Deprivation-induced cortical reorganization in children with cochlear implants

Developmental deprivation-induced perceptual and cortical processing deficits in awake-behaving animals

Sensory deprivation during development induces lifelong changes to central nervous system function that are associated with perceptual impairments. However, the relationship between neural and behavioral deficits is uncertain due to a lack of simultaneous measurements during task performance. Therefore, we telemetrically recorded from auditory cortex neurons in gerbils reared with developmental conductive hearing loss as they performed an auditory task in which rapid fluctuations in amplitude are detected. These data were compared to a measure of auditory brainstem temporal processing from each animal. We found that developmental HL diminished behavioral performance, but did not alter brainstem temporal processing. However, the simultaneous assessment of neural and behavioral processing revealed that perceptual deficits were associated with a degraded cortical population code that could be explained by greater trial-to-trial response variability. Our findings suggest that the perceptual limitations that attend early hearing loss are best explained by an encoding deficit in auditory cortex.

P1 cortical auditory evoked potential in children with unilateral or bilateral cochlear implants; implication for the timing of second cochlear implantation

OBJECTIVE

To examine maturation of the central auditory pathway, using P1 cortical auditory evoked potential (CAEP), in children who had received unilateral or bilateral cochlear implantation (CI).

STUDY DESIGN

Prospective study.

SETTING

Tertiary referral hospital.

METHODS

Twenty children who had received CI due to congenital, or prelingual, deafness participated in the study. Participants had received the 1st implant at a mean age of 3.4 ± 0.7 years; 16 had also received a 2nd CI for the contralateral ear, at a mean age of 11.1 ± 2.1 years. P1 CAEP was recorded while using the 1st implant and, for those who received contralateral CI, within 2 weeks of switching on the 2nd implant. Relations between P1 latency and duration with the 1st implant, and between age at 1st CI and P1 latency, were investigated. Relations between P1 latency with the 1st and 2nd implants, and between the interstage interval and difference between P1 latencies with the 1st and 2nd implants, were also examined.

RESULTS

P1 CAEP with the 1st implant was present in 16 of the 20 children. Mean P1 latency was shorter in the early CI group compared with the late CI group, but this difference was not statistically significant (p = 0.154). There was a significant negative correlation between the duration with the 1st implant and P1 latency (r = - 0.783, p < 0.001). Among the 16 children with sequential bilateral CI, P1 CAEP with the 2nd implant was present in 10. There was a significant negative correlation between the duration with the 1st implant before receiving the 2nd implant and P1 latency with the 2nd implant (r = - 0.710, p = 0.021); there was also a significant positive correlation between P1 latency with the 1st and 2nd implants (r = 0.722, p = 0.018). There was not a significant correlation between interstage interval and the difference between the two P1 latencies (r = - 0.430, p = 0.248).

CONCLUSION

Longer cochlear implant use is associated with shorter P1 latency. Unilateral hearing with the 1st implant may positively affect P1 latency with the 2nd CI ear. These findings imply that increased auditory experience may influence central auditory pathway maturation and that the degree of central auditory pathway maturation before the 2nd CI, rather than the timing when the surgery is received, may influence 2nd CI outcome in children with sequential bilateral cochlear implants.

The Role of Auditory Evoked Potentials in the Context of Cochlear Implant Provision

: Auditory evoked potentials (AEP) are highly demanded during the whole process of equipping patients with cochlear implants (CI). They play an essential role in preoperative diagnostics, intraoperative testing, and postoperative monitoring of auditory performance and success. The versatility of AEP's is essentially enhanced by their property to be evokable by acoustic as well as electric stimuli. Thus, the electric responses of the auditory system following acoustic stimulation and recorded by the conventional surface technique as well as by transtympanic derivation from the promontory (Electrocochleography [ECochG]) are used for the quantitative determination of hearing loss and, additionally, electrically evoked compound actions potentials (ECAP) can be recorded with the intracochlear electrodes of the implant just adjacent to the stimulation electrode to check the functional integrity of the device and its coupling to the auditory system. The profile of ECAP thresholds is used as basis for speech processor fitting, the spread of excitation (SOE) allows the identification of electrode mislocations such as array foldover, and recovery functions may serve to optimize stimulus pulse rate. These techniques as well as those relying on scalp surface activity originating in the brainstem or the auditory cortex accompany the CI recipient during its whole life span and they offer valuable insights into functioning and possible adverse effects of the CI for clinical and scientific purposes.

Somatosensory Cross-Modal Reorganization in Adults With Age-Related, Early-Stage Hearing Loss

Under conditions of profound sensory deprivation, the brain has the propensity to reorganize. For example, intact sensory modalities often recruit deficient modalities' cortices for neural processing. This process is known as cross-modal reorganization and has been shown in congenitally and profoundly deaf patients. However, much less is known about cross-modal cortical reorganization in persons with less severe cases of age-related hearing loss (ARHL), even though such cases are far more common. Thus, we investigated cross-modal reorganization between the auditory and somatosensory modalities in older adults with normal hearing (NH) and mild-moderate ARHL in response to vibrotactile stimulation using high density electroencephalography (EEG). Results showed activation of the somatosensory cortices in adults with NH as well as those with hearing loss (HL). However, adults with mild-moderate ARHL also showed robust activation of auditory cortical regions in response to somatosensory stimulation. Neurophysiologic data exhibited significant correlations with speech perception in noise outcomes suggesting that the degree of cross-modal reorganization may be associated with functional performance. Our study presents the first evidence of somatosensory cross-modal reorganization of the auditory cortex in adults with early-stage, mild-moderate ARHL. Our findings suggest that even mild levels of ARHL associated with communication difficulty result in fundamental cortical changes.

No evidence for enhanced processing of speech that is low-pass filtered near the edge frequency of cochlear dead regions in children

OBJECTIVES

Cochlear dead regions (DRs) are regions in the cochlea where the inner hair cells and/or neurons are not functioning. Adults with extensive high-frequency DRs have enhanced abilities in processing sounds with frequencies just below the edge frequency, f_edge, of the DR. It was assessed whether the same is true for children.

DESIGN

Performance was compared for children aged 8 to 13 years with: DRs (group DR), hearing impairment but without DRs (group NODR), and normal hearing (group NH). Seven ears in each group were tested. Each ear in the DR group was matched in age and low-frequency hearing with an ear in the NODR group, and in age with an ear in the NH group, giving seven "triplets". Within each triplet, the percent correct identification of vowel-consonant-vowel stimuli was measured using stimuli that were low-pass filtered at f_edge and 0.67f_edge, based on the ear with a DR. For the hearing-impaired ears, stimuli were given frequency-selective amplification as prescribed by DSL 4.1.

RESULTS

No significant differences in performance were found between groups for either low-pass cut-off frequency.

