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At least 1,063 records · Page 59Linked to original sources
PubMed2003

Differential activation in the medial temporal lobe during a sound-sequence discrimination task across age in human subjects.

To elucidate the brain mechanisms to encode sequential events, event-related potentials (ERPs) were recorded during a sound-sequence discrimination task using young and middle-aged adult subjects. In the task, a series of six or 12 kinds of natural sounds were sequentially presented; 70-80% of the stimuli were presented in a fixed order (Non-target), but the remaining stimuli, in a random order (Target). The subjects were instructed to detect the Targets and press a button at the end of each Target. In a control task, the same sounds were randomly presented (Control), and they were instructed to press the button at the end of each sound. Behavioral results indicated that the young subjects learned the task faster than did the middle-aged subjects. Positive ERP waves were evoked by Targets and Non-targets in the parieto-occipital area around 300-700 ms after stimulus onset. The mean amplitudes during this period in the young subjects were larger in Target than Control conditions, and those in Target condition were larger in the young than middle-aged subjects. Furthermore, the mean amplitudes in the Target condition were significantly correlated with behavioral performance. Equivalent dipoles for the ERPs evoked by Targets were estimated in the medial temporal lobe including the hippocampal formation and parahippocampal gyrus. The results suggest that the ERPs around 300-700 ms latency are involved in sound-sequence information processing. Furthermore, decrease in amplitudes of this positivity in the middle-aged subjects suggests that age-related memory decline is associated with deficits in encoding and retrieval of unfamiliar sequence.

Acoustic Stimulation↗
PubMed2002

The effect of eye position and background noise on vertical sound localization.

The influence of the eye position in combination with a simultaneously presented background (frame) sound on the auditory localization of a single (target) sound source was investigated in the median vertical plane (MVP). Five loudspeakers ranged from -20 degrees to +20 degrees with the center speaker at 0 degrees elevation. Listeners verbally estimated the position of a 500-ms noise stimulus, which was presented while they were fixating visual targets in various elevations. The perceived sound elevation appeared to be shifted 8.6 degrees on average towards the direction of eccentric gaze. When the target was temporarily embedded in a 2-s frame sound (emitted by one of the two outer loudspeakers) and the gaze was fixated at a straight-ahead position, the listeners consistently shifted the apparent target positions about 4 degrees away from the frame locations. This auditory contrast effect, which is consistent with earlier findings, remained even if the gaze direction deviated from straight ahead. It is concluded that the auditory contrast effect exists independently from the eye position effect and that the two effects act separately on auditory sound localization.

Acoustic Stimulation↗
PubMed1999

An interaction between PPADS, an ATP antagonist, and a moderately intense sound in the cochlea.

In the organ of Corti ionotropic receptors for ATP (ATPRs) on cells that are bathed by perilymph have been suggested to modulate cochlear mechanics. The purpose of the present study was to test the hypothesis that endogenous extracellular ATP acting through ATPRs is involved in modulating cochlear mechanics during moderately intense sound exposure. Guinea pigs were exposed to either: (1) a perilymphatic administration of pyridoxal-phosphate-6-azophenyl-2', 4'-disulfonic acid (PPADS, 1 mM), an ATP antagonist; (2) a moderately intense sound (6.7 kHz tone, 95 dB SPL, 15 min); or (3) a combination of both the PPADS and the sound. The effects on cochlear potentials (cochlear microphonic, CM; negative summating potential, SP; compound action potential of the auditory nerve, CAP; and N(1) latency) evoked by a 10 kHz tone pip were monitored. PPADS alone reduced the CAP and the SP and increased N(1) latency. The intense sound alone reduced the CAP and SP. The combination of PPADS with the intense tone induced reversible effects on cochlear potentials that were greater than induced by either treatment alone. The effect on N(1) latency and low intensity CM was a potentiation since the effect was greater than a simple addition of the effect of either treatment alone. The effects of the combination treatment on CAP, SP and high intensity CM were not different from additive. Results are consistent with the hypothesis that ATPRs in the organ of Corti are involved in modulating cochlear mechanics during moderately intense sound exposure.

