Normal hearing and language development in a deaf-born child

The effects of stimulus complexity on the preattentive processing of self-generated and nonself voices: An ERP study

The ability to differentiate one's own voice from the voice of somebody else plays a critical role in successful verbal self-monitoring processes and in communication. However, most of the existing studies have only focused on the sensory correlates of self-generated voice processing, whereas the effects of attentional demands and stimulus complexity on self-generated voice processing remain largely unknown. In this study, we investigated the effects of stimulus complexity on the preattentive processing of self and nonself voice stimuli. Event-related potentials (ERPs) were recorded from 17 healthy males who watched a silent movie while ignoring prerecorded self-generated (SGV) and nonself (NSV) voice stimuli, consisting of a vocalization (vocalization category condition: VCC) or of a disyllabic word (word category condition: WCC). All voice stimuli were presented as standard and deviant events in four distinct oddball sequences. The mismatch negativity (MMN) ERP component peaked earlier for NSV than for SGV stimuli. Moreover, when compared with SGV stimuli, the P3a amplitude was increased for NSV stimuli in the VCC only, whereas in the WCC no significant differences were found between the two voice types. These findings suggest differences in the time course of automatic detection of a change in voice identity. In addition, they suggest that stimulus complexity modulates the magnitude of the orienting response to SGV and NSV stimuli, extending previous findings on self-voice processing.

Mother-Infant Contingent Vocalizations in 11 Countries

Mother-infant vocal interactions serve multiple functions in child development, but it remains unclear whether key features of these interactions are community-common or community-specific. We examined rates, interrelations, and contingencies of vocal interactions in 684 mothers and their 5½-month-old infants in diverse communities in 11 countries (Argentina, Belgium, Brazil, Cameroon, France, Israel, Italy, Japan, Kenya, South Korea, and the United States). Rates of mothers' and infants' vocalizations varied widely across communities and were uncorrelated. However, collapsing the data across communities, we found that mothers' vocalizations to infants were contingent on the offset of the infants' nondistress vocalizing, infants' vocalizations were contingent on the offset of their mothers' vocalizing, and maternal and infant contingencies were significantly correlated. These findings point to the beginnings of dyadic conversational turn taking. Despite broad differences in the overall talkativeness of mothers and infants, maternal and infant contingent vocal responsiveness is found across communities, supporting essential functions of turn taking in early-childhood socialization.

Functional benefits of sequential bilateral cochlear implantation in children with long inter-stage interval between two implants

OBJECTIVES

Older children are increasingly deriving binaural benefits from sequential bilateral cochlear implantation, and this procedure should be considered by experienced cochlear implant centers. This study aimed to identify the influence of a long inter-stage interval between two implants in older children. Speech perception and everyday listening performance were investigated and analyzed according to the length of the inter-stage interval.

STUDY DESIGN AND SETTINGS

Forty-two children who received sequential bilateral cochlear implantation participated in this study. Their average ages at the first and second implantation were 4.2 and 9.7 years, respectively. All subjects acquired excellent speech performance from their first implant, and the mean inter-stage interval was 5.5 years. Speech perception in quiet was assessed by formal speech measures, and postoperative performance using the second implant only was compared with the preoperative performance. Speech perception in noise test was administered using three noise directions with noise (+10 dB signal-to-noise ratio) from front and 90° to each side, and the change in performance using the first implant only and both implants were analyzed across the three noise directions. Subjects were divided into three groups according to their inter-stage interval (group I, 3-4.9 years; group II, 5-6.9 years; and group III, 7-9.9 years), and the test results were compared between the groups. Functional hearing benefits in daily life were measured by a questionnaire before and after bilateral cochlear implantation.

RESULTS

The speech perception abilities in quiet using the second implant only improved quickly and were similar to those using the first implant only within 1 year after the second implantation. The scores for the monosyllabic word test (phoneme: p=0.052; word: p=0.125) and common phrases sentence test (p=0.062) 6 month after the second implantation, and the Categories of Auditory Performance score (p=1.000) 1 year after the second implantation using the second implant only did not differ significantly from those using the first implant only. Speech perception was significantly better using both implants than using the first implant in all three noise conditions (speech and noise in front: p=0.004; speech in front and noise to the first implant: p=0.003; speech in front and noise to the second implant: p<0.001), and the effect of noise direction was negligibly small. No salient influence of inter-stage interval was observed in both quiet and noise tests. The second and third groups with longer inter-stage intervals (>5 years) achieved performance close to the level of the first group with a shorter interval. These subjects obtained significantly better functional hearing benefits in the everyday environment with bilateral implants compared with the first implant (p=0.018).

CONCLUSION

The subjects in this study showed rapid postoperative progression within 6 months after the second implantation, and more listening benefits in noise and daily life with bilateral implants. This group of older children, who were good performers with the first implant, developed auditory perceptual competence in the second ear and achieved functional binaural benefits with their two implants. Sequential bilateral cochlear implantation should be recommended to this group of older children despite a long inter-stage interval between two implants.

