Spatial interactions and stimulus-response relations of unit responses evoked by somato-sensory stimuli in the feline caudal medullary reticular formation.

Responses of neurons in the bulbar reticular area to separate and simultaneous stimulation of the forelimbs were recorded extracellularly in chloralose-anaesthetized cats. On increasing the stimulus intensity the number of spikes per response increased while the initial latency and interspike intervals decreased in accordance with the functional property of the neuron. Responses evoked by simultaneous stimulation displayed more spikes and a shorter latency than those evoked by separate stimuli of corresponding intensities. The differences in the responses evoked simultaneously and the sums of responses evoked separately showed characteristic distributions as a function of the latter. Three types of distribution were distinguished. The results indicate that stimulus-response relations play a determining role in the mechanism of spatial integration.