Periodic Reporting for period 4 - EVOLOR (Cognitive Ageing in Dogs)
Reporting period: 2020-12-01 to 2021-05-31
Understanding how active, healthy ageing can be achieved is one of the most relevant problems today. The rapid ageing of the human population will significantly change society, creating health care and economic challenges. Translational work aiming to address which factors shape the trajectory of cognitive ageing is limited as the traditional animal model species do not spontaneously develop age-related neurodegenerative disorders. Laboratory animals are also kept under conditions that likely jeopardize the ecological validity of the findings.
The study of companion dog ageing is significant from at least two perspectives. Firstly, dogs are increasingly recognized as animal models in ageing research. They share our environment, are exposed to the same hazards, receive advanced medical care, display comparable socio-cognitive skills, and develop similar age-related pathologies.
Secondly, 87 million pet dogs live in Europe. The relatively extended lifespan in dogs artificially enhances the proportion of dogs with cognitive decline which is a serious welfare concern. Research could facilitate the early recognition and treatment of detrimental conditions in ageing dogs, as well as inform strategies for a preventive and predictive approach (e.g. feeding, physical and mental exercises).
Our project aimed to explore the cognitive ageing of family dogs using an interdisciplinary approach with behavioural, neuroscientific, and genetic testing methods. Our goal was twofold: to enhance translational research on cognitive ageing and increase canine welfare. We characterised the canine ageing phenotype with cross-sectional and longitudinal investigations and identified age-related biomarkers.
The study of companion dog ageing is significant from at least two perspectives. Firstly, dogs are increasingly recognized as animal models in ageing research. They share our environment, are exposed to the same hazards, receive advanced medical care, display comparable socio-cognitive skills, and develop similar age-related pathologies.
Secondly, 87 million pet dogs live in Europe. The relatively extended lifespan in dogs artificially enhances the proportion of dogs with cognitive decline which is a serious welfare concern. Research could facilitate the early recognition and treatment of detrimental conditions in ageing dogs, as well as inform strategies for a preventive and predictive approach (e.g. feeding, physical and mental exercises).
Our project aimed to explore the cognitive ageing of family dogs using an interdisciplinary approach with behavioural, neuroscientific, and genetic testing methods. Our goal was twofold: to enhance translational research on cognitive ageing and increase canine welfare. We characterised the canine ageing phenotype with cross-sectional and longitudinal investigations and identified age-related biomarkers.
Our results lend support to the dog’s potential as a model of cognitive ageing and provide knowledge relevant to the quality of life of dogs and owners alike. We described age-related changes in pet dogs' cognition, personality, vocalisation, sensory perception, brain activity, gut microbiome composition, and gene expression. Specifically, we found similarities with humans in 1) the age-related changes of memory, learning, and personality traits; 2) the “positivity effect”, i.e. a diminished reactivity to negative emotional stimuli in older dogs; 3) sleep spindles (EEG patterns in sleeping dogs’ brain) which can be used as a biomarker of cognitive ageing; 4) a negative association between memory performance and the levels of Actinobacteria in the gut, mimicking observations in people with Alzheimer’s disease; 5) genetic mutations, specific to 'Methuselah' (22-27-year-old) dogs in genes related to longevity; 6) age-related alterations of the mRNA transcriptome; 7) positive correlation between age, cognitive dysfunction score, and Abeta-42, an Alzheimer’s disease-associated protein in the brain. Tissues originated from our novel Canine Brain and Tissue Bank which is open to international collaborations.
1. Behaviour. We developed reliable and valid behaviour tests for measuring age-related cognitive and behavioural differences without large apparatuses or pre-training. We found a single, higher-order cognitive factor ("g", colloquially also known as “general intelligence”). We investigated g's change throughout four years in a longitudinal study and tested its relationship with various non-cognitive factors (age, environmental and demographic predictors, neural structure, and activity). Age has negative partial mediation effects on g through the personality facets Active engagement and Playfulness. The existence of a g factor is a promising development for the field of comparative cognition. It can help to study the evolutionary paths and social and ecological conditions leading to its emergence.
Dogs show similarities with humans in the personality traits as they age: e.g. interest in problem-solving rises until middle age before levelling off. In a longitudinal study, we detected individual differences in the age-related changes of personality traits.
We applied a training method for old dogs based on touchscreen technology. Trained dogs’ cognitive decline starts later. The method can increase the positive attitude of owners toward their old dogs.
We studied the processing of emotionally loaded stimuli in non-human animals for the first time and found that the "positivity effect" exists in dogs, i.e. similar to humans, old dogs react less to negative emotions, while the responsiveness toward positive emotions remains intact.
We investigated gut microbiome and vocalisations, too. Memory performance and age are associated with the composition of intestinal microbiota and vocal parameters also change with age: whines become more harmonic and show a higher non-linear phenomena ratio, suggesting loss in the precise neural control of the larynx.
Specifying the normal rates of cognitive decline in healthy dogs enables the easier detection of pathological decline therefore it contributes to dog welfare.
