Sleep macrostructure is modulated by positive and negative social experience in adult pet dogs

Abstract

The effects of emotionally valenced events on sleep physiology are well studied in humans and laboratory rodents. However, little is known about these effects in other species, despite the fact that several sleep characteristics differ across species and thus limit the generalizability of such findings. Here we studied the effect of positive and negative social experiences on sleep macrostructure in dogs, a species proven to be a good model of human social cognition. A non-invasive polysomnography method was used to collect data from pet dogs ( = 16) participating in 3-hour-long sleep occasions. Before sleep, dogs were exposed to emotionally positive or negative social interactions (PSI or NSI) in a within-subject design. PSI consisted of petting and ball play, while NSI was a mixture of separation, threatening approach and still face test. Sleep macrostructure was markedly different between pre-treatment conditions, with a shorter sleep latency after NSI and a redistribution of the time spent in the different sleep stages. Dogs' behaviour during pre-treatments was related to the macrostructural difference between the two occasions, and was further modulated by individual variability in personality. This result provides the first direct evidence that emotional stimuli affect subsequent sleep physiology in dogs.

Heart Rate and Heart Rate Variability during Sleep in Family Dogs (Canis familiaris). Moderate Effect of Pre-Sleep Emotions

“…Thus, for Study II, we analysed the ECG channel of polysomnography recordings conducted after a short positive versus a negative dog–human social interaction (see later). The original study [ 49 ] found that sleep macrostructure was markedly different between pre-treatment conditions, with a shorter sleep latency after the negative social interaction and a redistribution of the time spent in the different sleep stages. However, changes in cardiac activity have not been investigated in this context.…”

“…Dogs were not trained for the purpose of this experiment. (Note that originally N = 16 dogs participated in this experiment [ 49 ], however the ECG signal could not be analysed in case of 2 subjects due to artefacts impeding R peak detection.)…”

“…The negative social interaction (NSI) consisted of a separation episode when the dog was left alone (2 min), a threatening approach by an unfamiliar experimenter (1 min), and a still face situation (3 min). The sleep structure data following the PSI and NSI was reported in [ 49 ], see also that paper for further procedural details. The behaviour of the dogs during PSI and NSI was also reported in [ 49 ], with dogs during PSI receiving petting from and engaging in play with both the owner and the experimenter, while during NSI looking and standing at the door in separation, moving off to avoid the threatening human and averting gaze and vocalising during the sill face test.…”

“…It has been shown that dogs, despite displaying a polyphasic sleep structure, show several similarities to human sleep including the EEG spectra of the different sleep stages [ 46 ], as well as the interrelatedness of sleep and memory consolidation [ 47 , 48 ]. Furthermore, recently it was found that significant differences can be observed in the macrostructure of sleep following negative (threatening approach, separation) or positive (playing, petting) pre-treatments [ 49 ]. Data from these non-invasive studies is mostly in line with the decades of canine sleep research carried out with invasive methods, mainly focused on neurological conditions such as epilepsy [ 50 ] and narcolepsy [ 51 ].…”

“…Thus, Study I will provide descriptive data on dogs’ heart rate and heart rate variability during different stages of sleep after testing the effect of sampling length (20 s, 1 min, 5 min segments used for calculating heart rate data) as well as sample selection (longest period of the given sleep stage versus first occurrence of a given sleep stage). This is followed by Study II, testing the effect of pre-sleep positive and negative social interactions by analysing the ECG data from polysomnography recordings by [ 49 ].…”