Implications of developmental plasticity for the language acquisition of deaf children with cochlear implants

Hearing and sociality: the implications of hearing loss on social life

Hearing is essential to the formation of social relationships and is the principal afferent of social life. Yet hearing loss, which is one of the most prevalent forms of sensory disability worldwide and is critical for social development, has received little attention from the social interventionalist perspective. The purpose of this mini-review is to describe the basic neurobiological principles of hearing and to explore the reciprocal relationships between social support, hearing loss, and its psychosocial comorbidities. We also discuss the role of social enrichment in sensorineural recovery and identify open questions within the fields of hearing physiology and social networks.

Is Early Cochlear Implantation Leads to Better Speech and Language Outcomes?

A cochlear implant is an electronic sensory system that converts mechanical energy into coded electrical signals that directly activate the auditory nerve fibers. Present review article investigates the findings of previous research papers which have assessed speech and language outcome in children who underwent early cochlear implantation. Several databases, including PubMed, Google, Google Scholar, and Medline, were investigated for research papers on the speech and language outcomes of children who had early-life implants. According to previous research, early detection and intervention of hearing loss are critical for the growth of speech and language skills. The effect of early detection of hearing loss and early cochlear implantation on a child's overall speech-language and auditory growth is highlighted in this article.

Influence of cochlear implants on hearing-related quality of life: results from Chinese children with cochlear implants entering mainstream education

OBJECTIVES

This study aimed to 1) assess the hearing-related Quality of Life (QoL) of children with cochlear implants (CIs) in China and 2) investigate the impact of CI in children and of the socio-demographic backgrounds of their guardians on the hearing-related QoL of children with CIs in the Chinese mainstream education system.

METHODS

This study used the Mandarin Children with Cochlear Implants: Parental Perspectives questionnaire (MPP), which assessed the communication capability, auditory perception, self-independence, level of happiness with family, social interaction, academic performance, outcome assessment for CI, and level of family support in children with CIs. Both univariate and multiple linear regression analyses were performed to identify the relationship of CI in children and the socio-demographic backgrounds of their guardians with hearing-related QoL in children with CI.

RESULT

A total of 124 responses were collected, and they indicated satisfaction and improvement across all aspects of the MPP Questionnaire. Statistical analysis revealed that an earlier age of cochlear implantation (≤3 years old) could improve the communication capabilities, self-independence, social interaction performance, and academic performance of children with CIs. In addition, children with CI from the urban regions demonstrated better social interaction performance than that by those from the rural regions of China.

CONCLUSION

CIs can improve hearing-related QoL in children with pre-lingual or congenital hearing loss entering the mainstream education system in China. This study showed that early age of cochlear implantation was critical for successful long-term auditory development and academic achievement in children with CIs in China. Therefore, healthcare professionals and educators in China should advocate for CI for children with severe congenital or pre-lingual hearing loss.

Surgical considerations and speech outcomes in infants who undergo cochlear implantation. Experience of the King Abdullah Ear Specialist Center

Objectives:

To evaluate the feasibility and outcomes of cochlear implantation (CI) in infancy.

Methods:

All infants who underwent CI from January 2011 to October 2018 at a tertiary referral center in the Kingdom of Saudi Arabia were retrospectively reviewed. Demographic data, factors associated with early detection, and any surgical difficulties or postoperative complications were extracted from the medical records. The outcome of CI was determined by a speech pathologist.

Results:

Fifteen patients underwent CI during the study period (9 bilateral and performed simultaneously, 6 unilateral). The round window was difficult to identify in 5 cases. Incomplete electrode insertion because of cochlear ossification secondary to meningitis was documented in one patient. No major postoperative complications were encountered. The average auditory performance score was 7 and the speech intelligibility rating was 5.

Conclusions:

This study represents the largest national cohort of pediatric patients undergoing CI in infancy. In this series, the surgery was safe and the speech outcome was good. With implementation of the neonatal screening program in the Kingdom of Saudi Arabia, the number of infants undergoing CI is likely to increase in the near future, paving the way for more research in infant CI.

Development of auditory perception in preschool children

OBJECTIVE

The aim of this study was to determine whether the auditory skills presented by five-year-old children can predict their performance in auditory processing (AP) tests at seven years old.

