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Background: Evidence from motor and visual studies suggests that the ability to generalize learning gains to untrained conditions decreases as the training progresses. This decrease in generalization was suggested to reflect a shift from higher to lower levels of neuronal representations of the task following prolonged training. In the auditory modality, however, the few studies that tested the influence of prolonging training on generalization ability showed no decrease and sometimes even an increase in generalization., Objective: To test the impact of extending training in a basic psychoacoustic task on the ability to generalize the gains attained in training to untrained conditions., Design: Eighty-two young adults participated in two experiments that differed in the specific training regimen. In both experiments, training was conducted using a difference limen for frequency (DLF) task with an adaptive forced-choice procedure, for either a single- or nine-session training. Following training, generalization to the untrained ear and to an untrained frequency was assessed., Results: (a) Training induced significant learning (i.e., smaller DLF thresholds) following a single session of training, and more so following nine training sessions; (b) results from the combined data from both experiments showed that the ability to generalize the learning gains to the untrained ear and frequency was limited after the extended DLF training; (c) larger improvements under the trained condition resulted in smaller generalization to the untrained conditions., Conclusions: The findings of increased specificity with training in the auditory modality support the notion that gradual changes, both quantitative and qualitative, occur in the neural representations of an auditory task during its acquisition. These findings suggest common underlying mechanisms in basic skill learning across different modalities.

Background: The ability to discriminate between talkers assists listeners in understanding speech in a multitalker environment. This ability has been shown to be influenced by sensory processing of vocal acoustic cues, such as fundamental frequency (F0) and formant frequencies that reflect the listener's vocal tract length (VTL), and by cognitive processes, such as attention and memory. It is, therefore, suggested that children who exhibit immature sensory and/or cognitive processing will demonstrate poor voice discrimination (VD) compared with young adults. Moreover, greater difficulties in VD may be associated with spectral degradation as in children with cochlear implants., Objectives: The aim of this study was as follows: (1) to assess the use of F0 cues, VTL cues, and the combination of both cues for VD in normal-hearing (NH) school-age children and to compare their performance with that of NH adults; (2) to assess the influence of spectral degradation by means of vocoded speech on the use of F0 and VTL cues for VD in NH children; and (3) to assess the contribution of attention, working memory, and nonverbal reasoning to performance., Design: Forty-one children, 8 to 11 years of age, were tested with nonvocoded stimuli. Twenty-one of them were also tested with eight-channel, noise-vocoded stimuli. Twenty-one young adults (18 to 35 years) were tested for comparison. A three-interval, three-alternative forced-choice paradigm with an adaptive tracking procedure was used to estimate the difference limens (DLs) for VD when F0, VTL, and F0 + VTL were manipulated separately. Auditory memory, visual attention, and nonverbal reasoning were assessed for all participants., Results: (a) Children' F0 and VTL discrimination abilities were comparable to those of adults, suggesting that most school-age children utilize both cues effectively for VD. (b) Children's VD was associated with trail making test scores that assessed visual attention abilities and speed of processing, possibly reflecting their need to recruit cognitive resources for the task. (c) Best DLs were achieved for the combined (F0 + VTL) manipulation for both children and adults, suggesting that children at this age are already capable of integrating spectral and temporal cues. (d) Both children and adults found the VTL manipulations more beneficial for VD compared with the F0 manipulations, suggesting that formant frequencies are more reliable for identifying a specific speaker than F0. (e) Poorer DLs were achieved with the vocoded stimuli, though the children maintained similar thresholds and pattern of performance among manipulations as the adults., Conclusions: The present study is the first to assess the contribution of F0, VTL, and the combined F0 + VTL to the discrimination of speakers in school-age children. The findings support the notion that many NH school-age children have effective spectral and temporal coding mechanisms that allow sufficient VD, even in the presence of spectrally degraded information. These results may challenge the notion that immature sensory processing underlies poor listening abilities in children, further implying that other processing mechanisms contribute to their difficulties to understand speech in a multitalker environment. These outcomes may also provide insight into VD processes of children under listening conditions that are similar to cochlear implant users.