Adenosine Triphosphate↗
PubMed1995

Psychophysical tuning curve and critical band determined by masking in the presence of FM sounds.

Frequency modulation (FM) sounds were used as simultaneous maskers to estimate the psychophysical tuning curve (PTC). Maskers (800 ms duration) were FM sounds sweeping upward (1.2-->2.8 kHz) in Experiment I and downward (2.8-->1.2 kHz) in Experiment II. The signal was a pure tone of 2 kHz and the signal levels were 15-, 20-, 30-, and 35-dB SL. Masked PTCs were obtained as a function of masker frequency. The results were as follows: (i) When an upward-sweeping FM sound is used for high signal level, the slope of the PTC is shallower on the low frequency side and steeper on the high frequency side, and the 10-dB bandwidth of PTC coincides with that of the restricted PTC. (ii) When a downward-sweeping FM sound is used for the high signal level, the above relation for the PTC slope is reversed, and the 10-dB bandwidth for PTC coincides with that of unrestricted PTC. (iii) PTCs determined by masking in the presence of FM sounds apparently restrict the subject to listening to off-frequency, and it is shown that the bandwidth of PTC properly reflects the critical band. (iv) The properties of these PTCs can be easily explained by a neural network model of lateral inhibition, so we can accept a hypothesis that the hierarchical processing mechanism is incorporated within the inferior colliculus for parallel signal processing. (v) We conclude that the frequency resolution and the critical band filtering are, therefore, realized in a psychophysically relevant way in the auditory midbrain level.

Adult↗
PubMed2002

Cortical processing of speech sounds and their analogues in a spatial auditory environment.

We used magnetoencephalographic (MEG) measurements to study how speech sounds presented in a realistic spatial sound environment are processed in human cortex. A spatial sound environment was created by utilizing head-related transfer functions (HRTFs), and using a vowel, a pseudo-vowel, and a wide-band noise burst as stimuli. The behaviour of the most prominent auditory response, the cortically generated N1m, was investigated above the left and right hemisphere. We found that the N1m responses elicited by the vowel and by the pseudo-vowel were much larger in amplitude than those evoked by the noise burst. Corroborating previous observations, we also found that cortical activity reflecting the processing of spatial sound was more pronounced in the right than in the left hemisphere for all of the stimulus types and that both hemispheres exhibited contralateral tuning to sound direction.

Acoustic Stimulation↗
PubMed2002

Involuntary attention in children as a function of sound source location: evidence from event-related potentials.

OBJECTIVES: The present study addressed the question of whether location of the auditory stimulation source affects an involuntary attention triggering to the deviant sounds in a passive oddball paradigm in 8-10-year-old children. METHODS: Using free-field stimulation two late event-related potentials components were examined: the mismatch negativity (MMN), indexing preconscious sound change detection and the P3a, indexing involuntary attention switch. Data were registered to frequency changes in sounds of different complexities in two experimental conditions. In the 'in-front' condition, the sound sequences were presented through the loudspeakers situated in front of a participant on both sides of the video display. In the 'on-sides' condition, the sources of auditory and visual stimuli were separated by moving the loudspeakers to the sides of the participant. RESULTS: The MMN amplitude or the MMN and P3a latencies varied in neither stimulus class significantly as a function of sound location. However, significantly larger P3 amplitude was found in the 'in-front', as compared to the 'on-sides' condition. CONCLUSIONS: The present results indicate enhanced involuntary attention switching in children when unattended auditory events occur within the space attended actively for visual modality. Such study design favouring cross-modal integration can be advantageous when studying involuntary auditory attention and its impairment in children.

Acoustic Stimulation↗
PubMed2002

Two-dimensional positional mapping of gastrointestinal sounds in control and functional bowel syndrome patients.