DESIGN

Thirty-five children were evaluated for AP at two different times. At evaluation 1, the children were between 5 years 2 months and 6 years 1 month of age, and at evaluation 2, they were between 7 years 1 month and 7 years 8 months of age. The interval between the evaluations ranged from 18 to 23 months. After evaluation 2, the 7-year-olds were classified according to their performance on central AP tests. The children were divided into three groups: GI included nine children with at least two AP tests that scored two standard deviations below the mean and the presence of a speech complaint; GII included 18 children with at least two AP tests that scored two standard deviations below the mean and no speech complaints; and GIII included eight children with no more than one test scored two standard deviations below the mean and no speech disorders complaint. The analysis was performed considering each test individually and as a battery of applied tests. From the results obtained, a discriminant analysis was performed to assess the differences in test performance between the groups when the children were 5 years old.

RESULTS

The discriminant analysis showed that with the results obtained during evaluation 1, it was possible to predict which group 74.3% of the children would be classified into after evaluation 2. The percentage of correct classifications for each group was 77.8% for GI, 66.7% for GII and 87.5% for GIII. That is, 87.5% of the children who were classified as GIII after evaluation 2 had already demonstrated good auditory performance in the tests applied at 5 years of age.

CONCLUSIONS

Children who exhibited lower scores on AP tests at 7 years of age had demonstrated poor auditory perception at 5 years of age. This finding is relevant because it offers the possibility of stimulating or training these auditory skills in preschoolers to foster their development.

Prosody perception and production by children with cochlear implants

The perception and production of emotional and linguistic (focus) prosody were compared in children with cochlear implants (CI) and normally hearing (NH) peers. Thirteen CI and thirteen hearing-age-matched school-aged NH children were tested, as baseline, on non-verbal emotion understanding, non-word repetition, and stimulus identification and naming. Main tests were verbal emotion discrimination, verbal focus position discrimination, acted emotion production, and focus production. Productions were evaluated by NH adult Dutch listeners. All scores between groups were comparable, except a lower score for the CI group for non-word repetition. Emotional prosody perception and production scores correlated weakly for CI children but were uncorrelated for NH children. In general, hearing age weakly predicted emotion production but not perception. Non-verbal emotional (but not linguistic) understanding predicted CI children's (but not controls') emotion perception and production. In conclusion, increasing time in sound might facilitate vocal emotional expression, possibly requiring independently maturing emotion perception skills.

Cerebral plasticity: Windows of opportunity in the developing brain

BACKGROUND

Neuroplasticity refers to the inherently dynamic biological capacity of the central nervous system (CNS) to undergo maturation, change structurally and functionally in response to experience and to adapt following injury. This malleability is achieved by modulating subsets of genetic, molecular and cellular mechanisms that influence the dynamics of synaptic connections and neural circuitry formation culminating in gain or loss of behavior or function. Neuroplasticity in the healthy developing brain exhibits a heterochronus cortex-specific developmental profile and is heightened during "critical and sensitive periods" of pre and postnatal brain development that enable the construction and consolidation of experience-dependent structural and functional brain connections.

PURPOSE

In this review, our primary goal is to highlight the essential role of neuroplasticity in brain development, and to draw attention to the complex relationship between different levels of the developing nervous system that are subjected to plasticity in health and disease. Another goal of this review is to explore the relationship between plasticity responses of the developing brain and how they are influenced by critical and sensitive periods of brain development. Finally, we aim to motivate researchers in the pediatric neuromodulation field to build on the current knowledge of normal and abnormal neuroplasticity, especially synaptic plasticity, and their dependence on "critical or sensitive periods" of neural development to inform the design, timing and sequencing of neuromodulatory interventions in order to enhance and optimize their translational applications in childhood disorders of the brain.

METHODS

literature review.

