Horizontal-plane localization of noise and speech signals by postlingually deafened adults fitted with bilateral cochlear implants

OBJECTIVES: The main purpose of the study was to assess the ability of adults with bilateral cochlear implants to localize noise and speech signals in the horizontal plane. A second objective was to measure the change in localization performance in these adults between approximately 5 and 15 mo after activation. A third objective was to evaluate the relative roles of interaural level difference (ILD) and interaural temporal difference (ITD) cues in localization by these subjects. DESIGN: Twenty-two adults, all postlingually deafened and all bilaterally fitted with MED-EL COMBI 40+ cochlear implants, were tested in a modified source identification task. Subjects were tested individually in an anechoic chamber, which contained an array of 43 numbered loudspeakers extending from -90 degrees to +90 degrees azimuth. On each trial, a 200-msec signal (either a noise burst or a speech sample) was presented from one of 17 active loudspeakers (span: +/-80 degrees ), and the subject had to identify which source from the 43 loudspeakers in the array produced the signal. Subjects were tested in three conditions: left device only active, right device only active, and both devices active. Twelve of the 22 subjects were retested approximately 10 mo after their first test. In Experiment 2, the spectral content and rise-decay time of the noise stimulus were manipulated. RESULTS: The relationship between source azimuth and response azimuth was characterized in terms of the adjusted constant error (?). (1) With both devices active, ? for the noise stimulus varied from 8.1 degrees to 43.4 degrees (mean: 24.1 degrees ). By comparison, ? for a group of listeners with normal hearing ranged from 3.5 degrees to 7.8 degrees (mean: 5.6 degrees ). When subjects listened in unilateral mode (with one device turned off), ? was at or near chance (50.5 degrees ) in all cases. However, when considering unilateral performance on each subject's better side, average ? for the speech stimulus was 47.9 degrees , which was significantly (but only slightly) better than chance. (2) When listening bilaterally, error score was significantly lower for the speech stimulus (mean ? = 21.5 degrees ) than for the noise stimulus (mean ? = 24.1 degrees ). (3) As a group, the 12 subjects who were retested 10 mo after their first visit showed no significant improvement in localization performance during the intervening time. However, two subjects who performed very poorly during their first visit showed dramatic improvement (error scores were halved) over the intervening time. In Experiment 2, removing the high-frequency content of noise signals resulted in significantly poorer performance, but removing the low-frequency content or increasing the rise-decay time did not have an effect. CONCLUSIONS: In agreement with previously reported data, subjects with bilateral cochlear implants localized sounds in the horizontal plane remarkably well when using both of their devices, but they generally could not localize sounds when either device was deactivated. They could localize the speech signal with slightly, but significantly better accuracy than the noise, possibly due to spectral differences in the signals, to the availability of envelope ITD cues with the speech but not the noise signal, or to more central factors related to the social salience of speech signals. For most subjects the remarkable ability to localize sounds has stabilized by 5 mo after activation. However, for some subjects who perform poorly initially, there can be substantial improvement past 5 mo. Results from Experiment 2 suggest that ILD cues underlie localization ability for noise signals, and that ITD cues do not contribute.     

Self-reported benefits from successive bilateral cochlear implantation in post-lingually deafened adults: randomised controlled trial

Adult users of unilateral Nucleus CI24 cochlear implants with the SPEAK processing strategy were randomised either to receive a second identical implant in the contralateral ear immediately, or to wait 12 months while they acted as controls for late-emerging benefits of the first implant. Twenty four subjects, twelve from each group, completed the study. Receipt of a second implant led to improvements in self-reported abilities in spatial hearing, quality of hearing, and hearing for speech, but to generally non-significant changes in measures of quality of life. Multivariate analyses showed that positive changes in quality of life were associated with improvements in hearing, but were offset by negative changes associated with worsening tinnitus. Even in a best-case scenario, in which no worsening of tinnitus was assumed to occur, the gain in quality of life was too small to achieve an acceptable cost-effectiveness ratio. The most promising strategies for improving the cost-effectiveness of bilateral implantation are to increase effectiveness through enhanced signal processing in binaural processors, and to reduce the cost of implant hardware.     

