Auditory neglect and right parietal cortex.
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There is considerable interest in whether a deficit in temporal processing underlies specific learning and language disabilities in school-aged children. This view is particularly controversial in the area of developmental reading problems. The temporal-processing hypothesis was tested in a sample of normal children, 9-11 years of age, and in a sample of age-matched children with reading impairments, by assessing temporal-order discrimination. Five different binary temporal-order tasks were evaluated in the auditory and visual sensory modalities. Other basic discrimination abilities for single auditory stimuli were also assessed, including just noticeable differences (JNDs) for frequency and intensity and a simple threshold detection task. In these tasks, the temporal dimension was the duration of the individual stimuli (20 and 200 ms). All data were obtained using forced- choice psychophysical methods, either in a single-track adaptive format or using psychometric functions. The results from these experiments showed that children with reading impairments had deficits in temporal-order discrimination, but these effects were not modality specific. These same children also had significantly elevated frequency and intensity JNDs and their performance on these tasks were not dependent on stimulus duration. No group differences were observed on the threshold detection task, and the derived measurements of temporal integration (i.e. the threshold difference between the 20- and 200-ms stimuli) were considered normal, averaging 11.7 dB. As a whole, discrimination deficits observed in the reading-impaired group only occurred with suprathreshold stimuli. The deficits were neither modality specific nor temporal (duration) specific.
The binaural masking level difference (MLD) was measured at multiple masking levels (i.e. 500 Hz narrow band noise presented at 50-100 dB overall SPL) in normal hearing subjects and clinical subjects with varying types and degrees of hearing loss. MLD versus noise level (MLD-NL) functions then were derived for each subject. Some growth in the MLD-NL was seen in nearly all cases of hearing loss up to 70 dB in the poorer ear. These findings suggest that the MLD-NL function may provide the basis for extending the diagnostic usefulness of the MLD test in cases of substantive hearing loss.
The shape of the auditory filter at a given centre frequency can be estimated by measuring the threshold for detecting a sinusoid presented in a spectral notch in a noise masker, as a function of notch width. Laboratory studies using this method have typically been based on threshold measurements for between 13 and 19 notch widths. In this note, we describe how both the overall sharpness and asymmetry of the auditory filter in hearing-impaired subjects can be estimated with reasonable accuracy using only five notch widths. This considerably reduces the testing time needed, making it possible to apply the method in clinical testing.
Background noise limits for audiometry are determined by the effects of masking and are specified in international standards. The standards provide for audiometric testing over a range of audiometric frequencies extending down to 500 Hz or lower. The lowest frequency of testing is an important factor determining the admissible noise, and for certain applications it is appropriate to consider the limits applicable to testing over a more restricted range. Assessment of hearing disability in the UK is generally based on a consideration of pure-tone hearing threshold levels in the frequency range 1 kHz upwards. A modification of the standardized noise limits is proposed which allows some relaxation appropriate to this higher minimum frequency. For air-conduction audiometry, these modifications affect only the permissible background noise in the frequency range below 1 kHz. Where bone-conduction audiometry is required in order to quantify a conductive component of the hearing loss, the measurements need to be made on both ears with the non-test ear masked in both cases; the external background noise will thus only be heard monaurally and this justifies a correction to the noise limits compared with those appropriate to bone-conduction audiometry without masking.
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A 5-page questionnaire was sent to 500 audiologists who were randomly selected from the directory of members of the American Academy of Audiology to assess the clinical practices most commonly used by certified audiologists in the United States. Survey content was limited to only those practices and procedures routinely used by audiologists across the nation. The current results were then compared to those obtained in similar studies conducted in 1971, 1972, 1978, 1985, 1989, and 1994 to determine which clinical procedures are being retained, modified, or replaced.
