Human brain plasticity: evidence from sensory deprivation and altered language experience

Effect of guided implant placement learning experiences on freehand skills: A pilot study

OBJECTIVES

Guided implant systems can be used as a training approach for placing implants. This in vitro prospective randomized pilot study evaluated the learning progression and skill development in freehand placement of two implants supporting a three-unit fixed prosthesis on a simulation model among novice operators.

MATERIAL AND METHODS

Four senior dental students with no prior implant placement experience participated in the study. As a baseline, each student placed two mandibular and two maxillary implants by freehand technique on a simulation model. Sixteen consecutive guided placements using a static guide, dynamic navigation, and template-based guide followed totaling 32 guided implant placements into maxillary and mandibular models. Freehand implant placements before and after the various guided navigation attempts were compared to assess their impact on freehand skill. Metrics compared included surgical time, horizontal, vertical, and angulation discrepancies between the planned and placed implant positions measured on superimposed CBCT scans and analyzed with repeated measures regression with Tukey's adjusted pairwise comparisons (α = .05).

RESULTS

Before training with guided techniques, the average baseline freehand implant placement took 10.2 min and decreased to 8.2 after training but this difference was not statistically significant (p = .1670) There was marginal evidence of a significant difference in the 3D apex deviation with an average improvement of 0.89 mm (95% CI: -0.38, 2.16, p = .1120); and marginal evidence of a significant improvement in the overall angle with an average improvement of 3.74° (95% CI: -1.00, 8.48, p = .0869) between baseline and final freehand placement attempts.

CONCLUSIONS

Within the limitations of this pilot study, guided implant placement experiences did not significantly benefit or hinder freehand placement skills. Dental students should be exposed to various placement techniques to prepare them for clinical practice and allow them to make informed decisions on the best technique based on their skills and a given clinical scenario.

Mapping the unique neural engagement in deaf individuals during picture, word, and sign language processing: fMRI study

Employing functional magnetic resonance imaging (fMRI) techniques, we conducted a comprehensive analysis of neural responses during sign language, picture, and word processing tasks in a cohort of 35 deaf participants and contrasted these responses with those of 35 hearing counterparts. Our voxel-based analysis unveiled distinct patterns of brain activation during language processing tasks. Deaf individuals exhibited robust bilateral activation in the superior temporal regions during sign language processing, signifying the profound neural adaptations associated with sign comprehension. Similarly, during picture processing, the deaf cohort displayed activation in the right angular, right calcarine, right middle temporal, and left angular gyrus regions, elucidating the neural dynamics engaged in visual processing tasks. Intriguingly, during word processing, the deaf group engaged the right insula and right fusiform gyrus, suggesting compensatory mechanisms at play during linguistic tasks. Notably, the control group failed to manifest additional or distinctive regions in any of the tasks when compared to the deaf cohort, underscoring the unique neural signatures within the deaf population. Multivariate Pattern Analysis (MVPA) of functional connectivity provided a more nuanced perspective on connectivity patterns across tasks. Deaf participants exhibited significant activation in a myriad of brain regions, including bilateral planum temporale (PT), postcentral gyrus, insula, and inferior frontal regions, among others. These findings underscore the intricate neural adaptations in response to auditory deprivation. Seed-based connectivity analysis, utilizing the PT as a seed region, revealed unique connectivity pattern across tasks. These connectivity dynamics provide valuable insights into the neural interplay associated with cross-modal plasticity.

Level of Attention to Motherese Speech as an Early Marker of Autism Spectrum Disorder

Importance

Caregivers have long captured the attention of their infants by speaking in motherese, a playful speech style characterized by heightened affect. Reduced attention to motherese in toddlers with autism spectrum disorder (ASD) may be a contributor to downstream language and social challenges and could be diagnostically revealing.

Objective

To investigate whether attention toward motherese speech can be used as a diagnostic classifier of ASD and is associated with language and social ability.

Design, Setting, and Participants

This diagnostic study included toddlers aged 12 to 48 months, spanning ASD and non-ASD diagnostic groups, at a research center. Data were collected from February 2018 to April 2021 and analyzed from April 2021 to March 2022.

Exposures

Gaze-contingent eye-tracking test.

Main Outcomes and Measures

Using gaze-contingent eye tracking wherein the location of a toddler's fixation triggered a specific movie file, toddlers participated in 1 or more 1-minute eye-tracking tests designed to quantify attention to motherese speech, including motherese vs traffic (ie, noisy vehicles on a highway) and motherese vs techno (ie, abstract shapes with music). Toddlers were also diagnostically and psychometrically evaluated by psychologists. Levels of fixation within motherese and nonmotherese movies and mean number of saccades per second were calculated. Receiver operating characteristic (ROC) curves were used to evaluate optimal fixation cutoff values and associated sensitivity, specificity, positive predictive value (PPV), and negative predictive value. Within the ASD group, toddlers were stratified based on low, middle, or high levels of interest in motherese speech, and associations with social and language abilities were examined.

Results

A total of 653 toddlers were included (mean [SD] age, 26.45 [8.37] months; 480 males [73.51%]). Unlike toddlers without ASD, who almost uniformly attended to motherese speech with a median level of 82.25% and 80.75% across the 2 tests, among toddlers with ASD, there was a wide range, spanning 0% to 100%. Both the traffic and techno paradigms were effective diagnostic classifiers, with large between-group effect sizes (eg, ASD vs typical development: Cohen d, 1.0 in the techno paradigm). Across both paradigms, a cutoff value of 30% or less fixation on motherese resulted in an area under the ROC curve (AUC) of 0.733 (95% CI, 0.693-0.773) and 0.761 (95% CI, 0.717-0.804), respectively; specificity of 98% (95% CI, 95%-99%) and 96% (95% CI, 92%-98%), respectively; and PPV of 94% (95% CI, 86%-98%). Reflective of heterogeneity and expected subtypes in ASD, sensitivity was lower at 18% (95% CI, 14%-22%) and 29% (95% CI, 24%-34%), respectively. Combining metrics increased the AUC to 0.841 (95% CI, 0.805-0.877). Toddlers with ASD who showed the lowest levels of attention to motherese speech had weaker social and language abilities.

Conclusions and Relevance

In this diagnostic study, a subset of toddlers showed low levels of attention toward motherese speech. When a cutoff level of 30% or less fixation on motherese speech was used, toddlers in this range were diagnostically classified as having ASD with high accuracy. Insight into which toddlers show unusually low levels of attention to motherese may be beneficial not only for early ASD diagnosis and prognosis but also as a possible therapeutic target.

The Early Motor Repertoire in Preterm Infancy and Cognition in Young Adulthood: Preliminary Findings

OBJECTIVE

Preterm birth poses a risk to cognition during childhood. The resulting cognitive problems may persist into young adulthood. The early motor repertoire in infancy is predictive of neurocognitive development in childhood. Our present aim was to investigate whether it also predicts neurocognitive status in young adulthood.

METHOD

We conducted an explorative observational follow-up study in 37 young adults born at a gestational age of less than 35 weeks and/or with a birth weight below 1200 g. Between 1992 and 1997, these individuals were videotaped up until 3 months' corrected age to assess the quality of their early motor repertoire according to Prechtl. The assessment includes general movements, fidgety movements (FMs), and a motor optimality score (MOS). In young adulthood, the following cognitive domains were assessed: memory, speed of information processing, language, attention, and executive function.