Preservation of residual hearing in children and post-lingually deafened adults after cochlear implantation: an initial study

OBJECTIVE: To investigate whether the residual hearing of severely hearing-impaired children and adults could be preserved using the soft surgery approach. PATIENTS AND METHODS: This project employed a prospective study design. All testing and surgery took place in the Institute of Physiology and Pathology of Hearing, Warsaw, Poland. Twenty-six patients (7 children and 19 post-lingually deafened adults) with residual hearing were assessed. Subjects were assessed using conventional pure-tone audiometry at least 1 month prior to surgery. Cochlear implant surgery with a Med-El Combi 40/40+ standard electrode array was conducted, using the soft surgery approach. Pure-tone audiometry thresholds were re-assessed at least 1 month after surgery. The researchers assessed change in auditory thresholds using pure-tone audiometry to determine preservation of residual hearing. RESULTS: Sixteen of 26 patients (62%) retained their residual hearing within 5 dB HL of pre-operative scores. Only 5 of 26 patients (19%) lost all measurable residual hearing after cochlear implantation. This suggests that surgeons are often able to preserve residual hearing during cochlear implant surgery using the soft surgery technique. CONCLUSIONS: Preservation of residual hearing is an important consideration in cochlear implantation in the light of changing selection criteria for cochlear implant candidates, and as younger children are receiving implants. This is important, as we do not know yet the long-term effects of inner ear damage due to traumatic insertions of electrodes. This finding suggests a good prognosis for future possibilities of re-implantation.     

Objective methods in postlingually and prelingually deafened adults for programming cochlear implants: ESR and NRT

This study compared responses of prelingually and postlingually deafened adult Nucleus 24 cochlear implant users on two objective measures employed to predict programming levels: neural response telemetry (NRT) and electrically evoked stapedial reflexes (eSR). Thirty experienced postlingually and prelingually deafened adult implant users underwent standard behavioural judgements of maximum comfortable loudness levels (C levels) and thresholds (Ts) followed by eSR and NRT measurements. Two different programs were created based on both the subjective judgement and the objective estimates of C levels (eSR thresholds) and these were compared. Relationships between the subjective and the objective measures were statistically analysed. Maximum stimulation levels estimated by both eSR and NRT were highly correlated with C levels. Variability of NRT results was higher than for eSR results. Mean NRT thresholds for postlingually deafened patients were higher than for prelingually deafened patients. A number of prelingually deafened users could distinguish no difference between programs; however, the majority of postlingually deafened users were sensitive to the difference and many reported preference for the program with eSR-estimated C levels. Neural response telemetry thresholds and eSRTs obtained in Nucleus 24 patients are highly correlated with C levels and Ts. Results suggest that estimation of C levels and Ts using NRT or eSR requires different correction factors for prelingually versus postlingually deafened adult subjects.     

The relationship of inter-implant time and hearing outcomes for bilateral cochlear implants

PurposeDetermine the relationship between time elapsed between sequential bilateral cochlear implantation (BiCI) and speech intelligibility scores in post-lingually deafened adults.Materials and methodsRetrospective review of post-lingually deafened adults who received bilateral cochlear implants from January 1, 2011 to January 1, 2018 at an ambulatory tertiary referral center.Results113 patients (226 cochlear implants) were initially reviewed, with 56 patients (112 implants) being included in the final analysis. Median inter-implant interval was 187.5 days (IQ range 54.25–346.5). Maximum interval was 1787 days. Mean age at first implant was 60.66 ± 13.37. Bilateral AzBio score in quiet and inter-implant interval showed no significant correlation (r = 0.034, p = 0.815). There was no significant difference in mean bilateral AzBio scores in quiet between the simultaneous and sequential implantation groups (p = 0.22). Similar non-significant results were seen when examining the correlation between AzBio Difference and inter-implant interval (r = −0.07, p = 0.66). No significant result between mean AzBio Difference of simultaneous and sequential implant recipients was found (p = 0.06).ConclusionsFor the inter-implant intervals examined, there seems to be no significant decline in speech intelligibility scores for patients receiving sequential bilateral cochlear implants compared to simultaneously implanted patients. There was no significant correlation noted between increasing inter-implant intervals and speech intelligibility scores.     