Objectives: To assess discrimination of lexical stress pattern in infants with cochlear implant (CI) compared with infants with normal hearing (NH). While criteria for cochlear implantation have expanded to infants as young as 6 months, little is known regarding infants' processing of suprasegmental-prosodic cues which are known to be important for the first stages of language acquisition. Lexical stress is an example of such a cue, which, in hearing infants, has been shown to assist in segmenting words from fluent speech and in distinguishing between words that differ only the stress pattern. To date, however, there are no data on the ability of infants with CIs to perceive lexical stress. Such information will provide insight to the speech characteristics that are available to these infants in their first steps of language acquisition. This is of particular interest given the known limitations that the CI device has in transmitting speech information that is mediated by changes in fundamental frequency., Design: Two groups of infants participated in this study. The first group included 20 profoundly hearing-impaired infants with CI, 12 to 33 months old, implanted under the age of 2.5 years (median age of implantation = 14.5 months), with 1 to 6 months of CI use (mean = 2.7 months) and no known additional problems. The second group of infants included 48 NH infants, 11 to 14 months old with normal development and no known risk factors for developmental delays. Infants were tested on their ability to discriminate between nonsense words that differed on their stress pattern only (/dóti/ versus /dotí/ and /dotí/ versus /dóti/) using the visual habituation procedure. The measure for discrimination was the change in looking time between the last habituation trial (e.g., /dóti/) and the novel trial (e.g., /dotí/)., Results: (1) Infants with CI showed discrimination between lexical stress pattern with only limited auditory experience with their implant device, (2) discrimination of stress patterns in infants with CI was reduced compared with that of infants with NH, (3) both groups showed directional asymmetry in discrimination, that is, increased discrimination from the uncommon to the common stress pattern in Hebrew (/dóti/ versus /dotí/) compared with the reversed condition., Conclusions: The CI device transmitted sufficient acoustic information (amplitude, duration, and fundamental frequency) to allow discrimination between stress patterns in young hearing-impaired infants with CI. The present pattern of results is in support of a discrimination model in which both auditory capabilities and "top-down" interactions are involved. That is, the CI infants detected changes between stressed and unstressed syllables after which they developed a bias for the more common weak-strong stress pattern in Hebrew. The latter suggests that infants with CI were able to extract the statistical distribution of stress patterns by listening to the ambient language even after limited auditory experience with the CI device. To conclude, in relation to processing of lexical stress patterns, infants with CI followed similar developmental milestones as hearing infants thus establishing important prerequisites for early language acquisition.

Objectives: This study investigated the use of the Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) as a measure of early auditory skill development in aided infants and toddlers with varying degrees of hearing loss. Specific goals were (1) to rate the change in IT-MAIS score as a function of change in hearing thresholds achieved through amplification; (2) to establish the hierarchy of early auditory skill development for infants who use hearing aids (HAs) relative to what is known in infants with normal hearing; and (3) to analyze background information variables that may account for differences in IT-MAIS performance, as age and duration of HAs use., Design: The study included 106 infants and toddlers (47 girls and 59 boys) aged 7 to 36 months (mean = 19.02, SD = 7.7) with various degrees of sensorineural hearing loss (mean = 86.42 dB, SD = 22.52). Infants used bilateral digital HAs with a mean experience of 8 months. All participants attended the same early intervention program. After at least 2 months of HA use, parents were interviewed with the IT-MAIS questionnaire regarding the auditory behavior of their infants in everyday situations., Results: The results of the present study support the following outcomes: (1) on average, every 10 dB gain in pure-tone average scores (PTA4) threshold improved the IT-MAIS score by 10%; (2) infants who were part of the same unaided hearing categories appeared to have derived different benefits from amplification; (3) when reaching the same aided category, those infants who were originally in a better unaided hearing category achieved higher IT-MAIS scores than those who belonged to a worse unaided hearing category; (4) the hierarchy of auditory development in young aided infants with hearing loss followed that of normal hearing peers; and (5) 62.9% of the variance of IT-MAIS performance was explained by aided hearing level (50.3%), unaided hearing level (6.4%), and duration of HA use (6.2)%., Conclusions: The present study provides important information to assist clinicians and parents in setting realistic expectations regarding the auditory behavior of infants as a function of aided and unaided thresholds. It emphasizes the need for assessing functional hearing in young infants and not relying on hearing thresholds alone. Such data can also contribute to the decision-making process when selecting a sensory device (e.g., HA versus cochlear implant) for infants with hearing loss.

Objectives: The main purpose of the present study was to determine listening preference for child-directed speech (CDS) over static (white noise, WN) and dynamic (time-reversed speech, TRS) nonspeech stimuli in both normal-hearing (NH) infants and hearing-impaired infants with cochlear implants (CIs). A second purpose was to investigate the effect of auditory experience on listening preference for speech in both groups., Method: A total of 64 infants, 43 NH (age 6 to 20 mos) and 21 CI users (age 14 to 33 mos), were tested. Twenty-two NH infants and 12 infants with CIs were tested on their listening preference for CDS compared with WN. In addition, 21 NH infants and 9 infants with CIs were tested on their listening preference for CDS compared with TRS using the central fixation preference procedure., Results: NH infants and infants with CIs preferred listening to speech compared with WN and TRS. This preference was shown in infants with limited listening experience and increased significantly with auditory exposure for both NH infants and infants with CIs. The extent of preference for speech versus nonspeech among infants with CIs was significantly correlated with gross auditory and preverbal production skills (as measured by ITMAIS and PRISE tests, respectively) as well as with duration of auditory experience., Conclusions: The CI device provides sufficient information for the infants with CIs to follow early language processes similarly to NH infants.