Computerized auscultation of the abdomen provides a noninvasive and quantitative method to investigate gastrointestinal function. Two-dimensional mapping of bowel sound sites of origin, to the surface of the abdomen, was accomplished through simultaneous recording with three electronic stethoscopes. Control, irritable bowel syndrome, and nonulcer dyspepsia groups were studied. The predominant site of fasting sound production was the right lower quadrant in all except a subgroup of nonucler dyspepsia patients. The second most common site mapped to the area of the stomach. The region mapping to the small intestine was largely devoid of sound. The control group had a higher percentage of sounds in the 184- to 248-Hz range than the functional bowel patients (P < 0.001) for sounds mapping to the stomach region. We conclude that two-dimensional mapping may have the potential to allow for the meaningful and objective categorization of groups of functional bowel patients.

Adult↗
PubMed1996

Evidence for a sound movement area in the human cerebral cortex.

Human listeners can localize sounds by the difference in both arrival time (phase) and loudness between the two ears. Movement of the sound source modulates these cues, and responses to moving sounds have been detected in animals in primary auditory cortex and in humans in other cortical areas. Here we show that detection of changes in the interaural phase or amplitude difference occurs through a mechanism distinct from that used to detect changes in one ear alone. Moreover, a patient with a right hemisphere stroke is unable to detect sound movement, regardless of whether it is defined by phase or by loudness cues. We propose that this deficit reflects damage to a distinct cortical area, outside the classical auditory areas, that is specialized for the detection of sound motion. The deficit is analagous to cerebral akinotopsia (motion blindness) in the visual system, and so the auditory system may, like the visual system, show localization of specialized functions to different cortical regions.

Aged↗
PubMed2002

Efficient coding of natural sounds.

The auditory system encodes sound by decomposing the amplitude signal arriving at the ear into multiple frequency bands whose center frequencies and bandwidths are approximately exponential functions of the distance from the stapes. This organization is thought to result from the adaptation of cochlear mechanisms to the animal's auditory environment. Here we report that several basic auditory nerve fiber tuning properties can be accounted for by adapting a population of filter shapes to encode natural sounds efficiently. The form of the code depends on sound class, resembling a Fourier transformation when optimized for animal vocalizations and a wavelet transformation when optimized for non-biological environmental sounds. Only for the combined set does the optimal code follow scaling characteristics of physiological data. These results suggest that auditory nerve fibers encode a broad set of natural sounds in a manner consistent with information theoretic principles.

Animals↗
PubMed2000

Properties of sound.

Basic concepts about sound exposure are reviewed without extensive reliance on the technical details of physical acoustics or psychoacoustics. The frequencies and intensities of sounds that might be encountered in a hospital nursery are described. Examples of the nonlinear properties of sound levels are provided. The complexities of adding and subtracting decibels are discussed. Some important noise standards are reviewed, along with an explanation of why some sounds might be more annoying than others. A companion article in this issue gives practical information on how to make sound-level measurements.

Acoustics↗
PubMed1986

Articulation generalization of voiced-voiceless sounds in hearing-impaired children.

Eight hearing-impaired children participated in a study exploring the effect of training (+) or (-) voicing on generalization to cognates. In an experimental multiple baseline study across behaviors, children were trained on pairs of voiced and voiceless target sounds that they had previously omitted in final position. The pairs consisted of the /t/ and /g/ and the /d/ and /k/. When /t/ was trained, generalization was tested to (a) untrained words with the /t/ in the final position and (b) untrained words containing /d/ (the cognate) of the /t/. In like manner, when /d/ was trained, generalization was tested to both the /d/ and /t/ words. The /g/ and /k/ received identical treatment. A contrast procedure was used to teach the children to produce the final consonants. When training criterion was reached, generalization was tested. Results showed that 6 of the 8 children generalized both the voiced and unvoiced target sounds to 50% or more of the target sound probe items. Results also indicated that more generalization occurred to the voiceless cognate from voiced target sound training than occurred to voiced cognates from voiceless target sound training.

