STUDIES ON EFFECTS OF BRAIN STEM STIMULATION UPON MOTOR AND AUTONOMIC REFLEXES, WITH SPECIAL REFERENCES TO INTERRELATIONSHIPS BETWEEN EFFECTS

Abstract

The mechanisms of inhibitory and facilitatory effects of the brain stem reticular formation, upon motor and autonomic reflexes, such as monosynaptic reflex (MSR), polysynaptic reflex (PSR) of extensor and flexor motoneurons and galvanic skin reflex (GSR), were analyzed by stimulating single points in the brain stem with single or repetitive pulses. Experiments were conducted on 65 adult cats decerebrated at precollicular-chiasma level.
1. By repetitive stimulation of the same single points in the brain stem, generalized inhibitory and facilitatory effects upon these motor and autonomic reflexes were observed in the medial medulla oblongata and pons respectively, whereas from the lateral medulla oblongata and midbrain various combinations of inhibitory and facilitatory effects upon above noted 5 reflexes were obtained, with some differences of effects of laterality and with some special interrelationships between these effects.
2. Following single pulse stimulation of the brain stem, five different types of effect upon extensor MSR. were obtained. Among them, diphasic inhibitory type, viz., initial slight increase of amplitude of MSR followed by its marked decrease, was observed in relatively high percentages by stimulating points in the medial and lateral medulla oblongata and midbrain, from where simple inhibitory effects were induced by repetitive stimulation.
3. In regard to GSR, there was a close parallelism between the effects of brain stem stimulation upon GSR elicited by radial nerve stimulation and upon spontaneous variations of skin potentials especially in the case of inhibition.