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Updated: Jul 9, 2026
Quantifying Infra-slow Dynamics of Spectral Power and Heart Rate in Sleeping Mice
Published on: August 2, 2017
Characterization of the 7-12 Hz EEG oscillations during immobile waking and REM sleep in behaving rats
G Marini1, P Ceccarelli, M Mancia
1Centro di ricerca sperimentale sul sonno Giuseppe Moruzzi, Istituto di Fisiologia Umana II, Università degli Studi, via Mangiagalli 32, 20133 Milano, Italy. gabriella.marini@unimi.it
Objective:
The aim of this study was to examine whether the mu rhythm is also seen in the EEG of alert, undrugged and freely moving rats. The mu rhythm is a salient neocortical synchrony with dominant frequency in the 8-13 Hz band, initially recorded over the parietal and frontal areas of humans and subsequently investigated in monkeys and cats using the term sensorimotor rhythm. In the rat, these oscillations have been described only at single-unit level in the trigeminal system or in the cerebellar hemispheres.
Methods:
In order to identify this rhythm, according to the "functional topography" approach, we examined the shape, spectral content, spatial distribution in power spectra, and functional reactivity. Rats were implanted with multiple electrodes along the antero-posterior axes. Monopolar recordings and simultaneous continuous 24-h video were taken in natural dark-light cycles for 6 consecutive days. Brain mappings based on quantitative spectral analysis were made.
Results:
Spontaneous well-defined 7-12 Hz EEG oscillations were found during immobile wakefulness and REM sleep. Comparable features of these patterns indicated that they are largely analogous to the mu rhythm.
Conclusions:
The conservation of mu rhythm in the EEG across mammalian species with different cortical extension suggests that it is functionally important.
Significance:
Given the great interest aroused by the properties of the mirror neurons, reflected by the mu rhythm, the detailed characterization of this rhythm in rats during natural life may prove useful in prospective evolutionary studies.
Insights
Researchers identified a mu rhythm (8-13 Hz EEG oscillations) in freely moving rats, suggesting its functional importance across mammalian species. This finding may aid evolutionary studies on mirror neurons.
Area of Science:
- Neuroscience
- Comparative Mammalian Studies
Background:
- The mu rhythm, a neocortical synchrony (8-13 Hz), is well-documented in humans, monkeys, and cats.
- Previous rat studies described these oscillations only at the single-unit level in specific brain regions.
Purpose of the Study:
- To investigate the presence of mu rhythm in the electroencephalogram (EEG) of alert, freely moving rats.
- To characterize the mu rhythm's features in rats using a functional topography approach.
Main Methods:
- Implanted rats with multiple electrodes for EEG recordings.
- Utilized monopolar recordings and continuous 24-hour video monitoring over six days.
- Performed quantitative spectral analysis for brain mapping.
Main Results:
- Identified spontaneous, well-defined 7-12 Hz EEG oscillations during immobile wakefulness and REM sleep.
- Observed patterns analogous to the mu rhythm in rats.
Conclusions:
- The presence of mu rhythm in rats suggests its functional importance and conservation across mammalian species.
- Characterizing rat mu rhythm may benefit evolutionary studies on mirror neuron systems.
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