Kyphosis and bizarre patterns impair spontaneous gait performance in end-of-life mice with Alzheimer's disease pathology while gait is preserved in normal aging

An Open-Source Tool for Automated Human-Level Circling Behavior Detection

Quantifying behavior and relating it to underlying biological states is of paramount importance in many life science fields. Although barriers to recording postural data have been reduced by progress in deep-learning-based computer vision tools for keypoint tracking, extracting specific behaviors from this data remains challenging. Manual behavior coding, the present gold standard, is labor-intensive and subject to intra- and inter-observer variability. Automatic methods are stymied by the difficulty of explicitly defining complex behaviors, even ones which appear obvious to the human eye. Here, we demonstrate an effective technique for detecting one such behavior, a form of locomotion characterized by stereotyped spinning, termed 'circling'. Though circling has an extensive history as a behavioral marker, at present there exists no standard automated detection method. Accordingly, we developed a technique to identify instances of the behavior by applying simple postprocessing to markerless keypoint data from videos of freely-exploring (Cib2-/-;Cib3-/-) mutant mice, a strain we previously found to exhibit circling. Our technique agrees with human consensus at the same level as do individual observers, and it achieves >90% accuracy in discriminating videos of wild type mice from videos of mutants. As using this technique requires no experience writing or modifying code, it also provides a convenient, noninvasive, quantitative tool for analyzing circling mouse models. Additionally, as our approach was agnostic to the underlying behavior, these results support the feasibility of algorithmically detecting specific, research-relevant behaviors using readily-interpretable parameters tuned on the basis of human consensus.

Crosstalk of Alzheimer’s disease-phenotype, HPA axis, splenic oxidative stress and frailty in late-stages of dementia, with special concerns on the effects of social isolation: A translational neuroscience approach

Coping with emotional stressors strongly impacts older people due to their age-related impaired neuroendocrine and immune systems. Elevated cortisol levels seem to be associated with an increased risk of cognitive decline and dementia. In Alzheimer’s disease (AD), alterations in the innate immune system result in crosstalk between immune mediators and neuronal and endocrine functions. Besides, neuropsychiatric symptoms such as depression, anxiety, or agitation are observed in most patients. Here, we studied the psychophysiological response to intrinsic (AD-phenotype) and extrinsic (anxiogenic tests) stress factors and their relation to liver, kidneys, heart, and spleen oxidative status in 18-months-old female gold-standard C57BL/6 mice and 3xTg-AD mice model for AD. The emotional, cognitive, and motor phenotypes were assessed under three different anxiogenic conditions. Survival, frailty index, and immunoendocrine status (corticosterone levels and oxidative stress of peripheral organs) were evaluated. Genotype differences in neuropsychiatric-like profiles and cognitive disfunction in 3xTg-AD females that survived beyond advanced stages of the disease persisted despite losing other behavioral and hypothalamic–pituitary–adrenal (HPA) physiological differences. A secondary analysis studied the impact of social isolation, naturally occurring in 3xTg-AD mice due to the death of cage mates. One month of isolation modified hyperactivity and neophobia patterns and disrupt the obsessive-compulsive disorder-like digging ethogram. Frailty index correlated with spleen organometrics in all groups, whereas two AD-specific salient functional correlations were identified: (1) Levels of corticosterone with worse performance in the T-maze, (2) and with a lower splenic GPx antioxidant enzymatic activity, which may suppose a potent risk of morbidity and mortality in AD.

Impact of Behavioral Assessment and Re-Test as Functional Trainings That Modify Survival, Anxiety and Functional Profile (Physical Endurance and Motor Learning) of Old Male and Female 3xTg-AD Mice and NTg Mice with Normal Aging

Longitudinal approaches for disease-monitoring in old animals face survival and frailty limitations, but also assessment and re-test bias on genotype and sex effects. The present work investigated these effects on 56 variables for behavior, functional profile, and biological status of male and female 3xTg-AD mice and NTg counterparts using two designs: (1) a longitudinal design: naïve 12-month-old mice re-tested four months later; and (2) a cross-sectional design: naïve 16-month-old mice compared to those re-tested. The results confirmed the impact as (1) improvement of survival (NTg rested females), variability of gait (3xTg-AD 16-month-old re-tested and naïve females), physical endurance (3xTg-AD re-tested females), motor learning (3xTg-AD and NTg 16-month-old re-tested females), and geotaxis (3xTg-AD naïve 16-month-old males); but (2) worse anxiety (3xTg-AD 16-month-old re-tested males), HPA axis (3xTg-AD 16-month-old re-tested and naïve females) and sarcopenia (3xTg-AD 16-month-old naïve females). Males showed more functional correlations than females. The functional profile, biological status, and their correlation are discussed as relevant elements for AD-pathology. Therefore, repetition of behavioral batteries could be considered training by itself, with some variables sensitive to genotype, sex, and re-test. In the AD-genotype, females achieved the best performance in physical endurance and motor learning, while males showed a deterioration in most studied variables.