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Speech, vocabulary, and the education of children using cochlear implants: oral or total communication?

This study examines the relationship between the teaching method, oral or total communication, used at children's schools and children's consonant-production accuracy and vocabulary development over time. Children who participated in the study (N = 147) demonstrated profound sensorineural hearing loss and had used cochlear implants for between 6 months and 10 years. Educational programs that used an oral communication (OC) approach focused on the development of spoken language, whereas educational programs that used a total communication (TC) approach focused on the development of language using both signed and spoken language. Using Hierarchical Linear Modeling (HLM) we compared the consonant-production accuracy, receptive spoken vocabulary, and expressive spoken and/or signed vocabulary skills, over time, of children who were enrolled in schools that used either OC or TC approaches, while controlling for a number of variables. These variables included age at implantation, preoperative aided speech detection thresholds, type of cochlear implant device used, and whether a complete or incomplete active electrode array was implanted. The results of this study indicated that as they used their implants the children demonstrated improved consonant-production accuracy and expressive and receptive vocabulary over time, regardless of whether their school employed a TC or OC teaching method. Furthermore, there appeared to be a complex relationship among children's performance with the cochlear implant, age at implantation, and communication/teaching strategy employed by the school. Controlling for all variables, children in OC programs demonstrated, on average, superior consonant-production accuracy, with significantly greater rates of improvement in consonant-production accuracy scores over time compared to children in TC programs. However, there was no significant difference between OC and TC groups in performance or rate of growth in consonant-production accuracy when children received their implants before the age of 5 years. There was no significant difference between the OC and TC groups in receptive spoken vocabulary scores or in rate of improvement over time. However, children in the TC group achieved significantly higher receptive spoken vocabulary scores than children in the OC group if they received their implant before the age of 5 years. The TC group demonstrated superior scores and rates of growth on the expressive vocabulary measure (spoken and/or signed) when compared to the OC group if they received their implants during their preschool or early elementary school years. There was no significant difference if the children received their implants during middle elementary school. Regardless of whether children were in the OC or TC group, children who received their implants during preschool demonstrated stronger performance, on average, on all measures over time than children who received their implants during their elementary school years. The results of this study suggest that children may benefit from using cochlear implants regardless of the communication strategy/teaching approach employed by their school program and that other considerations, such as the age at which children receive implants, are more important. Implications and future research needs are discussed.

Child Language↗

Speech perception and talker segregation: effects of level, pitch, and tactile support with multiple simultaneous talkers.

Speech intelligibility was investigated by varying the number of interfering talkers, level, and mean pitch differences between target and interfering speech, and the presence of tactile support. In a first experiment the speech-reception threshold (SRT) for sentences was measured for a male talker against a background of one to eight interfering male talkers or speech noise. Speech was presented diotically and vibro-tactile support was given by presenting the low-pass-filtered signal (0-200 Hz) to the index finger. The benefit in the SRT resulting from tactile support ranged from 0 to 2.4 dB and was largest for one or two interfering talkers. A second experiment focused on masking effects of one interfering talker. The interference was the target talker's own voice with an increased mean pitch by 2, 4, 8, or 12 semitones. Level differences between target and interfering speech ranged from -16 to +4 dB. Results from measurements of correctly perceived words in sentences show an intelligibility increase of up to 27% due to tactile support. Performance gradually improves with increasing pitch difference. Louder target speech generally helps perception, but results for level differences are considerably dependent on pitch differences. Differences in performance between noise and speech maskers and between speech maskers with various mean pitches are explained by the effect of informational masking.

Acoustic Stimulation↗

Audiovestibular findings in patients with deafness caused by a mitochondrial susceptibility mutation and precipitated by an inherited nuclear mutation or aminoglycosides.