RESULTS

We discuss in details five patterns of neuroplasticity expressed by the developing brain: 1) developmental plasticity which is further classified into normal and impaired developmental plasticity as seen in syndromic autism spectrum disorders, 2) adaptive (experience-dependent) plasticity following intense motor skill training, 3) reactive plasticity to pre and post natal CNS injury or sensory deprivation, 4) excessive plasticity (loss of homeostatic regulation) as seen in dystonia and refractory epilepsy, 6) and finally, plasticity as the brain's "Achilles tendon" which induces brain vulnerability under certain conditions such as hypoxic ischemic encephalopathy and epileptic encephalopathy syndromes. We then explore the unique feature of "time-sensitive heightened plasticity responses" in the developing brain in the in the context of neuromodulation.

CONCLUSION

The different patterns of neuroplasticity and the unique feature of heightened plasticity during critical and sensitive periods are important concepts for researchers and clinicians in the field of pediatric neurology and neurodevelopmental disabilities. These concepts need to be examined systematically in the context of pediatric neuromodulation. We propose that critical and sensitive periods of brain development in health and disease can create "windows of opportunity" for neuromodulatory interventions that are not commonly seen in adult brain and probably augment plasticity responses and improve clinical outcomes.

Low surgical complication rates in cochlear implantation for young children less than 1 year of age

OBJECTIVE

To identify risk factors for perioperative morbidity among a large national cohort of pediatric patients undergoing cochlear implantation.

STUDY DESIGN

Retrospective study utilizing the American College of Surgeons National Surgical Quality Improvement Program Pediatric database (2012-2013).

METHODS

Pediatric cochlear implantation cases were identified using current procedural terminology 69930. Patients were categorized by age, and operative characteristics along with 30-day perioperative outcomes were analyzed.

RESULTS

We identified 1,351 cases of pediatric cochlear implantation. The median age was 3.6 years, and 73 patients were less than 1 year of age. Of 21 complication occurrences (1.55%), superficial incisional surgical site infection (SSI) was the most common (n = 13, 61.9%). Thirty-nine patients (2.9%) required readmission. The median operative time was 142 minutes, and the mean postoperative length of stay was 0.58 days. When comparing patients younger than 1 year old to those 1 year or older, no significant differences were noted in complication rate, postoperative length of stay, or reoperation rate. Patients less than 1 year of age were more likely to be readmitted (6.9% vs. 2.7%, P = 0.04) and had longer mean operative times (191 minutes vs. 160 minutes, P = 0.0015). Steroid use was a risk factor for unplanned reoperation, SSI, and readmission.

CONCLUSION

Despite a slight increase in readmission rates and operative times among patients less than 1 year of age, cochlear implantation appears to be safe in this population, with complication rates, reoperation rates, and postoperative lengths of stay similar to children undergoing the procedure at the current U.S. Food and Drug Administration-approved age of 1 year and older.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:720-724, 2017.

[Speech and general development in children receiving early cochlear implants]

BACKGROUND

After cochlear implantation, most parents expect a normal speech and general development of their child. However, it remains unclear how quickly after early cochlear implantation these children can compensate for their deficits compared to normal-hearing children.

METHODS

This study retrospectively analyzed ELFRA-1 questionnaire data from 40 children with borderline deafness or high-grade hearing loss (without other known impairments) who had undergone cochlear implantation at a university medical center before reaching 2 years of age. ELFRA-1 questionnaires were filled out parents assisted by specialists 12 months after implantation. Questions assessed the children's speech production and comprehension, as well as their use of gestures and fine motoric skills.

RESULTS

At an average hearing-age of 12 months, the children achieved normal values in all of the subgroups that were comparable to those of 12-month-old children without hearing impairments. A significant correlation (p = 0.01) between the individual subgroups of the ELFRA-1 (speech production, speech comprehension, gestures and fine motor skills) was observed. Unilingual educated children performed significantly better overall.

CONCLUSION

Within 12 months of receiving a cochlear implant, all children passed the four categories of the ELFRA-1. This demonstrates a rapid compensation of deficits in speech, motor skills and gesture development by children undergoing early cochlear implantation.