RESULTS

Participants in whom FMs were absent in infancy obtained lower scores on memory, speed of information processing, and attention than those with normal FMs. Participants with aberrant FMs, that is, absent or abnormal, obtained poorer scores on memory, speed of information processing speed, attention, and executive function compared to peers who had normal FMs. A higher MOS was associated with better executive function.

CONCLUSIONS

The quality of the early motor repertoire is associated with performance in various cognitive domains in young adulthood. This knowledge may be applied to enable the timely recognition of preterm-born individuals at risk of cognitive dysfunctions.

Associations among Visual, Auditory, and Olfactory Functions in Community-Based Older Adults: The Atherosclerosis Risk in Communities (ARIC) Study

PURPOSE

Objective examination of relationships among visual, hearing, and olfactory function may yield mechanistic insights and inform our understanding of the burden of multiple-sensory impairments.

METHODS

This cross-sectional study capitalized on continuous measures of visual acuity (VA), contrast sensitivity, pure tone audiometry, Quick Speech-in-Noise (QuickSIN), and Sniffin' Sticks from a subset of ARIC participants at two community sites (EyeDOC Study, 2017-2019). Scales of all measures were aligned such that higher values indicated greater impairment. Intersensory bivariate associations were assessed graphically, and correlations assessed using Kendall's tau. Intersensory associations, independent of age, education, smoking, diabetes, and hypertension, were examined using linear regression. Analyses were stratified by community/race (Washington County/White vs Jackson/Black) and sex (men vs women) to explore community-sex heterogeneity.

RESULTS

We included 834 participants (mean age, 79 years); 39% were from Jackson and 63% females. We found weak intersensory correlations (tau generally ≤0.15). In the demographics-adjusted regression models, results were heterogeneous across communities and sex. Worse near VA, contrast sensitivity, and olfaction were associated with worse QuickSIN and worse near VA was associated with worse olfaction in some but not all community/race-sex groups (e.g., Jackson/Black women, 0.1 logMAR worse near VA was associated with 0.27 units increase in QuickSIN [95% confidence interval, 0.10-0.45]). Associations were modestly attenuated by adjustment for the shared risk factors of smoking, diabetes, and hypertension.

CONCLUSIONS

Visual dysfunction showed little or no association with hearing or olfaction impairments, suggesting a modest role for shared risk factors.

TRANSLATIONAL RELEVANCE

Visually impaired individuals have only a modestly higher risk of other sensory impairment.

Evidence of visual crossmodal reorganization positively relates to speech outcomes in cochlear implant users

Deaf individuals who use a cochlear implant (CI) have remarkably different outcomes for auditory speech communication ability. One factor assumed to affect CI outcomes is visual crossmodal plasticity in auditory cortex, where deprived auditory regions begin to support non-auditory functions such as vision. Previous research has viewed crossmodal plasticity as harmful for speech outcomes for CI users if it interferes with sound processing, while others have demonstrated that plasticity related to visual language may be beneficial for speech recovery. To clarify, we used electroencephalography (EEG) to measure brain responses to a partial face speaking a silent single-syllable word (visual language) in 15 CI users and 13 age-matched typical-hearing controls. We used source analysis on EEG activity to measure crossmodal visual responses in auditory cortex and then compared them to CI users' speech-in-noise listening ability. CI users' brain response to the onset of the video stimulus (face) was larger than controls in left auditory cortex, consistent with crossmodal activation after deafness. CI users also produced a mixture of alpha (8-12 Hz) synchronization and desynchronization in auditory cortex while watching lip movement while controls instead showed desynchronization. CI users with higher speech scores had stronger crossmodal responses in auditory cortex to the onset of the video, but those with lower speech scores had increases in alpha power during lip movement in auditory areas. Therefore, evidence of crossmodal reorganization in CI users does not necessarily predict poor speech outcomes, and differences in crossmodal activation during lip reading may instead relate to strategies or differences that CI users use in audiovisual speech communication.

Impact of blindness onset on the representation of sound categories in occipital and temporal cortices

The ventral occipito-temporal cortex (VOTC) reliably encodes auditory categories in people born blind using a representational structure partially similar to the one found in vision (Mattioni et al.,2020). Here, using a combination of uni- and multivoxel analyses applied to fMRI data, we extend our previous findings, comprehensively investigating how early and late acquired blindness impact on the cortical regions coding for the deprived and the remaining senses. First, we show enhanced univariate response to sounds in part of the occipital cortex of both blind groups that is concomitant to reduced auditory responses in temporal regions. We then reveal that the representation of the sound categories in the occipital and temporal regions is more similar in blind subjects compared to sighted subjects. What could drive this enhanced similarity? The multivoxel encoding of the ‘human voice’ category that we observed in the temporal cortex of all sighted and blind groups is enhanced in occipital regions in blind groups , suggesting that the representation of vocal information is more similar between the occipital and temporal regions in blind compared to sighted individuals. We additionally show that blindness does not affect the encoding of the acoustic properties of our sounds (e.g. pitch, harmonicity) in occipital and in temporal regions but instead selectively alter the categorical coding of the voice category itself. These results suggest a functionally congruent interplay between the reorganization of occipital and temporal regions following visual deprivation, across the lifespan.

Impaired body-centered sensorimotor transformations in congenitally deaf people

Congenital deafness modifies an individual’s daily interaction with the environment and alters the fundamental perception of the external world. How congenital deafness shapes the interface between the internal and external worlds remains poorly understood. To interact efficiently with the external world, visuospatial representations of external target objects need to be effectively transformed into sensorimotor representations with reference to the body. Here, we tested the hypothesis that egocentric body-centred sensorimotor transformation is impaired in congenital deafness. Consistent with this hypothesis, we found that congenital deafness induced impairments in egocentric judgements, associating the external objects with the internal body. These impairments were due to deficient body-centred sensorimotor transformation per se, rather than the reduced fidelity of the visuospatial representations of the egocentric positions. At the neural level, we first replicated the previously well-documented critical involvement of the frontoparietal network in egocentric processing, in both congenitally deaf participants and hearing controls. However, both the strength of neural activity and the intra-network connectivity within the frontoparietal network alone could not account for egocentric performance variance. Instead, the inter-network connectivity between the task-positive frontoparietal network and the task-negative default-mode network was significantly correlated with egocentric performance: the more cross-talking between them, the worse the egocentric judgement. Accordingly, the impaired egocentric performance in the deaf group was related to increased inter-network connectivity between the frontoparietal network and the default-mode network and decreased intra-network connectivity within the default-mode network. The altered neural network dynamics in congenital deafness were observed for both evoked neural activity during egocentric processing and intrinsic neural activity during rest. Our findings thus not only demonstrate the optimal network configurations between the task-positive and -negative neural networks underlying coherent body-centred sensorimotor transformations but also unravel a critical cause (i.e. impaired body-centred sensorimotor transformation) of a variety of hitherto unexplained difficulties in sensory-guided movements the deaf population experiences in their daily life.

