Neonatal Cortical Auditory Evoked Potentials Are Affected by Clinical Conditions Occurring in Early Prematurity

A light in the darkness: Early phases of development and the emergence of cognition

During the prenatal period, the major brain development milestones are posed and calibrated through different mechanisms, among which endogenous activity, that prepares the "system" to face the external environment. However, the specific nature of the human nervous system, intended for brain plasticity that is varied by brain area and prolonged over time, requires much time for environmental experiences to shape the cerebral circuitries. Therefore, the neonate completely depends on the caregiver, and during the first months of postnatal life, it exhibits a transitory and limited repertoire of behaviors and skills that favors the mother in her new role. This transitory condition will gradually give way to more mature competencies, the milestones of which are posed within 2 years of age. This review takes a new perspective on early development and attempts to trace the remarkable changes from in-utero period to the second year of postnatal life, posing a bridge between the neurobiological substrate and behavioral development. We based our work on the "normal" development, pointing out the risks inherent in any development process.

The Impact of Motivation on Sustained Attention in Very Preterm and Term-born Children: An ERP Study

OBJECTIVE

To compare the effect of motivational features on sustained attention in children born very preterm and at term.

METHOD

EEG was recorded while 34 8-to-11-year-old children born very preterm and 34 term-born peers completed two variants of a cued continuous performance task (CPT-AX); a standard CPT-AX with basic shape stimuli, and structurally similar motivating variant, with a storyline, familiar characters, and feedback.

RESULTS

Higher hit rates, quicker response times and larger event-related potential (ERP) amplitudes were observed during the motivating, compared with the standard, task. Although groups did not differ in task performance, between-task differences in ERPs associated with orienting were larger in term-born than very preterm children.

CONCLUSION

The findings add to previous evidence of disruption to the brain networks that support salience detection and selective attention in children born preterm. Manipulations that increase intrinsic motivation can promote sustained attention in both term-born and very preterm children.

Mood and anxiety spectrum disorders detected by neuropsychiatric interviews in young adults born preterm: A prospective cohort study

BACKGROUND

Psychopathology has not yet been studied beyond pediatric age for all degrees of prematurity, including late-preterm, particularly in those who grew up with no apparent neurodevelopmental sequelae. This study aimed to examine psychopathological outcome following preterm birth and admission to neonatal intensive care in young adults without major neurodevelopmental and psychopathological problems that emerged during childhood.

METHODS

An Italian single-center prospective cohort study. Eighty-nine young adults (40 admitted to neonatal intensive care unit with less than 37 weeks of gestation and no medical history of other neurological or psychiatric conditions in childhood and 49 healthy peers born at term, matched by age, sex, and education) underwent neuropsychiatric interviews at the age of 20 ± 1 years; MINI International Neuropsychiatric Interview, Beck Depression Inventory and Barratt Impulsive Scale, results were correlated to individual neonatal data and cognitive measures.

RESULTS

We found a significantly higher prevalence of psychopathology at MINI score (22.5% vs. 4.2%; χ2 = 6.7; p = 0,010) and prevalence of previous stressful life events in the preterm compared to at-term group. B.D.I. (testing depression) and BIS-11(testing impulsivity) did not highlight a statistically significant difference between the groups. All patients had average I.Q., a statistically significant difference (p < 0.001) was observed between groups with a better performance in controls than cases.

CONCLUSIONS

Preterm infants attaining young adult age with otherwise typical development during childhood are at risk of psychopathology and lower resilience to stressful life events. The MINI interview could be a useful tool to highlight the psychopathology of preterm infants attaining adult age.

Postnatal abnormality in brainstem neural conduction in neonatal bronchopulmonary dysplasia survivors

OBJECTIVE

To investigate postnatal neural conduction in the auditory brainstem in neonatal bronchopulmonary dysplasia (BPD) survivors.

METHODS

Thirty-two very preterm BPD survivors were studied at 57-58 weeks of postconceptional age. Brainstem auditory-evoked response was studied using maximum length sequence. Wave latencies and intervals were analyzed in detail. The controls were 37 normal term infants and 35 very preterm non-BPD infants.

RESULTS

Compared with normal term controls, BPD survivors showed significantly shortened I-III interval but significantly prolonged III-V interval and greater III-V/I-III interval ratio. Compared with very preterm non-BPD controls, BPD survivors showed a significant shortening in waves III latency and I-III interval, moderate prolonged III-V interval, and significantly greater III-V/I-III interval ratio. These differences were generally similar at all click rates used. The slopes of latency- and interval-click rate functions in BPD survivors did not differ significantly from the two control groups.

CONCLUSIONS

Brainstem neural conduction in BPD survivors differed from normal term and age-matched non-BPD infants; neural maturation is accelerated in caudal brainstem regions but delayed in rostral regions. Neonatal BPD survivors are associated with differential maturation in neural conduction at caudal and rostral brainstem regions, which may constitute an important risk for postnatal neurodevelopment in BPD survivors.

