The reduced responsiveness of reticulospinal neurones to paired stimuli in cats.

In anaesthetized cats, the reactions of reticulospinal (RS) neurones were tested to paired stimuli applied at the periphery and in central structures (spinal cord funiculi, the reticular formation). This resulted in depression or disappearance of polysynaptic responses to the electrical testing stimuli. The intensity and duration of depression in the same animal after stimulation of peripheral and central structures was comparable, indicating that the responsible mechanisms act chiefly in the reticular formation itself. Polysynaptic discharges from RS neurones could be evoked from one source even when their responses to frequent stimulation of another source was depressed; this shows that attenuation affects reticular formation neurones before RS neurone level. Interposition of this mechanism between receptors and the RS system is very effective from the functional aspect: when the transmission and processing of a signal which does not bring any new information is minimized, the responses of the efferent RS system are minimized at the same instant.