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At least 1,027 records · Page 57Linked to original sources
PubMed1998

Inhibitory processes in auditory selective attention: evidence of location-based and frequency-based inhibition of return.

The possibility that there is an inhibitory component to auditory covert orienting was addressed. Each trial consisted of a cue followed by a target, and listeners were required to detect, localize, or identify the frequency of the target. At 150-msec stimulus onset asynchrony (SOA), performance was best when stimuli sounded from the same location or were of the same frequency. However, at 750-msec SOA, performance was best when stimuli differed in location or were of different frequencies. These results document the existence of both location-based and frequency-based auditory inhibition of return.

Attention↗
PubMed2005

Auditory spatial localization and attention deficits in autistic adults.

The objective of this study was to compare autistic adults and matched control subjects in their ability to focus attention selectively on a sound source in a noisy environment. Event-related brain potentials (ERPs) were recorded while subjects attended to a fast paced sequence of brief noise bursts presented in free-field at a central or peripheral location. Competing sequences of noise bursts at adjacent locations were to be ignored. Both behavioral measures of target detection and auditory ERP amplitudes indicated that control subjects were able to focus their attention more sharply on the relevant sound source than autistic subjects. These findings point to a fundamental deficit in the spatial focusing of auditory attention in autism, which may be a factor that impedes social interactions and sensory-guided behavior, particularly in noisy environments.

Adult↗
PubMed1995

Envelope coding in the lateral superior olive. I. Sensitivity to interaural time differences.

1. Interaural level differences (ILDs), created by the head and pinna, have long been known to be the dominant acoustic cue for azimuthal localization of high-frequency tones. However, psychophysical experiments have demonstrated that human subjects can also lateralize complex high-frequency sounds on the basis of interaural time differences (ITDs) of the signal envelope. The lateral superior olive (LSO) is one of two pairs of binaural nuclei where the primary extraction of binaural cues for sound source location occurs. "IE" cells in LSO are inhibited by stimuli to the contralateral and excited by stimuli to the ipsilateral ear, and their response rate is therefore dependent on ILD. Anatomic specializations in the afferent pathways to the LSO suggest that this circuit also has a function in the detection of timing cues. We hypothesized that, besides ILD sensitivity, the IE property also conveys a sensitivity to ITDs of amplitude-modulated (AM) tones and could provide the physiological substrate for the psychophysical effect mentioned above. 2. In extracellular recordings from binaural LSO cells in barbiturate-anesthetized cats, response rate was a periodic function of ITDs of AM stimuli, i.e., all cells displayed ITD sensitivity. Binaural responses were smaller than responses to stimulation of the ipsilateral ear alone and were minimal when the envelopes in both ears were in-phase or nearly so. There was good correspondence between responses to ITDs and to dynamic interaural phase differences (IPDs), created by a difference in the envelope frequency to the two ears. Qualitatively, the responses were consistent with the outcome of an IE operation on temporally structured inputs. 3. To compare the relative importance of ILD and ITD, responses to combinations of the two cues were obtained. Despite robust ITD sensitivity in all binaural LSO cells encountered, the changes in response rate that would occur in response to naturally occurring ITDs were small in comparison with the changes expected for naturally occurring ILDs. The main limitation on ITD sensitivity was a steep decline in average discharge rate as the modulation frequency exceeded several hundred Hertz. 4. ITD sensitivity was also present to broadband stimuli, again with minimal rates occurring near 0 ITD. The sensitivity depended in a predictable fashion on the passband of filtered noise and was absent to binaurally uncorrelated noise bands. In response to clicks, ILDs interacted with ITD in a complicated fashion involving amplitude and latency effects. 5. Three low-characteristic frequency (CF) LSO cells were encountered that were IE and showed ITD sensitivity to the fine structure of low-frequency stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2003

Full time directional versus user selectable microphone modes in hearing aids.

