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At least 1,099 records · Page 61Linked to original sources
PubMedDate not supplied

[Acoustic orientation of male Aedes diantaeus during mating].

The reaction of males of Aedes diantaeus to different auditory stimuli was studied in natural environment during swarming and under laboratory conditions. The males were attracted by 250-420 Hz that corresponds to the main frequencies of flight tones of sympatric females and the range of sensitivity of male Johnston's organs. Behavioural data show that in natural environment swarming males are attracted by flying conspecific and heterospecific females rather than by dead or immobilized females. Contact with heterospecific females always ended in parting of mosquitoes while contact with cospecific females resulted in pairing. Thus, swarming males of Aedes diantaeus localize females by their flight tones but recognize the females of their own species in contact.

Aedes↗
PubMed2005

Sensitivity of auditory cortical neurons to the locations of leading and lagging sounds.

We recorded unit activity in the auditory cortex (fields A1, A2, and PAF) of anesthetized cats while presenting paired clicks with variable locations and interstimulus delays (ISDs). In human listeners, such sounds elicit the precedence effect, in which localization of the lagging sound is impaired at ISDs less, similar10 ms. In the present study, neurons typically responded to the leading stimulus with a brief burst of spikes, followed by suppression lasting 100-200 ms. At an ISD of 20 ms, at which listeners report a distinct lagging sound, only 12% of units showed discrete lagging responses. Long-lasting suppression was found in all sampled cortical fields, for all leading and lagging locations, and at all sound levels. Recordings from awake cats confirmed this long-lasting suppression in the absence of anesthesia, although recovery from suppression was faster in the awake state. Despite the lack of discrete lagging responses at delays of 1-20 ms, the spike patterns of 40% of units varied systematically with ISD, suggesting that many neurons represent lagging sounds implicitly in their temporal firing patterns rather than explicitly in discrete responses. We estimated the amount of location-related information transmitted by spike patterns at delays of 1-16 ms under conditions in which we varied only the leading location or only the lagging location. Consistent with human psychophysical results, transmission of information about the leading location was high at all ISDs. Unlike listeners, however, transmission of information about the lagging location remained low, even at ISDs of 12-16 ms.

Acoustic Stimulation↗
PubMedDate not supplied

[Directionality of sound perception in the external ear of the dog].

Sound pressure level of tone was measured using a probe tube microphone at entrance to the dog's external meatus as a function of the azimuth of the sound source. It was demonstrated that directionality of the dog's external ear and corresponding values of interaural intensity differences (delta I) were gradually increased as the tone frequency raised from 0.5 to 40 kHz. Transfer in pinnae locations from lateral to frontal positions (one of the components of orientation reaction to an unexpected sound) resulted in some narrowing of directionality diagrams and in a displacement of their maxima towards the head midline. It was calculated that owing to this effects the extent of monotonic part of the function relating delta I and azimuth of a source were enlarged. The lateral pinnae position was suggested to be optimal for sound detection and the frontal one for localization of the moving sound source.

Acoustic Stimulation↗
PubMed1996

The role of individualized headphone calibration for the generation of high fidelity virtual auditory space.

The auditory system localizes a sound source on the basis of binaural cues as well as monaural cues provided by the outer ear. These cues are described by the head-related transfer functions (HRTFs). The individual variation in the frequency and amplitude of perceptually significant features in the human HRTFs raises the issue of whether a given listener can obtain adequate localization cues from stimuli based on another listener's HRTFs. This question can be addressed in "virtual auditory space," using headphone stimuli which are convolved with HRTFs and the inverse of the headphone transfer function (HpTF). Using an in-ear recording system we have measured HpTFs (Sennheiser 250 Linear) for both ears of ten subjects and found that they also display significant individual differences in the 4-10 kHz region. Therefore, the proper reconstruction of both individualized and nonindividualized HRTFs requires that the listener's HpTF be deconvolved from the stimulus. We have verified this acoustically using the in-ear recording system for both individualized and nonindividualized HRTFs. Finally, we show that the use of nonindividualized HpTFs creates considerable distortions in the 4-10 kHz range, which could partly account for the increased incidence of mislocalizations reported in previous virtual auditory space localization experiments.

Adult↗
PubMed2002

Horizontal localization and speech intelligibility with bilateral and unilateral hearing aid amplification.

