Biology session

INTRODUCTION Dogs (Canis familiaris) are excellent models of human behaviour as during domestication they have adapted to the same environment as humans. There have been many comparative studies on dog behaviour with a focus on psychiatric conditions, such as ageing. However several easily measurable and analysable psychophysiological variables that are related to age in humans are still largely unexplored in dogs. One such measure is rapid eye movement density (EMD) during REM sleep. The aim of this study was to reveal the relationship between the EMD and the age in dogs controlling for potential confounding variables such as sex, body size and REM sleep duration.

METHODS Thirty family dogs of different ages (9 months – 14.5 years old) and breeds participated in a three hours long non-invasive polysomnography test. The study was repeated on five dogs (1-3.5 years later). The signal of the electrooculogram (EOG) was used to detect the rapid eye movements during REM sleep, and EMD was calculated based on these data.

RESULTS The interaction of age and sex had a significant effect on the EMD. In male dogs EMD increased with age, whereas in females there was no such effect. In males there is no connection between the body mass and the EMD, in females a negative relation can be observed. Repeated studies show that EMD does not uniformly change with age in different individuals.

DISCUSSION Our results support that it is worth to study EMD as a simple psychophysiological variable in dogs, as similarly to human data a relationship can be observed between EMD and different variables.