A theory of the transition to critical period plasticity: inhibition selectively suppresses spontaneous activity

What causes critical periods (CPs) to open? For the best-studied case, ocular dominance plasticity in primary visual cortex in response to monocular deprivation (MD), the maturation of inhibition is necessary and sufficient. How does inhibition open the CP? We present a theory: the transition from pre-CP to CP plasticity arises because inhibition preferentially suppresses responses to spontaneous relative to visually driven input activity, switching learning cues from internal to external sources. This differs from previous proposals in (1) arguing that the CP can open without changes in plasticity mechanisms when activity patterns become more sensitive to sensory experience through circuit development, and (2) explaining not simply a transition from no plasticity to plasticity, but a change in outcome of MD-induced plasticity from pre-CP to CP. More broadly, hierarchical organization of sensory-motor pathways may develop through a cascade of CPs induced as circuit maturation progresses from "lower" to "higher" cortical areas.

Early intervention and assessment of speech and language development in young children with cochlear implants

OBJECTIVE

Age is one of the most important determinants of the benefit achieved in the cochlear implantation of pre-lingually deafened children. Earlier age at implantation increases the exposure of children with a hearing impairment to auditory stimuli. Earlier auditory stimulation enables children to better understand spoken language and to use spoken language themselves. Furthermore, there appears to be critical period under 2 years of age during which access to spoken language is essential in order for language development to proceed appropriately. The present study aimed to assess the impact of cochlear implantation under 2 years of age on subsequent speech and language development.

METHODS

28 children implanted with a cochlear implant prior to 2 years of age were included in this study and the effects of age at implantation were determined using a reception of grammar test, active vocabulary test and speech development test. Demographic features were described using descriptive statistics and data were compared to the normative values (T-values) of their hearing peers by t-test or Mann-Whitney U-test.

RESULTS

The present data indicates that overall children with a hearing impairment implanted at less than 2 years of age perform as well as or better than their hearing peers in speech and grammar development. Word Comprehension was significantly greater in children with a cochlear implant compared to their normative peers (p=0.003), whereas Phonological Working Memory for Nonsense Words was poorer (p=0.031). An effect of age on grammatical and speech development could be found for younger implanted children (<12 months), who reached higher scores than children implanted after 12 months of age.

CONCLUSIONS

The data suggests that early hearing loss intervention via cochlear implantation in children benefits the speech and language development of children. A potential sensitive period exists for implantation before 12 months of age. These outcomes support the recent trend toward early cochlear implantation in pre-lingually deaf children.

Universal newborn hearing screening programs in Italy: survey of year 2006

CONCLUSION

Our results suggest a rapid diffusion of newborn hearing screening programs in Italy and indicate that three conditions seem to play a crucial role in the implementation of Universal Newborn Hearing Screening (UNHS) programs: the size (>800 births/year) and location (metropolitan urban areas) of the hospital, and the presence of an audiologist in the UNHS coordinating team.

OBJECTIVES

The aim of this paper is to provide data on the degree of implementation and coverage of UNHS programs in Italy.

MATERIALS AND METHODS

Data were collected through a Screening Survey Questionnaire that was sent to all birthing hospitals active in Italy in 2006 and was filled in by the chief of the hospital or by the UNHS program coordinator.

RESULTS

In Italy UNHS coverage had undergone a steep increase from 29.3% in 2003 (156,048 newborns screened) to 48.4% in 2006 (262,103 screened). The majority of UNHS programs were implemented in the two most economically developed areas, i.e. in the north-west area (79.5%, 108,200 of 136,109 births), and in the north-east area (57.2%, 52,727 of 92,133 births), while a limited diffusion still remains in some areas, typically in the islands (11.3%, 7158 of 63,460 births).

Will they catch up? The role of age at cochlear implantation in the spoken language development of children with severe to profound hearing loss

PURPOSE

The authors examined the benefits of younger cochlear implantation, longer cochlear implant use, and greater pre-implant aided hearing to spoken language at 3.5 and 4.5 years of age.

METHOD

Language samples were obtained at ages 3.5 and 4.5 years from 76 children who received an implant by their 3rd birthday. Hierarchical linear modeling was used to identify characteristics associated with spoken language outcomes at the 2 test ages. The Preschool Language Scale (I. L. Zimmerman, V. G. Steiner, & R. E. Pond, 1992) was used to compare the participants' skills with those of hearing age-mates at age 4.5 years.