Speech intelligibility and horizontal localization of 19 subjects with mild-to-moderate hearing loss were studied in order to evaluate the advantages and disadvantages of bilateral and unilateral hearing aid (HA) fittings. Eight loudspeakers were arranged in a circular array covering the horizontal plane around the subjects. Speech signals of a sentence test were delivered by one, randomly chosen, loudspeaker. At the same time, the other seven loudspeakers emitted noise with the same long-term average spectrum as the speech signals. The subjects were asked to repeat the speech signal and to point out the corresponding loudspeaker. Speech intelligibility was significantly improved by HAs, bilateral amplification being superior to unilateral. Horizontal localization could not be improved by HA amplification. However, bilateral HAs preserved the subjects' horizontal localization, whereas unilateral amplification decreased their horizontal localization abilities. Front-back confusions were common in the horizontal localization test. The results indicate that bilateral HA amplification has advantages compared with unilateral amplification.

Aged↗
PubMedDate not supplied

Auditory localization for spatial orientation.

The use of three-dimensional auditory technology that provides localization of auditory cues presented through headphones is proposed as a means of providing supplemental information to pilots on the spatial orientation of an aircraft. This technique shows promise for reducing accidents due to spatial disorientation associated with high visual load. A study was conducted using United States Air Force pilots as subjects to determine desirable¿ cue characteristics for accurately localizing auditory cues using this technique. The study examined the use of 9 different cue types at each of 2 frequency levels. It was found that the accuracy of subjects' localization of cues in elevation was greatly enhanced by the use of multidimensional cues that provided redundant elevation information through varying frequencies and distance from the horizon cues in addition to the inherent spatial location information. Trade-offs in azimuth localization accuracy and response time were noted, however. Recommendations are made for further developing and investigating this technique for the aircraft spatial orientation task.

Accidents, Aviation↗
PubMed2006

Response preferences for "what" and "where" in human non-primary auditory cortex.

Primate studies suggest the auditory cortex is organized in at least two anatomically and functionally separate pathways: a ventral pathway specializing in object recognition and a dorsal pathway specializing in object localization. The current experiment assesses the validity of this model in human listeners using fMRI to investigate the neural substrates of spatial and non-spatial temporal pattern information. Targets were differentiated from non-targets on the basis of two levels of pitch information (present vs. absent, fixed vs. varying) and two levels of spatial information (compact vs. diffuse sound source, fixed vs. varying location) in a factorial design. Analyses revealed spatially separate responses to spatial and non-spatial temporal information. The main activation associated with pitch occurred predominantly in Heschl's gyrus (HG) and planum polare, while that associated with changing sound source location occurred posterior to HG, in planum temporale (PT). Activation common to both pitch and changing spatial location was located bilaterally in anterior PT. Apart from this small region of overlap, our data support the anatomical and functional segregation of 'what' and 'where' in human non-primary auditory cortex. Our results also highlight a distinction in the sensitivity of anterior and posterior fields of PT to non-spatial information and specify the type of spatial information that is coded within early areas of the spatial processing stream.

Adolescent↗
PubMed1959

Cortical correlated of auditory localization.

Responses were recorded simultaneously from a number of electrodes on the auditory cortex of one hemisphere of cats. Response amplitudes at different electrodes reached maxima and minima at different real or apparent locations of a click stimulus.

Acoustic Stimulation↗
PubMed1999

Modality-specific frontal and parietal areas for auditory and visual spatial localization in humans.

Although the importance of the posterior parietal and prefrontal regions in spatial localization of visual stimuli is well established, their role in auditory space perception is less clear. Using positron emission tomography (PET) during auditory and visual spatial localization in the same subjects, modality-specific areas were identified in the superior parietal lobule, middle temporal and lateral prefrontal cortices. These findings suggest that, similar to the visual system, the hierarchical organization of the auditory system extends beyond the temporal lobe to include areas in the posterior parietal and prefrontal regions specialized in auditory spatial processing. Our results may explain the dissociation of visual and auditory spatial localization deficits following lesions involving these regions.

Adult↗
PubMed1993

Comparison of nine methods of indicating the direction to objects: data from blind adults.

