Locomotor Activity

Physical movement or motor activity significantly declines with advancing age in humans (Bennett, 1998). Changes in physical activity become more severe in neurodegen-erative disorders and can take several forms including ceaseless walking, trailing and checking, and wandering (Folstein and Bylsma, 1999). We have observed similar changes in locomotor activity in the dog, which vary with cognitive impairment (Siwak et al., 2001, 2003). Locomotor activity in the dog is assessed with three different tests: the open field test (Siwak et al., 2001, 2002; Head et al., 1997), the home cage test (Siwak et al., 2002); and the Actiwatch® activity monitoring system (Siwak et al., 2003). The general finding is that locomotor activity decreases with age in the dog (Figure 35.5), but is dependent upon several factors including test situation, cognitive status, and previous experiences.

First, the environmental testing situation influences motor activity in dogs. In a novel environment, such as the open field arena, young and old dogs are aroused and responsive to the change in surroundings. Measures of locomotor activity are affected such that age-related decreases in activity are not observed. As the open field becomes familiar, locomotion declines in both young and aged dogs (Siwak et al., 2001, 2002). Familiar home cage environments may reflect more spontaneous activity, and age-related decreases in motor activity are more easily observed (Siwak et al., 2002).

Second, motor activity is related to cognitive impairment. When aged dogs are divided into cognitively impaired and unimpaired subgroups, robust differences in locomotor activity are observed (Siwak et al., 2001; Head et al., 1997). Aged dogs that are severely impaired on tests of cognitive function tend to be hyperactive compared to unimpaired aged dogs. This is consistent with studies in humans showing a relationship between hyperactivity and several disorders including dementia, autism, and attention deficit disorder (Folstein and Blysma, 1999; Castellanos et al., 2001). These increased levels of activity in impaired dogs may be a manifestation of neurodegenerative changes that contribute to cognitive impairment.

Third, previous rearing history or possible genetic factors may affect locomotion. Dogs born and raised in a laboratory are hyperactive compared to dogs reared outside of the laboratory (Fox, 1971; Siwak et al., 2003). Thus, environmental enrichment during the lifespan of the dog may interact with genetic factors and contribute to the severity of locomotor decline and cognitive dysfunction in aging (Siwak et al., 2001; Head et al., 1997).

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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