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The association between age and delta power activity, given weight. Darker and larger dots indicate larger dogs.
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Age-related differences in dog sleep and the age at which dogs reach adulthood as indexed by sleep electrophysiology are unknown. We assessed, in (1) a Juvenile sample (n = 60) of 2–14-month-old dogs (weight range: 4–68 kg), associations between age, sleep macrostructure, and non-rapid eye movement (NREM) EEG power spectrum, whether weight moderate...
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Citations
... In addition to exploring fundamental and comparative questions, researchers have also investigated the effect of biological variables such as age, sex, and weight on sleep activity. The effect of age on sleep macrostructure is significant, showing correlations with the power of some frequency bands [52]. Specifically, past 8 months of age, older dogs had higher powers of alpha, beta and gamma frequencies, and lower delta frequencies, compared to younger dogs. ...
The emerging field of canine cognitive neuroscience uses neuroimaging tools such as electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to map the cognitive processes of dogs to neural substrates in their brain. Within the past decade, the non-invasive use of EEG has provided real-time, accessible, and portable neuroimaging insight into canine cognitive processes. To promote systematization and create an overview of framings, methods and findings for future work, we provide a systematic review of non-invasive canine EEG studies (N=22), dissecting their study makeup, technical setup, and analysis frameworks and highlighting emerging trends. We further propose new directions of development, such as the standardization of data structures and integrating predictive modeling with descriptive statistical approaches. Our review ends by underscoring the advances and advantages of EEG-based canine cognitive neuroscience and the potential for accessible canine neuroimaging to inform both fundamental sciences as well as practical applications for cognitive neuroscience, working dogs, and human-canine interactions.
... To evaluate the consistency of behavior over an extended period, using a longer interval of assessment may be necessary. In addition, in a study that tracks individuals over an extended period, the lack of control for maturation can impede the accuracy of determining cause-and-effect relationships between study variables [98]. Therefore, to achieve more reliable results, we should include a control group that does not participate in the training and take age into account as a potential confounding variable. ...
Functional brain connectivity based on resting-state functional magnetic resonance imaging (fMRI) has been shown to be correlated with human personality and behavior. In this study, we sought to know whether capabilities and traits in dogs can be predicted from their resting-state connectivity, as in humans. We trained awake dogs to keep their head still inside a 3T MRI scanner while resting-state fMRI data was acquired. Canine behavior was characterized by an integrated behavioral score capturing their hunting, retrieving, and environmental soundness. Functional scans and behavioral measures were acquired at three different time points across detector dog training. The first time point (TP1) was prior to the dogs entering formal working detector dog training. The second time point (TP2) was soon after formal detector dog training. The third time point (TP3) was three months’ post detector dog training while the dogs were engaged in a program of maintenance training for detection work. We hypothesized that the correlation between resting-state FC in the dog brain and behavior measures would significantly change during their detection training process (from TP1 to TP2) and would maintain for the subsequent several months of detection work (from TP2 to TP3). To further study the resting-state FC features that can predict the success of training, dogs at TP1 were divided into a successful group and a non-successful group. We observed a core brain network which showed relatively stable (with respect to time) patterns of interaction that were significantly stronger in successful detector dogs compared to failures and whose connectivity strength at the first time point predicted whether a given dog was eventually successful in becoming a detector dog. A second ontologically based flexible peripheral network was observed whose changes in connectivity strength with detection training tracked corresponding changes in behavior over the training program. Comparing dog and human brains, the functional connectivity between the brain stem and the frontal cortex in dogs corresponded to that between the locus coeruleus and left middle frontal gyrus in humans, suggestive of a shared mechanism for learning and retrieval of odors. Overall, the findings point toward the influence of phylogeny and ontogeny in dogs producing two dissociable functional neural networks.
... One possibility is to find prolonged REM phases in the brachycephalic dog, since REM is abundant in the early development of some species and may, in fact, be a carry-over from fetal life (Zepelin et al. 2005). Under the latter hypothesis, we would also expect spectral properties of the non-REM sleep stage to be affected, as they rapidly change during early development [decrease in delta and increase in higher frequencies like beta, sigma, and theta until the dogs reach 14 months of age (Reicher et al. 2021)]. ...