OBJECTIVE: To characterize the audiological and vestibular changes associated with a mitochondrial DNA mutation in an Arab-Israeli family and in other families with mitochondrial predisposition to aminoglycoside-induced hearing loss. DESIGN: Evaluation of audiological (pure tone thresholds, speech reception thresholds, speech discrimination, tympanometry, acoustic reflex thresholds, tone decay, and auditory brain-stem evoked response recording) and vestibular (complete history, physical examination, and 2-channel electronystagmography) systems. In 5 patients, structural evaluation of the inner ear was done by magnetic resonance imaging. PATIENTS: Fifteen members of an Arab-Israeli family, and 1 Chinese woman with the same mitochondrial DNA mutation who experienced hearing loss after short-term exposure to streptomycin. RESULTS: Most of the patients had a profound hearing loss due to cochlear involvement. The hearing loss usually was not accompanied by notable peripheral vestibular dysfunction. In the patient with severe hearing loss after exposure to aminoglycoside, the vestibular function was completely normal. CONCLUSIONS: In most of the Arab-Israeli patients with congenital deafness, the vestibular system function was normal, in contrast to the frequency of vestibular abnormality among deaf children, which was described in the literature. This may be related to genetic predisposition to aminoglycoside-induced deafness.

Adult↗

Frequency discrimination and literacy skills in children with mild to moderate sensorineural hearing loss.

It has been suggested that specific reading disability (SRD) may be attributable to an impaired ability to perceive spectral differences between sounds that leads to a deficit in frequency discrimination and subsequent problems with language and literacy. The objective of the present study was three-fold. We aimed to (a) determine whether children with mild to moderate sensorineural hearing loss were impaired in their ability to discriminate frequency, (b) assess the extent to which any such deficits may be due to an inability to use information derived from phase locking, and (c) examine whether frequency discrimination abilities were predictive of measures of word and nonword reading and nonword repetition. Difference limens for frequency (DLFs) were obtained for 22 children with mild to moderate hearing loss (SNH group) and 22 age-matched controls (CA group) at central frequencies of 1 kHz, where phase-locking information is available, and 6 kHz, where it is not. A battery of standardized tests of language and literacy was also administered. The SNH group exhibited significantly elevated DLFs at both 1 and 6 kHz relative to controls, despite considerable variability of thresholds in both groups. Although no group differences were found for receptive and expressive vocabulary, receptive grammar, and nonword reading, the SNH group performed worse than controls on word reading and nonword repetition, even though word reading scores were age-appropriate. Frequency discrimination abilities were associated with reading and nonword repetition across groups, but these correlations largely disappeared when the two groups were analyzed separately. Together, these results provide evidence for a dissociation between impaired frequency discrimination and relatively "spared" language and literacy in children with mild to moderate sensorineural hearing loss. These results cast doubt on the assertion that a deficit in frequency discrimination necessarily leads to marked deficits in the development of language and literacy.

Adolescent↗

Robust adaptive microphone array processing for hearing aids: realistic speech enhancement.

The problem of combining the outputs of an array of microphones as a single input for a hearing aid is investigated. Emphasis is placed on the conservative prediction of realistically achievable performance gains provided by the array over a single microphone. Performance improvement is measured as a change in the speech reception threshold (SRT) between single microphone and multimicrophone conditions. Consistent with previous work, predictions of this change in SRT using intelligibility averaged gain, [symbol: see text] are shown to be good. Consequently, this measure is used, along with changes in signal-to-noise ratios (SNRs), to evaluate array performance. The results presented include the effects of acoustic headshadow, small room reverberation, microphone placement uncertainty, and desired speaker location uncertainty. It is in this context that realistic predictions of speech enhancement provided by robust adaptive microphone array processors are discussed. Performance improvements are demonstrated relative to the "best" single microphone in the array for three types of spatial filters: Fixed, robust block processed, and robust adaptive. The performance of the robust block processed arrays is shown to be attainable with adaptive implementations. One fundamental criterion employed in robust beamformer design directly limits the amount of cancellation of the desired signal that can occur.

Adult↗

Early otitis media and phonological development at age 2 years.

