Development of the auditory orientation response in the albino rat (Rattus norvegicus).

The development of head orientation to auditory stimulation was examined in rat pups at Postnatal Days 8, 11, 14, 17, and 20. The animals were tested in a quiet environment with single bursts of 65 dB (SPL) broad-band noise. A reflexive head turn toward the sound was first seen on Postnatal Day 14 and subsequently on Days 17 and 20. This result demonstrates that the onset of directional auditory responses occurred between Day 11 and Day 14. The role of binaural cues in early sound orientation was examined in 17-day-old pups with monaural ligation of the external meatus. These animals were unable to localize a sound source and consistently turned toward the side of the unligated ear regardless of the position of the stimulus. Thus binaural cues were shown to be important for head orientation to sound in early development. In a separate study, head orientation to high and low frequency tone pips was examined. Directional responses were first seen on Day 12 for a 16-kHz tone and Day 14 for a 2-kHz tone. These results indicate an earlier onset for orientation to high frequency sounds in the rat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory spatial responses of young guinea pigs (Cavia porcellus) during and after ear blocking.

Tested 30 newborn guinea pigs to determine their ability to approach an auditory stimulus early in development. Observations of the behavior of 1–4 day old Ss in a circular 8-choice maze revealed a pronounced tendency to orient toward and approach a tape-recorded signal of guinea pig vocalizations. The occurrence of approach responses was reduced to chance in Ss tested with one ear occluded by wax ear plugs which attenuated but did not totally eliminate sound. The effect of monaural ear blocks was more severe than binaural blocks, which reflects the importance of binaural cues in the maintenance of approach responses to sound. In a 2nd study with 40 Ss the ability of older animals, 11–31 days of age, was examined. Directional approach responses to sound were also evident at this age, and ear plugs disrupted performance only under monaural conditions. Furthermore, in Ss raised from birth with monaural ear blocks but tested without ear plugs, there was a subsequent disruption of performance for at least 21 days. Results indicate the importance of binaural cues in the development of early auditory spatial reponses and suggest the need for appropriate binaural experience for subsequent localization of sounds. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tinnitus and Hearing Loss in Hamsters (Mesocricetus auratus) Exposed to Loud Sound.

Hamsters were trained to go left and right to sounds on their left and right sides, respectively. Silent trials were occasionally given in which no sound was presented. Hamsters exposed to a loud 2- or 10-kHz tone in 1 ear often shifted their responding on the silent trials to the side of the exposed ear, suggesting that they perceived a sound in that ear (i.e., tinnitus). The degree of tinnitus was related to the degree of the accompanying hearing loss (estimated by the auditory brainstem response). However, a conductive hearing loss (plugging 1 ear) did not cause a hamster to test positive for tinnitus. Tinnitus could be demonstrated within minutes following tone exposure, indicating an immediate onset, as occurs in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pathophysiological mechanisms of hearing loss

An understanding of auditory transduction in the ear can contribute to a better comprehension of the pathophysiological mechanisms which give rise to hearing loss. The incoming sound sets up a mechanical traveling wave which begins at the base and progresses along the basilar membrane, reaching a point of maximal displacement. The region of maximal displacement is a function of stimulus frequency. The mechanical displacement, by directly opening ion channels in the stereocilia of the hair cells, induces changes in the electrical potential of the hair cells. This initial stage is called mechano-electrical transduction, and in the normal ear, is followed by a stage of electro-mechanical transduction based on the ability of the outer hair cells to respond to the electrical changes induced in them with a change in their length. This "electromotility" presumably provides mechanical feedback to the basilar membrane, augmenting its mechanical displacement. This is called the cochlear amplifier, providing the ear with improved sensitivity and frequency discrimination. Most forms of sensori-neural hearing losses (affecting the inner ear) are due to a lesion to some part of this cochlear amplifier (e.g. noise induced hearing loss, ototoxic drugs) and are therefore characterized by auditory threshold elevations and poorer frequency discrimination.     

