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A Boothroyd

Publications and source records attributed to A Boothroyd.

At least 19 recordsLinked to original sources
PubMed2001

Evaluation of the Computer-assisted Speech Perception Assessment Test (CASPA).

Interlist equivalency and short-term practice effects were evaluated for the recorded stimuli of the Computer-Assisted Speech Perception Assessment (CASPA) Test. Twenty lists, each consisting of 10 consonant-vowel-consonant words, were administered to 20 adults with normal hearing. The lists were presented at 50 dB SPL (Leq) in the presence of spectrally matched steady-state noise (55 dB SPL Leq). Phoneme recognition scores for the first list presented were significantly lower than for the second through the twentieth list presented, indicating a small practice effect. Phoneme scores for 4 of the lists (3, 6, 7, and 16) were significantly higher than scores for the remaining 16 lists by approximately 10 percentage points. Eliminating the effects of interlist differences reduced the 95 percent confidence interval of a test score based on a single list from 18.4 to 16.1 percentage points. Although interlist differences have only a small effect on confidence limits, some clinicians may wish to eliminate them by excluding lists 3, 6, 7, and 16 from the test. The practice effect observed here can be eliminated by administering one 10-word practice list before beginning the test.

Adult↗
PubMed2000

Cerebral arteriovenous malformation presenting as visual deterioration in a child.

A rare case of visual loss as the presenting feature of a central arteriovenous malformation involving the vein of Galen is reported. A 5-year-old girl with a history of deteriorating vision for the past 6 months was examined. Ocular examination showed a left hemianopia, left optic atrophy, and dilated vessels of the right optic disc. MRI revealed a massive deep-seated central arteriovenous malformation involving the vein of Galen. The mechanism of visual loss is likely to be a combination of ischaemic optic atrophy associated with a steal phenomenon and direct compression of the right optic radiation.

Child, Preschool↗
PubMed2000

Use of a simultaneous sentence perception test to enhance sensitivity to ease of listening.

The purpose of the study was to determine if a divided-attention, sentence-recall task was more sensitive to distortion of the speech signal than a conventional focused-attention task. The divided-attention task required listeners to repeat both of two sentences delivered simultaneously to the same ear. The focused-attention task required listeners to repeat a single sentence presented to one ear in quiet or in amplitude-modulated noise (0 dB signal-to-noise ratio). Distortion was introduced by peak clipping. Eighteen listeners with normal hearing were tested under three levels of peak clipping: 0 dB, 11 dB, and 29 dB (re: waveform peak). The effects of clipping were similar, on average, for simultaneous sentences and single sentences in noise. When data were separated by sentence length, however, the effects of clipping were found to be greater for the simultaneous-sentence task, but only for the short sentences (6 words or fewer). The simultaneous-sentence test, in its present form, is not more sensitive to the effects of clipping than is a single-sentence test in noise. Modification of the simultaneous-sentence test to include only short sentences, however, may provide greater test sensitivity than more conventional tests using single sentences in noise.

Adult↗
PubMed2000

Cortical, auditory, evoked potentials in response to changes of spectrum and amplitude.

The acoustic change complex (ACC) is a scalp-recorded negative-positive voltage swing elicited by a change during an otherwise steady-state sound. The ACC was obtained from eight adults in response to changes of amplitude and/or spectral envelope at the temporal center of a three-formant synthetic vowel lasting 800 ms. In the absence of spectral change, the group mean waveforms showed a clear ACC to amplitude increments of 2 dB or more and decrements of 3 dB or more. In the presence of a change of second formant frequency (from perceived /u/ to perceived /i/), amplitude increments increased the magnitude of the ACC but amplitude decrements had little or no effect. The fact that the just detectable amplitude change is close to the psychoacoustic limits of the auditory system augurs well for the clinical application of the ACC. The failure to find a condition under which the spectrally elicited ACC is diminished by a small change of amplitude supports the conclusion that the observed ACC to a change of spectral envelope reflects some aspect of cortical frequency coding. Taken together, these findings support the potential value of the ACC as an objective index of auditory discrimination capacity.

Acoustic Stimulation↗
PubMed2000

Speech recognition with reduced spectral cues as a function of age.

Adult listeners are able to recognize speech even under conditions of severe spectral degradation. To assess the developmental time course of this robust pattern recognition, speech recognition was measured in two groups of children (5-7 and 10-12 years of age) as a function of the degree of spectral resolution. Results were compared to recognition performance of adults listening to the same materials and conditions. The spectral detail was systematically manipulated using a noise-band vocoder in which filtered noise bands were modulated by the amplitude envelope from the same spectral bands in speech. Performance scores between adults and older children did not differ statistically, whereas scores by younger children were significantly lower; they required more spectral resolution to perform at the same level as adults and older children. Part of the deficit in younger children was due to their inability to utilize fully the sensory information, and part was due to their incomplete linguistic/cognitive development. The fact that young children cannot recognize spectrally degraded speech as well as adults suggests that a long learning period is required for robust acoustic pattern recognition. These findings have implications for the application of auditory sensory devices for young children with early-onset hearing loss.