RESULTS

Expected language scores increased with younger age at implant and lower pre-implant thresholds, even when compared at the same duration of implant use. Expected Preschool Language Scale scores of the children who received the implant at the youngest ages reached those of hearing age-mates by 4.5 years, but those children implanted after 24 months of age did not catch up with hearing peers.

CONCLUSION

Children who received a cochlear implant before a substantial delay in spoken language developed (i.e., between 12 and 16 months) were more likely to achieve age-appropriate spoken language. These results favor cochlear implantation before 24 months of age, especially for children with aided pure-tone average thresholds greater than 65 dB prior to surgery.

The Age at Which Young Deaf Children Receive Cochlear Implants and Their Vocabulary and Speech-Production Growth: Is There an Added Value for Early Implantation?

OBJECTIVE

The age at which a child receives a cochlear implant seems to be one of the more important predictors of his or her speech and language outcomes. However, understanding the association between age at implantation and child outcomes is complex because a child's age, length of device use, and age at implantation are highly related. In this study, we investigate whether there is an added value to earlier implantation or whether advantages observed in child outcomes are primarily attributable to longer device use at any given age.

DESIGN

Using hierarchical linear modeling, we examined latent-growth curves for 100 children who had received their implants when they were between 1 and 10 yr of age, had used oral communication, and had used their devices for between 1 and 12 yr. Children were divided into four groups based on age at implantation: between 1 and 2.5 yr, between 2.6 and 3.5 yr, between 3.6 and 7 yr, and between 7.1 and 10 yr.

RESULTS

Investigation of growth curves and rates of growth over time revealed an additional value for earlier implantation over and above advantages attributable to longer length of use at any given age. Children who had received their implants before the age of 2.5 yr had exhibited early bursts of growth in consonant-production accuracy and vocabulary and also had significantly stronger outcomes compared with age peers who had received their implants at later ages. The magnitude of the early burst diminished systematically with increasing age at implantation and was not observed for children who were older than 7 yr at implantation for consonant-production accuracy or for children who were over 3.5 yr old at implantation for vocabulary. The impact of age at implantation on children's growth curves differed for speech production and vocabulary.

CONCLUSIONS

There seems to be a substantial benefit for both speech and vocabulary outcomes when children receive their implant before the age of 2.5 yr. This benefit may combine a burst of growth after implantation with the impact of increased length of use at any given age. The added advantage (i.e., burst of growth) diminishes systematically with increasing age at implantation.

Song recognition by children and adolescents with cochlear implants

PURPOSE

To assess song recognition and pitch perception in prelingually deaf individuals with cochlear implants (CIs).

METHOD

Fifteen hearing children (5-8 years) and 15 adults heard different versions of familiar popular songs-original (vocal + instrumental), original instrumental, and synthesized melody versions-and identified the song in a closed-set task (Experiment 1). Ten CI users (8-18 years) and age-matched hearing listeners performed the same task (Experiment 2). Ten CI users (8-19 years) and 10 hearing 8-years-olds were required to detect pitch changes in repeating-tone contexts (Experiment 3). Finally, 8 CI users (6-19 years) and 13 hearing 5-year-olds were required to detect subtle pitch changes in a more challenging melodic context (Experiment 4).

RESULTS

CI users performed more poorly than hearing listeners in all conditions. They succeeded in identifying the original and instrumental versions of familiar recorded songs, and they evaluated them favorably, but they could not identify the melody versions. Although CI users could detect a 0.5-semitone change in the simple context, they failed to detect a 1-semitone change in the more difficult melodic context.

CONCLUSION

Current implant processors provide insufficient spectral detail for some aspects of music perception, but they do not preclude young implant users' enjoyment of music.

Development of audiovisual comprehension skills in prelingually deaf children with cochlear implants

OBJECTIVE

The present study investigated the development of audiovisual comprehension skills in prelingually deaf children who received cochlear implants.

DESIGN

We analyzed results obtained with the Common Phrases (Robbins et al., 1995) test of sentence comprehension from 80 prelingually deaf children with cochlear implants who were enrolled in a longitudinal study, from pre-implantation to 5 years after implantation.

