Melissa Smith’s research while affiliated with University of Bristol and other places

Chronic pain in humans is associated with impaired working memory but it is not known whether this is the case in long-lived companion animals, such as dogs, who are especially vulnerable to developing age-related chronic pain conditions. Pain-related impairment of cognitive function could have detrimental effects on an animal’s ability to engage with its owners and environment or to respond to training or novel situations, which may in turn affect its quality of life. This study compared the performance of 20 dogs with chronic pain from osteoarthritis and 21 healthy control dogs in a disappearing object task of spatial working memory. Female neutered osteoarthritic dogs, but not male neutered osteoarthritic dogs, were found to have lower predicted probabilities of successfully performing the task compared to control dogs of the same sex. In addition, as memory retention interval in the task increased, osteoarthritic dogs showed a steeper decline in working memory performance than control dogs. This suggests that the effects of osteoarthritis, and potentially other pain-related conditions, on cognitive function are more clearly revealed in tasks that present a greater cognitive load. Our finding that chronic pain from osteoarthritis may be associated with impaired working memory in dogs parallels results from studies of human chronic pain disorders. That female dogs may be particularly prone to these effects warrants further investigation.

Chronic pain in humans is associated with impaired working memory but it is not known whether this is the case in long-lived companion animals, such as dogs, who are especially vulnerable to developing age-related chronic pain conditions. Pain-related impairment of cognitive function could have detrimental effects on an animal’s ability to engage with its owners and environment or to respond to training or novel situations, which may in turn affect its quality of life. This study compared the performance of 20 dogs with chronic pain from osteoarthritis and 21 healthy control dogs in a disappearing object task of spatial working memory. Female neutered osteoarthritic dogs, but not male neutered osteoarthritic dogs, were found to have lower predicted probabilities of successfully performing the task compared to control dogs of the same sex. This shows that chronic pain from osteoarthritis may be associated with impaired working memory in dogs, a result which parallels findings from studies of human chronic pain disorders. That female dogs may be particularly prone to these effects warrants further investigation.

Human patients with chronic pain from osteoarthritis often report impaired sleep, but it is not yet known if sleep is also impaired in dogs with osteoarthritis. This study aimed to compare the night-time sleep behaviour of osteoarthritic (N=20) and healthy control (N=21) dogs over a 28-day period, using an actigraphic device (the FitBark activity monitor) and an owner questionnaire designed to measure sleep quality (the SNoRE). Actigraphic data were aggregated to estimate the time each dog spent resting each night, and questionnaires were completed every 7 days. Data were analysed using robust mixed-effects linear regression. The presence of clinical signs of osteoarthritis had a significant effect on actigraphic recordings, with osteoarthritic dogs spending lower proportions of the night period resting (and therefore higher proportions of the night period active) compared to control dogs (z=2.21; P=0.0268). However, there was no significant difference between the SNoRE scores of osteoarthritic and control dogs (z=-1.01, p=0.312). The actigraphic findings of this study suggest that dogs with osteoarthritis may experience impaired sleep, which could have important welfare implications and merits further study.

Variation in executive function and age-related cognitive decline may underlie the emergence of behaviour and welfare problems in dogs. A better understanding of such links, and of dog cognition in general, will be facilitated by the development of cognitive tasks that can be readily implemented, including with publicly-owned dogs that are available for relatively short testing periods. Working memory is a key component of cognitive and executive function that is often measured using tests such as delayed-non-match-to-sample or radial-arm maze which require extensive training and testing. Here we successfully adapt the Holeboard Task to measure working and reference memory in dogs, and show that another test of working memory, the Disappearing Object Task, can be performed in a single day. Working memory (p = 0.002) and reference memory (p < 0.001) scores in a 16-hole Holeboard Task (four holes baited) increased across sessions, with reference memory scores falling steeply as expected when the configuration of baited buckets changed. In the Disappearing Object Task dogs were able to successfully locate an object displaced behind one of four visual barriers, and their ability to do this fell as the memory retention interval (0 s, 30 s, 60 s, 120 s, 240 s) between hiding and locating the object increased (p < 0.001). Holeboard and Disappearing Object working memory measures were not correlated, possibly due to differences in the motivational context and exact learning demands of the tasks. In summary we show that the Holeboard Task can be adapted for use in dogs and that the Disappearing Object Task can be implemented in a single day. The latter task may be particularly useful for working memory studies of dogs owned by the public where prolonged access is often infeasible, and the three-day Holeboard Task is faster to implement than other commonly used laboratory-based tasks.

Syringomyelia is a common and chronic neurological disorder affecting Cavalier King Charles Spaniels. The condition is putatively painful, but evaluating the affective component of chronic pain in non-human animals is challenging. Here we employed two methods designed to assess animal affect - the judgement bias and reward loss sensitivity tests - to investigate whether Cavalier King Charles Spaniels with syringomyelia (exhibiting a fluid filled cavity (syrinx) in the spinal cord of ≥2 mm diameter) were in a more negative affective state than those without the condition. Dogs with syringomyelia did not differ in age from those without the condition, but owners reported that they scratched more (P < 0.05), in line with previous findings. They also showed a more negative judgement of ambiguous locations in the judgement bias task (P < 0.05), indicating a more negative affective state, but did not show a greater sensitivity to loss of food rewards. These measures were unaffected by whether the dog was or was not receiving pain-relieving medication. Across all subjects, dogs whose owners reported high levels of scratching showed a positive judgement bias (P < 0.05), indicating that scratching was not directly associated with a negative affective state. Tests of spontaneous behaviour (latency to jump up to or down from a 30 cm high platform) and physiology (thermography of the eye) did not detect any differences. These results provide initial evidence from the judgement bias task that syringomyelia may be associated with negative affect in dogs, and open the way for further and larger studies to confirm findings and investigate the effects of medication in more detail.