Functional overlap between regions involved in speech perception and in monitoring one's own voice during speech production

The fluency and the reliability of speech production suggest a mechanism that links motor commands and sensory feedback. Here, we examined the neural organization supporting such links by using fMRI to identify regions in which activity during speech production is modulated according to whether auditory feedback matches the predicted outcome or not and by examining the overlap with the network recruited during passive listening to speech sounds. We used real-time signal processing to compare brain activity when participants whispered a consonant-vowel-consonant word ("Ted") and either heard this clearly or heard voice-gated masking noise. We compared this to when they listened to yoked stimuli (identical recordings of "Ted" or noise) without speaking. Activity along the STS and superior temporal gyrus bilaterally was significantly greater if the auditory stimulus was (a) processed as the auditory concomitant of speaking and (b) did not match the predicted outcome (noise). The network exhibiting this Feedback Type x Production/Perception interaction includes a superior temporal gyrus/middle temporal gyrus region that is activated more when listening to speech than to noise. This is consistent with speech production and speech perception being linked in a control system that predicts the sensory outcome of speech acts and that processes an error signal in speech-sensitive regions when this and the sensory data do not match.

Auditory, speech and language development in young children with cochlear implants compared with children with normal hearing

OBJECTIVE

This study had two aims: (1) to document the auditory and lexical development of children who are deaf and received the first cochlear implant (CI) by the age of 16 months and the second CI by the age of 31 months and (2) to compare these children's results with those of children with normal hearing (NH).

METHODS

This longitudinal study included five children with NH and five with sensorineural deafness. All children of the second group were observed for 36 months after the first fitting of the device (cochlear implant). The auditory development of the CI group was documented every 3 months up to the age of two years in hearing age and chronological age and for the NH group in chronological age. The language development of each NH child was assessed at 12, 18, 24 and 36 months of chronological age. Children with CIs were examined at the same age intervals at chronological and hearing age.

RESULTS

In both groups, children showed individual patterns of auditory and language development. The children with CIs developed differently in the amount of receptive and expressive vocabulary compared with the NH control group. Three children in the CI group needed almost 6 months to make gains in speech development that were consistent with what would be expected for their chronological age. Overall, the receptive and expressive development in all children of the implanted group increased with their hearing age.

CONCLUSION

These results indicate that early identification and early implantation is advisable to give children with sensorineural hearing loss a realistic chance to develop satisfactory expressive and receptive vocabulary and also to develop stable phonological, morphological and syntactical skills for school life. On the basis of these longitudinal data, we will be able to develop new diagnostic tools that enable clinicians to assess child's progress in hearing and speech development.

Choosing for the child with cochlear implants: a note of precaution

Recent contributions to discussions on paediatric cochlear implantation in Norway indicate two mutually exclusive doctrines prescribing the best course of post-operative support for a child with cochlear implants; bilingually with sign language and spoken language simultaneously or primarily monolingually with speech only. This conflict constitutes an ethical problem for parents responsible for choosing between one of the two alternatives. This article puts forth the precautionary principle as a possible solution to this problem. Although scientific uncertainty exists in the case of both doctrines, there exists a scenario of possible irreversible harm to some of the children habilitated monolingually. An application of the precautionary principle may hence suggest that it is rational to agree on the bilingual approach, at least for the time-being.

Perspectives on multisensory experience and cognitive development in infants with cochlear implants

Infants learn about their environment through sensory exploration, acquiring knowledge that is important for cognitive development. However, little is known about the sensory exploration of infants with profound hearing loss before or after they receive cochlear implants. This paper reviews aspects of sensory perception and cognitive development in hearing infants, discusses the implications of delayed access to auditory information for multisensory perception and cognitive development in infants who use cochlear implants, and suggests several new directions for research addressing multisensory exploration and cognitive development in infants with cochlear implants.

Language achievement in children who received cochlear implants between 1 and 2 years of age: group trends and individual patterns

This study examined receptive and expressive vocabulary and grammar achievement of French-speaking children (n = 27) who received a cochlear implant (CI) between the age of 1 and 2. Standardized measures of language achievement were administered and the language levels attained by children with CIs were compared with that of the normative sample of same-age hearing peers for each measure. As a group, children exhibited language levels within normal limits in all standardized language measures. Examination of individual patterns revealed four different language profiles ranging from normal language levels in all domains to general language delay. Half the participants displayed language levels on par with similar-age peers at the word level; less than half the children obtained average performance at the sentence level. In three of these profiles, comprehension of sentences was impaired. Moreover, the age at implantation was not associated with language achievement. Findings suggest that receiving a CI between the age of 1 and 2 years does not ensure that language abilities will be within normal limits after up to 6 years of experience with the implant.

Functional outcome of sequential bilateral cochlear implantation in young children: 36 months postoperative results

OBJECTIVE

To examine the effects of sequential bilateral cochlear implantation (CI) on the life of young children after 36 months of bilateral implant use.