2. Neuroscience. Most notably, the Canine Brain and Tissue Bank (CBTB) emerged in the context of our work and quickly grew into one of the biggest biobanks for dogs. We developed a unique pet dog body donation protocol for owners who, in agreement with their veterinarian, voluntarily offer their dog’s body for research after medically reasoned euthanasia. We have established a state-of-the-art communication, transportation, and sampling system. We collect brain (cerebellum, cerebral cortex, and pons), muscle, skin, peripheral neural tissue (ganglions), thyroid gland, lymph node, cerebrospinal fluid (CSF), and buccal swab samples of deceased subjects, with the possibility to provide good quality samples for next-generation genomic technologies. The samples, together with thorough documentation of the dogs’ previous, repeatedly measured cognitive performance allow us to correlate the post-mortem physiological data with the behavioural measurements.
We also advanced the development of a new label-based brain atlas and a multimodal imaging atlas for dogs, as well as a method for extracting the resting-state network of dog brains from task-neutral fMRI recordings, and generating virtual endocranial casts for 400 dog breeds. Building upon the establishment of a non-invasive protocol for measuring EEG in dogs, the project led to the development of an automated detector for sleep spindles: thalamo-cortical discharges which can be detected with surface EEG during slow-wave sleep. We integrated these results with other advances in comparative (across species) sleep spindle research. The method can also be expected to inspire the development of similar EEG analysis tools for dogs (and possibly other animals) in the future.
3. Genetics. Our GWA study on extremely old dogs suggests that fine-tuning of genetic regulatory networks may play a pivotal role in ageing. Based on the tissues from the CBTB, we found (1) a novel age-related biomarker (CDKN2A mRNA) in the dog brain and muscle; (2) with a newly developed Luminex assay, a positive correlation between amyloid beta levels (the main biomarker of Alzheimer's disease) in three brain regions, age, and a canine cognitive dysfunction score, and (3) differentially expressed genes between young and old dogs' brains and blood, many of which were linked to neural function, immune system, and protein synthesis. The results further support the suitability of dogs in translational aging research.
Dogs show similarities with humans in the personality traits as they age: e.g. interest in problem-solving rises until middle age before levelling off. In a longitudinal study, we detected individual differences in the age-related changes of personality traits.
We applied a training method for old dogs based on touchscreen technology. Trained dogs’ cognitive decline starts later. The method can increase the positive attitude of owners toward their old dogs.
We studied the processing of emotionally loaded stimuli in non-human animals for the first time and found that the "positivity effect" exists in dogs, i.e. similar to humans, old dogs react less to negative emotions, while the responsiveness toward positive emotions remains intact.
We investigated gut microbiome and vocalisations, too. Memory performance and age are associated with the composition of intestinal microbiota and vocal parameters also change with age: whines become more harmonic and show a higher non-linear phenomena ratio, suggesting loss in the precise neural control of the larynx.
Specifying the normal rates of cognitive decline in healthy dogs enables the easier detection of pathological decline therefore it contributes to dog welfare.
2. Neuroscience. Most notably, the Canine Brain and Tissue Bank (CBTB) emerged in the context of our work and quickly grew into one of the biggest biobanks for dogs. We developed a unique pet dog body donation protocol for owners who, in agreement with their veterinarian, voluntarily offer their dog’s body for research after medically reasoned euthanasia. We have established a state-of-the-art communication, transportation, and sampling system. We collect brain (cerebellum, cerebral cortex, and pons), muscle, skin, peripheral neural tissue (ganglions), thyroid gland, lymph node, cerebrospinal fluid (CSF), and buccal swab samples of deceased subjects, with the possibility to provide good quality samples for next-generation genomic technologies. The samples, together with thorough documentation of the dogs’ previous, repeatedly measured cognitive performance allow us to correlate the post-mortem physiological data with the behavioural measurements.
We also advanced the development of a new label-based brain atlas and a multimodal imaging atlas for dogs, as well as a method for extracting the resting-state network of dog brains from task-neutral fMRI recordings, and generating virtual endocranial casts for 400 dog breeds. Building upon the establishment of a non-invasive protocol for measuring EEG in dogs, the project led to the development of an automated detector for sleep spindles: thalamo-cortical discharges which can be detected with surface EEG during slow-wave sleep. We integrated these results with other advances in comparative (across species) sleep spindle research. The method can also be expected to inspire the development of similar EEG analysis tools for dogs (and possibly other animals) in the future.
3. Genetics. Our GWA study on extremely old dogs suggests that fine-tuning of genetic regulatory networks may play a pivotal role in ageing. Based on the tissues from the CBTB, we found (1) a novel age-related biomarker (CDKN2A mRNA) in the dog brain and muscle; (2) with a newly developed Luminex assay, a positive correlation between amyloid beta levels (the main biomarker of Alzheimer's disease) in three brain regions, age, and a canine cognitive dysfunction score, and (3) differentially expressed genes between young and old dogs' brains and blood, many of which were linked to neural function, immune system, and protein synthesis. The results further support the suitability of dogs in translational aging research.