... Not only do young animals sleep longer, but in many altricial species (animals that are born relatively immature), the percentage of time spent in REM is highest during the first postnatal days and hypothesized to be a carry-over from fetal life [see Zepelin et al. (2005)]. As the newborns of humans (Kurth et al. 2015), dogs (Reicher et al. 2021), and rats (Jouvet-Mounier et al. 1969) progress in their development, REM durations decrease in favor of a more pronounced non-REM sleep stage. The current study alone cannot prove beyond doubt, however, that the higher percentage of REM sleep observed in brachycephalic dogs is a juvenile trait. ...
... Relative differences in REM between wolves and dogs, albeit preliminary, suggest a higher proportion of REM in the captive, hand-raised wolf (Reicher et al. 2022) and thus, REM duration as a potential marker of juvenile sleeping patterns needs to be taken with caution. Crucially, early development and maturation in dogs (Reicher et al. 2021) and humans (Kurth et al. 2015) is characterized by spectral changes in the non-REM sleep stage. We did not observe CI-dependent differences in non-REM power for the tested frequency bands. ...
The shape of the cranium is one of the most notable physical changes induced in domestic dogs through selective breeding and is measured using the cephalic index (CI). High CI (a ratio of skull width to skull length > 60) is characterized by a short muzzle and flat face and is referred to as brachycephaly. Brachycephalic dogs display some potentially harmful changes in neuroanatomy, and there are implications for differences in behavior, as well. The path from anatomy to cognition, however, has not been charted in its entirety. Here, we report that sleep-physiological markers of white-matter loss (high delta power, low frontal spindle frequency, i.e., spindle waves/s), along with a spectral profile for REM (low beta, high delta) associated with low intelligence in humans, are each linked to higher CI values in the dog. Additionally, brachycephalic subjects spent more time sleeping, suggesting that the sleep apnea these breeds usually suffer from increases daytime sleepiness. Within sleep, more time was spent in the REM sleep stage than in non-REM, while REM duration was correlated positively with the number of REM episodes across dogs. It is currently not clear if the patterns of sleep and sleep-stage duration are mainly caused by sleep-impairing troubles in breathing and thermoregulation, present a juvenile-like sleeping profile, or are caused by neuro-psychological conditions secondary to the effects of brachycephaly, e.g., frequent REM episodes are known to appear in human patients with depression. While future studies should more directly address the interplay of anatomy, physiology, and behavior within a single experiment, this represents the first description of how the dynamics of the canine brain covary with CI, as measured in resting companion dogs using a non-invasive sleep EEG methodology. The observations suggest that the neuroanatomical changes accompanying brachycephaly alter neural systems in a way that can be captured in the sleep EEG, thus supporting the utility of the latter in the study of canine brain health and function.
... In addition to exploring fundamental and comparative questions, researchers have also investigated the impact of biological variables such as age, sex, and weight on sleep activity. The impact of age on sleep macrostructure is significant, showing correlations with the power of some frequency bands [91]. Specifically, past 8 months of age, older dogs had higher powers of alpha, beta and gamma frequencies, and lower delta frequencies, compared to younger dogs. ...
A bstract
The emerging field of canine cognitive neuroscience uses neuroimaging tools such as electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to map the cognitive processes of dogs to neural substrates in their brain. Within the past decade, the non-invasive use of EEG has provided real-time, accessible, and portable neuroimaging insight into canine cognitive processes. To promote systematization and create an overview of framings, methods and findings for future work, we provide a systematic review of non-invasive canine EEG studies (N=22), dissecting their study makeup, technical setup, and analysis frameworks and highlighting emerging trends. We further propose new directions of development, such as the standardization of data structures and integrating predictive modeling with descriptive statistical approaches. Our review ends by underscoring the advances and advantages of EEG-based canine cognitive neuroscience and the potential for accessible canine neuroimaging to inform both fundamental sciences as well as practical applications for cognitive neuroscience, working dogs, and human-canine interactions.
... See Fig. 1 for electrode placement. Gold-coated Ag/ AgCl electrodes were used, secured by Signa Spray Electrode Solution (Parker, United States) and EC2 Grass To correct for differences in EEG filter characteristics across recording devices, a standard calibration process (dog 51,52 ; human 53,54 ) was implemented on devices (1) and (2). For more details, see Supplementary Information. ...