CONCLUSION

Unlike adults, the children with DRs did not show enhanced discrimination of speech stimuli with frequencies below f_edge.

Monitoring auditory cortical plasticity in hearing aid users with long latency auditory evoked potentials: a longitudinal study

OBJECTIVE

The objective of this study was to compare long-latency auditory evoked potentials before and after hearing aid fittings in children with sensorineural hearing loss compared with age-matched children with normal hearing.

METHODS

Thirty-two subjects of both genders aged 7 to 12 years participated in this study and were divided into two groups as follows: 14 children with normal hearing were assigned to the control group (mean age 9 years and 8 months), and 18 children with mild to moderate symmetrical bilateral sensorineural hearing loss were assigned to the study group (mean age 9 years and 2 months). The children underwent tympanometry, pure tone and speech audiometry and long-latency auditory evoked potential testing with speech and tone burst stimuli. The groups were assessed at three time points.

RESULTS

The study group had a lower percentage of positive responses, lower P1-N1 and P2-N2 amplitudes (speech and tone burst), and increased latencies for the P1 and P300 components following the tone burst stimuli. They also showed improvements in long-latency auditory evoked potentials (with regard to both the amplitude and presence of responses) after hearing aid use.

CONCLUSIONS

Alterations in the central auditory pathways can be identified using P1-N1 and P2-N2 amplitude components, and the presence of these components increases after a short period of auditory stimulation (hearing aid use). These findings emphasize the importance of using these amplitude components to monitor the neuroplasticity of the central auditory nervous system in hearing aid users.

Relations Between Self-reported Executive Functioning and Speech Perception Skills in Adult Cochlear Implant Users

HYPOTHESIS

As a result of their hearing loss, adults with cochlear implants (CIs) would self-report poorer executive functioning (EF) skills than normal-hearing (NH) peers, and these EF skills would be associated with performance on speech recognition tasks.

BACKGROUND

EF refers to a group of high order neurocognitive skills responsible for behavioral and emotional regulation during goal-directed activity, and EF has been found to be poorer in children with CIs than their NH age-matched peers. Moreover, there is increasing evidence that neurocognitive skills, including some EF skills, contribute to the ability to recognize speech through a CI.

METHODS

Thirty postlingually deafened adults with CIs and 42 age-matched NH adults were enrolled. Participants and their spouses or significant others (informants) completed well-validated self-reports or informant-reports of EF, the Behavior Rating Inventory of Executive Function - Adult (BRIEF-A). CI users' speech recognition skills were assessed in quiet using several measures of sentence recognition. NH peers were tested for recognition of noise-vocoded versions of the same speech stimuli.

RESULTS

CI users self-reported difficulty on EF tasks of shifting and task monitoring. In CI users, measures of speech recognition correlated with several self-reported EF skills.

CONCLUSION

The present findings provide further evidence that neurocognitive factors, including specific EF skills, may decline in association with hearing loss, and that some of these EF skills contribute to speech processing under degraded listening conditions.

Neural preservation underlies speech improvement from auditory deprivation in young cochlear implant recipients

Although cochlear implantation enables some children to attain age-appropriate speech and language development, communicative delays persist in others, and outcomes are quite variable and difficult to predict, even for children implanted early in life. To understand the neurobiological basis of this variability, we used presurgical neural morphological data obtained from MRI of individual pediatric cochlear implant (CI) candidates implanted younger than 3.5 years to predict variability of their speech-perception improvement after surgery. We first compared neuroanatomical density and spatial pattern similarity of CI candidates to that of age-matched children with normal hearing, which allowed us to detail neuroanatomical networks that were either affected or unaffected by auditory deprivation. This information enables us to build machine-learning models to predict the individual children's speech development following CI. We found that regions of the brain that were unaffected by auditory deprivation, in particular the auditory association and cognitive brain regions, produced the highest accuracy, specificity, and sensitivity in patient classification and the most precise prediction results. These findings suggest that brain areas unaffected by auditory deprivation are critical to developing closer to typical speech outcomes. Moreover, the findings suggest that determination of the type of neural reorganization caused by auditory deprivation before implantation is valuable for predicting post-CI language outcomes for young children.

Current audiological diagnostics

Today's audiological functional diagnostics is based on a variety of hearing tests, whose large number takes account of the variety of malfunctions of a complex sensory organ system and the necessity to examine it in a differentiated manner and at any age of life. The objective is to identify nature and origin of the hearing loss and to quantify its extent as far as necessary to dispose of the information needed to initiate the adequate medical (conservative or operational) treatment or the provision with technical hearing aids or prostheses. Moreover, audiometry provides the basis for the assessment of impairment and handicap as well as for the calculation of the degree of disability. In the present overview, the current state of the method inventory available for practical use is described, starting from basic diagnostics over to complex special techniques. The presentation is systematically grouped in subjective procedures, based on psychoacoustic exploration, and objective methods, based on physical measurements: preliminary hearing tests, pure tone threshold, suprathreshold processing of sound intensity, directional hearing, speech understanding in quiet and in noise, dichotic hearing, tympanogram, acoustic reflex, otoacoustic emissions and auditory evoked potentials. Apart from a few still existing gaps, this method inventory covers the whole spectrum of all clinically relevant functional deficits of the auditory system.

Excitation characteristic of a bipolar stimulus for broadband stimulation in measurements of electrically evoked auditory potentials

OBJECTIVE

The aim of this study was to determine the optimum electrical stimulation mode for the measurement of electrically evoked potentials. To quantify the broadband excitation electrically evoked compound action potentials were recorded in cochlear implant recipients. The full width half maximum was determined for spread of excitation along the electrode array.

DESIGN

Prospective clinical study.

STUDY SAMPLE

The study sample consisted of 20 adult cochlear implant users.

RESULTS

The applied alternating, intracochlear stimulation mode leads to neural excitation along approximately 80% of the length of the electrode array. The median of the full width at half maximum values covered the range of 18 electrodes on the implant array.

CONCLUSION

The bipolar, alternating, and intracochlear stimulation mode would provide a sufficient, broadband excitation of the spiral ganglion to measure electrically evoked auditory potentials.