Disturbed Balance of Inhibitory Signaling Links Hearing Loss and Cognition

Neuronal hyperexcitability in the central auditory pathway linked to reduced inhibitory activity is associated with numerous forms of hearing loss, including noise damage, age-dependent hearing loss, and deafness, as well as tinnitus or auditory processing deficits in autism spectrum disorder (ASD). In most cases, the reduced central inhibitory activity and the accompanying hyperexcitability are interpreted as an active compensatory response to the absence of synaptic activity, linked to increased central neural gain control (increased output activity relative to reduced input). We here suggest that hyperexcitability also could be related to an immaturity or impairment of tonic inhibitory strength that typically develops in an activity-dependent process in the ascending auditory pathway with auditory experience. In these cases, high-SR auditory nerve fibers, which are critical for the shortest latencies and lowest sound thresholds, may have either not matured (possibly in congenital deafness or autism) or are dysfunctional (possibly after sudden, stressful auditory trauma or age-dependent hearing loss linked with cognitive decline). Fast auditory processing deficits can occur despite maintained basal hearing. In that case, tonic inhibitory strength is reduced in ascending auditory nuclei, and fast inhibitory parvalbumin positive interneuron (PV-IN) dendrites are diminished in auditory and frontal brain regions. This leads to deficits in central neural gain control linked to hippocampal LTP/LTD deficiencies, cognitive deficits, and unbalanced extra-hypothalamic stress control. Under these conditions, a diminished inhibitory strength may weaken local neuronal coupling to homeostatic vascular responses required for the metabolic support of auditory adjustment processes. We emphasize the need to distinguish these two states of excitatory/inhibitory imbalance in hearing disorders: (i) Under conditions of preserved fast auditory processing and sustained tonic inhibitory strength, an excitatory/inhibitory imbalance following auditory deprivation can maintain precise hearing through a memory linked, transient disinhibition that leads to enhanced spiking fidelity (central neural gain⇑) (ii) Under conditions of critically diminished fast auditory processing and reduced tonic inhibitory strength, hyperexcitability can be part of an increased synchronization over a broader frequency range, linked to reduced spiking reliability (central neural gain⇓). This latter stage mutually reinforces diminished metabolic support for auditory adjustment processes, increasing the risks for canonical dementia syndromes.

Oxytocin Regulates Synaptic Transmission in the Sensory Cortices in a Developmentally Dynamic Manner

The development and stabilization of neuronal circuits are critical to proper brain function. Synapses are the building blocks of neural circuits. Here we examine the effects of the neuropeptide oxytocin on synaptic transmission in L2/3 pyramidal neurons of the barrel field of the primary somatosensory cortex (S1BF). We find that perfusion of oxytocin onto acute brain slices significantly increases the frequency of miniature excitatory postsynaptic currents (mEPSC) of S1BF L2/3 pyramidal neurons at P10 and P14, but reduces it at the later ages of P22 and P28; the transition occurs at around P18. Since oxytocin expression is itself regulated by sensory experience, we also examine whether the effects of oxytocin on excitatory synaptic transmission correlate with that of sensory experience. We find that, indeed, the effects of sensory experience and oxytocin on excitatory synaptic transmission of L2/3 pyramidal neurons both peak at around P14 and plateau around P18, suggesting that they regulate a specific form of synaptic plasticity in L2/3 pyramidal neurons, with a sensitive/critical period ending around P18. Consistently, oxytocin receptor (Oxtr) expression in glutamatergic neurons of the upper layers of the cerebral cortex peaks around P14. By P28, however, Oxtr expression becomes more prominent in GABAergic neurons, especially somatostatin (SST) neurons. At P28, oxytocin perfusion increases inhibitory synaptic transmission and reduces excitatory synaptic transmission, effects that result in a net reduction of neuronal excitation, in contrast to increased excitation at P14. Using oxytocin knockout mice and Oxtr conditional knockout mice, we show that loss-of-function of oxytocin affects baseline excitatory synaptic transmission, while Oxtr is required for oxytocin-induced changes in excitatory synaptic transmission, at both P14 and P28. Together, these results demonstrate that oxytocin has complex and dynamic functions in regulating synaptic transmission in cortical L2/3 pyramidal neurons. These findings add to existing knowledge of the function of oxytocin in regulating neural circuit development and plasticity.

Functional and structural brain connectivity in congenital deafness

Several studies have been carried out to verify neural plasticity and the language process in deaf individuals. However, further investigations regarding the intrinsic brain organization on functional and structural neural networks derived from congenital deafness are still an open question. The objective of this study was to investigate the main differences in brain organization manifested in congenitally deaf individuals, concerning the resting-state functional patterns, and white matter structuring. Functional and diffusion magnetic resonance imaging modalities were acquired from 18 congenitally deaf individuals and 18 age-sex-matched hearing controls. Compared to the hearing group, the deaf individuals presented higher functional connectivity among the posterior cingulate cortex node of the default mode network with visual and motor networks, lower functional connectivity between salience networks, language networks, and prominence of functional connectivity changes in the right hemisphere, mostly in the frontoparietal and temporal lobes. In terms of structural connectivity, we found changes mainly in the occipital and parietal lobes, involving both classical sign language support regions as well as concentrated networks for focus activity, attention, and cognitive filtering. Our findings demonstrated that the congenital deaf individuals who learned sign language developed significant brain functional and structural reorganization, which provides prominent support for large-scale brain networks associated with attention decision-making, environmental monitoring based on the movement of objects, and on the motor and visual controls.

The Neural Bases of Tinnitus: Lessons from Deafness and Cochlear Implants

Subjective tinnitus is the conscious perception of sound in the absence of any acoustic source. The literature suggests various tinnitus mechanisms, most of which invoke changes in spontaneous firing rates of central auditory neurons resulting from modification of neural gain. Here, we present an alternative model based on evidence that tinnitus is: (1) rare in people who are congenitally deaf, (2) common in people with acquired deafness, and (3) potentially suppressed by active cochlear implants used for hearing restoration. We propose that tinnitus can only develop after fast auditory fiber activity has stimulated the synapse formation between fast-spiking parvalbumin positive (PV⁺) interneurons and projecting neurons in the ascending auditory path and coactivated frontostriatal networks after hearing onset. Thereafter, fast auditory fiber activity promotes feedforward and feedback inhibition mediated by PV⁺ interneuron activity in auditory-specific circuits. This inhibitory network enables enhanced stimulus resolution, attention-driven contrast improvement, and augmentation of auditory responses in central auditory pathways (neural gain) after damage of slow auditory fibers. When fast auditory fiber activity is lost, tonic PV⁺ interneuron activity is diminished, resulting in the prolonged response latencies, sudden hyperexcitability, enhanced cortical synchrony, elevated spontaneous γ oscillations, and impaired attention/stress-control that have been described in previous tinnitus models. Moreover, because fast processing is gained through sensory experience, tinnitus would not exist in congenital deafness. Electrical cochlear stimulation may have the potential to reestablish tonic inhibitory networks and thus suppress tinnitus. The proposed framework unites many ideas of tinnitus pathophysiology and may catalyze cooperative efforts to develop tinnitus therapies.

White matter alteration in adults with prelingual deafness: A TBSS and SBM analysis of fractional anisotropy data

A loss of hearing in early life leads to diversifications of important white matter networks. Previous studies related to WM alterations in adult deaf individuals mainly involved univariate analysis of fractional anisotropy (FA) data and volumetric analysis, which yielded inconsistent results. To address this issue, we investigated the FA value alterations in 38 prelingual adult deaf individuals and compared the results with those obtained from the same number of adults with normal hearing by using univariate (tract-based spatial statistics) and multivariate (source-based morphometry) methods. The findings from tract-based spatial statistics suggested an increased FA value in regions such as the left cingulate gyrus, left inferior frontal occipital fasciculus, left inferior longitudinal fasciculus and superior corona radiata; however, the results indicated a decreased FA value in the left planum temporale of adult deaf individuals. While source-based morphometry analysis outlined higher FA values in regions such as bilateral lingual gyrus, bilateral cerebellum, bilateral putamen and bilateral caudate, a considerable decrease was observed in the bilateral superior temporal region of the deaf group. These alterations in multiple neural regions might be linked to the compensatory cross-modal reorganizations attributed to early hearing loss.

