Asymmetric tonic labyrinth reflexes and their interaction with neck reflexes in the decerebrate cat.

Abstract

SUMMARY1. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat-with CI and C2 spinal roots cut. Reflex effects were observed as changes in length of the isotonically loaded medial head of triceps.2. The tonic labyrinth reflexes acted asymmetrically on the medial head of triceps. Side-down rotation of the head produced shortening in medial triceps, whereas side-up rotations of the head resulted in a lengthening.3. The tonic neck reflexes acted asymmetrically on the medial head of triceps. Side-down rotations of the neck produced a lengthening of medial triceps, whereas side-up rotations of the neck resulted in shortening.4. Labyrinth and neck reflexes produce opposite effects on the same limb extensor muscle so that, if the neck innervation is intact, head tilting produces no change in muscle length.5. It is suggested that the interaction between the labyrinth and neck reflexes contributes to the stability of the trunk, allowing the head to move freely on the body without affecting this stability. Labyrinth and neck reflexes need therefore to be considered together as a single system.

The effect of cerebellectomy on the tonic labyrinth and neck reflexes in the decerebrate cat.

“…In the decerebrate cat with an intact cerebellum the tonic labyrinth reflexes, elicited by side-up and side-down head rotations, produced asymmetric length changes in the medial head of triceps in both forelimbs, as described by Lindsay, Roberts & Rosenberg (1976). After cerebellectomy, head movements in either direction produced reflex shortenings in the medial triceps in both forelimbs, in contrast to the normal reciprocal reflex length changes.…”

“…Fig. 1 A illustrates the normal asymmetric pattern of tonic labyrinth reflexes (Lindsay et al 1976) in which a left side-up head rotation produced a lengthening of the left medial triceps and a left side-down head rotation produced a shortening. The response in the same muscle to head rotation subsequent to cerebellectomy is illustrated in Fig.…”

“…For example, right-side down head or neck means that either the vertex of the skull or the axis vertebra was rotated toward the right medial triceps. Further details of the experimental preparation have been given earlier (Lindsay, et al 1976).…”

“…The effects of cerebellectomy are discussed in relation to the importance of the interaction between tonic labyrinth and neck reflexes in the successful maintenance of normal posture (Lindsay et al 1976). A preliminary report of this work was presented elesewhere (Lindsay & Rosenberg, 1977).…”

Interaction between the vestibulo‐collic reflex and the cervico‐collic stretch reflex in the decerebrate cat.

“…Since most movements of the head involve not only stimulation of vestibular receptors but also changes in length of the muscles of the neck, the interactions between the two reflexes are an essential part of the normal system for maintaining head stability. As pointed out by Lindsay, Roberts & Rosenberg (1976) in the context of neck and vestibular reflexes acting on the forelimbs, the head and neck reflex systems are perhaps best considered as an integrated functional unit. However, it should be emphasized that while vestibular reflexes are antagonized by neck reflexes in the forelimbs, allowing the head to move freely on the trunk (Lindsay et al 1976), in the neck muscles the two reflexes act synergistically to stabilize the head on the neck (Dutia & Hunter, 1985).…”