Cardiac rhythmic patterns in neuronal activity are related to the firing rate of the neurons: I. Brainstem reticular neurons of dogs.

Cardiac rhythmic discharge patterns (CRDP) of brainstem reticular neurons in anesthetized dogs were estimated by ECG-triggered post-event-time histograms (PETH). Modulations of the CRDP occur, whenever the firing levels of the neurons slowly change with periods longer than the cardiac cycle. Therefore, in the activity of one and the same neuron different types of CRDP can occur interlaced in time. 'Partial' PETHs calculated according to the discharge level of the neurons make these various CRDP obvious. On the other hand, the CRDP are not always so clear in the 'total' PETHs, taken from the continuous periods of activity. The meaning of these different CRDP for regulatory processes of the organism is discussed. We study the processing of the easily identifiable signal in neuron activity, i.e., cardiac rhythm, to illustrate how signal processing depends on the momentary activity level of the neurons which is influenced by other afferent signals and by inflows from central structures reaching the neurons.