Psychoacoustic performance and music and speech perception in prelingually deafened children with cochlear implants

The number of pediatric cochlear implant (CI) recipients has increased substantially over the past 10 years, and it has become more important to understand the underlying mechanisms of the variable outcomes in this population. In this study, psychoacoustic measures of spectral-ripple and Schroeder-phase discrimination, the Clinical Assessment of Music Perception, and consonant-nucleus-consonant (CNC) word recognition in quiet and spondee reception threshold (SRT) in noise tests have been presented to 11 prelingually deafened CI users, aged 8-16 years with at least 5 years of CI experience. The children's performance was compared to the previously reported results of postlingually deafened adult CI users. The average spectral-ripple threshold (n = 10) was 2.08 ripples/octave. The average Schroeder-phase discrimination was 67.3% for 50 Hz and 56.5% for 200 Hz (n = 9). The Clinical Assessment of Music Perception test showed that the average complex pitch direction discrimination was 2.98 semitones. The mean melody score was at a chance level, and the mean timbre score was 34.1% correct. The mean CNC word recognition score was 68.6%, and the mean SRT in steady noise was -8.5 dB SNR. The children's spectral-ripple resolution, CNC word recognition, and SRT in noise performances were, within statistical bounds, the same as in a population of postlingually deafened adult CI users. However, Schroeder-phase discrimination and music perception were generally poorer than in the adults. It is possible then that this poorer performance seen in the children might be partly accounted for by the delayed maturation in their temporal processing ability, and because of this, the children's performance may have been driven more by their spectral sensitivity.     

Perceptual benefit and functional outcomes for children using sequential bilateral cochlear implants

OBJECTIVE: To evaluate the additional perceptual benefit provided to children through the use of two cochlear implants in comparison to one after 6 to 13 mo experience with sequential bilateral implants. DESIGN: A second cochlear implant was received by 11 children. The principal selection criteria were being age 4 to 15 yr with a bilateral profound hearing loss and being a consistent user of a first implant with a commitment to use of a second implant. Horizontal localization was assessed by using pink noise bursts presented from a 180 degrees , eight-loudspeaker array. Speech perception was assessed by using a four-alternative forced-choice spondee test, with speech presented from in front and adaptive background noise presented from 90 degrees to the left or right. Both tests were completed in the first implant alone and bilateral conditions. A questionnaire measured the pre- to postoperative change in the parent's ratings of the child's performance in specific listening situations. Items were related to speech perception, spatial hearing, or other qualities of hearing. Regular parental reports of device use, attitude and performance were collected. Most subjects were assessed at 6 mo after surgery, with two assessed at 13 mo. RESULTS: The 11 subjects demonstrated a great range of outcomes. For one subject, only anecdotal data were collected. Speech perception testing indicated that when noise was presented ipsilateral to the first implant, 8 of 10 subjects showed a benefit in the bilateral condition. None of the nine subjects tested showed a benefit when noise was contralateral to the first implant. Generally, there was no benefit to localization in the bilateral condition. For eight subjects, postoperative performance ratings were generally higher than preoperative ratings, particularly in the spatial hearing section. Anecdotal reports indicated that most subjects had a negative attitude toward, and gained limited experience with, the second implant alone. The subjects developed a range of speech perception skills, from detection to conversation level. Regarding the use of bilateral implants, attitudes were more positive and device use was consistent for eight subjects, and six parents reported some evidence of improved performance in daily life. CONCLUSIONS: Children over age 4 yr may gain significant additional benefit from a second implant, including improved speech perception in some noise contexts and functional advantages in daily life. There is, however, no evidence from this study to suggest that binaural listening skills, including localization, will develop during the first 6 mo. Furthermore, some children who may be committed users of a first implant may not adapt to or benefit from a second implant during the first 6 mo of device use. Although the factors influencing benefit cannot be clearly identified, limited preoperative auditory experience with the second ear, a delay of years between implants, relatively advanced age, and lack of second-implant-alone experience do not preclude benefit. Continued evaluation of these and additional subjects will clarify the factors that do contribute to benefit. Such information will be vital in helping families of implanted children to make an informed decision regarding a second implant.     

Academic achievements and classroom performance in Mandarin-speaking prelingually deafened school children with cochlear implants

Objectives

To document academic achievements and classroom performance in 35 Mandarin-speaking, congenital/pre-lingual, deafened children who used cochlear implants (CIs) for 5–11 years. The possible associated factors were also analyzed.

Study design

Cross-sectional case series.

Methods

Standardized Chinese literacy ability and mathematics tests were administered to evaluate the academic achievement of these children. Raw scores derived from both literacy ability and mathematics tests were compared with normative data from children with normal hearing (NH). A modified Mandarin edition of the Screening Instrument for Targeting Educational Risk (SIFTER) and a Regular School Adjustment Scale (RSAS) for students with hearing impairments filled out by regular classroom teachers were used to assess the children's classroom performances.