Objectives: To investigate the effect of increasing acoustic-phonetic difficulty in children with cochlear implants (CI) by means of auditory event-related potentials (AERPs)., Design: AERPs were recorded from a group of ten 9- to 14-year-old prelingually deafened children who exhibited open-set speech recognition, using the Nucleus 22 CI for at least 5 years. AERPs were recorded in sound field while children were performing oddball discrimination tasks with increasing acoustic-phonetic demand. The tasks consisted pairs of naturally produced stimuli that differed by one phonetic feature: vowel place (/ki/ versus/ku/), vowel height (/ki/ versus /ke/), voicing (/ka/ versus /ga/), and place of articulation (/ka/ versus /ta/). Using a repeated measure design, the effect of increasing acoustic-phonetic difficulty on P3 latency, amplitude, and scalp distribution as well as on the simultaneously obtained behavioral measures, performance accuracy, and reaction time was evaluated., Results: AERPs elicited in the range of 350 msec poststimulus onset were contaminated by the CI stimulus artifact, thus enabling reliable identification of the P3 component only. Increasing acoustic-phonetic difficulty was manifested in all measures in a hierarchical manner: P3 latency and reaction time increased, whereas P3 amplitude and performance accuracy decreased. The correlations, however, between behavioral and electrophysiological measures were not significant. Further support for P3 sensitivity to increasing acoustic-phonetic demand was its absence in four of the 10 children, but only in the most difficult place of articulation task. P3 amplitude was maximal at the midline parietal cite, with equal amplitudes over the right and left scalp regardless of side of implant., Conclusions: The results underscore the significant value of the P3 potential as a sensitive neural index of speech-sound processing in children with CI. The similar hierarchy of acoustic-phonetic demand manifested in both behavioral and electrophysiological measures suggests that speech perception performance relates to neurophysiologic responses at cortical levels of the auditory system. Thus, recording the P3 potential to distinct phonetic contrasts may be useful for studying accessibility and neural encoding at the cortical level in CI recipients.

Objectives: To compare the vocalizations of hearing-impaired infants before and after cochlear implantation with those of a control group of hearing infants and to relate prelexical vocalizations by using the PRoduction Infant Scale Evaluation (PRISE) to early auditory skill attainments, using the Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) in normal-hearing and hearing-impaired (HI) infants before and after cochlear implantation., Design: A total of 187 infants participated in the study: 24 HI infants with severe-profound hearing loss (8 to 23 months of age) and 163 hearing infants (0.5 to 20 months of age). Prelexical vocalizations and early auditory skills were assessed by using parent questionnaires (PRISE and IT-MAIS, respectively) that reflect known milestones in the infant's vocal and auditory development. HI infant data were compared with hearing infant data according to chronological age and duration of device use (hearing aid or cochlear implant)., Results: Average PRISE score of aided HI infants before implantation was 50% or less (regardless of age). This score is comparable to that of hearing infants who are 6 to 7 months of age. After implantation, HI infants reached a score of 70% but did not reach normative performance. When HI infant data were compared with hearing infants by duration of device use, aided infants before implantation performed as well or worse than normative performance, whereas implanted infants performed as well as or better than hearing infants. Performance on individual PRISE questions showed limited ability by HI infants before implantation compared with hearing and implanted infants. A strong correlation was found between the IT-MAIS and the PRISE (r = 0.93 and r = 0.83, for hearing and HI infants, respectively)., Conclusions: The PRISE was found to be a versatile tool for implant team clinicians who are required to assess prelinguistic skills of infants. The findings suggest that early auditory skills are related to prelexical vocalization. The data also highlighted unanswered questions related to the importance of early fitting of hearing aids on vocalization before and after implantation.

The perception of initial consonant voicing, final consonant voicing, pitch change, and word stress, was measured in six normal subjects, by speechreading alone, by tactile transmission of fundamental voice frequency alone, and by the two in combination. Two tactile displays were used: a single-channel (temporal) display and a 16-channel (spatial) display. By speechreading alone, all contrasts except initial consonant voicing were partially perceptible. By both tactile aids alone, all four contrasts were partially perceptable. The addition of tactile input to speechreading provided better performance than that obtained by speechreading alone. The multichannel display was found to be significantly more effective than the single-channel for perception of pitch rise/fall only.

Recognition of words in conversational sentences of known topic was measured in nine normally hearing subjects by speechreading alone and by speechreading supplemented with auditory presentation of the output of an electroglottograph. Mean word recognition probability rose from 30% to 77% with the addition of the acoustic signal. When this signal was filtered to remove possible high-frequency spectral cues, the supplemented score fell, but only by a marginally significant 7 percentage points, supporting the conclusion that voice fundamental frequency was the principal source of enhancement. Enhancement occurred for all subjects, regardless of speechreading competence.