The effect of early otitis media on phonology and articulation in the presence of expressive language delay was investigated in 16 2-year-olds followed prospectively from birth. Eight of the children were designated otitis-positive and 8 were considered otitis-negative as determined by bilateral pneumatic otoscopy outcomes during year 1 of life. The groups differed significantly on measures of expressive, not receptive, language development. All members of the otitis-positive group were expressive language delayed. Phonological analyses were completed on spoken language samples elicited from each child at age 24 months. Results showed similar developmental tendencies in speech sound acquisition between the groups, but the otitis-positive group had established significantly fewer initial consonant phones and produced them less accurately than the otitis-negative subject group. The otitis-positive group acquired significantly fewer consonants with back place of articulation. Similar phonological error patterns of deletion and phoneme class deficiency were used by the groups, but the otitis-positive group used the error patterns more frequently. Findings here lend support to the otitis media effect as one of interaction among risk factors.

Articulation Disorders↗

The spatial unmasking of speech: evidence for better-ear listening.

Speech reception thresholds (SRTs) were measured for target speech presented concurrently with interfering speech (spoken by a different speaker). In experiment 1, the target and interferer were divided spectrally into high- and low-frequency bands and presented over headphones in three conditions: monaural, dichotic (target and interferer to different ears), and swapped (the low-frequency target band and the high-frequency interferer band were presented to one ear, while the high-frequency target band and the low-frequency interferer band were presented to the other ear). SRTs were highest in the monaural condition and lowest in the dichotic condition; SRTs in the swapped condition were intermediate. In experiment 2, two new conditions were devised such that one target band was presented in isolation to one ear while the other band was presented at the other ear with the interferer. The pattern of SRTs observed in experiment 2 suggests that performance in the swapped condition reflects the intelligibility of the target frequency bands at just one ear; the auditory system appears unable to exploit advantageous target-to-interferer ratios at different ears when segregating target speech from a competing speech interferer.

Acoustic Stimulation↗

Intelligibility of Dutch CVC syllables and sentences for listeners with normal hearing and with three types of hearing impairment.

Both meaningful (sense) and meaningless (nonsense) syllables of the consonant-vowel-consonant type (CVC syllables) and short sentences consisting of 8 or 9 syllables were presented in quiet and in noise to 20 young subjects with normal hearing and to three groups of 20 subjects each with presbycusis, with Menière's disease and with noise-induced hearing loss. All materials were uttered by a female speaker. The masking noise consisted of continuous noise shaped in accordance with the long-term average spectrum of the speaker. For each individual, the level of the noise was chosen halfway between the speech reception threshold (SRT) for sentences in quiet and 100 dBA. For all groups of subjects in quiet, the SRT for whole-sentence correct scores (sentence SRT) corresponded closely to the SRT for phoneme scores with sense CVC syllables in quiet (CVC phoneme SRT). Averaged across all groups of subjects, sentence SRT in quiet could be predicted within 4.2 dB from CVC phoneme SRT in quiet and sentence SRT in noise within 1.8 dB from CVC phoneme SRT in noise. The prediction error for sentence SRT in quiet using the pure-tone average (PTA) of 0.5, 1 and 2 kHz was 6.0 dB; for sentence SRT in noise using the PTA of 2 and 4 kHz, it was 2.1 dB. In view of the smaller measurement error, a direct measurement of sentence SRT in noise is advisable.

Adult↗

Defective auditory recognition after small hemorrhage in the inferior colliculi.