Adult↗
PubMed1999

Cortical, auditory, event-related potentials in response to periodic and aperiodic stimuli with the same spectral envelope.

OBJECTIVE: 1) To determine whether the N1-P2 acoustic change complex is elicited by a change of periodicity in the middle of an ongoing stimulus, in the absence of changes of spectral envelope or rms intensity. 2) To compare the N1-P2 acoustic change complex with the mismatch negativity elicited by the same stimuli in terms of amplitude and signal to noise ratio. DESIGN: The signals used in this study were a tonal complex and a band of noise having the same spectral envelope and rms intensity. For elicitation of the acoustic change complex, the signals were concatenated to produce two stimuli that changed in the middle (noise-tone, tone-noise). Two control stimuli were created by concatenating two copies of the noise and two copies of the tone (noise-only, tone-only). The stimuli were presented using an onset-to-onset interstimulus interval of 3 sec. For elicitation of the mismatch negativity, the tonal complex and noise band stimuli were presented using an oddball paradigm (deviant probability = 0.14) with an onset-to-onset interstimulus interval of 600 msec. The stimuli were presented via headphones at 80 dB SPL to 10 adults with normal hearing. Subjects watched a silent video during testing. RESULTS: The responses to the noise-only and tone-only stimuli showed a clear N1-P2 complex to the onset of stimulation followed by a sustained potential that continued until the offset of stimulation. The noise-tone and tone-noise stimuli elicited an additional N1-P2 acoustic change complex in response to the change in periodicity occurring in the middle. The acoustic change complex was larger for the tone-noise stimulus than for the noise-tone stimulus. A clear mismatch negativity was elicited by both the noise band and tonal complex stimuli. In contrast to the acoustic change complex, there was no significant difference in amplitude across the two stimuli. The acoustic change complex was a more sensitive index of peripheral discrimination capacity than the mismatch negativity, primarily because its average amplitude was 2.5 times as large. CONCLUSIONS: These findings indicate that both the acoustic change complex and the mismatch negativity are sensitive indexes of the neural processing of changes in periodicity, though the acoustic change complex has an advantage in terms of amplitude. The results support the possible utility of the acoustic change complex as a clinical tool in the assessment of peripheral speech perception capacity.

Adult↗
PubMed1998

Torsion of an ovarian cyst mimicking enteric duplication cyst on transabdominal ultrasound: two cases.

We describe two girls with abdominal cysts which demonstrated the "double wall" or "muscular rim" sign. On the basis of this, the diagnosis of duplication cyst was made in each case. At surgery, both were found to have ovarian cysts, and histology revealed prominent haemorrhage within the cyst wall. To our knowledge, there has been no previous report of a false-positive "double wall sign".

Adolescent↗
PubMed1998

Magnetic resonance--its current and future role in paediatric cardiac radiology.

Cardiac magnetic resonance (MR) has developed rapidly providing a method of both imaging congenital heart disease and assessing function using a variety of techniques. The aim of this review is to identify indications for MR and its relative strengths and weaknesses in comparison to other methods of cardiac imaging. A potential future role for MR is also discussed.

Blood Flow Velocity↗
PubMed1998

Age-related changes on a children's test of sensory-level speech perception capacity.

Normative data, as a function of age, were obtained on a test designed to assess sensory-level speech perception capacity, the Three-Interval Forced-Choice Test of Speech Pattern Contrast Perception, otherwise known as THRIFTSPAC (or THRIFT for short). Performance under the input modalities of hearing alone, speech-reading alone, and the two combined was measured in 44 normally developing children between the ages of 5 years 7 months and 10 years 9 months. Results revealed that within each condition there were significant influences of age on performance for children below age 7 years. These changes appeared to be related to cognitive and, possibly, to phonological development. Implications for the clinical implementation of THRIFT are discussed.

Age Factors↗
PubMed1998

Experiments with classroom FM amplification.