Brief Stimulus Exposure Fully Remediates Temporal Processing Deficits Induced by Early Hearing Loss

In childhood, partial hearing loss can produce prolonged deficits in speech perception and temporal processing. However, early therapeutic interventions targeting temporal processing may improve later speech-related outcomes. Gap detection is a measure of auditory temporal resolution that relies on the auditory cortex (ACx), and early auditory deprivation alters intrinsic and synaptic properties in the ACx. Thus, early deprivation should induce deficits in gap detection, which should be reflected in ACx gap sensitivity. We tested whether earplugging-induced, early transient auditory deprivation in male and female Mongolian gerbils caused correlated deficits in behavioral and cortical gap detection, and whether these could be rescued by a novel therapeutic approach: brief exposure to gaps in background noise. Two weeks after earplug removal, animals that had been earplugged from hearing onset throughout auditory critical periods displayed impaired behavioral gap detection thresholds (GDTs), but this deficit was fully reversed by three 1 h sessions of exposure to gaps in noise. In parallel, after earplugging, cortical GDTs increased because fewer cells were sensitive to short gaps, and gap exposure normalized this pattern. Furthermore, in deprived animals, both first-spike latency and first-spike latency jitter increased, while spontaneous and evoked firing rates decreased, suggesting that deprivation causes a wider range of perceptual problems than measured here. These cortical changes all returned to control levels after gap exposure. Thus, brief stimulus exposure, perhaps in a salient context such as the unfamiliar placement into a testing apparatus, rescued impaired gap detection and may have potential as a remediation tool for general auditory processing deficits.SIGNIFICANCE STATEMENT Hearing loss in early childhood leads to impairments in auditory perception and language processing that can last well beyond the restoration of hearing sensitivity. Perceptual deficits can be improved by training, or by acoustic enrichment in animal models, but both approaches involve extended time and effort. Here, we used a novel remediation technique, brief periods of auditory stimulus exposure, to fully remediate cortical and perceptual deficits in gap detection induced by early transient hearing loss. This technique also improved multiple cortical response properties. Rescue by this efficient exposure regime may have potential as a therapeutic tool to remediate general auditory processing deficits in children with perceptual challenges arising from early hearing loss.

Cortical maturation in children with cochlear implants: Correlation between electrophysiological and behavioral measurement

Central auditory pathway maturation in children depends on auditory sensory stimulation. The objective of the present study was to monitor the cortical maturation of children with cochlear implants using electrophysiological and auditory skills measurements. The study was longitudinal and consisted of 30 subjects, 15 (8 girls and 7 boys) of whom had a cochlear implant, with a mean age at activation time of 36.4 months (minimum, 17 months; maximum, 66 months), and 15 of whom were normal-hearing children who were matched based on gender and chronological age. The auditory and speech skills of the children with cochlear implants were evaluated using GASP, IT-MAIS and MUSS measures. Both groups underwent electrophysiological evaluation using long-latency auditory evoked potentials. Each child was evaluated at three and nine months after cochlear implant activation, with the same time interval adopted for the hearing children. The results showed improvements in auditory and speech skills as measured by IT-MAIS and MUSS. Similarly, the long-latency auditory evoked potential evaluation revealed a decrease in P1 component latency; however, the latency remained significantly longer than that of the hearing children, even after nine months of cochlear implant use. It was observed that a shorter P1 latency corresponded to more evident development of auditory skills. Regarding auditory behavior, it was observed that children who could master the auditory skill of discrimination showed better results in other evaluations, both behavioral and electrophysiological, than those who had mastered only the speech-detection skill. Therefore, cochlear implant auditory stimulation facilitated auditory pathway maturation, which decreased the latency of the P1 component and advanced the development of auditory and speech skills. The analysis of the long-latency auditory evoked potentials revealed that the P1 component was an important biomarker of auditory development during the rehabilitation process.

Altered Brain Functional Activity in Infants with Congenital Bilateral Severe Sensorineural Hearing Loss: A Resting-State Functional MRI Study under Sedation

Early hearing deprivation could affect the development of auditory, language, and vision ability. Insufficient or no stimulation of the auditory cortex during the sensitive periods of plasticity could affect the function of hearing, language, and vision development. Twenty-three infants with congenital severe sensorineural hearing loss (CSSHL) and 17 age and sex matched normal hearing subjects were recruited. The amplitude of low frequency fluctuations (ALFF) and regional homogeneity (ReHo) of the auditory, language, and vision related brain areas were compared between deaf infants and normal subjects. Compared with normal hearing subjects, decreased ALFF and ReHo were observed in auditory and language-related cortex. Increased ALFF and ReHo were observed in vision related cortex, which suggest that hearing and language function were impaired and vision function was enhanced due to the loss of hearing. ALFF of left Brodmann area 45 (BA45) was negatively correlated with deaf duration in infants with CSSHL. ALFF of right BA39 was positively correlated with deaf duration in infants with CSSHL. In conclusion, ALFF and ReHo can reflect the abnormal brain function in language, auditory, and visual information processing in infants with CSSHL. This demonstrates that the development of auditory, language, and vision processing function has been affected by congenital severe sensorineural hearing loss before 4 years of age.

Cross-modal plasticity in developmental and age-related hearing loss: Clinical implications

This review explores cross-modal cortical plasticity as a result of auditory deprivation in populations with hearing loss across the age spectrum, from development to adulthood. Cross-modal plasticity refers to the phenomenon when deprivation in one sensory modality (e.g. the auditory modality as in deafness or hearing loss) results in the recruitment of cortical resources of the deprived modality by intact sensory modalities (e.g. visual or somatosensory systems). We discuss recruitment of auditory cortical resources for visual and somatosensory processing in deafness and in lesser degrees of hearing loss. We describe developmental cross-modal re-organization in the context of congenital or pre-lingual deafness in childhood and in the context of adult-onset, age-related hearing loss, with a focus on how cross-modal plasticity relates to clinical outcomes. We provide both single-subject and group-level evidence of cross-modal re-organization by the visual and somatosensory systems in bilateral, congenital deafness, single-sided deafness, adults with early-stage, mild-moderate hearing loss, and individual adult and pediatric patients exhibit excellent and average speech perception with hearing aids and cochlear implants. We discuss a framework in which changes in cortical resource allocation secondary to hearing loss results in decreased intra-modal plasticity in auditory cortex, accompanied by increased cross-modal recruitment of auditory cortices by the other sensory systems, and simultaneous compensatory activation of frontal cortices. The frontal cortices, as we will discuss, play an important role in mediating cognitive compensation in hearing loss. Given the wide range of variability in behavioral performance following audiological intervention, changes in cortical plasticity may play a valuable role in the prediction of clinical outcomes following intervention. Further, the development of new technologies and rehabilitation strategies that incorporate brain-based biomarkers may help better serve hearing impaired populations across the lifespan.

Effect of hearing aids use on speech stimulus decoding through speech-evoked ABR

INTRODUCTION

The electrophysiological responses obtained with the complex auditory brainstem response (cABR) provide objective measures of subcortical processing of speech and other complex stimuli. The cABR has also been used to verify the plasticity in the auditory pathway in the subcortical regions.

OBJECTIVE

To compare the results of cABR obtained in children using hearing aids before and after 9 months of adaptation, as well as to compare the results of these children with those obtained in children with normal hearing.