Guanylate cyclase activity in the inner ear and auditory nerve of the rat

Novel molecular mediation in the sound transductional process is implicitly suggested. We investigated the presence of the cGMP-synthesis enzyme, guanylate cyclase, in Corti's organ and auditory nerve of the rat. The soluble guanylate cyclase activity found was sensitive to changes of sound intensity in the different acoustic media used, suggesting a potential role for the system that involves this enzyme. The guanylate cyclase activity appeared to be inversely related (in the inner ear) with the sound intensity to which the animals were exposed; different behavior was observed for the auditory nerve. The enzymatic activity found in Corti's organ, a direct bio-receptor of sound, represents the first reported enzymatic activity of this type in this tissue, which apparently could be influenced by the intensity of a physical stimulus such as sound. Finally, an adequate ionic environment appears to play a potential role in the expression of the changes observed, indicating that it may function according to the requirements of the biological sensor.     

Recalibrating the auditory system: A speed-accuracy analysis of intensity perception.

Recalibration in loudness perception refers to an adaptation-like change in relative responsiveness to auditory signals of different sound frequencies. Listening to relatively weak tones at one frequency and stronger tones at another makes the latter appear softer. The authors showed recalibration not only in magnitude estimates of loudness but also in simple response times (RTs) and choice RTs. RTs depend on sound intensity and may serve as surrogates for loudness. Most important, the speeded classification paradigm also provided measures of errors. RTs and errors can serve jointly to distinguish changes in sensitivity from changes in response criterion. The changes in choice RT under different recalibrating conditions were not accompanied by changes in error rates predicted by the speed-accuracy trade-off. These results lend support to the hypothesis that loudness recalibration does not result from shifting decisional criteria but instead reflects a change in the underlying representation of auditory intensity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human salmonellosis in Singapore

1. Cats with one cochlea destroyed were trained to localize sound. After behavioral measures of the animal's accuracy of localization were made, cortical auditory areas were ablated unilaterally. 2. The results showed: a) like binaural localization, monaural localization of sound in space, as measured by the ability of an animal to move toward a sound source, depends on integrity of auditory cortex; b) it is only ablation of cortex contralateral to the functional ear that seriously affects localizing behavior; ablation of cortex ipsilateral to the intact cochlea has little or no effect on localizing behavior. 3. To explain the results, we suggest that auditory cortex is essential for an organized perception of space including the relation of the animal's position to other objects in space. We also suggest that auditory cortex contralateral to a given ear is necessary in order for the animal to recognize that a stimulus is presented to that ear of, when both ears are intact, to recognize that the stimulus to the given ear differs in some way (intensity, time of arrival, sequential arrangement of sounds) from the stimulus to the opposite ear.     

Gram-scale synthesis of recombinant chitooligosaccharides in Escherichia coli

Basilar membrane (BM) noise, measured as a velocity signal under the quiet acoustic condition, was investigated in the guinea pig. The cochleas of anesthetized young healthy guinea pigs were surgically exposed and a hole was made on the lateral wall of the scala tympani of the first cochlear turn for visualization of the BM and measurement of the BM velocity with a laser interferometer. The amplitude and frequency of the BM velocity noise were analyzed by a spectrum analyzer under different conditions. The spectrum of the BM velocity noise was a band limited function with a peak velocity at the topographic best frequency of the measured location on the BM. The peak velocity ranged to about 8 microm/s and depended on the physiological condition of the cochlea. Saline blockage of the external auditory canal or the middle ear did not change the BM noise. BM noise was much smaller, or was not evident, when the cochlear sensitivity decreased. The suppression tuning curve of the BM velocity noise indicates that the maximum suppression caused by an acoustic pure tone occurred at the best frequency location. A low sound level wide band acoustic noise given to the external ear canal produced a spectrum function having the same frequency and amplitude response as the BM noise. Electrical stimulation of the crossed olivocochlear bundle significantly depresses the BM velocity noise. These data demonstrate that the BM noise is a representation of internal rather than external noise. The amplitude and frequency of the BM noise reflect the usual cochlear sensitivity and frequency selectivity. Since the organ of Corti in the sensitive cochlea is a highly sensitive and tuned mechanical system, the internal (to the animal) noise responsible for the BM noise may originate from mechanical vibrations remote from the cochlea and propagated to the ear, or may be caused by Brownian motion of cellular structures in the cochlea.     