Results

The mean standard T-scores for Chinese literacy ability and mathematics ability were 48.6 and 50.3 (NORM = 50 ± 10), respectively. A total of 85.7% of children with CIs scored within or above the normal range of their age-matched hearing peers in Chinese literacy ability, and 82.9% were within normal ranges in mathematics ability. The SIFTER results showed that 45.7% failure was noted on the communication subscale, and the RSAS also indicated 40% of CI students to have communication problems. The academic subscale scores on the SIFTER were associated with the children's Chinese literacy abilities. The Verbal Comprehension Index (VCI) of the Wechsler IQ test IV was related to the children's mathematics abilities.

Conclusions

The academic achievements of Mandarin-speaking children who receive CIs from a young age and are integrated into mainstream elementary school system appear to fall within the normal range of their age-matched hearing counterparts after 5–11 years of use. This study strongly suggests the need for future ongoing support for these children in communication field.     

Lexical tone recognition in noise in normal-hearing children and prelingually deafened children with cochlear implants

Abstract

Objective: The purpose of the present study was to investigate Mandarin tone recognition in background noise in children with cochlear implants (CIs), and to examine the potential factors contributing to their performance. Design: Tone recognition was tested using a two-alternative forced-choice paradigm in various signal-to-noise ratio (SNR) conditions (i.e. quiet,?+12,?+6, 0, and ?6?dB). Linear correlation analysis was performed to examine possible relationships between the tone-recognition performance of the CI children and the demographic factors. Study sample: Sixty-six prelingually deafened children with CIs and 52 normal-hearing (NH) children as controls participated in the study. Results: Children with CIs showed an overall poorer tone-recognition performance and were more susceptible to noise than their NH peers. Tone confusions between Mandarin tone 2 and tone 3 were most prominent in both CI and NH children except for in the poorest SNR conditions. Age at implantation was significantly correlated with tone-recognition performance of the CI children in noise. Conclusions: There is a marked deficit in tone recognition in prelingually deafened children with CIs, particularly in noise listening conditions. While factors that contribute to the large individual differences are still elusive, early implantation could be beneficial to tone development in pediatric CI users.     

Language and theory-of-mind development in prelingually deafened children with cochlear implants: a preliminary investigation

One cognitive domain in which deaf children are known to lag behind their hearing peers is that of 'theory of mind'. Impoverished early conversational experience and deprivation of discussion about intangible mental states are seen as likely contributors to this deficit. The present study explored the relation between language and theory-of-mind capabilities in prelingually deafened children aged 4 to 11 years who were cochlear implant users. The children completed theory-of-mind tasks that indexed their ability to reason about conflicting mental representations, namely the understanding of false belief and the distinction between appearance and reality. Controlling for age, language ability was found to correlate positively and reliably with theory-of-mind performance.     

Prosody perception and musical pitch discrimination in adults using cochlear implants

Objectives: This study investigated prosodic perception and musical pitch discrimination in adults using cochlear implants (CI), and examined the relationship between prosody perception scores and non-linguistic auditory measures, demographic variables, and speech recognition scores. Design: Participants were given four subtests of the PEPS-C (profiling elements of prosody in speech-communication), the adult paralanguage subtest of the DANVA 2 (diagnostic analysis of non verbal accuracy 2), and the contour and interval subtests of the MBEA (Montreal battery of evaluation of amusia). Study sample: Twelve CI users aged 25;5 to 78;0 years participated. Results: CI participants performed significantly more poorly than normative values for New Zealand adults for PEPS-C turn-end, affect, and contrastive stress reception subtests, but were not different from the norm for the chunking reception subtest. Performance on the DANVA 2 adult paralanguage subtest was lower than the normative mean reported by Saindon (2010) Saindon M.R. 2010. Music Processing in Deaf Adults with Cochlear Implants. Master's thesis. University of Toronto. Available: https://tspace.library.utoronto.ca/bitstream/1807/25790/6/Saindon_Mathieu_R_201011_MA_thesis.pdf [Google Scholar]. Most of the CI participants performed at chance level on both MBEA subtests. Conclusion: CI users have difficulty perceiving prosodic information accurately. Difficulty in understanding different aspects of prosody and music may be associated with reduced pitch perception ability.     

Comparison of bilateral and unilateral cochlear implants in children with sequential surgery

Objective

The objective of this study was to evaluate the effect of bilateral versus unilateral cochlear implants and the importance of the inter-implant interval.