IMPACT

We found that brainstem neural conduction at PCA 57-58 weeks in neonatal BPD survivors differs from normal term and age-matched non-BPD infants. No major differences were found between normal term and very preterm non-BPD infants in brainstem auditory conduction. Neural conduction in BPD survivors is accelerated in caudal brainstem regions but delayed in rostral regions. Neonatal BPD survivors are associated with differential maturation in neural conduction at caudal and rostral brainstem regions. The abnormality may constitute an important risk for postnatal neurodevelopment in BPD survivors.

Structural and functional brain asymmetries in the early phases of life: a scoping review

Asymmetry characterizes the brain in both structure and function. Anatomical asymmetries explain only a fraction of functional variability in lateralization, with structural and functional asymmetries developing at different periods of life and in different ways. In this work, we perform a scoping review of the cerebral asymmetries in the first brain development phases. We included all English-written studies providing direct evidence of hemispheric asymmetries in full-term neonates, foetuses, and premature infants, both at term post-conception and before. The final analysis included 57 studies. The reviewed literature shows large variability in the used techniques and methodological procedures. Most structural studies investigated the temporal lobe, showing a temporal planum more pronounced on the left than on the right (although not all data agree), a morphological asymmetry already present from the 29th week of gestation. Other brain structures have been poorly investigated, and the results are even more discordant. Unlike data on structural asymmetries, functional data agree with each other, identifying a leftward dominance for speech stimuli and an overall dominance of the right hemisphere in all other functional conditions. This generalized dominance of the right hemisphere for all conditions (except linguistic stimuli) is in line with theories stating that the right hemisphere develops earlier and that its development is less subject to external influences because it sustains functions necessary to survive.

Cortical auditory-evoked potential as a biomarker of central auditory maturation in term and preterm infants during the first 3 months

OBJECTIVES

To analyze central auditory maturation in term and preterm infants during the first 3 months of life by comparing the latency and amplitude of cortical auditory-evoked potential at different frequencies.

METHODS

In this study, 17 term and 18 preterm infants were examined; all had tested positive on the neonatal hearing screening test. Cortical auditory potential was investigated during the first and third months of life. The response of the cortical auditory-evoked potential was investigated at frequencies of 500, 1000, 2000, and 4000 Hz. The latency and amplitude of the cortical response were automatically detected and manually analyzed by three researchers with experience in electrophysiology. The results were compared using analysis of variance and the Bonferroni test. A significance level of 5% was used for all analyses.

RESULTS

Latency values of cortical auditory-evoked potential in the first month of birth were significantly higher than those in the third month, and latency values of the preterm group were higher than those of the term group, regardless of the frequency and time of evaluation. In general, the latency of the cortical auditory-evoked potential was higher at high frequencies. Amplitude values in the third month of life were significantly higher than those in the first month for term and preterm infants.

CONCLUSION

Central auditory maturation was observed in both groups but with different results between those born at term and preterm, with latencies of cortical auditory-evoked potential higher for the preterm group and at high frequencies.

Neonatal spectral EEG is prognostic of cognitive abilities at school age in premature infants without overt brain damage

Prematurity is a prototype of biological risk that could affect the late neurocognitive outcome; however, the condition itself remains a non-specific marker. This longitudinal 6-year study aimed to evaluate the prognostic role of neonatal spectral EEG in premature infants without neurological complications. The study cohort was 26 children born 23-34 gestational ages; all neonates underwent multichannel EEG recordings at 35 weeks post-conception. EEG data were transformed into the frequency domain and divided into delta (0.5-4 Hz), theta (5-7 Hz), alpha (8-13 Hz), and beta (14-20 Hz) frequency bands. At 6 years, a neuropsychological and behavioral evaluation was performed. Correlations between spectral bands and neuropsychological assessments were performed with a conservative and robust Bayesian correlation model using weakly informative priors. The correlation of neuropsychological tasks to spectral frequency bands highlighted a significant association with visual and auditory attention tests. The performance on the same tests appears to be mainly impaired.Conclusions: We found that spectral EEG frequencies are independent predictors of performance in attention tasks. We hypothesized that spectral EEG might reflect early circuitries' imbalance in the reticular ascending system and cumulative effect on ongoing development, pointing to the importance of early prognostic instruments. What is Known: • Prematurity is a non-specific marker of late neurocognitive risk. • Precise prognostic instruments are lacking, mostly in patients with low-grade conditions. What is New: • Longitudinal long-term studies are scarce but crucial for the inferential attributive process. • Spectral EEG frequencies are independent predictors of performance in attention tasks.