From a sample of 35 adolescents, 17 were chosen who represented extremes of self-reported drug use and delinquent behavior. Three comparison groups were derived: Group 1, n = 7, high drug use/high delinquency; Group 2, n = 4 no drug use/high delinquency; Group 3, n = 6, no drug use/no delinquency. The three groups were similar for age, IQ, race and neighborhood characteristics. Group 1 showed significantly more drug use than Groups 2 and 3; Groups 1 and 2 had comparable levels of delinquency which were significantly greater than Group 3. The subjects performed the auditory oddball task under conditions of low and high background noise. In the high background noise condition, Group 1 had longer latency P300 responses than Groups 2 and 3, while Group 2 had smaller N100 amplitude than Groups 1 and 3. Performance was similar for each group and no group differences occurred in the low background noise condition. The results support and extend previous research on the relationship between attentional and cognitive processes, and delinquent and drug using behaviors.
Electrolarynx (EL) speech provides a valuable means of verbal communication for the laryngectomees. Yet EL speech tends to be less intelligible speech due to the presence of background noise. This paper addresses the issue of EL speech enhancement. The proposed approach takes into account the frequency-domain masking properties of the human auditory system for a subtractive-type enhancement process. Subtractive-type algorithms can efficiently reduce the radiated noise of EL speech but not to reduce the additive noise from the environment due to the use of fixed subtraction parameters. Considering the particular characteristics of EL speech, a new computationally efficient algorithm based on the perceptual weighting technique is developed to adapt the subtraction parameters. This leads to a significant reduction of the unnatural structure of the residual noise. Acoustic and perceptual experiments confirm that the enhanced EL speech is more pleasant to human listeners and the proposed algorithm results in improved performance over classical subtractive-type algorithms.
A typology of reading disability was derived from a cluster analysis of psychological and educational tests administered to 63 moderately to severely reading-disabled children and adolescents. The quality of the cluster solution was evaluated through the use of statistics designed to measure the degree to which the clusters were compact and well separated. The values of the evaluation statistics for the reading clusters were compared to the distribution of these statistics in a sample of 100 cluster solutions from comparable simulated data sets. The results of this comparison suggest that the derived reading-disability clusters represent true subtypes rather than a random partitioning of a homogeneous group of subjects. The commonalities among subjects in the same clusters appear to be such as to permit hypotheses about treatment based on cluster membership. The clusters included a language disorder with associated deficits in auditory memory and sound blending, an auditory processing disorder, a mixed auditory and visual processing disorder, and an auditory memory and visual processing disorder. This study did not find the "normal" and visual-perceptual subtypes reported in some other recent investigations.
This article overviews some recent advances in our understanding of temporal processes in auditory perception. It begins with the premise that hearing is the online perceptual elaboration of acoustic events distributed in time. It examines studies of gap detection for two reasons: first, to probe the temporal acuity of auditory perception in its own right and, second, to show how studies of gap detection have provided new insights into the processes involved in speech perception and into the architecture of auditory spatial perceptual mechanisms. The implications of these new data for our comprehension of some central auditory processing disorders are examined.
In the past several years, a number of scales have been developed that elicit a patient's self-assessment of the severity of his or her voice problem. The Voice Related Quality of Life Measure (V-RQOL) assesses a patient's perception of the impact of the voice problem on quality of life. Although this tool assesses the patient's perception of the voice disorder, it may not reflect the severity of dysphonia as perceived by a clinician. The GRBAS is an auditory-perceptual scale developed in Japan and used by clinicians to categorize the voice using five descriptive perceptual parameters: overall grade or severity (G), roughness of the voice (R), breathiness (B), asthenia (A), and strain (S). The purpose of this research is to determine the relationship between the patient's perception of voice related quality of life using the V-RQOL and the clinician's perception of voice severity using the GRBAS scale. Fifty patients with a complaint of a voice disorder completed the V-RQOL prior to their examination. In addition, 45 patients without voice complaints (controls) also completed the V-RQOL. All patients and control subjects were assessed by one of the voice clinicians using the GRBAS. For 25 of the subjects, both clinicians provided GRBAS perceptual ratings. Each of the two groups, were subsequently divided into subgroups consisting of those age 66 years and under and those over 66 years of age. The results indicate that the two clinicians were highly reliable in rating severity in the normal and voice disordered groups using the GRBAS scale. The results also indicate that perceived voice severity and voice-related quality of life are related; however, the relationship is a moderate one, which suggests that factors other than those directly related to voice quality may contribute to responses on voice assessment scales completed by patients. The relationship was stronger for the subgroup under 66 years old compared with the subgroup 66 years and older.
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