... In our study, although there was a large age variability, we did not separate our subjects in different age groups due to the sparse literature on clear age ranges from puppies to senior dogs (e.g. 51 ). Furthermore, in dogs, it is not clear at what age the onset of SWA decrease occurs and what other factors affect it. ...
... Furthermore, in dogs, it is not clear at what age the onset of SWA decrease occurs and what other factors affect it. For instance, in our previous study, we found that SWA was not only associated with age, but with dogs' weight as well; larger-sized dogs had more SWA than smallersized ones (for more details, see 51 ). In addition, most recent studies mapped different topographical features in ADHD children, using high-resolution EEG method 18,20 . ...
Subjective sleep disturbances are reported by humans with attention-deficit/hyperactivity disorder (ADHD). However, no consistent objective findings related to sleep disturbances led to the removal of sleep problems from ADHD diagnostic criteria. Dogs have been used as a model for human ADHD with questionnaires validated for this purpose. Also, their sleep physiology can be measured by non-invasive methods similarly to humans. In the current study, we recorded spontaneous sleep EEG in family dogs during a laboratory session. We analyzed the association of sleep macrostructure and deep sleep (NREM) slow-wave activity (SWA) with a validated owner-rated ADHD questionnaire, assessing inattention (IA), hyperactivity/impulsivity (H/I) and total (T) scores. Higher H/I and T were associated with lower sleep efficiency and longer time awake after initial drowsiness and NREM. IA showed no associations with sleep variables. Further, no association was found between ADHD scores and SWA. Our results are in line with human studies in which poor sleep quality reported by ADHD subjects is associated with some objective EEG macrostructural parameters. This suggests that natural variation in dogs’ H/I is useful to gain a deeper insight of ADHD neural mechanisms.
... See Fig. 1 for electrode placement. Gold-coated Ag/ AgCl electrodes were used, secured by Signa Spray Electrode Solution (Parker, United States) and EC2 Grass To correct for differences in EEG filter characteristics across recording devices, a standard calibration process (dog 51,52 ; human 53,54 ) was implemented on devices (1) and (2). For more details, see Supplementary Information. ...
... In our study, although there was a large age variability, we did not separate our subjects in different age groups due to the sparse literature on clear age ranges from puppies to senior dogs (e.g. 51 ). Furthermore, in dogs, it is not clear at what age the onset of SWA decrease occurs and what other factors affect it. ...
... Furthermore, in dogs, it is not clear at what age the onset of SWA decrease occurs and what other factors affect it. For instance, in our previous study, we found that SWA was not only associated with age, but with dogs' weight as well; larger-sized dogs had more SWA than smallersized ones (for more details, see 51 ). In addition, most recent studies mapped different topographical features in ADHD children, using high-resolution EEG method 18,20 . ...
Subjective sleep disturbances are reported by humans with attention-deficit/hyperactivity disorder (ADHD). However, no consistent objective findings related to sleep disturbances led to sleep problems removal from ADHD diagnostic criteria. As a model for human ADHD with questionnaires validated for this purpose, dogs have been used also because their sleep physiology can be measured by non-invasive methods similarly to humans. We recorded spontaneous sleep EEG in family dogs during a laboratory session. We analyzed the association of sleep macrostructure and deep sleep (NREM) slow-wave activity (SWA) with a validated owner-rated ADHD questionnaire, assessing inattention (IA), hyperactivity/impulsivity (H/I) and total (T) scores. Higher H/I and T were associated with lower sleep efficiency and longer time awake after initial drowsiness and NREM. IA showed no associations with sleep variables. Further, no association was found between ADHD scores and SWA. Our results are in line with human studies in which poor sleep quality reported by ADHD subjects is associated with some objective EEG macrostructural parameters. This suggests that dogs’ H/I natural variation is useful to gain a deeper insight of ADHD neural mechanisms.
... Since selective breeding of dogs might have affected the developmental trajectories of breeds differently 49 , possibly affecting their sleep EEG as well, we selected a sample of various different breeds and mongrels in our study. They were selected from a database of previously published dog polysomnography experiments 50,51 . The 10 puppies were between the age of 3-5 months (Mage = 3.9, SD = 0.9; all purebreds from 9 different breeds; 5 females; all intact). ...