Predictors of Parental Presence in the Neonatal Intensive Care Unit

BACKGROUND

Parental presence in the neonatal intensive care unit (NICU) may affect preterm infants' developmental outcomes. However, few studies have described predictors of parental presence in the NICU.

PURPOSE

To identify sociodemographic, clinical, environmental, and maternal psychological factors that predict parent presence in the NICU.

METHODS

Using a prospective cohort design, 66 preterm infants between 32 and 40 weeks' corrected gestational age were recruited at 2 level III NICUs in the United States. Data for length of parental presence were collected for 48 consecutive hours from daily visitation logs and medical records. A general linear model was estimated to identify significant predictors of parental presence.

RESULTS

Parental presence varied considerably, with a mean percentage of visitation time of 32.40%. The number of children at home (P = .003), presence of neurological comorbidity (P < .001), room type (P < .001), surgical history (P < .001), and perceived stressfulness of the NICU (P = .03) each had large main effects on parental presence, and room type and surgical history (P = .004) had a large interaction effect on parental presence. These predictors accounted for 65.8% of the variance in parental presence.

IMPLICATIONS FOR RESEARCH

Future research aimed at understanding predictors of parent presence is essential for developing interventions and designing NICUs that support parental presence.

IMPLICATIONS FOR PRACTICE

Understanding factors that contribute to parental presence may help healthcare providers identify infants at risk for low parental presence and thus be able to provide greater support to these infants and their families. As a result, this may help improve outcomes and attachment.

Early childhood bilingualism: effects on brain structure and function

Growing up in a bilingual environment is becoming increasingly common. Yet, we know little about how this enriched language environment influences the connectivity of children's brains. Behavioural research in children and adults has shown that bilingualism experience may boost executive control (EC) skills, such as inhibitory control and attention. Moreover, increased structural and functional (resting-state) connectivity in language-related and EC-related brain networks is associated with increased executive control in bilingual adults. However, how bilingualism factors alter brain connectivity early in brain development remains poorly understood. We will combine standardised tests of attention with structural and resting-state functional magnetic resonance imaging (MRI) in bilingual children. This study will allow us to address an important field of inquiry within linguistics and developmental cognitive neuroscience by examining the following questions: Does bilingual experience modulate connectivity in language-related and EC-related networks in children? Do differences in resting-state brain connectivity correlate with differences in EC skills (specifically attention skills)? How do bilingualism-related factors, such as age of exposure to two languages, language usage and proficiency, modulate brain connectivity? We will collect structural and functional MRI, and quantitative measures of EC and language skills from two groups of English-Greek bilingual children - 20 simultaneous bilinguals (exposure to both languages from birth) and 20 successive bilinguals (exposure to English between the ages of 3 and 5 years) - and 20 English monolingual children, 8-10 years old. We will compare connectivity measures and attention skills between monolinguals and bilinguals to examine the effects of bilingual exposure. We will also examine to what extent bilingualism factors predict brain connectivity in EC and language networks. Overall, we hypothesize that connectivity and EC will be enhanced in bilingual children compared to monolingual children, and each outcome will be modulated by age of exposure to two languages and by bilingual language usage.

Early childhood bilingualism: effects on brain structure and function

Growing up in a bilingual environment is becoming increasingly common. Yet, we know little about how this enriched language environment influences the connectivity of children's brains. Behavioural research in children and adults has shown that bilingualism experience may boost executive control (EC) skills, such as inhibitory control and attention. Moreover, increased structural and functional (resting-state) connectivity in language-related and EC-related brain networks is associated with increased executive control in bilingual adults. However, how bilingualism factors alter brain connectivity early in brain development remains poorly understood. We will combine standardised tests of attention with structural and resting-state functional magnetic resonance imaging (MRI) in bilingual children. This study will allow us to address an important field of inquiry within linguistics and developmental cognitive neuroscience by examining the following questions: Does bilingual experience modulate connectivity in language-related and EC-related networks in children? Do differences in resting-state brain connectivity correlate with differences in EC skills (specifically attention skills)? How do bilingualism-related factors, such as age of exposure to two languages, language usage and proficiency, modulate brain connectivity? We will collect structural and functional MRI, and quantitative measures of EC and language skills from two groups of English-Greek bilingual children - 20 simultaneous bilinguals (exposure to both languages from birth) and 20 successive bilinguals (exposure to English between the ages of 3 and 5 years) - and 20 English monolingual children, 8-10 years old. We will compare connectivity measures and attention skills between monolinguals and bilinguals to examine the effects of bilingual exposure. We will also examine to what extent bilingualism factors predict brain connectivity in EC and language networks. Overall, we hypothesize that connectivity and EC will be enhanced in bilingual children compared to monolingual children, and each outcome will be modulated by age of exposure to two languages and by bilingual language usage.

Categorical representation from sound and sight in the ventral occipito-temporal cortex of sighted and blind

Is vision necessary for the development of the categorical organization of the Ventral Occipito-Temporal Cortex (VOTC)? We used fMRI to characterize VOTC responses to eight categories presented acoustically in sighted and early blind individuals, and visually in a separate sighted group. We observed that VOTC reliably encodes sound categories in sighted and blind people using a representational structure and connectivity partially similar to the one found in vision. Sound categories were, however, more reliably encoded in the blind than the sighted group, using a representational format closer to the one found in vision. Crucially, VOTC in blind represents the categorical membership of sounds rather than their acoustic features. Our results suggest that sounds trigger categorical responses in the VOTC of congenitally blind and sighted people that partially match the topography and functional profile of the visual response, despite qualitative nuances in the categorical organization of VOTC between modalities and groups.

The world is full of rich and dynamic visual information. To avoid information overload, the human brain groups inputs into categories such as faces, houses, or tools. A part of the brain called the ventral occipito-temporal cortex (VOTC) helps categorize visual information. Specific parts of the VOTC prefer different types of visual input; for example, one part may tend to respond more to faces, whilst another may prefer houses. However, it is not clear how the VOTC characterizes information.

One idea is that similarities between certain types of visual information may drive how information is organized in the VOTC. For example, looking at faces requires using central vision, while looking at houses requires using peripheral vision. Furthermore, all faces have a roundish shape while houses tend to have a more rectangular shape. Another possibility, however, is that the categorization of different inputs cannot be explained just by vision, and is also be driven by higher-level aspects of each category. For instance, how humans use or interact with something may also influence how an input is categorized. If categories are established depending (at least partially) on these higher-level aspects, rather than purely through visual likeness, it is likely that the VOTC would respond similarly to both sounds and images representing these categories.

Now, Mattioni et al. have tested how individuals with and without sight respond to eight different categories of information to find out whether or not categorization is driven purely by visual likeness. Each category was presented to participants using sounds while measuring their brain activity. In addition, a group of participants who could see were also presented with the categories visually. Mattioni et al. then compared what happened in the VOTC of the three groups – sighted people presented with sounds, blind people presented with sounds, and sighted people presented with images – in response to each category.