Perceptual restoration of obliterated sounds.

When portions of a signal are masked in noisy environments, perceptual restoration can be accomplished through auditory induction (AI). There are 2 classes of AI: (a) temporal induction (TI), which restores contextually appropriate segments of a signal masked at both ears by transient noises; and (b) contralateral induction (CI), which restores a signal masked at one ear when it is heard at the other. TI can prevent fragmentation of steady sounds and can permit comprehension of speech that would otherwise be unintelligible, while CI can prevent mislocalization of a sound source to the side of the unmasked ear. Both classes of AI are subtractive processes requiring that the neural units corresponding to the perceptually restored sound be among those stimulated by the louder interrupting sound. The rules governing AI provide information concerning general principles underlying perceptual organization in hearing. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Head-related transfer functions of the barn owl: measurement and neural responses

Sounds arriving at the eardrum are filtered by the external ear and associated structures in a frequency and direction specific manner. When convolved with the appropriate filters and presented to human listeners through headphones, broadband noises can be precisely localized to the corresponding position outside of the head (reviewed in Blauert, 1997). Such a 'virtual auditory space' can be a potentially powerful tool for neurophysiological and behavioral work in other species as well. We are developing a virtual auditory space for the barn owl, Tyto alba, a highly successful auditory predator that has become a well-established model for hearing research. We recorded catalogues of head-related transfer functions (HRTFs) from the frontal hemisphere of 12 barn owls and compared virtual and free sound fields acoustically and by their evoked neuronal responses. The inner ca. 1 cm of the ear canal was found to contribute little to the directionality of the HRTFs. HRTFs were recorded by inserting probetube microphones to within about 1 or 2 mm of the eardrum. We recorded HRTFs at frequencies between 2 and 11 kHz, which includes the frequencies most useful to the owl for sound localization (3-9 kHz; Konishi, 1973). Spectra of virtual sounds were within +/- 1 dB of amplitude and +/- 10 degrees of phase of the spectra of free field sounds measured near to the eardrum. The spatial pattern of responses obtained from neurons in the inferior colliculus were almost indistinguishable in response to virtual and to free field stimulation.     

Effects of ear plugging on single-unit azimuth sensitivity in cat primary auditory cortex. I. Evidence for monaural directional cues

1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Neurons, sensitive to sound direction in the horizontal plane (azimuth), were identified by their responses to noise bursts, presented in the free field, that varied in azimuth and sound pressure level (SPL). SPLs typically varied between 0 and 80 dB and were presented at each azimuth that was tested. Each azimuth-sensitive neuron responded well to some SPLs at certain azimuths and did not respond well to any SPL at other azimuths. This report describes AI neurons that were sensitive to the azimuth of monaurally presented noise bursts. 2. Unilateral ear plugging was used to test each azimuth-sensitive neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the concha and ear canal, attenuated sound reaching the tympanic membrane by 25-70 dB. Binaural interactions were inferred by comparing responses obtained under binaural (no plug) and monaural (ear plug) conditions. 3. Of the total sample of 131 azimuth-sensitive cells whose responses to ear plugging were studied, 27 were sensitive to the azimuth of monaurally presented noise bursts. We refer to these as monaural directional (MD) cells, and this report describes their properties. The remainder of the sample consisted of cells that either required binaural stimulation for azimuth sensitivity (63/131), because they were insensitive to azimuth under unilateral ear plug conditions or responded too unreliably to permit detailed conclusions regarding the effect of ear plugging (41/131). 4. Most (25/27) MD cells received either monaural input (MD-E0) or binaural excitatory/inhibitory input (MD-EI), as inferred from ear plugging. Two MD cells showed other characteristics. The contralateral ear was excitatory for 25/27 MD cells. 5. MD-E0 cells (22%, 6/27) were monaural. They were unaffected by unilateral ear plugging, showing that they received excitatory input from one ear, and that stimulation of the other ear was without apparent effect. On the other hand, some monaural cells in AI were insensitive to the azimuth of noise bursts, showing that sensitivity to monaural directional cues is not a property of all monaural cells in AI. 6. MD-EI cells (70%, 19/27) exhibited an increase in responsiveness on the side of the plugged ear, showing that they received excitatory drive from one ear and inhibitory drive from the other. MD-EI cells remained azimuth sensitive with the inhibitory ear plugged, showing that they were sensitive to monaural directional cues at the excitatory ear.(ABSTRACT TRUNCATED AT 400 WORDS)     

