We have successfully measured the sleep electroencephalogram (EEG) of 12 family cats
during an afternoon nap using a completely noninvasive methodology originally developed
and validated for family dogs. Extracting both macrostructural and spectral sleep
variables from the acquired data, we: (1) provided a descriptive analysis of sleep
structure in cats and the power spectral density (PSD) distribution considering 3
sleep stages—drowsiness, non-rapid eye movement (NREM), and rapid eye movement (REM)
sleep; and (2) compared the results to those obtained in family dogs measured under
the same conditions and using the same methodology. Importantly, our description of
sleep structure and PSD distribution in cats proved to be comparable to those of earlier
invasive studies, highlighting that appropriate noninvasive methodologies may provide
a viable alternative to those that are invasive in some cases. While no macrostructural
differences were found between the sleep of cats and dogs, and the characteristic
PSDs were mostly similar across sleep stages within the 2 species, the high-frequency
resolution comparison of PSD distributions revealed differences between the 2 species
in all sleep stages (concerning the delta, theta, alpha, sigma, and beta bands in
drowsiness and NREM sleep; and the delta, alpha, and sigma bands in REM sleep). Potential
factors underlying these differences are discussed, including differences in circadian
rhythms, sleep homeostatic regulation, experienced stress, or even differential attitudes
toward owners—highlighting important links between sleep characteristics and often
more complex neural and behavioral features.
