dogs were tested on a series of problems, in which reward was obtained when the animal responded selectively to the object closest to a thin wooden block, which served as a landmark. In Experiment 1, dogs were first trained to respond to a landmark placed directly on top of coaster, landmark 0 (L0). In the next phase of testing, the landmark was moved at successively greater distances (1, 4 or 10 cm) away from the reward object. Learning varied as a function of age group, food group, and task. The young dogs learned all of the tasks more quickly than the old dogs. The aged dogs on the enriched food learned L0 significantly more rapidly than aged dogs on control food. A higher proportion of dogs on the enriched food learned the task, when the distance was increased to 1cm. Experiment 2 showed that accuracy decreased with increased distance between the reward object and landmark, and this effect was greater in old animals. Experiment 3 showed stability of performance, despite using a novel landmark, and new locations, indicating that dogs learned the landmark concept. Experiment 4 found age impaired long-term retention of the landmark task. These results indicate that allocentric spatial learning is impaired in an age-dependent manner in dogs, and that age also affects performance when the distance between the landmark and target is increased. In addition, these results both support a role of oxidative damage in the development of age-associated cognitive dysfunction and indicate that short-term administration of a food enriched with supplemental antioxidants and mitochondrial cofactors can partially reverse the deleterious effects of aging on cognition.

Abstract: In healthy man, conditions that change muscle O2 delivery affect the achievable maximum rate of O2 uptake (V[dot above]O2,max) as well as the metabolic (e.g. lactate threshold, LT) and gas exchange (e.g. gas exchange threshold, Tge) responses to incremental exercise. Inclined (I) compared to level (L) running increases locomotory muscle EMG at a given speed in the horse, indicative of elevated metabolic demand. To our knowledge, the effect of treadmill incline on V[dot above]O2,max, LT and Tge has not been addressed in the exercising quadruped. We used blood sampling and breath-by-breath expired gas analysis to test the hypothesis that I (10 % gradient) would increase V[dot above]O2,max and the rate of O2 uptake (V[dot above]O2) at LT and Tge in six Thoroughbred horses during incremental running to volitional fatigue. V[dot above]O2,max was significantly higher for I (I, 77.8 ± 4.1; L, 65.5 ± 5.3 l min-1; P < 0.05), but peak plasma lactate concentration was not (I, 28.0 ± 3.7; L, 25.9 ± 3.0 mM). Arterial PCO2 increased to 62.1 ± 3.3 and 57.9 ± 2.7 Torr (I vs. L; P < 0.05), yet despite this relative hypoventilation, a distinct Tge was present. This Tge occurred at a significantly different absolute (I, 49.6 ± 3.2; L, 42.4 ± 3.2 l min-1; P < 0.05), but nearly identical relative V[dot above]O2 (I, 63.6 ± 1.2; L, 63.9 ± 1.6 % V[dot above]O2,max) in I and L. Similarly, LT occurred at a significantly greater absolute V[dot above]O2 (I, 37.3 ± 2.8; L, 26.9 ± 2.1 l min-1), but a relative V[dot above]O2 that was not different (I, 47.9 ± 2.1; L, 43.9 ± 4.5 % V[dot above]O2,max). In addition, Tge occurred at a significantly higher (P [less-than-or-equal] 0.05) absolute and relative V[dot above]O2 than LT for both I and L tests. In conclusion, V[dot above]O2,max is higher during inclined than level running and both LT and Tge in the horse occur at a similar percentage of V[dot above]O2,max irrespective of the absolute level of V[dot above]O2,max. In contrast to humans, LT is a poor analogue of Tge in the horse.

Abstract: Weaving, a common locomotor stereotypy, has been associated with social isolation in stabled horses. In this study we investigated the effect of provision of mirrors on weaving as this may have a similar effect to access to conspecifics. The behaviour of six known weavers, each in one of three locations within a working equine yard, was recorded, 5 days a week for 12 weeks. After a pre-trial period of a week, one horse in each of the three locations was provided with a 1mx1.5m mirror for 5 weeks, after which time the mirrors were removed and placed in the stables of the other three subjects for the next 5 weeks. All mirrors were then removed and the horses observed for a final week (post-trial period). The provision of a mirror significantly reduced the incidence of both stereotypic weaving (P<0.001) and nodding (P<0.05) for the 5 weeks of treatment but did not affect the time the horses spent standing active, dozing or ingesting. The mirror may mimic visual contact with conspecifics (minimising the social isolation of the stable) and/or provide environmental distraction or additional visual stimuli, altering the horses' perception of the environment and their resultant responses to it. The use of mirrors in the stable appears to be a more effective treatment of weaving than many current popular treatments, including weaving bars.