Mechanisms involved in the cat's blink reflex.

Abstract

AbstractTapping on the cat's facial skin elicits two successive reflex discharges in the orbicularis oculi. The responses have similar thresholds and are most readily evoked from the skin overlying the muscle. Both discharges result also on tapping on a skin flap over the muscle, whereas tapping on the muscle belly is ineffective. Similar responses are elicited on electrical stimulation of low‐threshold trigeminal afferents; the central relay time indicates that the early response is mediated through a polysynaptic reflex arc. Stimulation of high‐threshold afferents in the facial nerve may give a long latency reflex response in the orbicularis oculi and facilitate transmission of a short‐latency reflex response in the same muscle set up by stimulation of trigeminal afferents. Recordings from peripheral filaments provide no evidence for the presence of afferent fibers from muscle spindles or other types of proprioceptors in the facial and trigeminal nerves. A twitch contraction of the orbicularis oculi elicits a high‐amplitude reflex response in the muscle through activation of trigeminal exteroceptive afferents; the possibility is considered that such afferents may serve a proprioceptive function in monitoring the degree of contraction of the facial muscles.