Neonatal sound deprivation affects brain stem auditory nuclei

CBA/J mice deprived of airborne sound stimulation during postnatal development have smaller globular cells in the ventral cochlear nucleus and smaller neurons in the medial nucleus of the trapezoid body than do normal control mice. The sound deprivation in these mice is similar to that experienced by persons with pure congenital conductive hearing losses. Even more profound central neural changes were found in auditory nuclei in the brain stem of a congenitally sensorineural deaf human.     

Echocardiographic spectrum of supracardiac total anomalous pulmonary venous connection

We report an unusual case of a 13-year-old girl with a benign osteoma associated with a cholesteatoma in the external auditory canal and serous otitis media. The osteoma was located in the antero-inferior wall of the right external auditory canal. A cholesteatoma was present between the osteoma and the tympanic membrane. Computed tomography revealed a soft tissue density within the external auditory canal and in the middle ear cleft. The shadow in the middle ear cleft was considered to represent the serous otitis media. Surgical removal of the osteoma and cholesteatoma proved successful, and no recurrences or complications have occurred in the first year postoperatively.     

Hemispheric specialization and ear advantages in processing speech.

Reviews research on the hemispheric asymmetry model of relative ear advantages in the processing of auditory stimuli. Physiological studies of activation of the hemispheres in humans support left-hemisphere speech-processing specialization and contralateral sound field dominance. Electrophysiological studies in animals, effects of commissurotomy, hemispherectomy, and unilateral temporal lobe lesions on dichotic performance in humans, as well as stimulus dominance effects in intact Ss indicate that the assumption of ipsilateral sensory pathway suppression during competitive stimulation is unwarranted. Dichotic presentation is not necessary to produce a right-ear advantage (REA), and selective attention to one or the other ear frequently tends to alter the magnitude of the REA. A modified structural model that incorporates the effects of directed attention is proposed. (3? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hearing in the parakeet (Melopsittacus undulatus): Absolute thresholds, critical ratios, frequency difference limens, and vocalizations.

In Exps I and II avoidance conditioning and the method of limits were used to measure absolute auditory thresholds, masked thresholds, and critical ratios in 4 parakeets. The same procedure was then used in Exps III and IV to study frequency difference limens in 6 additional Ss. The power spectrum and "constancy of intonation" of the parakeet call were also measured and related to the absolute and differential frequency sensitivity. The mechanism of frequency analysis in the parakeet ear is considered in relation to the present results and to the anatomical and functional differences between the avian and mammalian auditory systems. (71 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prenatal auditory experience directs species-typical perceptual responsiveness in bobwhite quail chicks (Colinus virginianus).

The present study examined the role of the relationship between pre- and postnatal stimulus cues in directing perceptual preferences of bobwhite quail chicks. Bobwhite quail were exposed to either prenatal auditory or prenatal auditory-visual stimulation. Both prenatal auditory and auditory-visual stimulation resulted in accelerated responsiveness to combined postnatal auditory-visual cues. However, whether or not subjects displayed accelerated perceptual responsiveness depended on the relationship between the nature of the pre- and postnatal auditory stimuli used. These results demonstrate the salience of auditory cues in directing early postnatal perceptual behavior in precocial birds and help to explicate why prior research in this area has found that augmented prenatal sensory stimulation can result in either accelerated or decelerated patterns of perceptual functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Change deafness and the organizational properties of sounds.