The experiment revealed that the VOTC organizes both auditory and visual information in a similar way. However, there were more similarities between the way blind people categorized auditory information and how sighted people categorized visual information than between how sighted people categorized each type of input. Mattioni et al. also found that the region of the VOTC that responds to inanimate objects massively overlapped across the three groups, whereas the part of the VOTC that responds to living things was more variable.

These findings suggest that the way that the VOTC organizes information is, at least partly, independent from vision. The experiments also provide some information about how the brain reorganizes in people who are born blind. Further studies may reveal how differences in the VOTC of people with and without sight affect regions typically associated with auditory categorization, and potentially explain how the brain reorganizes in people who become blind later in life.

A conceptual framework for plasticity in the developing brain

In this chapter, we highlight the various definitions of early brain plasticity commonly used in the scientific literature. We then present a conceptual framework of early brain plasticity that focuses on plasticity at the level of the synapse (synaptic plasticity) and the level of the network (connectivity). The proposed framework is organized around three main domains through which current theories and principles of early brain plasticity can be integrated: (1) the mechanisms of plasticity and constraints at the synaptic level and network connectivity, (2) the importance of temporal considerations related to the development of the immature brain, and (3) the functions early brain plasticity serve. We then apply this framework to discuss some clinical disorders caused by and/or associated with impaired plasticity mechanisms. We propose that a careful examination of the relationship between mechanisms, constraints, and functions of early brain plasticity in health and disease may provide an integrative understanding of the current theories and principles generated by experimental and observational studies.

What and How the Deaf Brain Sees

Over the past decade, there has been an unprecedented level of interest and progress into understanding visual processing in the brain of the deaf. Specifically, when the brain is deprived of input from one sensory modality (such as hearing), it often compensates with supranormal performance in one or more of the intact sensory systems (such as vision). Recent psychophysical, functional imaging, and reversible deactivation studies have converged to define the specific visual abilities that are enhanced in the deaf, as well as the cortical loci that undergo crossmodal plasticity in the deaf and are responsible for mediating these superior visual functions. Examination of these investigations reveals that central visual functions, such as object and facial discrimination, and peripheral visual functions, such as motion detection, visual localization, visuomotor synchronization, and Vernier acuity (measured in the periphery), are specifically enhanced in the deaf, compared with hearing participants. Furthermore, the cortical loci identified to mediate these functions reside in deaf auditory cortex: BA 41, BA 42, and BA 22, in addition to the rostral area, planum temporale, Te3, and temporal voice area in humans; primary auditory cortex, anterior auditory field, dorsal zone of auditory cortex, auditory field of the anterior ectosylvian sulcus, and posterior auditory field in cats; and primary auditory cortex and anterior auditory field in both ferrets and mice. Overall, the findings from these studies show that crossmodal reorganization in auditory cortex of the deaf is responsible for the superior visual abilities of the deaf.

Sign language experience redistributes attentional resources to the inferior visual field

While a substantial body of work has suggested that deafness brings about an increased allocation of visual attention to the periphery there has been much less work on how using a signed language may also influence this attentional allocation. Signed languages are visual-gestural and produced using the body and perceived via the human visual system. Signers fixate upon the face of interlocutors and do not directly look at the hands moving in the inferior visual field. It is therefore reasonable to predict that signed languages require a redistribution of covert visual attention to the inferior visual field. Here we report a prospective and statistically powered assessment of the spatial distribution of attention to inferior and superior visual fields in signers - both deaf and hearing - in a visual search task. Using a Bayesian Hierarchical Drift Diffusion Model, we estimated decision making parameters for the superior and inferior visual field in deaf signers, hearing signers and hearing non-signers. Results indicated a greater attentional redistribution toward the inferior visual field in adult signers (both deaf and hearing) than in hearing sign-naïve adults. The effect was smaller for hearing signers than for deaf signers, suggestive of either a role for extent of exposure or greater plasticity of the visual system in the deaf. The data provide support for a process by which the demands of linguistic processing can influence the human attentional system.

Area-dependent change of response in the rat's inferior colliculus to intracochlear electrical stimulation following neonatal cochlear damage

To understand brain changes caused by auditory sensory deprivation, we recorded local-field potentials in the inferior colliculus of young adult rats with neonatal cochlear damage produced by systemic injections of amikacin. The responses were elicited by electrical stimulation of the entire cochlea and recorded at various locations along a dorsolateral-ventromedial axis of the inferior colliculus. We found that hair cells were completely destroyed and spiral ganglion neurons were severely damaged in the basal cochleae of amikacin-treated animals. Hair cells as well as spiral ganglion neurons were damaged also in the middle and apical areas of the cochlea, with the damage being greater in the middle than the apical area. Amplitudes of local-field potentials were reduced in the ventromedial inferior colliculus, but enhanced in the dorsolateral inferior colliculus. Latencies of responses were increased over the entire structure. The enhancement of responses in the dorsolateral inferior colliculus was in contrast with the damage of hair cells and spiral ganglion cells in the apical part of the cochlea. This contrast along with the overall increase of latencies suggests that early cochlear damage can alter neural mechanisms within the inferior colliculus and/or the inputs to this midbrain structure.

Excitatory and inhibitory synapse reorganization immediately after critical sensory experience in a vocal learner

Excitatory and inhibitory synapses are the brain’s most abundant synapse types. However, little is known about their formation during critical periods of motor skill learning, when sensory experience defines a motor target that animals strive to imitate. In songbirds, we find that exposure to tutor song leads to elimination of excitatory synapses in HVC (used here as a proper name), a key song generating brain area. A similar pruning is associated with song maturation, because juvenile birds have fewer excitatory synapses, the better their song imitations. In contrast, tutoring is associated with rapid insertion of inhibitory synapses, but the tutoring-induced structural imbalance between excitation and inhibition is eliminated during subsequent song maturation. Our work suggests that sensory exposure triggers the developmental onset of goal-specific motor circuits by increasing the relative strength of inhibition and it suggests a synapse-elimination model of song memorization.

A wide range of species use complex sounds to communicate, including humans and songbirds like zebra finches. During a critical period of learning, infants and young animals learn how to remember and discriminate this ‘language’ from other sounds. However, the changes that happen in the brain during this learning period are not well understood.

The process of learning forms new connections between neurons in the brain and prunes away old connections. These connections, known as synapses, come in different types. Signals sent across excitatory synapses increase the activity of the receiving neuron, while signals sent across inhibitory synapses reduce neuron activity.

What happens to the synapses in the brain during the critical period? To find out, Huang et al. used electron microscopy to examine the brains of young zebra finches that either had never heard birdsong, or had just heard birdsong for the first time. A single day of hearing song dramatically shifted the balance of excitatory and inhibitory synapses in the main vocal control area of the young birds’ brains. The number of excitatory synapses decreased, and the number of inhibitory synapses increased.

The balance between excitation and inhibition is important for the brain to work correctly. Therefore, as well as helping us to understand how infants learn their first language, the results presented by Huang et al. could also help us to improve treatments for conditions where this balance goes wrong, such as mood disorders. For example, tailoring the time point of medication intake in combination with sensory exposure therapies could improve how effectively either one works.