OBJECTIVES: 1) To quantify the benefits of FM amplification for persons with severe and profound hearing loss; 2) to compare a body-worn and a behind-the-ear FM system; 3) to measure the effects of reducing FM microphone sensitivity relative to hearing aid sensitivity. DESIGN: Recognition of phonemes in lists of consonant-vowel-consonant words was measured in 13 teenage students with severe and profound hearing loss. Presentation was by live voice at 10 feet from the listeners and 12 inches from the FM microphone/transmitter. Students listened: a) via a body-worn and a behind-the-ear system; b) with the FM microphone/transmitter on and off; c) in noise and in quiet. Systems were adjusted so that sinusoidal inputs of 65 dB SPL gave equal gains via the FM and hearing aid microphones. In a follow-up study, the gain via the FM microphone was reduced so that a sinusoidal input of 65 dB SPL into the hearing aid microphone produced the same output as a sinusoidal input of 80 dB into the FM microphone (as recommended in American Speech-Language-Hearing Association, 1994). RESULTS: 1) Addition of the FM microphone signal to that available from the hearing aid microphone was equivalent, on average, to doubling the number of independent channels of information available to the listeners. 2) FM benefit was present in both quiet and noise but was somewhat greater in noise. 3) Contrary to prediction, however, noise interfered with phoneme recognition even under the aid+FM condition. 4) Differences between the body-worn and behind-the-ear systems were small, but there was a measurable advantage for the body-worn system under the aid+FM condition. 5) Reducing FM microphone sensitivity by 15 dB virtually eliminated the FM benefit. 6) Forty-four percent of the variance in phoneme recognition (averaged across listening conditions) could be explained by better-ear, three-frequency average pure-tone threshold. 7) Vowels were recognized more easily than consonants, and initial consonants were recognized more easily than final consonants, but the FM benefit was present for all three phonemes. CONCLUSIONS: The findings confirm the value of FM amplification for persons with severe and profound hearing loss, in both quiet and noise. The negative effects of noise were not completely eliminated, however, under the aid+FM condition. This finding can be attributed to a reduction of gain in the FM channel, when speech input was used, because of compression limiting in the microphone transmitter. The superiority of the body-worn system under the aid+FM condition suggests a need for higher saturation sound pressure level in the behind-the-ear system when used with persons having severe and profound hearing loss. The findings do not support use of an "equal output" criterion for adjusting relative gains via the FM and hearing aid microphones--at least for persons with very severe and profound hearing loss operating under the conditions tested in this study.

Adolescent↗
PubMed1998

Cortical evoked response to acoustic change within a syllable.

OBJECTIVE: To investigate whether the evoked potential to a complex naturally produced speech syllable could be decomposed to reflect the contributions of the acoustic events contained in the constituent phonemes. DESIGN: Auditory cortical evoked potentials N1 and P2 were obtained in eight adults with normal hearing. Three naturally produced speech stimuli were used: 1) the syllable [sei]; 2) the sibilant [s], extracted from the syllable; 3) the vowel [ei] extracted from the syllable. The isolated sibilant and vowel preserved the same time relationships to the sampling window as they did in the complete syllable. Evoked potentials were collected at Fz, Cz, Pz, A1, and A2, referenced to the nose. RESULTS: In the group mean waveforms, clear responses were observed to both the sibilant and the isolated vowel. Although the response to the [s] was weaker than that to [ei], both had N1 and P2 components with latencies, in relation to sound onset, appropriate to cortical onset potentials. The vowel onset response was preserved in the response to the complete syllable, though with reduced amplitude. This pattern was observable in six of the eight waveforms from individual subjects. CONCLUSIONS: It seems likely that the response to [ei] within the complete syllable reflects changes of cortical activation caused by amplitude or spectral change at the transition from consonant to vowel. The change from aperiodic to periodic stimulation may also produce changes in cortical activation that contribute to the observed response. Whatever the mechanism, the important conclusion is that the auditory cortical evoked potential to complex, time-varying speech waveforms can reflect features of the underlying acoustic patterns. Such potentials may have value in the evaluation of speech perception capacity in young hearing-impaired children.

Adult↗
PubMed1997

Radiation exposure to children during cardiac catheterization.

The purpose of this study was to assess the suitability of different radiation dosimetry methods and record radiation exposures during paediatric catheterization. Three methods of dosimetry were employed: thermoluminescent dosimetry (TLD), dose-area product and calculation of entrance surface dose from calibrated exposure factors. Examinations included bi-plane fluoroscopy, and cineangiography for diagnosis and treatment of congenital heart disease. The most suitable method of radiation dosimetry for cardiac catheterization is the use of calculated entrance dose or a dose-area product meter. Children were exposed to high levels of radiation during cardiac catheterization but there was a wide variation in radiation dosage. Careful consideration should be given to the suitability of radiation dosimetry for cardiac catheterization.

Adolescent↗
PubMed1997

Auditory development of the hearing child.