... We have also found age-related differences in the sleep EEG spectrum in both species, with the proportion of delta power, 'slow wave' activity being lower in senior animals. Although the literature is rather scarce regarding similar changes in non-human animals except for some notable examples 86 , a recent study has identified agerelated sleep pattern changes in young dogs 51 . Specifically, between the ages of 8-14 months, larger-sized and older dogs had less delta and had more theta and alpha power activity. ...
... Representative EEG traces of NREM sleep from different ages of (a-d) dogs and (e-h) wolves. EEG traces of 6-month-old and 1-year-old dogs are from a previous dog polysomnography study51 . ...
Sleep research greatly benefits from comparative studies to understand the underlying physiological and environmental factors affecting the different features of sleep, also informing us about the possible evolutionary changes shaping them. Recently, the domestic dog became an exceedingly valuable model species in sleep studies, as the use of non-invasive polysomnography methodologies enables direct comparison with human sleep data. In this study, we applied the same polysomnography protocol to record the sleep of dog’s closest wild relative, the wolf. We measured the sleep of seven captive (six young and one senior), extensively socialized wolves using a fully non-invasive sleep EEG methodology, originally developed for family dogs. We provide the first descriptive analysis of the sleep macrostructure and NREM spectral power density of wolves using a completely non-invasive methodology. For (non-statistical) comparison, we included the same sleep data of similarly aged dogs. Although our sample size was inadequate to perform statistical analyses, we suggest that it may form the basis of an international, multi-site collection of similar samples using our methodology, allowing for generalizable, unbiased conclusions. As we managed to register both macrostructural and spectral sleep data, our procedure appears to be suitable for collecting valid data in other species too, increasing the comparability of non-invasive sleep studies.
... The aim of this study was to explore whether dogs with clinical signs of osteoarthritis also display impaired sleep compared to healthy control dogs. Polysomnography can distinguish true sleep and wakefulness periods as well as different sleep stages and has been developed for use in dogs by Kis et al. (2014), initially in a canine sleep laboratory with researchers on hand to place electrodes, but more recently in dog owners' homes allowing in situ night-time recordings of up to 3 h duration (Reicher et al., 2021). Given the aim of recording sleep over a 28-day period, it was considered unlikely that sufficient owner compliance including regular and correct placement of electrodes could be achieved each night across the study period in owners' homes. ...
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.
... Additionally, in dogs, similarly to humans [36], the sleep pattern can also be affected by several factors such as age [30,37,38]. In the case of juvenile dogs, age was positively associated with drowsiness duration (2-8 months old). ...
... In the case of juvenile dogs, age was positively associated with drowsiness duration (2-8 months old). Further, age (8-14 months old) was negatively associated with delta and positively with alpha power activities [37]. In the case of adult dogs (2-8 years old), NREM delta activity showed a negative association, while NREM alpha activity showed a positive association with age [30]. ...
... The sleep occasion occurred in a relatively active day [37,42]. Before the measurements, the experimenter (E) explained the procedure to the owner while the dog was allowed to explore the room for 5 to 10 min. ...
Affective neuroscience studies have demonstrated the impact of social interactions on sleep quality. In humans, trait-like social behaviors, such as attachment, are related to sleep brain activity patterns. Our aim was to investigate associations between companion dogs’ spontaneous brain activity during sleep (in the presence of the owner) and their relevant behavior in a task-free social context assessing their attachment towards the owner. In random order, each dog participated in a non-invasive sleep electroencephalogram (EEG) measurement and in the Strange Situation Test (SST) to assess their attachment behavior. We found that higher attachment scores were associated with more time spent in NREM sleep, lower NREM alpha power activity and lower NREM alpha–delta anticorrelation. Our results reveal that, when dogs sleep in a novel environment in the company of their owners, differences in their attachment are reflected in their sleep EEG characteristics. This could be best explained by the different degree that owners could be used as a safe haven in an unfamiliar environment and during the unusual procedure of the first EEG measurement.
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Citation: Carreiro, C.; Reicher, V.; Kis, A.; Gácsi, M. Attachment towards the Owner Is Associated with Spontaneous Sleep EEG Parameters in Family Dogs. Animals 2022, 12, 895. https://www.mdpi.com/2076-2615/12/7/895