Methods

Seventy-three prelingually deaf children received sequential bilateral cochlear implants. Speech recognition in quiet with the first, second and with both implants simultaneously was evaluated at the time of the second implantation and after 12 and 24 months.

Results

Mean bilateral speech recognition 12 and 24 months after the second implantation was significantly higher than that obtained with either the first or the second implant. The addition of a second implant was demonstrated to have a beneficial effect after both 12 and 24 months. Speech recognition with the second implant increased significantly during the first year. A small, non-significant improvement was observed during the second year. The inter-implant interval significantly influenced speech recognition with the second cochlear implant both at 12 and 24 months, and bilateral speech recognition at 12 months, but not at 24 months.

Conclusions

A small, but statistically significant improvement in speech recognition was found with bilateral cochlear implants compared with a unilateral implant. A major increase in speech recognition occurred with the second cochlear implant during the first year. A shorter time interval between the two implantations resulted in better speech recognition with the second implant. However, no definitive time-point was found for when the second implant could no longer add a positive effect.     

Measuring listening effort expended by adolescents and young adults with unilateral or bilateral cochlear implants or normal hearing

Abstract

Objectives

To compare the listening effort expended by adolescents and young adults using implants versus their peers with normal hearing when these two groups are achieving similar speech perception scores. The study also aimed to compare listening effort expended by adolescents and young adults with bilateral cochlear implants when using two implants versus one.

Methods

Eight participants with bilateral cochlear implants and eight with normal hearing aged 10–22 years were included. Using a dual-task paradigm, participants repeated consonant–nucleus–consonant (CNC) words presented in noise and performed a visual matching task. Signal-to-noise ratios were set individually to ensure the word perception task was challenging but manageable for all. Reduced performance on the visual task in the dual-task condition relative to the single-task condition was indicative of the effort expended on the listening task.

Results

The cochlear implant group, when using bilateral implants, expended similar levels of listening effort to the normal hearing group when the two groups were achieving similar speech perception scores. For three individuals with cochlear implants, and the group, listening effort was significantly reduced with bilateral compared to unilateral implants.

Discussion

The similar amount of listening effort expended by the two groups indicated that a higher signal-to-noise ratio overcame limitations in the auditory information received or processed by the participants with implants. This study is the first to objectively compare listening effort using two versus one cochlear implant. The results provide objective evidence that reduced listening effort is a benefit that some individuals gain from bilateral cochlear implants.     

Sensitivity to interaural level and envelope time differences of two bilateral cochlear implant listeners using clinical sound processors

OBJECTIVES: To assess the sensitivity of two bilateral cochlear implant users to interaural level and time differences (ILDs and ITDs) for various signals presented through the auxiliary inputs of clinical sound processors that discard fine timing information and only preserve envelope cues. DESIGN: In a lateralization discrimination experiment, the just noticeable difference (JND) for ILDs and envelope ITDs was measured by means of an adaptive 2-AFC method. Different stimuli were used, including click trains at varying repetition rates, a speech fragment, and noise bursts. For one cochlear implant listener and one stimulus, the sensitivity to envelope ITDs was also determined with the method of constant stimuli. The dependency of ILD-JNDs on the interaural place difference was studied with stimulation at single electrode pairs by using sinusoidal input signals in combination with appropriate single-channel processor fittings. In a lateralization position experiment, subjects were required to use a visual pointer on a computer screen to indicate in-the-head positions for blocks of stimuli containing either ILD or ITD cues. All stimuli were loudness balanced (before applying ILD) and fed directly into the auxiliary inputs of the BTE processors (TEMPO+, Med-El Corp.). The automatic gain control and the processors' microphones were deactivated. RESULTS: Both cochlear implant listeners were highly sensitive to ILDs in all broadband stimuli used; JNDs approached those of normal-hearing listeners. Pitch-matched single electrode pairs showed significantly lower ILD-JNDs than pitch-mismatched electrode pairs. Envelope ITD-JNDs of cochlear implant listeners obtained with the adaptive method were substantially higher and showed a higher test-retest variability than waveform ITD-JNDs of normal-hearing control listeners and envelope ITD-JNDs of normal-hearing listeners reported in the literature for comparable signals. The envelope ITD-JNDs for the click trains were significantly lower than for the speech token or the noise bursts. The best envelope ITD-JND measured was ca. 250 mus for the click train at 100 cycles per sec. Direct measurement of the psychometric function for envelope ITD by the method of constant stimuli showed discrimination above chance level down to 150 micros. The lateralization position experiment showed that both ILDs and envelope ITDs can lead to monotonic changes in lateral percept. CONCLUSIONS: The two cochlear implant users tested showed strong effects of ILDs in various broadband stimuli with respect to JNDs as well as lateralization position. The high dependency of ILD-JNDs on the interaural pitch difference suggests the potential importance of pitch-matched assignment of electrodes in the two ears by the speech processors. Envelope ITDs appear to be more ambiguous cues than ILDs, as reflected by the higher and more variable JNDs compared with normal-hearing listeners. The envelope ITD-JNDs of cochlear implant listeners depended on the stimulus.     