OBJECTIVE: The purpose of this experiment was to systematically examine hearing aid benefit as measured by speech recognition and self-assessment methods across omnidirectional and directional hearing aid modes. These data were used to compare directional benefit as measured by speech recognition in the laboratory to hearing aid wearer's perceptions of benefit in everyday environments across full-time directional, full-time omnidirectional, and user selectable directional fittings. Identification of possible listening situations that resulted in different self reported hearing aid benefit as a function of microphone type was a secondary objective of this experiment. DESIGN: Fifteen adults with symmetrical, sloping sensorineural hearing loss were fitted bilaterally with in-the-ear (ITE) directional hearing aids. Measures of hearing aid benefit included the Profile of Hearing Aid Benefit (PHAB), the Connected Sentence Test (CST), the Hearing in Noise Test (HINT), and a daily use log. Additionally, two new subscales were developed for administration with the PHAB. These subscales were developed to specifically address situations in which directional hearing aids may provide different degrees of benefit than omnidirectional hearing aids. Participants completed these measures in three conditions: omnidirectional only (O), directional only with low-frequency gain compensation (D), and user-selectable directional/omnidirectional (DO). RESULTS: Results from the speech intelligibility in noise testing indicated significantly more hearing aid benefit in directional modes than omnidirectional. PHAB results indicated more benefit on the background noise subscale (BN) in the DO condition than in the O condition; however, this directional advantage was not present for the D condition. Although the reliability of the newly proposed subscales is as yet unknown, the data were interpreted as revealing a directional advantage in situations where the signal of interest was in front of the participant and a directional disadvantage in situations where the signal of interest was behind the listener or localization was required. CONCLUSIONS: Laboratory directional benefit is reflected in self-assessment measures that focus on listening in noise when the sound source of interest is in front of the listener. The use of a directional hearing aid mode; however, may have either a positive, a neutral, or a negative impact on hearing aid benefit measured in noisy situations, depending on the specific listening situation.

Aged↗
PubMed1984

The psychophysical basis of monaural localization.

Listeners were required to locate, monaurally, noise bursts emanating from the horizontal plane ipsilateral to the functioning ear. Loudspeakers were positioned from 0 through 180 degrees azimuth, separated by 15 degrees. Stimulus bandwidth was 1.0 kHz, and centered at 4.0-14.0 kHz in steps of 0.5 kHz. The location judgments were governed by the frequency composition of the stimuli, not by their place of origin. With a miniature microphone positioned at the entrance of the external ear canal, the relative amplification provided by the pinna was obtained for the stimuli employed in the localization tests. For each differently centered noise burst, that loudspeaker position re other positions which was associated with the greatest amplification of the stimulus was the one most likely to have been chosen as the source of that stimulus during the localization tests.

Auditory Perception↗
PubMed2004

New genus with two new species of capsalid monogeneans from dasyatids in the Gulf of California.

We propose Listrocephalos n. gen. (Monogenea: Capsalidae: Entobdellinae) for 2 new capsalid species that infect the skin of 2 species of diamond stingrays (Dasyatidae) in the Gulf of California. We also provide additional observations on 2 previously described capsalid species, which infect the external body surface of stingrays and are currently in Entobdella Blainville in Lamarck, 1818, and transfer them to the proposed new genus. The members of this genus, Listrocephalos corona (Hargis, 1955) n. comb. (type species), Listrocephalos guberleti (Caballero and Bravo-Hollis, 1962) n. comb., Listrocephalos kearni n. sp., and Listrocephalos whittingtoni n. sp., differ from other entobdellines by the combination of having an anterolateral adhesive pad comprising 2 ventral columns of raised ovoid structures, I pair of glands that flank the preoral depression, a discoid and aseptate haptor that lacks a marginal valve but has clover-shaped papillae dispersed radially over its entire ventral surface, minute and nonoverlapping median haptoral sclerites, a bizarre chamber yielding a duct that opens on the surface of the penis, separate genital pores, and a gland of Goto located between the testes and ovary. Listrocephalos kearni n. sp. infects Dasyatis brevis and is most easily distinguished from its congeners by the combination of lacking penis tubules and having a convoluted proximal portion of the vas deferens that occupies the space between the ootype and ovary. Listrocephalos whittingtoni n. sp. infects Dasyatis longa and is most easily distinguished from its congeners by the combination of having penis tubules and a vaginal pore that is located posterior to the level of the uterus. We report specimens of L. corona from the ventral body surface of Dasyatis say from a new locality, Mississippi Sound, as well as specimens of L. guberleti from the skin of 2 new hosts, Urobatis maculatus and Urobatis concentricus, and a new locality, Elkhorn Slough, California. We provide a diagnostic key and a table of records for Listrocephalos spp.

