Reflex Modification Audiometry: Assessment of Acoustic Sensory Processing in the Term Neonate

Abstract

A B S T R A a . Behavioral and physiological work in animals and adult humans have established the sensitivity of various procedures and allowed delineation of the neuroanatomical pathways involved in sensory processing. Herein we used the glabellar reflex and reflex modification procedures to assess acoustic sensory processing capabilities in the term newborn infant. The eyeblink-eliciting device consisted of a miniature solenoid which could deliver a controlled tap. A photoreflective densitometer attached to a TDH-39 earphone assessed the eyeblinks. A total of 98 term infants was studied to determine how a response to a reflex-eliciting event (tap) was modified (either augmented or inhibited) by a mild exteroceptive stimulus (tone) which was presented at an appropriate lead interval. Ninety adult subjects were given identical testing procedures and their data were compared to that of the infants. The results of this study showed that newborn infants reliably exhibited an eyeblink response after a tap to the glabella. With fixed intensity tones, frequencies from 1 to 4 kHz produced equivalent amounts of reflex augmentation in infants and adult subjects. Blink amplitude increased as a function of increased tap and tone intensity in both infants and adults. State change was shown to affect the amplitude of the reflexive eyeblink, but not the augmentation effect. However, neonates failed to show inhibition to either acoustic or tactile stimuli at an interstimulus interval that produced significant inhibition in the adult. These data indicate that reflex modification procedures provide an objective assessment of acoustic sensory processing in the term neonate. Further, they not only suggest that areas of the central nervous system that process sensory stimuli are not fully developed even at term birth, but that the neural system for augmentation and inhibition may be independent of each other. (Pediatr Res 23: 357-363, 1988) Abbreviation ical and electrophysiological measures, reflex behavior, and learning procedures. Not all of these methods are useful at all ages; not all provide objective measurement of auditory perception.The purpose herein was to investigate the applicability of a psychophysical approach, based on behavioral phenomenon called reflex modification, to objectively assess acoustic sensory competence in the term infant (2, 3). This testing procedure originated in the observation that a variety of auditory and nonauditory stimuli consistently evoked a startle reflex in both humans and animals, the most constant component of which was the eyeblink (4-7). Subsequent investigation established that the elicited reflex could be modulated in amplitude by a variety of sensory stimuli and that the changes in eyeblink response produced by these stimuli could be monitored by measuring the amplitude of the blink component of the reflex (8, 9). Our study used a tone as a reflex-modifying event and a tap to the glabella as the reflex-eliciting stimulus. By varying the characteristics of the tone and its tempo...

Comparison of five sedation scoring systems by means of auditory evoked potentials

“…The Newcastle sedation score developed by Cook [17] was based on the Glasgow Coma scale (GCS). The amplitude of the blink reflex increases as a function of an increased tap [22]. In comparison with the original GCS used as a sedation scoring system, it achieved an identical r 2 of 0.59.…”

Preweaning Sensorimotor Deficits and Adolescent Hypersociability in <b><i>Grin1</i></b> Knockdown Mice

“…However, prepulse inhibition may be reduced or absent in neonates, indicating that further maturation of brain structures is necessary to obtain levels of sensorimotor gating found in school-age children and adults [32–34]. Similarly, startle responses to an acoustic stimulus can be found in mice at the time of ear opening (PDs 12–13) [20], while the time course for maturation of prepulse inhibition can extend beyond the postweaning period [17].…”

Prepulse inhibition of the startle eyeblink as an indicator of temporal summation

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