Cognitive functions and aging in the dog: Acquisition of nonspatial visual tasks.

Abstract

Old, middle-aged, and young dogs were compared on discrimination and reversal learning and on acquisition of a delayed-nonmatching-to-sample (DNMS) test of recognition memory. DNMS acquisition was acquired more rapidly by young dogs. Reversal deficits were found between aged mixed-breed dogs and young beagles, but not between old and young beagles. Aged beagles also showed unexpected deficits in reward approach and object approach learning. Aged mixed-breed dogs did not show deficits in reward approach and object approach learning, but they learned the discrimination task more slowly than the age-matched beagles. A detailed analysis of response patterns indicated that once present, the development of side preferences contributed to deficits of old dogs in discrimination learning. In the discrimination reversal, old dogs were more persistent in responding to the previously rewarded stimulus object. Findings suggest that the dog, like other species, shows age-dependent deterioration in cognitive function, the extent of deterioration is a function of both task and previous experience, and at least part of the deterioration is a result of increased behavioral rigidity. Results also indicate that it is important to control for breed differences and previous experience.

Assessment of nutritional interventions for modification of age-associated cognitive decline using a canine model of human aging

“…Our results indicate that cognitive function declines with age in dogs, but that the decline is domain, or task, specific and sensitive to previous experience. Procedural learning and memory, as well as simple discrimination learning, are generally insensitive to aging (Milgram et al 1994). By contrast, tests of executive function, such as discrimination reversal learning (Milgram et al 1994;Tapp et al 2003a), and working memory (Adams et al 2000b;Head et al 1995), such as a delayednonmatching-to-position (DNMP) task (Chan et al 2002), are highly sensitive to aging.…”

“…In other instances, age sensitivity depends on prior test experience. Naïve young and aged dogs do not differ in their ability to learn relatively simple size discrimination tasks (Milgram et al 1994). Once both groups have repeated experience on discrimination learning tasks, however, age differences emerge in that aged dogs require more trials to learn the task than do young dogs (Milgram 2003).…”

“…Using a cross-sectional approach, we have established that tasks dependent on frontal lobe function, in particular tests of executive function (Milgram et al 1994;Tapp et al 2003a) and visuospatial working memory (Chan et al 2002), are notably sensitive to age (Adams et al 2000b;Head et al 1995). In a study of 109 dogs (manuscript in preparation), a statistically significant impairment in both acquisition of the DNMP using a 5-s delay and memory capacity were detected as early as six years of age (Figure 1) (Araujo 2004;Araujo et al 2004a).…”

Prevalence of behavioral changes in senile dogs

“…Pathological aging with behavioral changes has been described in aged dogs as Canine Svicero et al Cognitive Dysfunction Syndrome (CDS), which has clinical, imaging, and histopathological findings similar to human Alzheimer's disease (MILGRAM et al, 1994;CUMMINGS et al, 1996b, c). The main categories describing the clinical signs compatible with CDS is described by DISHA: disorientation; altered Interactions with people or other pets; Sleep-wake cycle alterations, House-soiling and altered Activity level (LANDESBERG et al, 2003).…”

“…Dogs have a shorter lifespan compared to humans; and therefore, the aging process is accelerated in these animals (LANDSBERG & RUEHL, 1997;HEIBLUM et al, 2007;HEAD, 2004). The behavioral changes of old dogs may be considered as part of the normal aging process, or may be attributed towards pathological aging caused by a brain disease that affects learning, motor activity and memory (MILGRAM et al, 1994;LANDSBERG & RUEHL, 1997;RUEHL & HART, 1998;ADAMS et al, 2000;CHAN et al, 2002).…”