Child↗
PubMed2001

Tracheal sounds and airflow dynamics in surgically treated unilateral vocal fold paralysis.

The aim of this study was to investigate the changes in tracheal sounds and airflow dynamics in patients who underwent surgical medialization of a unilaterally paralysed vocal fold. Ten adults with unilateral vocal fold paralysis but no history of pulmonary diseases were included. Vocal fold medialization was performed by an injection of autologous fascia into the paralysed vocal fold. Recording of tracheal sounds, flow-volume spirometry and body plethysmography were carried out before and 4-14 months after the operation. The mean number of inspiratory wheezes per respiratory cycle increased from 0.02 (range 0-0.10) to 0.42 (range 0-0.86) and the mean number of expiratory wheezes per respiratory cycle from 0.03 (range 0-0.20) to 0.36 (range 0-0.89). The increment was statistically significant (P=0.03 and P=0.04, respectively). The mean expiratory sound amplitude, in terms of root mean square (RMS), increased from 31.5 dB (range 24.0-38.0) to 34.9 dB (range 25-42) (P=0.03) and the average peak inspiratory flow (PIF) decreased from 4.63 l s-1 (range 2.84-7.51) to 4.03 l s-1 (range 2.27-6.68) (P=0.01). The results indicate that when the paralysed vocal fold is brought into midline by a surgical procedure, the prevalence of inspiratory and expiratory wheezes increases and sound intensity rises. According to this preliminary data tracheal sound analysis gives additional information for the assessment of the subtle changes in the larynx.

Aged↗
PubMed2002

Acoustic characteristics of sounds from temporomandibular joints with and without effusion: an MRI study.

Joint effusion has been associated with temporomandibular joint (TMJ) pain but can only be diagnosed by magnetic resonance imaging (MRI). For screening of patients with suspected effusion a simple and less expensive method would be desirable. We recorded joint sounds during jaw opening and closing movement from 34 TMJs with internal derangement (ID). Seventeen joints had joint effusion seen on MRI. Spectrograms of the sounds were displayed as waterfall plots showing profiles of the consecutive Hamming windows. If the profiles were similar, as judged by initial evaluation, the displayed pattern was classified as stable. If some profiles were distinctly deviating in their pattern, this was classified as unstable. Joints with effusion showed unstable sound pattern more often than joints without effusion (P < 0.001). It was concluded that TMJ sound analyses have a potential to identify joints with effusion based on their unstable sound pattern.

Adult↗
PubMed2002

Localization of TMJ sounds to side.

Differential diagnosis depends in cases with disk displacement on accurate identification of sound source. Mistakes may occur when clicking from one temporomandibular joint (TMJ) is heard on both sides of the head at auscultation and neither examiner nor patient, is sure about side. The hypothesis was that the head tissues affect spectral characteristics of TMJ sounds and that differences due to different positioning of sensors can be used in localization of source. The aim was to compare bilateral electronic recordings of unilateral TMJ sounds to obtain and compare attenuation, phase shift and time delay. Recordings were made from 12 subjects with unilateral clicking. Small electret condenser microphones, bandwidth 40-20 000 Hz, were placed at the openings of the auditory canals and the sounds were recorded at a sampling rate of 48 000 Hz. The head tissues acted as a filter causing a frequency dependent attenuation and phase shift. There was a time difference between the ipsi- and the contra lateral recordings, the latter always having a longer delay time (range 0.2-1.2 ms, group mean 0.68 ms, s.d. 0.292 ms). In conclusion, spectral analysis of bilateral electronic TMJ sound recordings is of diagnostic value when bilateral clicking is heard at auscultation and can help to avoid diagnosing a silent joint as clicking.

Adult↗
PubMed2003

The dynamic range of TMJ sounds.

