Enhanced spatial ability in aged dogs following dietary and behavioural enrichment

Cognitive Changes Associated with Aging and Physical Disease in Dogs and Cats

Behavior changes may indicate primary physical disease or primary behavioral disorders in veterinary patients. It is imperative to recognize that secondary behavioral problems can develop due to medical causes. The incidence of systemic disease increases with age and behavior manifestations can be similar to those expected with cognitive dysfunction syndrome. In this article, we review basic concepts of cognition, aging, and cognitive dysfunction syndrome. Additionally, we provide information regarding factors that influence cognition, and the role medical conditions have on the behavior of aging pets.

Relationship between diet quality and cognition depends on socioeconomic position in healthy older adults

Both diet quality and socioeconomic position (SEP) have been linked to age-related cognitive changes, but there is little understanding of how the socioeconomic context of dietary intake may shape its cognitive impact. We examined whether equal adherence to "prudent" and "Western" dietary patterns, identified by principal components analysis, was associated with global cognitive function [Modified Mini-Mental State Examination (3MS)] in independently living older adults with different SEPs (aged 68-84 y; n = 1099). The interaction of dietary pattern adherence with household income, educational attainment, occupational prestige, and a composite indicator of SEP combining all 3 was examined in multiple-adjusted mixed models over 3 y of follow-up in participants of the NuAge study (Quebec Longitudinal Study on Nutrition and Successful Aging). Adherence to the prudent pattern (vegetables, fruits, fish, poultry, and lower-fat dairy products) was related to higher 3MS scores at recruitment only in the upper categories of income [parameter estimate (B): 0.56; 95% CI: 0.11, 1.01], education (B: 0.44; 95% CI: 0.080, 0.80), or composite SEP (B: 0.37; 95% CI: 0.045, 0.70). High prudent pattern adherence was associated with less cognitive decline only in those with low composite SEP (B: 0.25; 95% CI: 0.0094, 0.50). Conversely, adherence to the Western pattern (meats, potatoes, processed foods, and higher-fat dairy products) was associated with more cognitive decline (B: -0.23; 95% CI: -0.43, -0.032) only in those with low educational attainment. In summary, among individuals with equivalent diet quality, the magnitude and characteristics of the diet-cognition relationship depended on their socioeconomic circumstances. These results suggest that interventions promoting retention of cognitive function through improved diet quality would provide maximum benefit to those with relatively low SEP.

Variations in the nature of behavioral experience can differentially alter the consequences of developmental exposures to lead, prenatal stress, and the combination

Behavioral experience (BE) can critically influence later behavior and brain function, but the central nervous system (CNS) consequences of most developmental neurotoxicants are examined in the absence of any such context. We previously demonstrated marked differences in neurotransmitter changes produced by developmental lead (Pb) exposure ± prenatal stress (PS) depending upon whether or not rats had been given BE (Cory-Slechta, D. A., Virgolini, M. B., Rossi-George, A., Weston, D., and Thiruchelvam, M. (2009). The current study examined the hypothesis that the nature of the BE itself would be a critical determinant of outcome in mice that had been continually exposed to 0 or 100 ppm Pb acetate in drinking water alone or in combination with prenatal restraint stress. Half of the offspring in each of the four resulting groups/gender were exposed to positively reinforced (food-rewarded Fixed Interval schedule-controlled behavior) or negatively reinforced (inescapable forced swim) BE. Brain monoamines and amino acids differed significantly in relation to BE, even in control animals, as did the trajectory of effects of Pb ± PS, particularly in frontal cortex, hippocampus (both genders), and midbrain (males). In males, Pb ± PS-related changes in neurotransmitters correlated with behavioral performance. These findings suggest that CNS consequences of developmental toxicants studied in the absence of a broader spectrum of BEs may not necessarily be predictive of human outcomes. Evaluating the role of specific BEs as a modulator of neurodevelopmental insults offers the opportunity to determine what specific BEs may ameliorate the associated impacts and can assist in establishing underlying neurobiological mechanisms.

