Simultaneous changes of rhythmic organization in brainstem neurons, respiration, cardiovascular system and EEG between 0.05 Hz and 0.5 Hz

Several neurons from different regions of the brainstem of anesthetized dogs were simultaneously recorded, together with various parameters of the cardiovascular system, respiration, efferent sympathetic neural activities and cortical activity. Often rhythmic changes of activity in the range 0.05-0.5 Hz could be observed in the simultaneously recorded signals. The rhythms were analysed in time domain and by power spectra and their changes depicted over the time. The most striking rhythms between 0.05 Hz and 0.5 Hz are the respiratory rhythm and those rhythms that originate in reticular neurons of the common brainstem system as well as their respective harmonics, i.e. the ranges around the integer multiple frequencies of these basic rhythms. The observed oscillations can vanish and reappear at times. Frequencies of basic oscillations and harmonics and their amplitudes an subject to distinct slow modulations. These modulations can have irregular as well as regular courses. The different rhythms can appear separately or simultaneously in the single signals. The most important phenomenon to be observed is that the rhythms mutually influence their frequencies, which follows the rules of 'relative coordination' as described by E. v. Hoist. Such changes of rhythmic activities generally also concern the ranges of harmonics of the basic rhythms. Rhythmic influences on peripheral functional systems, e.g. the cardiovascular system, are most distinct at times when the different rhythms overlap in their frequency ranges. This holds not only for the ranges of basic frequencies, but also for the ranges of their harmonics. Further it was found that rhythms with the some basic frequencies may not only appear simultaneously, but also al various times in the different functional systems. The temporal course of changes of these rhythms, their interactions and their influence on the processing of cardiac rhythmic neuronal discharge patterns is demonstrated. The meaning of the mutually influencing rhythms for the functional organization of central nervous structures is discussed. (C) 1998 Elsevier Science B.V.