Differential effect of at rest eye closure and orbicularis oculi contraction (squinting) on acoustic reflex Free

Previous eye closure studies have suggested muscle tension is responsible for acoustic reflex (AR) enhancement during light eye closure (A. L. Corcoran, M.Sc. dissertation, University of South‐hampton, England, 1976). AR threshold and magnitude were determined for nine normal hearing adults under counterbalanced conditions: (1) eyes open, (2) lightly closed, and (3) tightly closed (contraction of orbicularis oculi). For a 1‐kHz stimulus a 1.1 dB difference was noted between thresholds for eyes open or lightly closed. Squinting however, resulted in a significant 3.6‐ and 4.7‐dB enhancement over the eyes open and closed conditions, respectively. Broadband noise stimuli resulted in a marked enhancement of 9.8 dB while squinting. All conditions differed significantly for the noise stimuli. AR magnitude, however, did not differ across eye closure conditions for either stimuli. Results are compared with previous data on the effects of visual, tactile, olfactory, and mental tasks [Robinette et al., J. Acoust. Soc. Am. Suppl. 1 64, S107 (1978).]