Feasibility of an intensive outpatient Perception-Action Approach intervention for children with cerebral palsy: a pilot study

PURPOSE

The purpose of this pilot study was (1) to evaluate feasibility of attendance and parent satisfaction with an intensive outpatient physical and occupational therapy program for young children with spastic cerebral palsy (CP) and (2) to examine changes in motor function. Methods: Sixteen children with CP, age range 18-36 months (mean 24.3 ± 6.3 months), received physical and occupational therapy sessions (30 minutes each) 5 days per week for 12 weeks. Attendance rates and parent satisfaction were assessed. Change in motor function using a one-group pre-post design was evaluated using the Gross Motor Function Measure-66 (GMFM-66), Quality of Upper Extremity Skills Test, and Pediatric Evaluation of Disability Inventory. GMFM-66 outcomes were also compared with expected outcomes using previously published normative developmental trajectories of children receiving standard therapies. Results: An average of 82% of scheduled outpatient physical and occupational therapies for 16 children were completed and the 11 parents who completed the Hills and Kitchen's Physiotherapy Outpatient Satisfaction Questionnaire were satisfied with the therapies and with their child's progress. Participants showed notable, statistically significant improvement across all activity-related measures. Conclusion: An intensive protocol of outpatient therapies utilizing Perception-Action Approach was feasible for most families of young children with spastic CP to attend at the outpatient clinic location. As this was not an experimental study, no reliable conclusions related to efficacy can be made, but the promising results suggest that further research into the effectiveness of intensive protocols is worthwhile.

Why Does the Cortex Reorganize after Sensory Loss?

A growing body of evidence demonstrates that the brain can reorganize dramatically following sensory loss. Although the existence of such neuroplastic crossmodal changes is not in doubt, the functional significance of these changes remains unclear. The dominant belief is that reorganization is compensatory. However, results thus far do not unequivocally indicate that sensory deprivation results in markedly enhanced abilities in other senses. Here, we consider alternative reasons besides sensory compensation that might drive the brain to reorganize after sensory loss. One such possibility is that the cortex reorganizes not to confer functional benefits, but to avoid undesirable physiological consequences of sensory deafferentation. Empirical assessment of the validity of this and other possibilities defines a rich program for future research.

Modeling the Nature of Grammar and Vocabulary Trajectories From Prekindergarten to Third Grade

PURPOSE

This study investigated the longitudinal development of 2 important contributors to reading comprehension, grammar, and vocabulary skills. The primary interest was to examine the trajectories of the 2 skill areas from preschool to 3rd grade.

METHOD

The study involved a longitudinal sample of 420 children from 4 sites. Language skills, including grammar and vocabulary, were assessed annually with multiple measures. Multivariate latent growth curve modeling was used to examine the developmental trajectories of grammar and vocabulary, to test the correlation between the 2 domains, and to investigate the effects of demographic predictors on language growth.

RESULTS

Results showed that both grammar and vocabulary exhibited decelerating growth from preschool to Grade 2. In Grade 3, grammar growth further flattened, whereas vocabulary continued to grow stably. Growth of vocabulary and grammar were positively correlated. Demographic characteristics, such as child gender and family socioeconomic status, were found to predict the intercept but not the slope of the growth trajectories.

CONCLUSIONS

Children's growth in grammar skills is differentiated in a number of important ways from their growth in vocabulary skills. Results of this study suggest the need to differentiate these dimensions of language when seeking to closely examine growth from preschool to primary grades.

Creative music therapy to promote brain structure, function, and neurobehavioral outcomes in preterm infants: a randomized controlled pilot trial protocol

BACKGROUND

Preterm birth is associated with increased risk of neurological impairment and deficits in cognition, motor function, and behavioral problems. Limited studies indicate that multi-sensory experiences support brain development in preterm infants. Music appears to promote neurobiological processes and neuronal learning in the human brain. Creative music therapy (CMT) is an individualized, interactive therapeutic approach based on the theory and methods of Nordoff and Robbins. CMT may promote brain development in preterm infants via concurrent interaction and meaningful auditory stimulation. We hypothesize that preterm infants who receive creative music therapy during neonatal intensive care admission will have developmental benefits short- and long-term brain function.

METHODS/DESIGN

A prospective, randomized controlled single-center pilot trial involving 60 clinically stable preterm infants under 32 weeks of gestational age is conducted in preparation for a multi-center trial. Thirty infants each are randomized to either standard neonatal intensive care or standard care with CMT. Music therapy intervention is approximately 20 min in duration three times per week. A trained music therapist sings for the infants in lullaby style, individually entrained and adjusted to the infant's rhythm and affect. Primary objectives of this study are feasibility of protocol implementation and investigating the potential mechanism of efficacy for this new intervention. To examine the effect of this new intervention, non-invasive, quantitative magnetic resonance imaging (MRI) methods at corrected age and standardized neurodevelopmental assessments using the Bayley Scales of Infant and Toddler Development third edition at a corrected age of 24 months and Kaufman Assessment Battery for Children at 5 years will be performed. All assessments will be performed and analyzed by blinded experts.

DISCUSSION

To our knowledge, this is the first randomized controlled clinical trial to systematically examine possible effects of creative music therapy on short- and long-term brain development in preterm infants. This project lies at the interface of music therapy, neuroscience, and medical imaging. New insights into the potential role and impact of music on brain function and development may be elucidated. If such a low-cost, low-risk intervention is demonstrated in a future multi-center trial to be effective in supporting brain development in preterm neonates, findings could have broad clinical implications for this vulnerable patient population.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02434224.

Systematic review of maternal voice interventions demonstrates increased stability in preterm infants

We systematically reviewed how effectively maternal voice interventions supported the clinical outcomes and development of preterm infants. A total of 512 preterm infants were included in 15 studies with different designs, from January 2000 to July 2015. Live and recorded maternal voice interventions were associated with the physiologic and behavioural stabilisation of preterm infants, with fewer cardiorespiratory events, but the evidence was insufficient to evaluate the long-term effects. Well-defined determinants and clear setting conditions are needed for such interventions.

CONCLUSION

Further research that investigates the long-term efficacy and effects of live maternal voices on preterm infant development is needed.

Disentangling Linguistic Modality Effects in Semantic Processing

Sensory systems are essential for perceiving and conceptualizing our semantic knowledge about the world and the way we interact with it. Despite studies reporting neural changes to compensate for the absence of a given sensory modality, studies focusing on the assessment of semantic processing reveal poor performances by deaf individuals when compared with hearing individuals. However, the majority of those studies were not performed in the linguistic modality considered the most adequate to their sensory capabilities (i.e., sign language). Therefore, this exploratory study was developed focusing on linguistic modality effects during semantic retrieval in deaf individuals in comparison with their hearing peers through a category fluency task. Results show a difference in performance between the two linguistic modalities by deaf individuals as well as in the type of linguistic clusters most chosen by participants, suggesting a complex clustering tendency by deaf individuals.

How Does Experience Shape Early Development? Considering the Role of Top-Down Mechanisms

Perceptual development requires infants to adapt their perceptual systems to the structures and statistical information of their environment. In this way, perceptual development is not only important in its own right, but is a case study for behavioral and neural plasticity-powerful mechanisms that have the potential to support developmental change in numerous domains starting early in life. While it is widely assumed that perceptual development is a bottom-up process, where simple exposure to sensory input modifies perceptual representations starting early in the perceptual system, there are several critical phenomena in this literature that cannot be explained with an exclusively bottom-up model. This chapter proposes a complementary mechanism where nascent top-down information, feeding back from higher-level regions of the brain, helps to guide perceptual development. Supporting this theoretical proposal, recent behavioral and neuroimaging studies have established that young infants already have the capacity to engage in top-down modulation of their perceptual systems.