Change blindness, or the failure to detect (often large) changes to visual scenes, has been demonstrated in a variety of different situations. Failures to detect auditory changes are far less studied, and thus little is known about the nature of change deafness. Five experiments were conducted to explore the processes involved in change deafness by measuring explicit change detection as well as auditory object encoding. The experiments revealed that considerable change deafness occurs, even though auditory objects are encoded quite well. Familiarity with the objects did not affect detection or recognition performance. Whereas spatial location was not an effective cue, fundamental frequency and the periodicity/aperiodicity of the sounds provided important cues for the change-detection task. Implications for the mechanisms responsible for change deafness and auditory sound organization are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Penicillium marneffei fungemia in an AIDS patient: the first case report in Taiwan

The microbiology of in 55 ear aspirates obtained from 34 children with chronic otorrhea was studied. Aspiration of the middle ear exudate was done immediately following removal of tympanostomy tube (TT). The middle ear aspirates and swab specimens of the external auditory canals were cultured for aerobic and anaerobic bacteria. Sixty-five isolates were recovered only from the middle ears, 73 only from the external ear canals, and 73 were present at both sites. Analysis of the 138 middle ear isolates demonstrated the recovery of aerobic bacteria only in 28 patients (50%), anaerobes only in seven (13%), and both aerobes and anaerobes in 20 (36%). There were 77 aerobic and 61 anaerobic isolates. Commonly recovered aerobes were Pseudomonas aeruginosa (17 isolates), Staphylococcus aureus (11), Proteus sp. (7), Moraxella catarrhalis (6), Klebsiella pneumoniae (5) and non-typable Haemophilus influenzae (5). Commonly isolated anaerobes were Peptostreptococcus sp. (25 isolates), Prevotella sp. (10), Bacteroides sp. (8) and Fusobacterium sp. (6). Pseudomonas aeruginosa and S. aureus were more often isolated in children older then 6 years. These findings demonstrate the polymicrobial bacteriology of TT-related otorrhea in children. Specimens collected from the external auditory canals can be misleading. Reliable information can be obtained from the ear exudes when collected through the TT or through the open perforation after their removal.     

Precision of auditory localization in human infants.

The precision of auditory localization in 26- to 30-week old infants was measured with a test based on the adult minimum audible angle. In this test, the horizontal angle between loudspeakers was varied systematically to determine thresholds for discriminating rightward versus leftward sound displacements. Infants were presented with sounds that shifted from straight ahead to the left or right, and observers judged from the infants' eye and head movements to which side the sound had shifted. From trial to trial, the size of the shift was decreased after correct responding and increased after incorrect responding. Infants discriminated sound displacements of about 19°, considerably less accurate than adult values of 1–2°. These findings are discussed in terms of their methodological implications and the development of sensitivity to information for sound localization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonatal habituation and dishabituation to tactile stimulation during sleep.

Two experiments examined habituation and dishabituation of behavioral responding to repeated presentations of a tactile stimulus (brush stroke) in 48 newborns during the 1st epoch of active-quiet sleep following a feeding. Exp I demonstrated habituation to a repeatedly presented brush stroke to the ear but failed to demonstrate dishabituation (i.e., response recovery) to the original brush stroke following an intense auditory stimulus (86 dB rattle sound). A post hoc control group showed that the intense auditory stimulus had suppressed subsequent responding to the tactile stimulus. Exp II replicated the habituation phase of Exp I and demonstrated response recovery to stimulation at a novel tactile site and to an auditory probe. Results indicate that the habituation paradigm used in infancy research could be successfully extended to the tactile modality. It is also suggested that prior auditory stimulation, but not prior tactile stimulation, might direct attention away from a subsequently presented tactile stimulus. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)