Auditory perception is defined, here, as the interpretation of sensory evidence, derived from sound, in terms of the objects and events that caused the sound. Like other kinds of perception, it involves the use, not only of sensory evidence, but also of contextual evidence, prior knowledge, memory, attention, and processing skills. Auditory speech perception is special because the events to be perceived are those of language. Similarly, the listener's knowledge base and processing skills must include those related to language in general, and spoken language in particular. The auditory system is complete and functional at birth but myelination continues for several years in the higher auditory pathways. This pattern of anatomical maturation is reflected in electrophysiological responses. Similarly, infants display sophisticated discrimination and recognition ability but psychoacoustic performance does not reach adult levels for several years. Empirical data on the development of auditory processing are sparse, but much work has been done on auditory speech perception. Infants at 6 months demonstrate the beginnings of phonemic classification, and performance improves during childhood in a variety of areas. These include: phonetic contrast perception, phoneme recognition, perception of speech in noise, selective attention, and the use of linguistic context. Experience obviously plays a key role in the development of the knowledge and skills required for auditory perception in general and auditory speech perception in particular. It is tempting to assume that the sensory evidence available to the developing child is determined only by the functional integrity of the peripheral auditory system, independent of auditory experience. There is, however, increasing evidence in animals of the influence of auditory experience on the organization of the auditory pathways. Such organization could increase the sensory evidence made available from patterns of neural excitation produced in the cochlea.

Adolescent↗
PubMed1997

Auditory capacity of hearing-impaired children using hearing aids and cochlear implants: issues of efficacy and assessment.

The immediate goal of sensory assistance is to provide as much sensory evidence as possible about the sound patterns of speech. To determine how well this goal has been met calls for tests that are sensitive to sensory capacity and insensitive to linguistic and cognitive status. At the same time, the results should have predictive validity in terms of the potential for developing speech perception skills. This paper describes data obtained from paediatric hearing aid and cochlear implant users by means of an imitative test of phonetic contrast perception (IMSPAC). It is shown that the primary predictor of IMSPAC performance for aided subjects is degree of hearing loss, with little or no influence of age and communication mode. The primary predictors for Nucleus implantees, however, are communication mode and duration of use. The distribution of scores in the implant group is similar to that of hearing aid users with hearing losses in the 90 to 99 dB range. The more successful implantees (mostly, but not only, orally trained) perform like hearing aid users with hearing losses in the 70 to 89 dB range. The hearing aid data suggest that the IMSPAC test is effective in measuring auditory sensory capacity without confounding by linguistic status. If this is true, the implant data must be interpreted as evidence of the development of auditory perceptual skills during the post-implant period. This interpretation carries important implications for issues of cortical plasticity, acclimatization, the management of childhood deafness, and the evaluation of sensory aid efficacy.

Adolescent↗
PubMed1996

Speechreading enhancement: a comparison of spatial-tactile display of voice fundamental frequency (F0) with auditory F0.

In two experiments, subjects repeated video-recorded sentences presented via speechreading with and without enhancement by a sensory input derived from the acoustic speech signal. Enhancement was measured as percentage increase in recognized words. In experiment 1, tactile presentation of fundamental frequency (F0) provided, after training, for three of four postlingually deafened adults a mean enhancement of 11%. In experiment 2, using six hearing adults, the auditory presentation of F0 provided a mean enhancement of 50%. This value fell, but only to 37%, when the F0 signal was derived from the processor of the tactile aid used in experiment 1. From these experiments it can be concluded that the unexpectedly small enhancement found in experiment 1 is probably due both to the fact that this tactile aid was not providing effective access to all of the information available in the F0 contour and to limitations related to the tactile processing ability of the kinaesthetic system.

Adult↗
PubMed1996

Effects of spectral smearing on phoneme and word recognition.

The principal goal was to measure the effects, on speech perception, of loss of spectral detail in the acoustic signal. Spectral smearing was produced by multiplying the speech waveform by low-pass filtered noise. Performance was measured in normal adults as the percentage of phonemes correctly repeated in lists of monosyllabic words. A smearing bandwidth of 250 Hz (i.e., each tonal component of the instantaneous spectrum replaced by a 250-Hz band of noise) had a small but significant effect on phoneme recognition. A smearing bandwidth of 8000 Hz was required to reduce phoneme recognition to a value that was indistinguishable from that produced by complete smearing. Vowels were somewhat more susceptible to the effects of spectral smearing than were consonants, and initial consonants were more susceptible than were final consonants. In an analysis of errors, place of consonant articulation was more susceptible than either manner of articulation or voicing. These findings are attributable to differences in the relative importance of spectral and temporal cues. Word recognition was more susceptible to the effects of spectral smearing than was phoneme recognition, but this finding was predictable on the basis of the known nonlinear relationship between the two measures. In a second experiment, smearing bandwidths of 707 and 2000 Hz increased phoneme recognition threshold by 12.9 and 16.4 dB, respectively, compared to that found without smearing. (Phoneme recognition threshold is defined, here, as the signal-to-noise ratio at which phoneme recognition is 50% of the value obtained in quiet.) The data are consistent with the hypothesis that reduced spectral resolution affects phoneme recognition to the extent that it reduces access to the formant patterns in the spectral envelope.

Adult↗