Leveraging the Skills of Nurses and the Power of Language Nutrition to Ensure a Better Future for Children

BACKGROUND

Early language exposure is critical for language acquisition and significantly influences a child's literacy skills. However, preterm infants may experience language deprivation in the neonatal intensive care unit. Nurses are vital to helping parents understand their critical role in early language development.

PURPOSE

To discuss the impact of language-rich interactions and interventions that promote early language exposure, or Language Nutrition, by parents and caregivers on the long-term developmental, language, and educational outcomes of high-risk infants.

METHODS/SEARCH STRATEGY

A literature search was conducted using PubMed and Web of Science to identify articles that examined the influence of language interactions with high-risk infants on developmental outcomes. Recent campaigns touting the importance of early language exposure were identified through the Bridging the Word Gap Research Network.

FINDINGS/RESULTS

Increasing preterm infants' exposure to Language Nutrition improves their language development, promotes parent-infant attachment, and decreases parent stress. In addition, it may result in greater neuroplasticity and volume of the auditory cortex. Several campaigns have been developed to increase children's access to Language Nutrition and can be implemented into everyday pediatric and neonatal care.

IMPLICATIONS FOR PRACTICE

Pediatric, neonatal nurses and advanced practice nurses are uniquely positioned to play a transformational role in high-risk infants' developmental trajectory by educating parents about the importance of Language Nutrition and supporting parents as they engage with their infant.

IMPLICATIONS FOR RESEARCH

Studies investigating the population-level impact of interventions aimed at increasing infants' access to Language Nutrition as well as studies identifying effective ways to communicate messages about Language Nutrition are warranted.

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.

Early but not late blindness leads to enhanced arithmetic and working memory abilities

Behavioural and neurophysiological evidence suggest that vision plays an important role in the emergence and development of arithmetic abilities. However, how visual deprivation impacts on the development of arithmetic processing remains poorly understood. We compared the performances of early (EB), late blind (LB) and sighted control (SC) individuals during various arithmetic tasks involving addition, subtraction and multiplication of various complexities. We also assessed working memory (WM) performances to determine if they relate to a blind person's arithmetic capacities. Results showed that EB participants performed better than LB and SC in arithmetic tasks, especially in conditions in which verbal routines and WM abilities are needed. Moreover, EB participants also showed higher WM abilities. Together, our findings demonstrate that the absence of developmental vision does not prevent the development of refined arithmetic skills and can even trigger the refinement of these abilities in specific tasks.

Reorganization of Human Cerebral Cortex: The Range of Changes Following Use and Injury

Animal and human research over the past decades have increasingly detailed the brain’s capacity for reorganization of neural network architecture to adapt to environmental needs. In this article, the authors outline the range of reorganization of human representational cortex, encompassing 1) reconstruction in concurrence with enhanced behaviorally relevant afferent activity (examples include skilled musicians and blind Braille readers); 2) injury-related response dynamics as, for instance, driven by loss of input (examples include stroke, amputation, or in blind individuals); and 3) maladaptive reorganization pushed by the interaction between neuroplastic processes and aberrant environmental requirements (examples include synchronicity of input nurturing focal hand dystonia). These types of neuroplasticity have consequences for both understanding pathological dynamics and therapeutic options. This will be illustrated in examples of motor and language rehabilitation after stroke, the treatment of focal hand dystonia, and concomitants of injury-related reorganization such as phantom limb pain.

Auditory-Processing Malleability

Auditory processing forms the basis of humans' ability to engage in complex behaviors such as understanding spoken language or playing a musical instrument. Auditory processing is not a rigid, encapsulated process; rather, it interacts intimately with other neural systems and is affected by experience, environmental influences, and active training. Auditory processing is related to language and cognitive function, and impaired auditory processing negatively affects the quality of life of many people. Recent studies suggest that the malleability of the auditory system may be used to study the interaction between sensory and cognitive processes and to enhance human well-being.

Effects of Early and Late Bilingualism on Resting-State Functional Connectivity

Of current interest is how variations in early language experience shape patterns of functional connectivity in the human brain. In the present study, we compared simultaneous (two languages from birth) and sequential (second language learned after age 5 years) bilinguals using a seed-based resting-state MRI approach. We focused on the inferior frontal gyrus (IFG) as our ROI, as recent studies have demonstrated both neurofunctional and neurostructural changes related to age of second language acquisition in bilinguals in this cortical area. Stronger functional connectivity was observed for simultaneous bilinguals between the left and right IFG, as well as between the inferior frontal gyrus and brain areas involved in language control, including the dorsolateral prefrontal cortex, inferior parietal lobule, and cerebellum. Functional connectivity between the left IFG and the right IFG and right inferior parietal lobule was also significantly correlated with age of acquisition for sequential bilinguals; the earlier the second language was acquired, the stronger was the functional connectivity. In addition, greater functional connectivity between homologous regions of the inferior frontal gyrus was associated with reduced neural activation in the left IFG during speech production. The increased connectivity at rest and reduced neural activation during task performance suggests enhanced neural efficiency in this important brain area involved in both speech production and domain-general cognitive processing. Together, our findings highlight how the brain's intrinsic functional patterns are influenced by the developmental timeline in which second language acquisition occurs.

SIGNIFICANCE STATEMENT

Of current interest is how early life experience leaves its footprint on brain structure and function. In this regard, bilingualism provides an optimal way to determine the effects of the timing of language learning because a second language can be learned from birth or later in life. We used resting-state fMRI to look at simultaneous and sequential bilinguals who differed only in age of acquisition, and found stronger connectivity between language and cognitive control regions in bilinguals who learned their two languages simultaneously, a pattern that was associated with more efficient brain activation during speech. Our findings highlight how functional connections in the brain differ depending upon when learning takes place.

Cross-Modal and Intra-Modal Characteristics of Visual Function and Speech Perception Performance in Postlingually Deafened, Cochlear Implant Users

Evidence of visual-auditory cross-modal plasticity in deaf individuals has been widely reported. Superior visual abilities of deaf individuals have been shown to result in enhanced reactivity to visual events and/or enhanced peripheral spatial attention. The goal of this study was to investigate the association between visual-auditory cross-modal plasticity and speech perception in post-lingually deafened, adult cochlear implant (CI) users. Post-lingually deafened adults with CIs (N = 14) and a group of normal hearing, adult controls (N = 12) participated in this study. The CI participants were divided into a good performer group (good CI, N = 7) and a poor performer group (poor CI, N = 7) based on word recognition scores. Visual evoked potentials (VEP) were recorded from the temporal and occipital cortex to assess reactivity. Visual field (VF) testing was used to assess spatial attention and Goldmann perimetry measures were analyzed to identify differences across groups in the VF. The association of the amplitude of the P1 VEP response over the right temporal or occipital cortex among three groups (control, good CI, poor CI) was analyzed. In addition, the association between VF by different stimuli and word perception score was evaluated. The P1 VEP amplitude recorded from the right temporal cortex was larger in the group of poorly performing CI users than the group of good performers. The P1 amplitude recorded from electrodes near the occipital cortex was smaller for the poor performing group. P1 VEP amplitude in right temporal lobe was negatively correlated with speech perception outcomes for the CI participants (r = -0.736, P = 0.003). However, P1 VEP amplitude measures recorded from near the occipital cortex had a positive correlation with speech perception outcome in the CI participants (r = 0.775, P = 0.001). In VF analysis, CI users showed narrowed central VF (VF to low intensity stimuli). However, their far peripheral VF (VF to high intensity stimuli) was not different from the controls. In addition, the extent of their central VF was positively correlated with speech perception outcome (r = 0.669, P = 0.009). Persistent visual activation in right temporal cortex even after CI causes negative effect on outcome in post-lingual deaf adults. We interpret these results to suggest that insufficient intra-modal (visual) compensation by the occipital cortex may cause negative effects on outcome. Based on our results, it appears that a narrowed central VF could help identify CI users with poor outcomes with their device.