RESULTS

The results revealed that prelingually deaf children with cochlear implants performed better under audiovisual (AV) presentation compared with auditory-alone (A-alone) or visual-alone (V-alone) conditions. AV sentence comprehension skills were found to be strongly correlated with several clinical outcome measures of speech perception, speech intelligibility, and language. Finally, pre-implantation V-alone performance on the Common Phrases test was strongly correlated with 3-year postimplantation performance on clinical outcome measures of speech perception, speech intelligibility, and language skills.

CONCLUSIONS

The results suggest that lipreading skills and AV speech perception reflect a common source of variance associated with the development of phonological processing skills that is shared among a wide range of speech and language outcome measures.

Is there a critical period for cochlear implantation in congenitally deaf children? Analyses of hearing and speech perception performance after implantation

A range of basic and applied studies have demonstrated that during the development of the auditory system, early experimental manipulations or clinical interventions are generally more effective than those made later. We present a short review of these studies. We investigated this age-related plasticity in relation to the timing of cochlear implantation in deaf-from-birth children. Cochlear implantation is a standard intervention for providing hearing in children with severe to profound deafness. An important practical question is whether there is a critical period or cutoff age of implantation after which hearing outcomes are significantly reduced. In this article, we present data from prelingually deaf children (mostly congenitally deaf) implanted at ages ranging from 1 to 15 years. Each child was tested with auditory and speech understanding tests before implantation, and at regular intervals up to 8 years postimplantation. We measured the improvement in performance of speech understanding tests in younger implanted children and compared it with the results of those implanted at a later age. We also used a binary partitioning algorithm to divide the data systematically at all ages at implant to determine the optimum split, i.e., to determine the age at implant which best separates performance of early implanted versus later implanted children. We observed distinct age-of-implant cutoffs, and will discuss whether these really represent critical periods during development.

Integrated technology for evaluation of brain function and neural plasticity

The study of neural plasticity has expanded rapidly in the past decades and has shown the remarkable ability of the developing, adult, and aging brain to be shaped by environmental inputs in health and after a lesion. Robust experimental evidence supports the hypothesis that neuronal aggregates adjacent to a lesion in the sensorimotor brain areas can take over progressively the function previously played by the damaged neurons. It definitely is accepted that such a reorganization modifies sensibly the interhemispheric differences in somatotopic organization of the sensorimotor cortices. This reorganization largely subtends clinical recovery of motor performances and sensorimotor integration after a stroke. Brain functional imaging studies show that recovery from hemiplegic strokes is associated with a marked reorganization of the activation patterns of specific brain structures. To regain hand motor control, the recovery process tends over time to bring the bilateral motor network activation toward a more normal intensity/extent, while overrecruiting simultaneously new areas, perhaps to sustain this process. Considerable intersubject variability exists in activation/hyperactivation pattern changes over time. Some patients display late-appearing dorsolateral prefrontal cortex activation, suggesting the development of "executive" strategies to compensate for the lost function. The AH in stroke often undergoes a significant "remodeling" of sensory and motor hand somatotopy outside the "normal" areas, or enlargement of the hand representation. The UH also undergoes reorganization, although to a lesser degree. Although absolute values of the investigated parameters fluctuate across subjects, secondary to individual anatomic variability, variation is minimal with regards to interhemispheric differences, due to the fact that individual morphometric characters are mirrored in the two hemispheres. Excessive interhemispheric asymmetry of the sensorimotor hand areas seems to be the parameter with highest sensitivity in describing brain reorganization after a monohemispheric lesion, and mapping motor and somatosensory cortical areas through focal TMS, fMRI, PET, EEG, and MEG is useful in studying hand representation and interhemispheric asymmetries in normal and pathologic conditions. TMS and MEG allow the detection of sensorimotor areas reshaping, as a result of either neuronal reorganization or recovery of the previously damaged neural network. These techniques have the advantage of high temporal resolution but also have limitations. TMS provides only bidimensional scalp maps, whereas MEG, even if giving three-dimensional mapping of generator sources, does so by means of inverse procedures that rely on the choice of a mathematical model of the head and the sources. These techniques do not test movement execution and sensorimotor integration as used in everyday life. fMRI and PET may provide the ideal means to integrate the findings obtained with the other two techniques. This multitechnology combined approach is at present the best way to test the presence and amount of plasticity phenomena underlying partial or total recovery of several functions, sensorimotor above all. Dynamic patterns of recovery are emerging progressively from the relevant literature. Enhanced recruitment of the affected cortex, be it spared perilesional tissue, as in the case of cortical stroke, or intact but deafferented cortex, as in subcortical strokes, seems to be the rule, a mechanism especially important in early postinsult stages. The transfer over time of preferential activation toward contralesional cortices, as observed in some cases, seems, however, to reflect a less efficient type of plastic reorganization, with some aspects of maladaptive plasticity. Reinforcing the use of the affected side can cause activation to increase again in the affected side with a corresponding enhancement of clinical function. Activation of the UH MI may represent recruitment of direct (uncrossed) corticospinal tracts and relate more to mirror movements, but it more likely reflects activity redistribution within preexisting bilateral, large-scale motor networks. Finally, activation of areas not normally engaged in the dysfunctional tasks, such as the dorsolateral prefrontal cortex or the superior parietal cortex in motor paralysis, might reflect the implication of compensatory cognitive strategies. An integrated approach with technologies able to investigate functional brain imaging is of considerable value in providing information on the excitability, extension, localization, and functional hierarchy of cortical brain areas. Deepening knowledge of the mechanisms regulating the long-term recovery (even if partial), observed for most neurologic sequelae after neural damage, might prompt newer and more efficacious therapeutic and rehabilitative strategies for neurologic diseases.

