Development Of Auditory Sensitivity Research Articles

Development of auditory sensitivity in the barn owl

Adult barn owl hearing is acute, but development of this sense is not well understood. We, therefore, measured auditory brainstem responses in barn owls from before the onset of hearing (posthatch day 2, or P2) to adulthood (P69). The first consistent responses were detected at P4 for 1 and 2kHz, followed by responses to 0.5 and 4kHz at P9, and 5kHz at P13. Sensitivity to higher frequencies increased with age, with responses to 12kHz appearing about 2months after hatching, once the facial ruff was mature. Therefore, these altricial birds achieve their sensitivity to sound during a prolonged period of development, which coincides with maturation of the skull and facial ruff (Haresign and Moiseff in Auk 105:699-705, 1988).

Effects of Visual Deprivation on the Development of Auditory Sensitivity during Formation of the Freezing Reaction in Pied Flycatcher Nestlings

Recording of evoked potentials from the higher center of the auditory system - field L of the nidopallidum - was used to study the formation of auditory sensitivity in normally developing and visually deprived pied flycatcher nestlings aged 6-9 days. Restriction of visual afferentation was found to produce significant reductions in the absolute threshold of auditory evoked potentials in the frequency range of the species-specific food call (1-3 kHz) during the period at which vision acquires a role in providing sensory support for feeding behavior in control nestlings (six days). In the frequency range of the species-specific alarm call (4-5 kHz), the thresholds of auditory evoked potentials were significantly lower than those in controls during the period at which vision acquires a role in providing sensory support for defensive behavior (8-9 days). Taking account of previous data showing decreases in the efficiency of acoustic signals in evoking freezing reactions in visually deprived nestlings, it is suggested that defensive behavior develops not simply as a response to the acoustic alarm call or tones imitating it, but as a system whose complete formation and functioning require integration of a series of factors, including visual afferentation.

Development of auditory sensitivity in children who stutter and fluent children.

The purpose of this study was to establish whether there are any differential changes in auditory sensitivity over ages in a variety of peripheral and central auditory tasks between participants who stutter and participants who do not stutter. The auditory sensitivity of 37 participants who stutter and 44 participants who do not stutter, ages between 8 and 19 yr, assigned to three age categories, were obtained in five listening conditions: Pure tone threshold, simultaneous masking, backward masking, notched backward masking, and simple dichotic (simultaneous) masking. Across all listening conditions and both talker groups, thresholds decreased over age. The thresholds of participants who do not stutter decreased for simultaneous, backward, and notched backward masking conditions over the 8- to 19-year age range. Analysis of each condition only showed significant improvement over age groups for backward masking for the participants who stutter. These results indicate that auditory sensitivity for sounds in noise continues to develop through to teenage, and a different pattern of auditory development exists for the participants who stutter compared with participants who do not stutter.

Delay in the development of auditory sensitivity in nestlings and reorganization of feeding behavior.

Delay in the development of auditory sensitivity in nestlings and reorganization of feeding behavior.

Preliminary observations on the development of auditory sensitivity in infants with Down syndrome.

Hearing loss commonly is associated with Down syndrome, but little is known about the development of auditory sensitivity in individuals with Down syndrome. This study had two objectives: 1) to determine whether an observer-based procedure can be used to assess the behavioral sensitivity of infants with Down syndrome, and 2) to provide preliminary information about the early course of hearing development among infants with Down syndrome. Behavioral measures of sensitivity were made in 16 infants with Down syndrome using an observer-based procedure. Ten of the infants were followed longitudinally between 2 and 12 mo of age. All infants passed a screening auditory brain stem response at 20 dB nHL during the study and completed screening tympanometry at each test session. The infants detected a 4000 Hz tone at levels ranging from 25 to 50 dB SPL; psychometric functions and thresholds for the tone were obtained. Infants with Down syndrome completed 80% of the test sessions they began, a rate similar to that seen in normally developing infants in the same type of study. Performance improved with increasing stimulus level, as one would expect, and thresholds were obtained from 15 of 16 infants for at least one age. The performance of infants with Down syndrome generally improved with age. The sensitivity of 2- to 3-mo-olds was poorer than that of older infants, but little if any improvement in sensitivity occurred between 4 and 12 mo. This pattern is similar to that seen in normally developing infants. Thresholds of infants with Down syndrome were 10 to 25 dB higher than those reported for normally developing infants. The psychometric functions of infants with Down syndrome were shallower than the psychometric functions of normally developing infants, and the slope of the psychometric functions did not change with age. Infants with Down syndrome achieved only 75 to 80% correct at any of the levels tested, 5 to 10% poorer than reported for other infants. These characteristics of the psychometric functions of the infants with Down syndrome suggest that they are inattentive during testing more often than are normally developing infants. An observer-based procedure can be used to obtain reasonable thresholds from infants with Down syndrome who are as young as 2 mo of age. Both sensory and nonsensory factors could contribute to the threshold elevation seen in infants with Down syndrome. At least on preliminary examination, the course of auditory sensitivity development of infants with Down syndrome is qualitatively similar to that seen in normally developing infants.

Development of brainstem auditory pathway in mallard duck embryos and hatchlings.

