Abstract
Functional hemispheric asymmetry was evidenced in many species during sleep. Dogs seem to show hemispheric asymmetry during wakefulness; however, their asymmetric neural activity during sleep was not yet explored. The present study investigated interhemispheric asymmetry in family dogs using non-invasive polysomnography. EEG recordings during 3-h-long afternoon naps were carried out (N = 19) on two occasions at the same location. Hemispheric asymmetry was assessed during NREM sleep, using bilateral EEG channels. To include periods with high homeostatic sleep pressure and to reduce the variance of the time spent in NREM sleep between dogs, the first two sleep cycles were analysed. Left hemispheric predominance of slow frequency range was detected in the first sleep cycle of sleep recording 1, compared to the baseline level of zero asymmetry as well as to the first sleep cycle of sleep recording 2. Regarding the strength of hemispheric asymmetry, we found greater absolute hemispheric asymmetry in the second sleep cycle of sleep recording 1 and 2 in the frequency ranges of alpha, sigma and beta, compared to the first sleep cycle. Differences between sleep recordings and consecutive sleep cycles might be indicative of adaptation-like processes, but do not closely resemble the results described in humans.
Highlights
Functional hemispheric asymmetry was evidenced in many species during sleep
Since the first sleep cycle of sleep recording 1 significantly deviated from the hypothetical zero asymmetry as well as from the first cycle of sleep recording 2, we further examined whether the left hemispheric predominance in the low frequency band showed a relation with the degree of the first-night effect (FNE)
We found interhemispheric differences regarding the direction of hemispheric asymmetry
Summary
Functional hemispheric asymmetry was evidenced in many species during sleep. Dogs seem to show hemispheric asymmetry during wakefulness; their asymmetric neural activity during sleep was not yet explored. Functional asymmetry of the brain occurs if the right and left hemispheres intercede different behavioural and cognitive processes[1] This phenomenon generally exists in a wide range of non-human species, including insects, fish, amphibians and birds[2,3,4,5,6]. In addition to the investigation of awake functioning with fMRI (e.g.20,21) and EEG (e.g.22,23), dogs’ natural sleep architecture has been widely studied by non-invasive polysomnography (PSG) adapted to dogs (for review[24,25]). This method has been successfully conducted in several studies investigating the sleep architecture with pre-sleep experiences, such as memory c onsolidation[26], emotion p rocessing[27] and sensitivity to the location
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