Antioxidants in the canine model of human aging

Oxidative damage can lead to neuronal dysfunction in the brain due to modifications to proteins, lipids and DNA/RNA. In both human and canine brain, oxidative damage progressively increases with age. In the Alzheimer's disease (AD) brain, oxidative damage is further exacerbated, possibly due to increased deposition of beta-amyloid (Aβ) peptide in senile plaques. These observations have led to the hypothesis that antioxidants may be beneficial for brain aging and AD. Aged dogs naturally develop AD-like neuropathology (Aβ) and cognitive dysfunction and are a useful animal model in which to test antioxidants. In a longitudinal study of aging beagles, a diet rich in antioxidants improved cognition, maintained cognition and reduced oxidative damage and Aβ pathology in treated animals. These data suggest that antioxidants may be beneficial for human brain aging and for AD, particularly as a preventative intervention. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

BDNF increases with behavioral enrichment and an antioxidant diet in the aged dog

The aged canine (dog) is an excellent model for investigating the neurobiological changes that underlie cognitive impairment and neurodegeneration in humans, as canines and humans undergo similar pathological and behavioral changes with aging. Recent evidence indicates that a combination of environmental enrichment and antioxidant-fortified diet can be used to reduce the rate of age-dependent neuropathology and cognitive decline in aged dogs, although the mechanisms underlying these changes have not been established. We examined the hypothesis that an increase in levels of brain-derived neurotrophic factor (BDNF) is one of the factors underlying improvements in learning and memory. Old, cognitively impaired animals that did not receive any treatment showed a significant decrease in BDNF mRNA in the temporal cortex when compared with the young group. Animals receiving either an antioxidant diet or environmental enrichment displayed intermediate levels of BDNF mRNA. However, dogs receiving both an antioxidant diet and environmental enrichment showed increased levels of BDNF mRNA when compared with untreated aged dogs, approaching levels measured in young animals. BDNF receptor TrkB mRNA levels did not differ between groups. BDNF mRNA levels were positively correlated with improved cognitive performance and inversely correlated with cortical Aβ((1-42)) and Aβ((1-40)) levels. These findings suggest that environmental enrichment and antioxidant diet interact to maintain brain levels of BDNF, which may lead to improved cognitive performance. This is the first demonstration in a higher animal that nonpharmacological changes in lifestyle in advanced age can upregulate BDNF to levels approaching those in the young brain.

Magnetic resonance imaging of the canine brain at 7 T

The purpose of this study was to describe relevant canine brain structures as seen on T2-weighted images following magnetic resonance (MR) imaging at 7 T and to compare the results with imaging at 1.5 T. Imaging was performed on five healthy laboratory beagle dogs using 1.5 and 7 T clinical scanners. At 1.5 T, spin echo images were acquired, while gradient echo images were acquired at 3 T. Image quality and conspicuity of anatomic structures were evaluated qualitatively by direct comparison of the images obtained from the two different magnetic fields. The signal-to-nose ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared between 1.5 and 7 T. The T2-weighted images at 7 T provided good spatial and contrast resolution for the identification of clinically relevant brain anatomy; these images provided better delineation and conspicuity of the brain stem and cerebellar structures, which were difficult to unequivocally identify at 1.5 T. However, frontal and parietal lobe and the trigeminal nerve were difficult to identify at 7 T due to susceptibility artifact. The SNR and CNR of the images at 7 T were significantly increased up to 318% and 715% compared with the 1.5 T images. If some disadvantages of 7 T imaging, such as susceptibility artifacts, technical difficulties, and high cost, can be improved, 7 T clinical MR imaging could provide a good experimental and diagnostic tool for the evaluation of canine brain disorders.

Oxidative damage and cognitive dysfunction: antioxidant treatments to promote healthy brain aging

Oxidative damage in the brain may lead to cognitive impairments in aged humans. Further, in age-associated neurodegenerative disease, oxidative damage may be exacerbated and associated with additional neuropathology. Epidemiological studies in humans show both positive and negative effects of the use of antioxidant supplements on healthy cognitive aging and on the risk of developing Alzheimer disease (AD). This contrasts with consistent behavioral improvements in aged rodent models. In a higher mammalian model system that naturally accumulates human-type pathology and cognitive decline (aged dogs), an antioxidant enriched diet leads to rapid learning improvements, memory improvements after prolonged treatment and cognitive maintenance. Cognitive benefits can be further enhanced by the addition of behavioral enrichment. In the brains of aged treated dogs, oxidative damage is reduced and there is some evidence of reduced AD-like neuropathology. In combination, antioxidants may be beneficial for promoting healthy brain aging and reducing the risk of neurodegenerative disease.