METHODS

Fourteen children with normal hearing (Control Group - CG) and 18 children with mild to moderate bilateral sensorineural hearing loss (Study Group - SG), aged 7-12 years, were evaluated. The children were submitted to pure tone and vocal audiometry, acoustic immittance measurements and ABR with speech stimulus, being submitted to the evaluations at three different moments: initial evaluation (M0), 3 months after the initial evaluation (M3) and 9 months after the evaluation (M9); at M0, the children assessed in the study group did not use hearing aids yet.

RESULTS

When comparing the CG and the SG, it was observed that the SG had a lower median for the V-A amplitude at M0 and M3, lower median for the latency of the component V at M9 and a higher median for the latency of component O at M3 and M9. A reduction in the latency of component A at M9 was observed in the SG.

CONCLUSION

Children with mild to moderate hearing loss showed speech stimulus processing deficits and the main impairment is related to the decoding of the transient portion of this stimulus spectrum. It was demonstrated that the use of hearing aids promoted neuronal plasticity of the Central Auditory Nervous System after an extended time of sensory stimulation.

Template Subtraction to Remove CI Stimulation Artifacts in Auditory Steady-State Responses in CI Subjects

Cochlear implant (CI) stimulation artifacts are currently removed from electrically evoked steady-state response (EASSR) measurements based on a linear interpolation (LI) over the artifact-contaminated signal parts. LI is only successful if CI stimulation artifacts are shorter than the interpulse interval, i.e., for contralateral channels and stimulation pulse rates up to 500 pulses per second (pps). The objective of this paper is to develop and evaluate a template subtraction (TS) method to remove continuous CI stimulation artifacts in order to accurately measure EASSRs. The template construction (TC) is based on an EEG recording containing CI stimulation artifacts but no synchronous neural response. The constructed templates are subtracted from the recording of interest. Response amplitudes and latencies are compared for the TS and LI method, and for different TC durations. The response amplitudes and latencies in contralateral channels are the same after TS and LI, as expected. In ipsilateral channels, response amplitudes and latencies are within the expected range only after TS. The TC duration can be reduced from 5 min to 1 min without a significant effect on response latency. TS with a TC duration of only 1 min allows to remove all CI stimulation artifacts in individual contra- and ipsilateral EEG recording channels.

Cortical Auditory Evoked Potentials Reveal Changes in Audibility with Nonlinear Frequency Compression in Hearing Aids for Children: Clinical Implications

Hearing loss in children is detected soon after birth via newborn hearing screening. Procedures for early hearing assessment and hearing aid fitting are well established, but methods for evaluating the effectiveness of amplification for young children are limited. One promising approach to validating hearing aid fittings is to measure cortical auditory evoked potentials (CAEPs). This article provides first a brief overview of reports on the use of CAEPs for evaluation of hearing aids. Second, a study that measured CAEPs to evaluate nonlinear frequency compression (NLFC) in hearing aids for 27 children (between 6.1 and 16.8 years old) who have mild to severe hearing loss is reported. There was no significant difference in aided sensation level or the detection of CAEPs for /g/ between NLFC on and off conditions. The activation of NLFC was associated with a significant increase in aided sensation levels for /t/ and /s/. It also was associated with an increase in detection of CAEPs for /t/ and /s/. The findings support the use of CAEPs for checking audibility provided by hearing aids. Based on the current data, a clinical protocol for using CAEPs to validate audibility with amplification is presented.

Maturation of the Central Auditory Nervous System in Children with Auditory Processing Disorder

Neurodevelopmental delay has been proposed as the underlying cause of the majority of cases of auditory processing disorder (APD). The current study employs the cortical auditory evoked potential (CAEP) to assess if maturational differences of the central auditory nervous system (CANS) can be identified between children who do and do not meet the diagnostic criterion for APD. The P1-N1 complex of the CAEP has previously been used for tracking development of the CANS in children with hearing impairment. Twenty-seven children (7 to 12 years old) who failed an APD behavioral test battery were age-matched (within 3 months) to children who had passed the same battery. CAEP responses to 500-Hz tone burst stimuli were recorded and analyzed for latency and amplitude measures. The P1-N1 complex of the CAEP, which has previously been used for tracking development of the CANS in children with hearing impairment, showed significant group differences. The children diagnosed with APD showed significantly increased latency (∼10 milliseconds) and significantly reduced amplitude (∼10 μV) of the early components of the CAEP compared with children with normal auditory processing. No significant differences were seen in the later P2 wave. The normal developmental course is for a decrease in latency and increase in amplitude as a function of age. The results of this study are, therefore, consistent with an immaturity of the CANS as an underlying cause of APD in children.

Results of Postoperative, CT-based, Electrode Deactivation on Hearing in Prelingually Deafened Adult Cochlear Implant Recipients

OBJECTIVE

To test the use of a novel, image-guided cochlear implant (CI) programming (IGCIP) technique on prelingually deafened, adult CI recipients.

STUDY DESIGN

Prospective unblinded study.

SETTING

Tertiary referral center.

PATIENTS

Twenty-six prelingually deafened adult CI recipients with 29 CIs (3 bilateral).

INTERVENTION(S)

Temporal-bone CT scans were used as input to a series of semiautomated computer algorithms which estimate the location of electrodes in reference to the modiolus. This information was used to selectively deactivate suboptimally located electrodes, i.e., those for which the distance from the electrode to the modiolus was further than a neighboring electrode to the same site. Patients used the new IGCIP program exclusively for 3-5 weeks.

MAIN OUTCOME MEASURE(S)

Minimum Speech Test Battery (MSTB), quality of life (QOL), and spectral modulation detection (SMD).

RESULTS

On average one-third of electrodes were deactivated. At the group level, no significant differences were noted for MSTB measures nor for QOL estimates. Average SMD significantly improved after IGCIP reprogramming, which is consistent with improved spatial selectivity. Using 95% confidence interval data for CNC, AzBio, and BKB-SIN at the individual level, 76 to 90% of subjects demonstrated equivocal or significant improvement. Ultimately 21 of 29 (72.41%) elected to keep the IGCIP map because of perceived benefit often substantiated by improvement on either MSTB, QOL, and/or SMD.

CONCLUSIONS

Knowledge of the geometric relationship between CI electrodes and the modiolus appears to be useful in adjusting CI maps in prelingually deafened adults. Long-term improvements may be observed resulting from improved spatial selectivity and spectral resolution.

Topographical functional connectivity patterns exist in the congenitally, prelingually deaf

Congenital deafness causes large changes in the auditory cortex structure and function, such that without early childhood cochlear-implant, profoundly deaf children do not develop intact, high-level, auditory functions. But how is auditory cortex organization affected by congenital, prelingual, and long standing deafness? Does the large-scale topographical organization of the auditory cortex develop in people deaf from birth? And is it retained despite cross-modal plasticity? We identified, using fMRI, topographic tonotopy-based functional connectivity (FC) structure in humans in the core auditory cortex, its extending tonotopic gradients in the belt and even beyond that. These regions show similar FC structure in the congenitally deaf throughout the auditory cortex, including in the language areas. The topographic FC pattern can be identified reliably in the vast majority of the deaf, at the single subject level, despite the absence of hearing-aid use and poor oral language skills. These findings suggest that large-scale tonotopic-based FC does not require sensory experience to develop, and is retained despite life-long auditory deprivation and cross-modal plasticity. Furthermore, as the topographic FC is retained to varying degrees among the deaf subjects, it may serve to predict the potential for auditory rehabilitation using cochlear implants in individual subjects.