We report the case of a male patient with a traumatic small hemorrhage partially involving the bilateral inferior colliculi without evidence of a temporal lobe lesion. He was unable to comprehend spoken words although he had intact speech production, reading and writing abilities. Comprehension of environmental sounds was also affected. Among the receptive musical abilities, discrimination of intensity, tone and rhythm were preserved, while recognition of melody was impaired. Audiometry showed normal thresholds for pure tone. Waves I-IV of brainstem auditory evoked potentials were elicited normally, whereas the wave V was elicited with reduced amplitude and prolonged latencies on both sides. The main component of middle latency auditory evoked potentials, which is evoked over both hemispheres by monaural stimulation to either side in normal subjects, was elicited only over the hemisphere contralateral to the ear receiving stimulation. Our patient's auditory findings were similar to those usually found in generalized auditory agnosia. Auditory agnosia is usually considered as a sign of a bitemporal cortical or subcortical disorder, but, in our patient, a brainstem disorder caused a disturbance of auditory recognition similar to auditory agnosia due to a bitemporal lesion. Our patient's auditory findings may belong to the category of a brainstem auditory-processing disorder brought on by a small hemorrhage in the inferior colliculi. In addition, the impairment in our patient implies that, in the neural processing of musical parameters, the decoding of intensity, tone and rhythm is accomplished at the level of inferior colliculus, whereas further cortical processing is necessary for the appropriate recognition of melody.

Auditory Perception↗

Contributions of comodulation masking release and temporal resolution to the speech-reception threshold masked by an interfering voice.

Two experiments are presented to explain the difference in speech-reception threshold (SRT) between conditions with a steady-state noise masker or an interfering voice. Literature shows for normal hearing a masking release of 6-8 dB with an interfering voice and a substantial reduction of this release with hearing impairment. In experiment I the possible role of comodulation masking release (CMR) is investigated by manipulating the comodulation in the interfering voice by the introduction of temporal shift among filter bands of various width. The spectral spread of masking from the manipulated interfering voice was controlled by interleaving the mutually shifted speech bands with 1/3-octave bands of noise. Although comodulation in the interfering speech appears to be very important for the low SRT, the contribution of across-frequency processing of masker fluctuations--commonly considered as the origin of CMR--is only 1.3 dB. In experiment II the level dependence of masking release with an interfering voice is investigated. The data fit in with the hypothesis by Festen and Plomp [J. Acoust. Soc. Am. 88, 1725-1736 (1990)] that the release from masking with an interfering voice is limited by forward masking. It appears that up to about 55 dBA the release from masking increases with level up to about 7 dB. Above 55 dBA the difference in SRT obtained with a noise masker or an interfering voice is constant due to the limited average modulation depth of speech.

Acoustic Stimulation↗

Effect of reducing slow temporal modulations on speech reception.

The effect of reducing low-frequency modulations in the temporal envelope on the speech-reception threshold (SRT) for sentences in noise and on phoneme identification was investigated. For this purpose, speech was split up into a series of frequency bands (1/4, 1/2, or 1 oct wide) and the amplitude envelope for each band was high-pass filtered at cutoff frequencies of 1, 2, 4, 8, 16, 32, 64, or 128 Hz, or infinity (completely flattened). Results for 42 normal-hearing listeners show: (1) A clear reduction in sentence intelligibility with narrow-band processing for cutoff frequencies above 64 Hz; and (2) no reduction of sentence intelligibility when only amplitude variations below 4 Hz are reduced. Based on the modulation transfer function of some conditions, it is concluded that fast multichannel dynamic compression leads to an insignificant change in masked SRT. Combining these results with previous data on low-pass envelope filtering (temporal smearing) [Drullman et al., J. Acoust. Soc. Am. 95, 1053-1064 (1994)] shows that at 8-10 Hz the temporal modulation spectrum is divided into two equally important parts. Vowel and consonant identification with nonsense syllables were studied for cutoff frequencies of 2, 8, 32, 128 Hz, and infinity, processed in 1/4-oct bands. Results for 12 subjects indicate that, just as for low-pass envelope filtering, consonants are more affected than vowels. Errors in vowel identification mainly consist of reduced recognition of diphthongs and of durational confusions. For the consonants there are no clear confusion patterns, but stops appear to suffer least. In most cases, the responses tend to fall into the correct category (stop, fricative, or vowel-like).

Acoustic Stimulation↗