It is of clinical interest to record the amplitudes of temporomandibular joint (TMJ) sounds. The aim was to test the hypothesis that sealing the meatus, when placing a microphone in the ear canal affects such recording by increasing the sound pressure level (SPL). Bilateral recordings of 249 TMJ clickings were made from three subjects, using sampling rates of 48 or 96 kHz and 24 bits A/D conversion, with and without the ear canals sealed by Silicone putty. The peak-to-peak equivalent sound pressure level (peSPL) was higher (P < 0.001) when the ear canal was sealed (range of mean differences was 8.3-24.9 dB peSPL). This means that the signal to noise ratio can be improved by sealing the meatus because the electronic noise level is not increased. Most important is that the dynamic range of the clicking sounds was 62 dB that is larger than the effective dynamic range of a 16 bits sound card. Future studies are needed to establish normative peSPL values. However, cards with at least 24 bits A/D conversion will be required, especially in patients with suspected disc displacement with reduction, where the difference in loudness between opening and closing clicking often is large.

Auscultation↗
PubMed1990

Intrauterine sound levels: intrapartum assessment with an intrauterine microphone.

The complex mechanisms responsible for fetal hearing are in place and functional by 26 weeks of gestation, but little is known about the acoustic milieu of the amniotic cavity. We placed an electrically isolated microphone in the uterus of nine term gravid volunteers after amniorrhexis. Baseline levels of intrauterine sound were 72 to 88 db. Transabdominal vibroacoustic stimulation with an artificial larynx produced peak mixed frequency sound levels of 91 to 111 db. We conclude that the term fetus in labor is exposed to physiologic sound levels higher than we had anticipated; the application of a quantifiable sound stimulus to the maternal abdominal wall results in a small increment in intrauterine sound; and within the limits specified, experimental fetal acoustic stimulation should pose no major risks.

Acoustic Stimulation↗
PubMed2006

The effect of optokinetic stimulation on orientation of sound lateralization.

CONCLUSIONS: The current study demonstrates that sound lateralization sensitivity during interaural time difference (ITD) discrimination may be altered by optokinetic (OK) stimulation, and that sound lateralization sensitivity of ITD discrimination may be more susceptible to OK stimulation than that of interaural intensity difference (IID) discrimination. These data suggest that nystagmus or the sensation of self-rotation induced by OK stimulation influences auditory afferent information such as sound lateralization. OBJECTIVE: Using dichotic sound, the effect of optokinetic stimulation on the orientation of sound lateralization was investigated in humans. MATERIALS AND METHODS: Subjects were studied by testing ITD and IID discrimination during OK stimulation. RESULTS: At 90 degrees/s of the light stripes angular velocity the amplitudes for the ITD discrimination tests during OK stimulation were significantly greater than those either before the beginning of OK stimulation or at 30 degrees/s (p<0.05). No significant difference in the amplitude for the IID discrimination test was observed between the results obtained before and during OK stimulation. During OK stimulation, all subjects felt that their perceptual body axes shifted toward the quick phase of OK nystagmus. In 8 of 12 subjects, the median line of amplitude for the ITD discrimination test shifted to the quick phase side of the OK nystagmus.

Adult↗
PubMed2006

Contributions of binaural information to the separation of different sound sources.

Binaural hearing aids potentially provide binaural cues that can improve the dectability and the spatial separation of multiple sound sources. This paper considers the use of binaural cues and the resultant spatial percepts on listeners' ability to separate simultaneous sound sources. In backgrounds with continuous noise or multiple talkers, the main problem is the detection of individual acoustic components. On the other hand, if a single masking sound is very similar to the target, and both target and masker are spectro-temporally sparse, as is the case with speech, the main problem, at least for listeners with normal hearing, is to decide whether a particular spectro-temporal feature belongs to the target source and to track that source across time. Although the subjective location of a sound source can help in grouping features across time, its effect is most easily observed in the absence of other differences between the sound sources.

Environment↗