[Pathophysiology of hearing loss : Classification and treatment options]

From the therapeutic perspective, the etiology and pathophysiology of hearing loss can be classified based on the extent of the primary cause. Hearing loss can have very different consequences for cell preservation in the organ of Corti and the spiral ganglion. These not only have implications for prosthetic therapy outcome, but may also influence the potential for future causal molecular therapies. Etiologies leading to deficits that are limited to one or a few molecules without having an effect on cell survival have the greatest potential for future causal therapy using molecular and cellular approaches. Preliminary success for molecular therapy was recently reported in animal experiments. Unfortunately, the incidence of these types of hearing loss is very low and in the future the therapy of hearing loss will therefore also require several different approaches. In addition to peripheral pathophysiology, hearing loss has consequences on the functioning of the brain, which can vary greatly due to individual adaptation to the situation without hearing. The authors therefore argue for individualization of the diagnostics and therapy that focus not only the symptom of hearing loss, but also the individual pathophysiology and consequences. Only with individualized therapy can the success of treating hearing disorders be significantly improved.

A Systematic Review to Define the Speech and Language Benefit of Early (<12 Months) Pediatric Cochlear Implantation

Objective: This review aimed to evaluate the additional benefit of pediatric cochlear implantation before 12 months of age considering improved speech and language development and auditory performance. Materials and Methods: We conducted a search in PubMed, EMBASE and CINAHL databases and included studies comparing groups with different ages at implantation and assessing speech perception and speech production, receptive language and/or auditory performance. We included studies with a high directness of evidence (DoE). Results: We retrieved 3,360 articles. Ten studies with a high DoE were included. Four articles with medium DoE were discussed in addition. Six studies compared infants implanted before 12 months with children implanted between 12 and 24 months. Follow-up ranged from 6 months to 9 years. Cochlear implantation before the age of 2 years is beneficial according to one speech perception score (phonetically balanced kindergarten combined with consonant-nucleus-consonant) but not on Glendonald auditory screening procedure scores. Implantation before 12 months resulted in better speech production (diagnostic evaluation of articulation and phonology and infant-toddler meaningful auditory integration scale), auditory performance (Categories of Auditory Performance-II score) and receptive language scores (2 out of 5; Preschool Language Scale combined with oral and written language skills and Peabody Picture Vocabulary Test). Conclusions: The current best evidence lacks level 1 evidence studies and consists mainly of cohort studies with a moderate to high risk of bias. Included studies showed consistent evidence that cochlear implantation should be performed early in life, but evidence is inconsistent on all speech and language outcome measures regarding the additional benefit of implantation before the age of 12 months. Long-term follow-up studies are necessary to provide insight on additional benefits of early pediatric cochlear implantation.

The Perception of Stress Pattern in Young Cochlear Implanted Children: An EEG Study

Children with sensorineural hearing loss may (re)gain hearing with a cochlear implant—a device that transforms sounds into electric pulses and bypasses the dysfunctioning inner ear by stimulating the auditory nerve directly with an electrode array. Many implanted children master the acquisition of spoken language successfully, yet we still have little knowledge of the actual input they receive with the implant and specifically which language sensitive cues they hear. This would be important however, both for understanding the flexibility of the auditory system when presented with stimuli after a (life-) long phase of deprivation and for planning therapeutic intervention. In rhythmic languages the general stress pattern conveys important information about word boundaries. Infant language acquisition relies on such cues and can be severely hampered when this information is missing, as seen for dyslexic children and children with specific language impairment. Here we ask whether children with a cochlear implant perceive differences in stress patterns during their language acquisition phase and if they do, whether it is present directly following implant stimulation or if and how much time is needed for the auditory system to adapt to the new sensory modality. We performed a longitudinal ERP study, testing in bimonthly intervals the stress pattern perception of 17 young hearing impaired children (age range: 9–50 months; mean: 22 months) during their first 6 months of implant use. An additional session before the implantation served as control baseline. During a session they passively listened to an oddball paradigm featuring the disyllable “baba,” which was stressed either on the first or second syllable (trochaic vs. iambic stress pattern). A group of age-matched normal hearing children participated as controls. Our results show, that within the first 6 months of implant use the implanted children develop a negative mismatch response for iambic but not for trochaic deviants, thus showing the same result as the normal hearing controls. Even congenitally deaf children show the same developing pattern. We therefore conclude (a) that young implanted children have early access to stress pattern information and (b) that they develop ERP responses similar to those of normal hearing children.

Cross-Modal Re-Organization in Clinical Populations with Hearing Loss

We review evidence for cross-modal cortical re-organization in clinical populations with hearing loss. Cross-modal plasticity refers to the ability for an intact sensory modality (e.g., vision or somatosensation) to recruit cortical brain regions from a deprived sensory modality (e.g., audition) to carry out sensory processing. We describe evidence for cross-modal changes in hearing loss across the age-spectrum and across different degrees of hearing impairment, including children with profound, bilateral deafness with cochlear implants, single-sided deafness before and after cochlear implantation, and adults with early-stage, mild-moderate, age-related hearing loss. Understanding cross-modal plasticity in the context of auditory deprivation, and the potential for reversal of these changes following intervention, may be vital in directing intervention and rehabilitation options for clinical populations with hearing loss.

The effect of early auditory experience on the spatial listening skills of children with bilateral cochlear implants

OBJECTIVES

Both electrophysiological and behavioural studies suggest that auditory deprivation during the first months and years of life can impair listening skills. Electrophysiological studies indicate that 3½ years may be a critical age for the development of symmetrical cortical responses in children using bilateral cochlear implants. This study aimed to examine the effect of auditory experience during the first 3½ years of life on the behavioural spatial listening abilities of children using bilateral cochlear implants, with reference to normally hearing children. Data collected during research and routine clinical testing were pooled to compare the listening skills of children with bilateral cochlear implants and different periods of auditory deprivation.

METHODS

Children aged 4-17 years with bilateral cochlear implants were classified into three groups. Children born profoundly deaf were in the congenital early bilateral group (received bilateral cochlear implants aged ≤3½ years, n=28) or congenital late bilateral group (received first implant aged ≤3½ years and second aged >3½ years, n=38). Children with some bilateral acoustic hearing until the age of 3½ years, who subsequently became profoundly deaf and received bilateral cochlear implants, were in the acquired/progressive group (n=16). There were 32 children in the normally hearing group. Children completed tests of sound-source localization and spatial release from masking (a measure of the ability to use both ears to understand speech in noise).