Neural response telemetry in 12- to 24-month-old children

The minimum age for cochlear implantation has been reduced to 12 months in an effort to provide auditory stimulation to children with hearing loss during early development. Because behavioral measures in such young children are limited, objective measures such as the electrically evoked compound action potential (EAP) from the auditory nerve are needed to facilitate measurement of stimulation level requirements. We assessed EAPs recorded by the Nucleus 24 neural response telemetry (NRT) system in children who underwent implantation between 12 and 24 months of age. We recorded EAPs in 37 such children (mean age at implantation, 18.1+/-3.6 months). The EAPs were of large amplitude, and thresholds fell between behavioral T and C levels. A correction factor applied to EAP thresholds provided useful predictions of T levels. The EAPs can be used to ensure that even very young children receive auditory stimulation with their cochlear implants upon device activation.

The effects of chronic intracochlear electrical stimulation on inferior colliculus spatial representation in adult deafened cats

Previous studies have shown that chronic electrical stimulation through a cochlear implant causes significant alterations in the central auditory system of neonatally deafened cats. The goal of this study was to investigate the effects of chronic stimulation in the mature auditory system. Normal hearing adult animals were deafened by ototoxic drugs and received daily electrical stimulation over periods of 4-6 months. In terminal physiology experiments, response thresholds to pulsatile and sinusoidal signals were recorded within the inferior colliculus (IC). Using previously established methods, spatial tuning curves (STCs; threshold vs. IC depth functions) were constructed, and their widths measured to infer spatial selectivity. The IC spatial representations were similar for pulsatile and sinusoidal stimulation when phase duration was taken into consideration. However, sinusoidal signals consistently elicited much lower thresholds than pulsatile signals, a difference not solely attributable to differences in charge/phase. The average STC width was significantly broader in the adult deafened/stimulated animals than in controls (adult deafened/unstimulated cats), suggesting that electrical stimulation can induce spatial expansion of the IC representation of the chronically stimulated cochlear sector. Further, results in these adult animals were not significantly different from results in neonatally deafened, early stimulated animals, suggesting that a similar degree of plasticity was induced within the auditory midbrains of mature animals.

Mechanisms of postnatal neurobiological development: implications for human development

This review focuses on the postnatal neuroanatomical changes that arise during the first years of human life. Development is characterized by 2 major organizational periods. The first period begins at conception and includes the major histogenetic events such as neurulation, proliferation, migration, and differentiation. It has been proposed that these events may be controlled by genetic and epigenetic events, which give rise to neural structures that are amenable to external influence. The second period is a time of reorganization in the human cortex. These events occur during gestation and continue postnatally, possibly through the 2nd decade of life. This stage is characterized by dendritic and axonal growth, synapse production, neuronal and synaptic pruning, and changes in neurotransmitter sensitivity. Although the initiation of these events is influenced by endogenous signals, further neural maturation is primarily influenced by exogenous signals. To illustrate both the progressive and regressive events during the postnatal period, we use examples from the development of the human cortex.

