Observations on Blink Reflexes

A reflex wink, which resulted from a tap over the supraorbital region of the face, was described by Overend (1896).He observed that the reflex was the product of facial stimulation, for it was present in the blind.In the 25 years following this discovery it was realized that reflex winking (unilateral con- traction of the homolateral orbicularis oculi) or blinking (bilateral contraction) could be elicited from many areas of the face, and some of these facial reflexes became incorporated into the routine examination of the nervous system (Weingrow, 1933).Wartenberg (1945) has admirably described the confusion that has resulted from the failure to recognize the essential identity of the facial reflexes, response to glabella tap has been particularly studied, as it is the best known of the facial reflexes (apart from the corneal reflex) and is still often employed by clinical neurologists in Great Britain.In the second part of the paper it will be shown how disease of the nervous system and of individual cranial nerves may affect the blink reflexes and their latencies.The third part of the paper will deal with some experiments on the origin, nature, and pathways of the afferents responsible for the reflex to glabella tap. METHODSGlabella tap was performed by tapping a circular metal plate, 1k in. in diameter, which was placed over the glabella.The stimulus was therefore rather diffuse and not painful.A metal thimble was used to tap, and contact between it and the metal plate completed a circuit which triggered the suppressed beams of a cathode ray oscilloscope.The same device provided a loud click stimulus when placed directly over an ear.The cornea was stimulated with a small loop of stainless steel wire, and the contact it made with the cornea completed a circuit which triggered the sweeps of a cathode ray oscilloscope.Supra-orbital nerves were stimulated through the skin 93 2