Spontaneous K-complexes in behaving rats.

The K-complex (KC) is an electrographic rhythmic pattern present in human and cat sleep EEG. In long-term multisite videoEEG recordings in behaving Sprague-Dawley (SD) rats, well-defined spontaneous KCs were observed during sleep. Sprague-Dawley rats were implanted with multiple electrodes bilaterally along the antero-posterior axes at the locations F1, F2, F7, F8, T3, T4, P3, P4, all against a ground reference placed in the midline above the cerebellum. Multiple, closely spaced cortical electrodes allowed two-dimensional surface brain mapping of the power spectra distribution. Two silver wires were also inserted into nuchal muscles to record EMG activity. Each rat was monopolarly recorded from 0900 h to 1500 h in a natural dark-light rodents, we examined the patterns of appearance in various conditions, the progression through a full sleep-waking cycle, the shape, density, spectral components, and spatial distribution in power spectra. The rat KC appears to share similar features with the human and cat KC.