Management of the hearing impaired infant

With the advent of new testing methods for screening and confirmation of hearing loss in the newborn and setting up neonatal screening programs across the country, significant number of children with hearing loss are being diagnosed very early. Although still considered as one of the best behavioural tests in the competent hands, distraction testing is becoming superseded by more refined and controlled techniques such as visual reinforcement audiometry which is capable of determining a more complete audiometric profile of an infant from about the age of 6 months. A combination of these methods has allowed audiologists to bring down the average age of diagnosis of permanent congenital hearing impairment (PCHI) from over 2 years to well below 12 months. At the same time, increasingly complex and sophisticated hearing instruments are being developed to address traditional problems and also to deliver better amplified speech. Habilitating a neonate with a hearing loss is often challenging and requires a significant amount of resources, expertise and experience. Determining the infant's amplification needs could be difficult, as often the audiometric information is not complete. Further, selecting a suitable hearing instrument for an infant from a vast range is not easy and measuring the outcome after fitting hearing aids, especially in a few months old infant, can be extremely hard. With professionals becoming more confident in implanting younger children and realizing the benefits of early implantation, especially for speech & language development, there is a growing demand for referring infants as early as possible to the implant teams. Providing amplification is only the beginning of the process of habilitation. A multidisciplinary team approach is extremely important in this process and inclusion of the parents in the multidisciplinary team managing the infant often leads to a much improved outcome. There is growing evidence that early diagnosis and habilitation of PCHI leads to better speech and language development and more children being educated in the mainstream setting.

Universal newborn hearing screening coming soon: "hear's" why

Screening the hearing of all newborns, both NICU and well nursery, is rapidly becoming the standard of care. The impetus for universal newborn hearing screening (UNHS) has come from outside the domain of nursing and the newborn nursery. Because nursing will be involved in nearly all aspects of UNHS, nurses need a thorough knowledge base about permanent childhood hearing loss (PCHL) and UNHS. Technology exisits today that can objectively and physiologically screen for this condition at a cost comparable to metabolic screening. PCHL occurs more than twice as often as all the hemoglobinopathies and inborn errors of metabolism combined. Undiagnosed hearing loss often leads to permanent developmental delays. The ultimate goal of early diagnosis and intervention for a congenital hearing loss is to enable the child to develop language and communication skills that correspond to his chronological age and innate cognitive abilities.

Cochlear implant/Deaf World dispute: different bottom elephants

OBJECTIVE

To examine the controversy between the proponents of cochlear implantation in children and the Deaf World opponents with the hope of offering a method for decreasing the acrimony of opposing positions. STUDY DESIGN AND SETTING (METHODS): The opposing arguments will be presented from a review of pertinent literature. The systemic philosophic process of bottom elephant analysis will be elucidated. Contrasting models of power will be described.

RESULTS

The application of the bottom elephant analysis of each group's position plus a paradigm shift in the utilization of power offers possibilities for the implementation of mutually respectful dialogue that does not undermine each group's stature.

CONCLUSION AND SIGNIFICANCE

Philosophic analysis and paradigm shift could lead to improvement in the interaction of cochlear implant proponents and Deaf World opponents.

Timbre-specific enhancement of auditory cortical representations in musicians

Neural imaging studies have shown that the brains of skilled musicians respond differently to musical stimuli than do the brains of non-musicians, particularly for musicians who commenced practice at an early age. Whether brain attributes related to musical skill are attributable to musical practice or are hereditary traits that influence the decision to train musically is a subject of controversy, owing to its pedagogic implications. Here we report that auditory cortical representations measured neuromagnetically for tones of different timbre (violin and trumpet) are enhanced compared to sine tones in violinists and trumpeters, preferentially for timbres of the instrument of training. Timbre specificity is predicted by a principle of use-dependent plasticity and imposes new requirements on nativistic accounts of brain attributes associated with musical skill.