Nine methods of indicating the direction to object locations were tested on twenty blind adult subjects. The task was to indicate the location of active auditory targets distributed in a semicircle with a 1.7 m radius around the subject. Target location, practice, and feedback were systematically varied for each method. The greatest accuracy and lowest variability were found for pointing methods that used body parts (directing the nose at the target, facing it with the chest, and pointing with the index finger) and extensions of body parts (pointing with a hand-held cane or with a short stick). Two less accurate methods involved rotating a dial. The least accurate methods involved drawing and a verbal description in terms of clockface labels. Method interacted significantly with target location, and with individual differences. In general, the body-part and extension method were affected less than other methods by target location and individual differences. The findings suggest that a pointing response that uses body part or an extension of a body part is the best choice for experimental or diagnostic measurement of object location by blind subjects. Differences between the results of this study of blind subjects and auditory localization accuracy in sighted subjects are discussed, and the implications for spatial processing in the blind are considered.

Adult↗
PubMed2005

Validity, internal consistency, and test/retest reliability of a localization disabilities and handicaps questionnaire.

Psychometric evaluations were performed on a self-perceived localization disabilities and handicaps questionnaire. Twenty individuals with normal hearing bilaterally, twenty with profound unilateral hearing impairment (UHI), and ten with any degree of bilateral hearing impairment participated. Each subject completed the questionnaire. Comparisons of the responses of the subjects with normal hearing and those with UHI revealed significant differences among the groups for both disabilities and handicaps, establishing construct validity. Cronbach's Alpha correlational analyses of the responses of all subjects with hearing impairment revealed correlations of .900 (disabilities) and .800 (handicaps), establishing internal consistency. Each participant with hearing impairment was asked to complete the questionnaire again after three weeks. Pearson's correlational analyses of the responses at time one versus time two revealed correlations of .900 (disabilities) and .700 (handicaps), establishing test/retest reliability. This questionnaire is an appropriate tool for investigating the self-perceived localization disabilities and handicaps of individuals with hearing impairment.

Adult↗
PubMed1984

Concurrent minimum audible angle: a re-examination of the concept of auditory spatial acuity.

Minimum audible angle was measured for simultaneous acoustic events. Localization of concurrent events was found to be a direct function of the spectral differences between the events, the angle between the sources, and the location of the sources within the field defined by the subject. In the latter case, the m.a.a. was smallest with sources placed symmetrically about the listener's median plane and maximal at the extreme lateral portions. Post-hoc tests were completed which indicate that the spectral limits for concurrent localization is dependent both upon the angular separation of the sources and the position within the field as defined by the locus of the subject. The functions obtained approach the values reported by Mills [J. Acoust. Soc. Am. 30, 237-246(1958)] as the temporal overlap between the concurrent events decreased. The present results suggest that a single localization function may exist with the optimal performance observed with fully successive stimuli and poorest performance in the condition involving simultaneous events. The implications of these results are discussed.

Auditory Perception↗
PubMedDate not supplied

Characteristics of neuronal responses in the sensorimotor cortex of the cat to monaural and binaural stimulation.

The dependence of neuronal responses in the sensorimotor cortex (SMC) of the cat upon localization parameters of dichotically presented auditory signals was studied in acute experiments. Binaural stimulation was more effective than either monaural stimulation. It was shown that spatial-localization parameters of auditory-stimulus source such as interaural differences in intensity and time are reflected by the characteristics of neuronal responses in the SMC; moreover, in 67-88% of cases the most pronounced responses were observed for small, close to zero, temporal and amplitudinal interaural shifts. It was found that SMC neuronal background activity may be altered by signals simulating directed movement of the sound source in the horizontal plane.

Animals↗
PubMed1984

Electronystagmography and horizontal directionalization.

A series of 22 patients complaining of disorders of equilibrium or hearing thought to be due to Central Nervous System (CNS) dysfunction has been studied. Data were obtained for electronystagmography (ENG), horizontal directionalization (HD), the staggered spondee word test (SSW), brainstem auditory evoked responses (BSER) and the Chocholle test of binaural interaction of pure tones (CH). The central ENG abnormalities found were spontaneous central vestibular nystagmus, paroxysmal central positional nystagmus, gaze paretic nystagmus, impaired optokinetic nystagmus, impaired smooth pursuit eye movements and impaired fixation-suppression of caloric nystagmus. HD results showed a weak link with hearing loss (HL). The central ENG abnormality most closely associated with impairment of HD was abnormal smooth pursuit eye movements. No significant relationship could be established between any two of the tests studied. The limited localizing value of the tests is discussed together with the contribution they make towards the diagnosis of the patient complaining of dizziness.