Development of auditory and language skills in children using cochlear implants with two signal processing strategies

IntroductionThe increase in the spectral information offered by the sound processing strategy HiRes 120 has led to great expectations for the pediatric population. Due to a shorter duration of auditory deprivation and higher neural plasticity, children could benefit more substantially from the spectral information of this sound processing strategy.ObjectiveTo compare auditory and language skills in Brazilian children with cochlear implants using the HiRes and HiRes 120 sound processing strategies.MethodsThirty children, aged 1–3 years, with congenital hearing loss, were divided into two groups, according to the signal processing strategy adjusted at the time of the cochlear implant activation. The assessed children were matched according to chronological age and the time of the cochlear implant use. The auditory and language skills were evaluated longitudinally through the Infant-Toddler Meaningful Auditory Integration Scale and Production Infant Scale Evaluation, carried out before surgery, and 3, 6 and 12 months after device implantation. The Mann–Whitney test was applied for the comparison between the two groups with a 5% significance level.ResultsThe findings indicated development of hearing and language skills in the first year of cochlear implant use; however, there was no statistically significant difference in the evolution of such skills due to the adjusted processing strategy in the activation of the cochlear implant electrodes.ConclusionThe development of auditory and language skills in the assessed children was similar during the entire study period, regardless of which signal processing strategy was used.     

人工耳蜗术后患儿听阈评估

目的分析人工耳蜗对患者的听觉康复作用,比较声场和头戴式耳机两种人工耳蜗术后助听听阈评估方法的优劣。方法重度和极重度感音神经性听力损失患者27例接受人工耳蜗植入,男性18例,女性9例,植入年龄跨度1.7至18.6岁,平均7.6±5.4岁。开机后分别采用声场扬声器和TDH39头戴式耳机评估患者0.25k、0.5k、1.0k、2.0k、4.0kHz的助听听阈,TDH39耳机还可测试8.0kHz的助听听阈。使用配对t检验对两种方法所得结果进行比较。结果使用声场扬声器得到的助听听阈3FA(即0.5k、1.0k、2.0kHz平均听阈)为39.4±7.7dBHL,4FA(即0.5k、1.0k、2.0k、4.0kHz平均听阈)为37.5±7.3dBHL。使用TDH39头戴式耳机测得的助听听阈3FA为39.3±6.1dBHL,4FA为38.4±5.7dBHL。两者所测得的3FA(P=0.8801)和4FA(P=0.2133)均无统计学差异。使用两种方式测得的0.25kHz(P=0.8756)、0.5kHz(P=0.0630)、1.0kHz(P=0.1980)、2.0kHz(P=0.6866)助听听阈均无统计学差异,4.0kHz(P=0.0062)耳机测试听阈低于声场结果。结论人工耳蜗植入可帮助重度和极重度感音神经性听力损失患者实现良好的听敏度。使用头戴式耳机可获得可靠的植入后助听听阈,比声场测试更加简便易行。     

Working-memory capacity and phonological processing in deafened adults and individuals with a severe hearing impairment

The purpose of the present article is to review a number of studies conducted in our own laboratory with respect to working memory capacity and phonological processing in deafened adults and individuals with a severe hearing impairment, and how these two cognitive components relate to speech processing. The results demonstrate that one specific component in the phonological processing system (i.e., the phonological representation system) is deteriorating, whereas other parts are preserved intact. The characteristic of the individual's phonological representation is further correlated with success in speech reading and speech understanding with some cochlear implant systems. Working memory capacity is a capacity that remains intact despite a long duration of deafness/severe hearing loss. The size of the working memory is related to skill in speech reading and level of speech understanding with cochlear implants and perceived effort in a noisy environment.