Cortical Plasticity and Reorganization in Pediatric Single-sided Deafness Pre- and Postcochlear Implantation: A Case Study

HYPOTHESIS

The purpose of this study was to examine changes in cortical development and neuroplasticity in a child with single-sided deafness (SSD) before and after cochlear implantation (CI).

BACKGROUND

The extent to which sensory pathways reorganize in childhood SSD is not well understood and there is currently little evidence demonstrating the efficacy of CI in children with SSD.

METHODS

High-density 128-channel electroencephalography (EEG) was used to collect cortical auditory evoked potentials (CAEP), cortical visual evoked potentials (CVEP), and cortical somatosensory evoked potentials (CSSEP) in a child with SSD, pre-CI and at subsequent sessions until approximately 3 years post-CI in her right ear which occurred at age 9.86 years. Behavioral correlates of speech perception and sound localization were also measured.

RESULTS

Pre-CI, high-density EEG showed evidence of delayed auditory cortical response morphology, auditory cortical development strongly contralateral (to the normal hearing ear), evidence of increased cognitive load, and cross-modal reorganization by the visual and somatosensory modalities. The post-CI developmental trajectory provided clear evidence of age-appropriate development of auditory cortical responses, and decreased cross-modal reorganization, consistent with improved speech perception and sound localization.

CONCLUSION

Post-CI, the child demonstrated age-appropriate auditory cortical development and improved speech perception and sound localization suggestive of significant benefits from cochlear implantation. Reversal of somatosensory recruitment was clearly apparent, and only a residual amount of visual cross-modal plasticity remained postimplantation. Overall, our results suggest that CI in pediatric SSD patients may benefit from a highly plastic cortex in childhood.

The onset of visual experience gates auditory cortex critical periods

Sensory systems influence one another during development and deprivation can lead to cross-modal plasticity. As auditory function begins before vision, we investigate the effect of manipulating visual experience during auditory cortex critical periods (CPs) by assessing the influence of early, normal and delayed eyelid opening on hearing loss-induced changes to membrane and inhibitory synaptic properties. Early eyelid opening closes the auditory cortex CPs precociously and dark rearing prevents this effect. In contrast, delayed eyelid opening extends the auditory cortex CPs by several additional days. The CP for recovery from hearing loss is also closed prematurely by early eyelid opening and extended by delayed eyelid opening. Furthermore, when coupled with transient hearing loss that animals normally fully recover from, very early visual experience leads to inhibitory deficits that persist into adulthood. Finally, we demonstrate a functional projection from the visual to auditory cortex that could mediate these effects.

Visual and auditory systems influence each other during development. Here, the authors show that the onset of eyelid opening regulates critical points during which the auditory cortex is sensitive to hearing loss or the restoration of hearing

Mother's voice and heartbeat sounds elicit auditory plasticity in the human brain before full gestation

Brain development is largely shaped by early sensory experience. However, it is currently unknown whether, how early, and to what extent the newborn's brain is shaped by exposure to maternal sounds when the brain is most sensitive to early life programming. The present study examined this question in 40 infants born extremely prematurely (between 25- and 32-wk gestation) in the first month of life. Newborns were randomized to receive auditory enrichment in the form of audio recordings of maternal sounds (including their mother's voice and heartbeat) or routine exposure to hospital environmental noise. The groups were otherwise medically and demographically comparable. Cranial ultrasonography measurements were obtained at 30 ± 3 d of life. Results show that newborns exposed to maternal sounds had a significantly larger auditory cortex (AC) bilaterally compared with control newborns receiving standard care. The magnitude of the right and left AC thickness was significantly correlated with gestational age but not with the duration of sound exposure. Measurements of head circumference and the widths of the frontal horn (FH) and the corpus callosum (CC) were not significantly different between the two groups. This study provides evidence for experience-dependent plasticity in the primary AC before the brain has reached full-term maturation. Our results demonstrate that despite the immaturity of the auditory pathways, the AC is more adaptive to maternal sounds than environmental noise. Further studies are needed to better understand the neural processes underlying this early brain plasticity and its functional implications for future hearing and language development.

Synchronization to auditory and visual rhythms in hearing and deaf individuals

A striking asymmetry in human sensorimotor processing is that humans synchronize movements to rhythmic sound with far greater precision than to temporally equivalent visual stimuli (e.g., to an auditory vs. a flashing visual metronome). Traditionally, this finding is thought to reflect a fundamental difference in auditory vs. visual processing, i.e., superior temporal processing by the auditory system and/or privileged coupling between the auditory and motor systems. It is unclear whether this asymmetry is an inevitable consequence of brain organization or whether it can be modified (or even eliminated) by stimulus characteristics or by experience. With respect to stimulus characteristics, we found that a moving, colliding visual stimulus (a silent image of a bouncing ball with a distinct collision point on the floor) was able to drive synchronization nearly as accurately as sound in hearing participants. To study the role of experience, we compared synchronization to flashing metronomes in hearing and profoundly deaf individuals. Deaf individuals performed better than hearing individuals when synchronizing with visual flashes, suggesting that cross-modal plasticity enhances the ability to synchronize with temporally discrete visual stimuli. Furthermore, when deaf (but not hearing) individuals synchronized with the bouncing ball, their tapping patterns suggest that visual timing may access higher-order beat perception mechanisms for deaf individuals. These results indicate that the auditory advantage in rhythmic synchronization is more experience- and stimulus-dependent than has been previously reported.

Cochlear implantation (CI) for prelingual deafness: the relevance of studies of brain organization and the role of first language acquisition in considering outcome success

Cochlear implantation (CI) for profound congenital hearing impairment, while often successful in restoring hearing to the deaf child, does not always result in effective speech processing. Exposure to non-auditory signals during the pre-implantation period is widely held to be responsible for such failures. Here, we question the inference that such exposure irreparably distorts the function of auditory cortex, negatively impacting the efficacy of CI. Animal studies suggest that in congenital early deafness there is a disconnection between (disordered) activation in primary auditory cortex (A1) and activation in secondary auditory cortex (A2). In humans, one factor contributing to this functional decoupling is assumed to be abnormal activation of A1 by visual projections-including exposure to sign language. In this paper we show that that this abnormal activation of A1 does not routinely occur, while A2 functions effectively supramodally and multimodally to deliver spoken language irrespective of hearing status. What, then, is responsible for poor outcomes for some individuals with CI and for apparent abnormalities in cortical organization in these people? Since infancy is a critical period for the acquisition of language, deaf children born to hearing parents are at risk of developing inefficient neural structures to support skilled language processing. A sign language, acquired by a deaf child as a first language in a signing environment, is cortically organized like a heard spoken language in terms of specialization of the dominant perisylvian system. However, very few deaf children are exposed to sign language in early infancy. Moreover, no studies to date have examined sign language proficiency in relation to cortical organization in individuals with CI. Given the paucity of such relevant findings, we suggest that the best guarantee of good language outcome after CI is the establishment of a secure first language pre-implant-however that may be achieved, and whatever the success of auditory restoration.

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.