Biomedical subjects

Y L Werner

Publications and source records attributed to Y L Werner.

8 recordsLinked to original sources

PubMed2001

Effects of surgery and other experimental factors on the evaluation of middle ear function in gekkonoid lizards.

This study examines three artificial factors likely to cause variation between results from different investigations of auditory function, at least in lizards. Controlled tests were performed on gecko lizards, by external laser interferometry of the middle ear transfer function at the tympanic membrane (TM). In conclusion, studies of middle ear function should examine motion both at the insertion of the columella-extracolumella shaft onto the TM, and at the tip of the extracolumellar pars inferior, because the internal proportions and function of the extracolumellar lever vary among species. At least in scansorial geckos, auditory experiments may be conducted with the animal on its back, as this posture introduces no acoustic artifacts. Positioning the subject on its belly, with the throat resting on the substrate, imposes small but significant artifacts on middle ear function. Similar artifacts occur with the belly up but the throat loaded with a modeling clay plate. The surgical fenestration of the ventral throat wall, common in auditory studies on lizards, causes (at least in Eublepharis) artificial enhancement of sensitivity at low frequencies and erratic responses at high frequencies.

Animals↗

PubMed1998

How body size affects middle-ear structure and function and auditory sensitivity in gekkonoid lizards.

Gekkonoid lizards increase in body size throughout life, and the present study investigates whether changes in auditory function accompany these increases. Middle-ear structures in four groups of animals, adults and juveniles of two gekkonoid species (Eublepharis macularius and Oedura marmorata), were examined. Tympanic membrane velocity and phase were also measured in all four groups. An indication of peripheral auditory function was obtained for each group by measuring compound action potentials (CAPs) from the round window membrane. The middle-ear contribution to CAP thresholds was obtained by comparing threshold levels of the CAP response with and without an intact middle-ear system. The results from these studies indicated that significant changes occurred in middle-ear structure, tympanic membrane velocity and CAP threshold between the younger and older animals. In addition, the adults of both species exhibited better auditory function when the acoustic stimulus was delivered to the tympanic membrane than when it was delivered to the columella footplate. The findings show clearly that increased body size (or age) is accompanied by functional changes in the auditory periphery.

Action Potentials↗

PubMed1976

Optimal temperatures for inner-ear performance in gekkonoid lizards.

Temperature effects on the cochlear alternating potentials are described in lizards of the Eublepharidae (4 spp. and subspp.), Diplodactylinae (2 spp.), Gekkoninae (7 spp. and subspp.) and Sphaerodactylidae (1 sp.). Pure tones (50-15,000 Hz) were applied to the anaesthetized gecko's external ear. Sound intensity needed for a standard response was plotted (db versus frequency). A total of 249 such sensitivity functions were obtained from 50 animals, at temperatures of 15-40 degrees C. For each species, an optimal sensitivity function is definable by its extreme sensitivity and relative smoothness. This is obtained throughout a specific optimal temperature range. At lower temperatures, the function is less sensitive and its best sensitivity is at a lower frequency. The specific optimal cochlear temperature range resembles the specific ecological temperature preferendum where known. Both are broader in gekkonoid than in iguanid lizards. The temperature effects on the sensitivity function occur even with aerial or mechanical stimulation at the oval window after middle ear extirpation. Hence they arise in the inner ear. Their magnitude (db/ degrees C) is half that known from auditory nerve potentials. When accurate auditory data are desired, the specific optimal temperature and its possible seasonal variation require consideration. This increases the need for proper identification of subjects by name and origin, and for monitoring experimental thermal parameters, including pre-experimental acclimation.

Acoustic Stimulation↗

PubMed1971