METHOD

Thirty-five children were assessed prior to and 3 until 36 months after activation of the second CI. Main outcome measures were: the Categories of Auditory Performance (CAP), Speech Intelligibility Rating (SIR), communication mode, classroom placement, parent reports and the Würzburg questionnaire. Results were analysed separately for children younger and older than 6 years at the time of the second implantation.

RESULTS

At the 3-year test interval, 80% of the younger children attended mainstream schools and were comprehensible for all listeners. They all used oral communication and almost 70% of them could have a conversation over the telephone. After 3 years of bilateral implant use less than 50% of the older children obtained the highest score on the SIR and CAP. Approximately 70% of them was integrated in mainstream schools and used oral communication. All parents reported a more natural communication and an improved quality of life.

CONCLUSIONS

Sequential bilateral implantation seems to offer a wide range of participation benefits to all children and facilitates the social intercourse with their hearing environment.

Delayed auditory pathway maturation in the differential diagnosis of hypoacusis in young children

Auditory deficiencies have profound implications for the development of communication abilities, social exchange, and cognitive skills. Although advances in technological instrumentation have decreased the age at which it is possible to detect auditory deficits, an absence of electrophysiological or behavioral reaction to sound does not always reflect hypoacusis. The objective of this study was to evaluate the evolution of audition in a group of children referred for therapy to the CINDA Foundation (Center for Research and Information in Auditory Deficiencies) in Bogota, Colombia, with an initial diagnosis of severe to profound sensorineural hearing loss. We evaluated 25 patients younger than 2.5 years of age with a protocol which included auditory evoked potentials, behavioral responses (tonal audiometry-responses to voice and startle) and language observation. After evaluation, the children began a program of auditory stimulation with audiological follow-up for a period of 6 months to 1 year. The audiological follow-up of the children after auditory stimulation showed significant improvements in both electrophysiological and behavioral indices of their hearing levels (p<.001, one-tailed Wilcoxon exact test). We found a high percentage of children in early stages of auditory maturation with a false diagnosis of hypoacusis (32%). The absence of response may result from compromised auditory reception or processing. Thus, delayed maturation of the auditory pathway should be considered in the differential diagnosis of young children with sensorineural hearing loss.

Hearing benefits of second-side cochlear implantation in two groups of children

OBJECTIVE

To investigate the additional bilateral benefits of a second cochlear implant (CI) in a group of young children (<6 years of age) and a group of older children (>6 years of age).

METHOD

This is a Belgian tertiary multi-centre study in which 33 CI-children with a second implant between the age of 2 and 12 participated. Assessments took place pre-second implant and at several time intervals post-fitting on pure tone audiometry and speech recognition in quiet and noise (+10 dBSNR). Testing was done with the first and second implant alone and bilaterally. Results were analysed separately for children younger and older than 6 years at the time of implantation of the 2nd CI.

RESULTS

After 18 months of bilateral implant use all children obtained significantly higher hearing thresholds in the bilateral condition in comparison to both the unilateral conditions (p(CI1)=0.035/p(CI2)=0.042 for the younger children and p(CI1)=0.021/p(CI2)=0.007 for the older children). The speech recognition scores in quiet were for all children superior in the bilateral condition (p(CI2)=0.011 for the younger children and p(CI1)=0.016/p(CI2)=0.003 for the older children). In the noisy condition only significant bilateral better results were obtained in the group of younger children (p(CI1)=0.028/p(CI2)=0.034).

CONCLUSIONS

Bilateral cochlear implantation offers advantages to all children. Even for the children who received a second implant after the age of 6 a progress is determined after 18 months. However, the data appear to show a beneficial performance for those children who received their second implant before the age of 6, especially in the more challenging conditions.

Cortical Activity at Rest Predicts Cochlear Implantation Outcome

The functional status of central neural pathways, in particular their susceptibility to plasticity and functional reorganization, may influence speech performance of deaf cochlear implant users. In this paper, we sought to determine how brain metabolic activity measured before implantation relates to cochlear implantation outcome, that is, speech perception. In 22 prelingually deaf children between 1 and 11 years, we correlated preoperative glucose metabolism as measured by F-18 fluorodeoxyglucose positron emission tomography with individual speech perception performance assessed 3 years after implantation, while factoring out the confounding effect of age at implantation. Whereas age at implantation was positively correlated with increased activity in the right superior temporal gyrus, speech scores were selectively associated with enhanced metabolic activity in the left prefrontal cortex and decreased metabolic activity in right Heschl's gyrus and in the posterior superior temporal sulcus. These results reinforce the notion that implantation should be performed as early as possible to prevent cross-modal takeover of auditory regions and suggest that rehabilitation strategies may be more efficient if they capitalize on general cognitive functions instead of only targeting specialized circuits dedicated to auditory and audiovisual pattern recognition.