RESULTS

The acquired/progressive group localized more accurately than both groups of congenitally deaf children (p<0.05). All three groups of children with cochlear implants showed similar spatial release from masking. The normally hearing group localized more accurately than all groups with bilateral cochlear implants and displayed more spatial release from masking than the congenitally deaf groups on average (p<0.05).

CONCLUSION

Children with bilateral cochlear implants and early experience of acoustic hearing showed more accurate localization skills, on average, than children born profoundly deaf.

Audiomotor Integration in Minimally Conscious State: Proof of Concept!

Patients suffering from chronic disorders of consciousness (DOC) are characterized by profound unawareness and an impairment of large-scale cortical and subcortical connectivity. In this study, we applied an electrophysiological approach aimed at identifying the residual audiomotor connectivity patterns that are thought to be linked to awareness. We measured some markers of audiomotor integration (AMI) in 20 patients affected by DOC, before and after the application of a repetitive transcranial magnetic stimulation protocol (rTMS) delivered over the left primary motor area (M1), paired to a transauricular alternating current stimulation. Our protocol induced potentiating of the electrophysiological markers of AMI and M1 excitability, paired to a clinical improvement, in all of the patients with minimally conscious state (MCS) but in none of those suffering from unresponsive wakefulness syndrome (UWS). Our protocol could be a promising approach to potentiate the functional connectivity within large-scale audiomotor networks, thus allowing clinicians to differentiate patients affected by MCS from UWS, besides the clinical assessment.

Development of Sound Localization Strategies in Children with Bilateral Cochlear Implants

Localizing sounds in our environment is one of the fundamental perceptual abilities that enable humans to communicate, and to remain safe. Because the acoustic cues necessary for computing source locations consist of differences between the two ears in signal intensity and arrival time, sound localization is fairly poor when a single ear is available. In adults who become deaf and are fitted with cochlear implants (CIs) sound localization is known to improve when bilateral CIs (BiCIs) are used compared to when a single CI is used. The aim of the present study was to investigate the emergence of spatial hearing sensitivity in children who use BiCIs, with a particular focus on the development of behavioral localization patterns when stimuli are presented in free-field horizontal acoustic space. A new analysis was implemented to quantify patterns observed in children for mapping acoustic space to a spatially relevant perceptual representation. Children with normal hearing were found to distribute their responses in a manner that demonstrated high spatial sensitivity. In contrast, children with BiCIs tended to classify sound source locations to the left and right; with increased bilateral hearing experience, they developed a perceptual map of space that was better aligned with the acoustic space. The results indicate experience-dependent refinement of spatial hearing skills in children with CIs. Localization strategies appear to undergo transitions from sound source categorization strategies to more fine-grained location identification strategies. This may provide evidence for neural plasticity, with implications for training of spatial hearing ability in CI users.

Cross-modal reorganization in cochlear implant users: Auditory cortex contributes to visual face processing

There is converging evidence that the auditory cortex takes over visual functions during a period of auditory deprivation. A residual pattern of cross-modal take-over may prevent the auditory cortex to adapt to restored sensory input as delivered by a cochlear implant (CI) and limit speech intelligibility with a CI. The aim of the present study was to investigate whether visual face processing in CI users activates auditory cortex and whether this has adaptive or maladaptive consequences. High-density electroencephalogram data were recorded from CI users (n=21) and age-matched normal hearing controls (n=21) performing a face versus house discrimination task. Lip reading and face recognition abilities were measured as well as speech intelligibility. Evaluation of event-related potential (ERP) topographies revealed significant group differences over occipito-temporal scalp regions. Distributed source analysis identified significantly higher activation in the right auditory cortex for CI users compared to NH controls, confirming visual take-over. Lip reading skills were significantly enhanced in the CI group and appeared to be particularly better after a longer duration of deafness, while face recognition was not significantly different between groups. However, auditory cortex activation in CI users was positively related to face recognition abilities. Our results confirm a cross-modal reorganization for ecologically valid visual stimuli in CI users. Furthermore, they suggest that residual takeover, which can persist even after adaptation to a CI is not necessarily maladaptive.

Cortical development and neuroplasticity in Auditory Neuropathy Spectrum Disorder

Cortical development is dependent to a large extent on stimulus-driven input. Auditory Neuropathy Spectrum Disorder (ANSD) is a recently described form of hearing impairment where neural dys-synchrony is the predominant characteristic. Children with ANSD provide a unique platform to examine the effects of asynchronous and degraded afferent stimulation on cortical auditory neuroplasticity and behavioral processing of sound. In this review, we describe patterns of auditory cortical maturation in children with ANSD. The disruption of cortical maturation that leads to these various patterns includes high levels of intra-individual cortical variability and deficits in cortical phase synchronization of oscillatory neural responses. These neurodevelopmental changes, which are constrained by sensitive periods for central auditory maturation, are correlated with behavioral outcomes for children with ANSD. Overall, we hypothesize that patterns of cortical development in children with ANSD appear to be markers of the severity of the underlying neural dys-synchrony, providing prognostic indicators of success of clinical intervention with amplification and/or electrical stimulation. This article is part of a Special Issue entitled <Auditory Synaptology>.

P300 in individuals with sensorineural hearing loss

Introduction

Behavioral and electrophysiological auditory evaluations contribute to the understanding of the auditory system and of the process of intervention.

Objective

To study P300 in subjects with severe or profound sensorineural hearing loss.

Methods

This was a descriptive cross-sectional prospective study. It included 29 individuals of both genders with severe or profound sensorineural hearing loss without other type of disorders, aged 11 to 42 years; all were assessed by behavioral audiological evaluation and auditory evoked potentials.

Results

A recording of the P3 wave was obtained in 17 individuals, with a mean latency of 326.97 ms and mean amplitude of 3.76 V. There were significant differences in latency in relation to age and in amplitude according to degree of hearing loss. There was a statistically significant association of the P300 results with the degrees of hearing loss (p = 0.04), with the predominant auditory communication channels (p < 0.0001), and with time of hearing loss.

Conclusions

P300 can be recorded in individuals with severe and profound congenital sensorineural hearing loss; it may contribute to the understanding of cortical development and is a good predictor of the early intervention outcome.

Pairing Speech Sounds With Vagus Nerve Stimulation Drives Stimulus-specific Cortical Plasticity

BACKGROUND

Individuals with communication disorders, such as aphasia, exhibit weak auditory cortex responses to speech sounds and language impairments. Previous studies have demonstrated that pairing vagus nerve stimulation (VNS) with tones or tone trains can enhance both the spectral and temporal processing of sounds in auditory cortex, and can be used to reverse pathological primary auditory cortex (A1) plasticity in a rodent model of chronic tinnitus.