The development of the brainstem auditory evoked potential (BAEP) was studied in mallard duck (Anas platyrhynchos) embryos and hatchlings from 5-6 days before hatching through two days after hatching in response to tone pips of different frequencies. BAEPs showed a different time of onset and a different rate of development for low, middle, and high frequencies. Although auditory sensitivity in the mid-frequency range (1.0, 1.5, 2.0, and 3.0 kHz) appeared 1-2 days later than in the low-frequency range, development of the BAEPs in the mid-frequency range was almost complete by hatching. In contrast, the development of auditory sensitivity in the low- and high-frequency ranges continued to develop after hatching. Accelerated development of BAEPs to middle frequencies during the embryonic period and to high frequencies after hatching was correlated with the ducklings' exposure to their own mid-frequency and high-frequency vocalizations before and after hatching, respectively.

Early auditory and visual function in normal and hyperthyroid rats

The development of auditory sensitivity and visual acuity was studied in both normal rat pups and their developmentally accelerated hyperthyroid littermates utilizing unconditioned behavioral responses to carefully controlled stimulation. Hyperthyroidism was induced by injections of l-thyroxine sodium solution (1 μg/g body wt) on postnatal Days 1–4. Auditory development was assessed by observing startle reactions to discrete pure-tone stimuli. One and four kHz tones (98–99 dB) elicited initial behavioral responses in subjects from both groups 1–2 days prior to ear opening. Responsiveness to 16 kHz tones (108 dB) emerged on the day of ear opening. Normal pups exhibited reactions to 40 kHz tones (111 dB) 1–2 days after ear opening but the high-frequency sensitivity of the hyperthyroid subjects developed much more slowly. By 18 days postpartum, subjects in both groups exhibited similar auditory abilities. The optomotor reflex (optokinetic nystagmus) was employed to measure the development of visual acuity. Normal and hyperthyroid subjects were tested at the time of eye-opening (Days 14–15 and Days 12–13, respectively) and at equal chronological ages. Hormone-treated subjects had finer visual acuity than normal subjects on postnatal Day 12. However, when matched for eye-opening, the acuity of normal subjects was superior. No differences were encountered when subjects in both groups were tested at 19 days of age. The results in discussion indicate that hyperthyroidism accelerates the development of auditory and visual function, but suggests that the ears and eyes of hyperthyroid subjects open to reveal sensory-perceptual apparatus which is less mature than that of somatically matched normal littermates.

Auditory Sensitivity in the Rana catesbeiana Tadpole

Auditory sensitivity in 6 bullfrog tadpoles (Rana catesbeiana) was investi- gated electrophysiologically. Tonal stimulus intensities that elicited a standard sensory potential of 0.1 ,v in the inner ear showed a response range from 100 Hz to 4000 Hz with maximum sensitivity near one dyne/cm2 (0.1 N/m2) in the lower portion of the range. These potentials also indicated that tadpoles lack the place mechanism of adult frogs. * * * While many articles have appeared assessing hearing in fishes and adult amphibians, especially frogs, no work on larval amphibians has been reported. Larval amphibians are particularly interesting because their hearing apparatus with columellar connections between an internal air bladder and the inner ear parallels that in ostariophysian fishes with their Weberian ossicles. At metamorphosis the frog ear becomes more typically like that of other terrestrial vertebrates with an external ear drum and a columellar connection to the inner ear. The roles of the round and oval windows of the inner ear even reverse during metamorphosis (van Bergeijk, 1967). Thus the lack of data on the development of auditory sensitivity in amphibian larvae leaves a considerable hiatus in the understanding of vertebrate hearing in general. The present study employs electrophysiological techniques to explore the auditory sensitivity of the bullfrog (Rana catesbeiana) tadpole.

Effects of auditory deprivation on the development of auditory sensitivity in albino rats

Twenty albino rats were confined for 8 months post-natally to a highly sound-attenuated environment and were tested subsequently for hearing sensitivity. Comparisons were made with their control littermates, reared under ordinary ambient noise conditions. Surface auditory evoked cortical potentials were summated for 45 or 75 responses at each of seven pure tone frequencies. Threshold determinations were made between 30 dB and 75 dB, SPL. Several animals were retested after subsequent ambient noise exposure for 48 h and for 3 weeks. Statistical comparisons of threshold responses between the deprived animals and their control littermates showed a significant loss of sensitivity after deprivation and some regain of sensitivity after subsequent exposure to ambient noise. Relationships between environmental stimulation and neural functioning are considered.

RECEPTIVE FIELDS OF CELLS IN STRIATE CORTEX OF VERY YOUNG, VISUALLY INEXPERIENCED KITTENS.

RECEPTIVE FIELDS OF CELLS IN STRIATE CORTEX OF VERY YOUNG, VISUALLY INEXPERIENCED KITTENS.

EFFECTS OF VISUAL DEPRIVATION ON MORPHOLOGY AND PHYSIOLOGY OF CELLS IN THE CATS LATERAL GENICULATE BODY.

EFFECTS OF VISUAL DEPRIVATION ON MORPHOLOGY AND PHYSIOLOGY OF CELLS IN THE CATS LATERAL GENICULATE BODY.