Abstract
The sleeping activity of family dogs has been studied increasingly in the past years. Recently, a validated, non-invasive polysomnographic method has been developed for dogs, enabling the parallel recording of several neurophysiological signals on non-anesthetized family dogs, including brain activity (EEG), eye movements (EOG), cardiac (ECG), and respiratory activity (PNG). In this study, we examined the ECG (N = 30) and respiratory signals (N = 19) of dogs during a 3-h sleep period in the afternoon, under laboratory conditions. We calculated four time-domain heart rate variables [mean heart rate (HR), SDNN, RMSSD, and pNN50] from the ECG and the estimated average respiratory frequency from the respiratory signal. We analyzed how these variables are affected by the different sleep-wake phases (wakefulness, drowsiness, NREM, and REM) as well as the dogs’ sex, age and weight. We have found that the sleep-wake phase had a significant effect on all measured cardiac parameters. In the wake phase, the mean HR was higher than in all other phases, while SDNN, RMSSD, and pNN50 were lower than in all other sleep phases. In drowsiness, mean HR was higher compared to NREM and REM phases, while SDNN and RMSSD was lower compared to NREM and REM phases. In REM, SDNN, and RMSSD was higher than in NREM. However, the sleep-wake phase had no effect on the estimated average respiratory frequency of dogs. The dogs’ sex, age and weight had no effect on any of the investigated variables. This study represents a detailed analysis of the cardiac and respiratory activity of dogs during sleep. Since variations in these physiological signals reflect the dynamics of autonomic functions, a more detailed understanding of their changes may help us to gain a better understanding of the internal/emotional processes of dogs in response to different conditions of external stimuli. As such, our results are important since they are directly comparable to human findings and may also serve as a potential basis for future studies on dogs.
Highlights
Dogs (Canis familiaris) have been proposed as a suitable model for studying the evolution of human cognition and social cognitive processes due to their evolutionary adaptation to the human environment and human-analog socio-cognitive skills
The mean heart rate (HR) of dogs was different depending on the phase (F3,108 = 22.36, p < 0.001), being higher in the wake phase than in all sleep phases (p < 0.001 for all pairwise contrasts), and it was higher in drowsiness compared to the NREM (p = 0.001) and REM (p = 0.004) (Figure 4)
The sleep-wake phase had a significant effect on the SDNN parameter of dogs (F3,108 = 24.341, p < 0.001)
Summary
Dogs (Canis familiaris) have been proposed as a suitable model for studying the evolution of human cognition and social cognitive processes due to their evolutionary adaptation to the human environment and human-analog socio-cognitive skills (behavioral: Miklósi and Topál, 2013; neural mechanisms: Bunford et al, 2017). Considering our shared history dating back at least 14000 years (Savolainen et al, 2002; Miklósi, 2008), dogs represent the main subject of studies concentrating on the relationship between humans and animals (Hosey and Melfi, 2014). The human-animal bond is characterized as a mutually beneficial and dynamic relationship between people and animals (Hosey and Melfi, 2014) and there has been a lot of studies concentrating on the effect of dogs on humans. We still don’t have much information about the effect of humans on the physiological and neurobiological dynamics of dogs
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