OBJECTIVE/HYPOTHESIS

We predicted that pairing VNS with speech sounds would strengthen the A1 response to the paired speech sounds.

METHODS

The speech sounds 'rad' and 'lad' were paired with VNS three hundred times per day for twenty days. A1 responses to both paired and novel speech sounds were recorded 24 h after the last VNS pairing session in anesthetized rats. Response strength, latency and neurometric decoding were compared between VNS speech paired and control rats.

RESULTS

Our results show that VNS paired with speech sounds strengthened the auditory cortex response to the paired sounds, but did not strengthen the amplitude of the response to novel speech sounds. Responses to the paired sounds were faster and less variable in VNS speech paired rats compared to control rats. Neural plasticity that was specific to the frequency, intensity, and temporal characteristics of the paired speech sounds resulted in enhanced neural detection.

CONCLUSION

VNS speech sound pairing provides a novel method to enhance speech sound processing in the central auditory system. Delivery of VNS during speech therapy could improve outcomes in individuals with receptive language deficits.

Profound childhood hearing loss in a South Africa cohort: risk profile, diagnosis and age of intervention

OBJECTIVE

To describe profound childhood hearing loss in a South African population of pediatric cochlear implant recipients in terms of risk profile, and age of diagnosis and intervention.

METHODS

A retrospective review of patient files for 264 pediatric cochlear implant recipients from five cochlear implant programs was conducted. Data was captured from 264 eligible subjects, of which all were implanted between 1996 and 2013 and PCEHL was confirmed under the age of 5 years old. Data collected included demographical information, risk factors from case histories, diagnostic test procedures conducted, diagnosis (type, onset and degree of hearing loss) and documented ages of caregiver suspicion, initial diagnosis and intervention.

RESULTS

Risk factors for permanent childhood hearing loss were present in 51.1% of cases, with the most prevalent risks being NICU admittance (28.1%), family history of childhood hearing loss (19.6%) and prematurity (15.1%). An associated syndrome was diagnosed in 10% of children and 23.5% presented with at least one additional developmental condition. Hearing loss for most (77.6%) children was confirmed as congenital/early onset, while 20.3% presented with postnatal onset of hearing loss. ANSD was diagnosed in 5% of children, with admittance to NICU (80%) and hyperbilirubinemia (50%) being the most prevalent risk factors for these cases. Hearing loss was typically diagnosed late (15.3 months), resulting in delayed initial hearing aid fitting (18.8 months), enrollment in early intervention services (19.5 months) and eventual cochlear implantation (43.6 months).

CONCLUSION

Most prevalent risk factors in profound childhood hearing loss were admittance to NICU, family history and prematurity. Diagnosis and intervention was typically delayed predisposing this population to poorer outcomes.

Auditory neural myelination is associated with early childhood language development in premature infants

BACKGROUND

Auditory neural myelination (ANM) as evaluated by auditory brainstem evoked response (ABR) during the neonatal period has been used as a surrogate outcome for long-term neurodevelopment. The validity of ANM as a surrogate outcome for long-term neurodevelopment has not been well studied.

AIM

Evaluate the association of ABR I-V interpeak latency (IPL), an index of ANM, at 35 week postmenstrual age (PMA) with language outcome at 3 years of age.

DESIGN

Prospective study.

SUBJECTS

24-33 week gestational age (GA) infants were eligible if they did not meet exclusion criteria: craniofacial malformation, chromosomal disorders, deafness, auditory dys-synchrony, TORCH infection, or non-English speaking parents. Infants with malignancy, head injury, encephalopathy, meningitis, blindness, or who died or relocated were also excluded.

OUTCOME MEASURES

ABRs were performed at 35 week PMA using 80 dB nHL and I-V IPL (ms) measured. Auditory Comprehension (AC) and Expressive Communication (EC) were evaluated by a speech-language pathologist at 3 years of age using Preschool Language Scale.

RESULTS

Eighty infants were studied. The mean GA and birth weight of infants were 29.2 weeks and 1336 g, respectively. There was association of worse ear I-V IPL and better ear I-V IPL with AC (Coefficient-5.4, 95% CI: -9.8 to -0.9 and Coefficient-5.5, 95% CI: -10 to-0.9, respectively) and EC (Coefficient-5.6, 95% CI: -9.5 to-1.8 and Coefficient-6.7, 95% CI: -10.6 to-2.7, respectively) after controlling for confounders.

CONCLUSION

The neonatal I-V IPL is a predictor of language development at 3 years of age in preterms.

Neurocognitive risk in children with cochlear implants

IMPORTANCE

Children who receive a cochlear implant (CI) for early severe to profound sensorineural hearing loss may achieve age-appropriate spoken language skills not possible before implantation. Despite these advances, reduced access to auditory experience may have downstream effects on fundamental neurocognitive processes for some children with CIs.

OBJECTIVE

To determine the relative risk (RR) of clinically significant executive functioning deficits in children with CIs compared with children with normal hearing (NH).

DESIGN, SETTING, AND PARTICIPANTS

In this prospective, cross-sectional study, 73 children at a hospital-based clinic who received their CIs before 7 years of age and 78 children with NH, with average to above average mean nonverbal IQ scores, were recruited in 2 age groups: preschool age (age range, 3-5 years) and school age (age range, 7-17 years). No children presented with other developmental, cognitive, or neurologic diagnoses.

INTERVENTIONS

Parent-reported checklist measures of executive functioning were completed during psychological testing sessions.

MAIN OUTCOMES AND MEASURES

Estimates of the RR of clinically significant deficits in executive functioning (≥1 SDs above the mean) for children with CIs compared with children with NH were obtained based on 2 parent-reported child behavior checklists of everyday problems with executive functioning.

RESULTS

In most domains of executive functioning, children with CIs were at 2 to 5 times greater risk of clinically significant deficits compared with children with NH. The RRs for preschoolers and school-aged children, respectively, were greatest in the areas of comprehension and conceptual learning (RR [95% CI], 3.56 [1.71-7.43] and 6.25 [2.64-14.77]), factual memory ( 4.88 [1.58-15.07] and 5.47 [2.03-14.77]), attention (3.38 [1.03-11.04] and 3.13 [1.56-6.26]), sequential processing (11.25 [1.55-81.54] and 2.44 [1.24-4.76]), working memory (4.13 [1.30-13.06] and 3.64 [1.61-8.25] for one checklist and 1.77 [0.82-3.83] and 2.78 [1.18-6.51] for another checklist), and novel problem-solving (3.93 [1.50-10.34] and 3.13 [1.46-6.67]). No difference between the CI and NH samples was found for visual-spatial organization (2.63 [0.76-9.03] and 1.04 [0.45-2.40] on one checklist and 2.86 [0.98-8.39] for school-aged children on the other checklist).