Adult↗
PubMed2002

Expansion of the tonotopic area in the auditory cortex of the blind.

A part of the core area of the auditory cortex was examined in nine blind and 10 sighted individuals by magnetic source imaging and was found to be enlarged by a factor of 1.8 in the blind compared with the sighted humans. Moreover, the latency of the N1m component of the auditory-evoked magnetic response was significantly decreased in the blind. The development of use-dependent cortical reorganization may be a consequence of the absence of visual input in combination with enhanced auditory activity generated by the long-term concentration by blind individuals on nonvisual cues to interact appropriately with the environment. It is consistent with and well suited to mediate the demonstrated increased ability of the blind to accurately localize acoustic sources in peripheral auditory fields and to decode speech.

Acoustic Stimulation↗
PubMed2001

Gravitoinertial force magnitude and direction influence head-centric auditory localization.

We measured the influence of gravitoinertial force (GIF) magnitude and direction on head-centric auditory localization to determine whether a true audiogravic illusion exists. In experiment 1, supine subjects adjusted computer-generated dichotic stimuli until they heard a fused sound straight ahead in the midsagittal plane of the head under a variety of GIF conditions generated in a slow-rotation room. The dichotic stimuli were constructed by convolving broadband noise with head-related transfer function pairs that model the acoustic filtering at the listener's ears. These stimuli give rise to the perception of externally localized sounds. When the GIF was increased from 1 to 2 g and rotated 60 degrees rightward relative to the head and body, subjects on average set an acoustic stimulus 7.3 degrees right of their head's median plane to hear it as straight ahead. When the GIF was doubled and rotated 60 degrees leftward, subjects set the sound 6.8 degrees leftward of baseline values to hear it as centered. In experiment 2, increasing the GIF in the median plane of the supine body to 2 g did not influence auditory localization. In experiment 3, tilts up to 75 degrees of the supine body relative to the normal 1 g GIF led to small shifts, 1--2 degrees, of auditory setting toward the up ear to maintain a head-centered sound localization. These results show that head-centric auditory localization is affected by azimuthal rotation and increase in magnitude of the GIF and demonstrate that an audiogravic illusion exists. Sound localization is shifted in the direction opposite GIF rotation by an amount related to the magnitude of the GIF and its angular deviation relative to the median plane.

Adult↗
PubMed2001

Group II metabotropic glutamate receptors are differentially expressed in the medial nucleus of the trapezoid body in the developing and adult rat.

The existence of a neuronal-glial signalling through the activation of neurotransmitter receptors expressed in glia is well-documented. In excitatory synapses, glutamate released from presynaptic terminals activates not only postsynaptic receptors, but also ionotropic and metabotropic glutamate receptors localized in the glia ensheathing the synapses. The medial nucleus of the trapezoid body of the auditory system is involved in the localization of sounds in the space. In this nucleus, the large excitatory synaptic terminals formed by the calyces of Held on the principal globular cell bodies are wrapped by astrocytic processes. Since these synapses are functional from early postnatal days, glia receiving excitatory synaptic signals from the calyces may participate in modulating the maturation and development of the system. Groups I and II of metabotropic glutamate receptors (mGluRs) have been localized in glial cells in different brain regions. To investigate whether group II mGluRs are present in the medial nucleus of the trapezoid body, we have studied the pattern of expression of mGluR2/3 in the developing and mature nucleus by means of immunocytochemichal methods. The most remarkable finding was the switch in the occurrence of mGluR2/3 from glial to neuronal compartments. Thus, a preferential localization of mGluR2/3 immunoreactivity was observed in astrocytic processes surrounding the calyces of Held during the early postnatal development. In contrast, the main feature in adult rats was the presence of the group II mGluRs in presynaptic calyces of Held and postsynaptic principal globular cells.From these observations we suggest a role for group II mGluRs in neuronal-glial signalling in the calyx of Held-principal globular neuron synapses. Activation of these receptors might be relevant to the maturation and modulation of synaptic transmission in the medial nucleus of the trapezoid body.

Aging↗