Animals↗
PubMed2002

Physiology of the auditory afferents in an acoustic parasitoid fly.

The fly, Ormia ochracea, possess a novel auditory organ, which allows it to detect airborne sounds. The mechanical coupling of its pair of tympanal membranes provides the basis for a unique means of sensing the direction of a sound source. In this study, we characterized the neuroanatomy, frequency tuning, and neurophysiological response properties of the acoustic afferents. Our experiments demonstrate that the fly's nervous system is able to encode and localize the direction of a sound source, although the binaural auditory cues available in the acoustic sound field are miniscule. Almost all of the acoustic afferents recorded in this study responded to short and long sound pulses with a phasic burst of one to four action potentials. A few afferents responded tonically for the duration of the sound stimulus. A prominent class of afferents responds to suprathreshold stimuli with only a single spike discharge, independent of stimulus level, frequency, or duration. We also tested the response of the afferents to speakers separated by 180 degrees along the azimuth of the fly. We found that the afferent responses have a shorter latency because of ipsilateral stimulation. This could be a temporal code of the direction of a sound source. The threshold frequency tuning for the afferents revealed a range of sensitivities to the frequency of the cricket host's calling song frequency. The difference in the number of afferents above threshold on either side of the animal is a population code, which can also be used for sound localization.

Acoustic Stimulation↗
PubMed1983

The usefulness of chest radiographs in first asthma attacks.

To assess the value of routine chest radiography during acute first attacks of asthma, we studied 371 consecutive children over one year of age who presented with an initial episode of wheezing. Three hundred fifty children (94.3 per cent) had radiographic findings that were compatible with uncomplicated asthma and were considered negative. Twenty-one (5.7 per cent) had positive findings: atelectasis and pneumonia were noted in seven, segmental atelectasis in six, pneumonia in five, multiple areas of subsegmental atelectasis in two, and pneumomediastinum in one. The patients with positive films were more likely to have a respiratory rate above 60 or a pulse rate above 160 (P less than 0.001), localized rales or localized decreased breath sounds before treatment (P less than 0.01), and localized rales (P less than 0.005) and localized wheezing (P less than 0.02) after treatment; also, these patients were admitted to the hospital more often (P less than 0.001). Ninety-five per cent (20 of 21) of the children with positive films could be identified before treatment on the basis of a combination of tachypnea, tachycardia, fever, and localized rales or localized decreased breath sounds. Most first-time wheezers will not have positive radiographs; careful clinical evaluation should reveal which patients will have abnormal radiographs and will therefore benefit from the procedure.

Asthma↗
PubMed2002

What is the nature of multisensory interaction between octavolateralis sub-systems?

The octavolateralis system consists of several submodalities, including the inertial-sensitive inner ear, the pressure-sensitive ear/air cavity complex (when present), and acceleration- and velocity-sensitive components of the lateral line system (canal and superficial neuromasts, respectively). All four of these channels are responsive to many of the same stimulus sources, particularly moving or vibrating objects within a short distance from the receiver. We therefore argue that the octavolateralis system is an excellent model for the study of multisensory interactions. We focus on the possible ways in which these channels may contribute to source localization mechanisms and to the multisensory guidance of behaviors with strong directional components (e.g., predator avoidance, prey capture and mate attraction). Finally, we define four ways in which information from multiple senses might interact. These include fractionation, synergy, accessory stimulation, and complementation. Although evidence for all types of octavolateralis interactions can be found, the primary modes of interaction appear to be complementation and fractionation. For example, the inertial and pressure-sensitive submodalities of the auditory system provide complementary pieces of information about the direction (e.g., left/right) and polarity (advancing or receding) of a moving source. In contrast, the lateral line canal system subserves short-range localization tasks, whereas the auditory system may subserve longer-range detection and localization tasks.

Animals↗