CONCLUSIONS AND RELEVANCE

A large proportion of children with CIs are at risk for clinically significant deficits across multiple domains of executive functioning, a rate averaging 2 to 5 times that of children with NH for most domains. Screening for risk of executive functioning deficits should be a routine part of the clinical evaluation of all children with deafness and CIs.

Revisiting the adaptive and maladaptive effects of crossmodal plasticity

One of the most striking demonstrations of experience-dependent plasticity comes from studies of sensory-deprived individuals (e.g., blind or deaf), showing that brain regions deprived of their natural inputs change their sensory tuning to support the processing of inputs coming from the spared senses. These mechanisms of crossmodal plasticity have been traditionally conceptualized as having a double-edged sword effect on behavior. On one side, crossmodal plasticity is conceived as adaptive for the development of enhanced behavioral skills in the remaining senses of early-deaf or blind individuals. On the other side, crossmodal plasticity raises crucial challenges for sensory restoration and is typically conceived as maladaptive since its presence may prevent optimal recovery in sensory-re-afferented individuals. In the present review we stress that this dichotomic vision is oversimplified and we emphasize that the notions of the unavoidable adaptive/maladaptive effects of crossmodal reorganization for sensory compensation/restoration may actually be misleading. For this purpose we critically review the findings from the blind and deaf literatures, highlighting the complementary nature of these two fields of research. The integrated framework we propose here has the potential to impact on the way rehabilitation programs for sensory recovery are carried out, with the promising prospect of eventually improving their final outcomes.

Audiotactile interaction can change over time in cochlear implant users

Recent results suggest that audiotactile interactions are disturbed in cochlear implant (CI) users. However, further exploration regarding the factors responsible for such abnormal sensory processing is still required. Considering the temporal nature of a previously used multisensory task, it remains unclear whether any aberrant results were caused by the specificity of the interaction studied or rather if it reflects an overall abnormal interaction. Moreover, although duration of experience with a CI has often been linked with the recovery of auditory functions, its impact on multisensory performance remains uncertain. In the present study, we used the parchment-skin illusion, a robust illustration of sound-biased perception of touch based on changes in auditory frequencies, to investigate the specificities of audiotactile interactions in CI users. Whereas individuals with relatively little experience with the CI performed similarly to the control group, experienced CI users showed a significantly greater illusory percept. The overall results suggest that despite being able to ignore auditory distractors in a temporal audiotactile task, CI users develop to become greatly influenced by auditory input in a spectral audiotactile task. When considered with the existing body of research, these results confirm that normal sensory interaction processing can be compromised in CI users.

Correlation of neurocognitive processing subtypes with language performance in young children with cochlear implants

OBJECTIVES

Test data were used to explore the neurocognitive processing of a group of children with cochlear implants (CIs) whose language development is below expectations.

METHODS

This cross-sectional study examines the relationship between neurocognitive processing, as assessed by the Kaufman Assessment Battery for Children-Second Edition, and verbal language standard scores, assessed using either the Comprehensive Assessment of Spoken Language or the Clinical Evaluation of Language Fundamentals in 22 school-age children with CIs. Processing scores of CI recipients with language scores below expectations were compared to those of children meeting or exceeding language expectations. Multiple linear regression estimated the associations of simultaneous and sequential processing with language scores.

RESULTS

Though simultaneous processing scores between the two groups were similar, the mean sequential processing score (91.2) in the below expectations group (n = 13) was significantly lower (P = 0.002) than that of children (n = 9) meeting expectations (110.8). After adjusting for age at implantation, a 10-point higher sequential processing score was associated with a 7.4 higher language score (P = 0.027).

DISCUSSION

Simultaneous processing capacity was at least within the average range of cognitive performance, and was not associated with language performance in children with CIs. Conversely, reduced sequential processing capacity was significantly associated with lower language scores.

CONCLUSION

Neurocognitive skills, specifically cognitive sequencing, serial ordering, and auditory-verbal memory may be targets for therapeutic intervention. Intensive cognitive and educational habilitation and in milieu intervention may improve language learning in children with CIs.

Developmental and cross-modal plasticity in deafness: evidence from the P1 and N1 event related potentials in cochlear implanted children

Cortical development is dependent on extrinsic stimulation. As such, sensory deprivation, as in congenital deafness, can dramatically alter functional connectivity and growth in the auditory system. Cochlear implants ameliorate deprivation-induced delays in maturation by directly stimulating the central nervous system, and thereby restoring auditory input. The scenario in which hearing is lost due to deafness and then reestablished via a cochlear implant provides a window into the development of the central auditory system. Converging evidence from electrophysiologic and brain imaging studies of deaf animals and children fitted with cochlear implants has allowed us to elucidate the details of the time course for auditory cortical maturation under conditions of deprivation. Here, we review how the P1 cortical auditory evoked potential (CAEP) provides useful insight into sensitive period cut-offs for development of the primary auditory cortex in deaf children fitted with cochlear implants. Additionally, we present new data on similar sensitive period dynamics in higher-order auditory cortices, as measured by the N1 CAEP in cochlear implant recipients. Furthermore, cortical re-organization, secondary to sensory deprivation, may take the form of compensatory cross-modal plasticity. We provide new case-study evidence that cross-modal re-organization, in which intact sensory modalities (i.e., vision and somatosensation) recruit cortical regions associated with deficient sensory modalities (i.e., auditory) in cochlear implanted children may influence their behavioral outcomes with the implant. Improvements in our understanding of developmental neuroplasticity in the auditory system should lead to harnessing central auditory plasticity for superior clinical technique.

Cross-modal re-organization in adults with early stage hearing loss

Cortical cross-modal re-organization, or recruitment of auditory cortical areas for visual processing, has been well-documented in deafness. However, the degree of sensory deprivation necessary to induce such cortical plasticity remains unclear. We recorded visual evoked potentials (VEP) using high-density electroencephalography in nine persons with adult-onset mild-moderate hearing loss and eight normal hearing control subjects. Behavioral auditory performance was quantified using a clinical measure of speech perception-in-noise. Relative to normal hearing controls, adults with hearing loss showed significantly larger P1, N1, and P2 VEP amplitudes, decreased N1 latency, and a novel positive component (P2') following the P2 VEP. Current source density reconstruction of VEPs revealed a shift toward ventral stream processing including activation of auditory temporal cortex in hearing-impaired adults. The hearing loss group showed worse than normal speech perception performance in noise, which was strongly correlated with a decrease in the N1 VEP latency. Overall, our findings provide the first evidence that visual cross-modal re-organization not only begins in the early stages of hearing impairment, but may also be an important factor in determining behavioral outcomes for listeners with hearing loss, a finding which demands further investigation.