Detecting neurodevelopmental trajectories in congenital heart diseases with a machine-learning approach

We aimed to delineate the neuropsychological and psychopathological profiles of children with congenital heart disease (CHD) and look for associations with clinical parameters. We conducted a prospective observational study in children with CHD who underwent cardiac surgery within five years of age. At least 18 months after cardiac surgery, we performed an extensive neuropsychological (intelligence, language, attention, executive function, memory, social skills) and psychopathological assessment, implementing a machine-learning approach for clustering and influencing variable classification. We examined 74 children (37 with CHD and 37 age-matched controls). Group comparisons have shown differences in many domains: intelligence, language, executive skills, and memory. From CHD questionnaires, we identified two clinical subtypes of psychopathological profiles: a small subgroup with high symptoms of psychopathology and a wider subgroup of patients with ADHD-like profiles. No associations with the considered clinical parameters were found. CHD patients are prone to high interindividual variability in neuropsychological and psychological outcomes, depending on many factors that are difficult to control and study. Unfortunately, these dysfunctions are under-recognized by clinicians. Given that brain maturation continues through childhood, providing a significant window for recovery, there is a need for a lifespan approach to optimize the outcome trajectory for patients with CHD.

Tracking evoked responses to auditory and visual stimuli in fetuses exposed to maternal high-risk conditions

Magnetoencephalography (MEG) has been successfully applied to record fetal auditory (auditory evoked response [AER]) and visual evoked responses (VER). In this study, we report the AER and VER development trajectory by tracking the evoked response detectability and latency from recordings starting at 27 weeks of gestation in pregnancies classified as high risk. Fetal MEG and ultrasound recordings were performed on 158 pregnant women, and the total number of fetal auditory and visual tests conducted was 321 and 237, respectively. The overall evoked response analysis showed 237 AER (73.8%) and 164 VER detections (69.2%). The mean AER latency was 290.7 (SD 125.5) ms and the mean VER latency was 293.7 (SD 114.5) ms. The rate of decrease (95% confidence limits) in average AER and VER first-peak latency between 100-350 ms was 1.97 (-1.86, +5.81) ms/week and 1.35 (-3.83, +6.53) ms/week, respectively. This trend in high-risk fetuses conforms to the general trajectory of decrease in latency with gestational age progression, even though this decrease was non-significant, as reported in the case of normal growing fetuses. Although there was a significant difference in detection rates between male and female fetuses, this was not reflected in either latency values or the sensory modality applied. Furthermore, the main factors that had the most significant effect on response detectability included the presence of intervening layers of adipose tissue between the fetal head and stimulus source and an increase in the maternal body mass index.

Early exposure to environment sounds and the development of cortical auditory evoked potentials of preterm infants during the first 3 months of life

OBJECTIVE

Preterm infants are exposed earlier than their term counterparts to unattenuated sounds from the external environment during the sensitive period of the organization of the auditory cortical circuitry. In the current study, we investigate the effect of preterm birth on the course of development of auditory cortical areas by evaluating how gestational age (GA) correlates with the latency of the P1 component of the cortical auditory evoked potential (CAEP) of two experimental groups measured at 1 or 3 months of age.

RESULTS

Our sample consisted of 23 infants delivered at GA ranging from 31.28 to 41.42 weeks and separated into two groups evaluated transversally at 1 or 3 months of corrected age (CA). In the group evaluated at 1-month CA, the latency of the component P1 was similar in both terms and infants classified as late-preterm (GA > 32 weeks). However, in the group evaluated at 3 months CA, P1 latency was significantly smaller in preterms. These preliminary results suggest an acceleration of the development of auditory cortical pathways in preterms, probably due to their early exposure to socially relevant auditory stimuli from the external environment.

White matter injury and neurodevelopmental disabilities: A cross-disease (dis)connection

White matter (WM) injury, once known primarily in preterm newborns, is emerging in its non-focal (diffused), non-necrotic form as a critical component of subtle brain injuries in many early-life diseases like prematurity, intrauterine growth restriction, congenital heart defects, and hypoxic-ischemic encephalopathy. While advances in medical techniques have reduced the number of severe outcomes, the incidence of tardive impairments in complex cognitive functions or psychopathology remains high, with lifelong detrimental effects. The importance of WM in coordinating neuronal assemblies firing and neural groups synchronizing within multiple frequency bands through myelination, even mild alterations in WM structure, may interfere with the cognitive performance that increasing social and learning demands would exploit tardively during children growth. This phenomenon may contribute to explaining longitudinally the high incidence of late-appearing impairments that affect children with a history of perinatal insults. Furthermore, WM abnormalities have been highlighted in several neuropsychiatric disorders, such as autism and schizophrenia. In this review, we gather and organize evidence on how diffused WM injuries contribute to neurodevelopmental disorders through different perinatal diseases and insults. An insight into a possible common, cross-disease, mechanism, neuroimaging and monitoring, biomarkers, and neuroprotective strategies will also be presented.

Electroencephalographic functional connectivity in extreme prematurity: a pilot study based on graph theory

BACKGROUND

Connectivity studies based on functional magnetic resonance imaging (MRI) provided new insights in neonatal brain development but cannot be performed at bedside in the clinical setting. The electroencephalogram (EEG) connectivity has been less studied, particularly using the new approach based on graph theory. This study aimed to explore the functional EEG connectivity using graph theory analysis at an early post-conception age in extremely premature and late-preterm babies free of medical complications and overt brain damage.

METHODS

Sixteen neonates (8 extremely low gestational age (ELGA) and 8 late-preterm infants), both groups having performed multichannel EEG recordings at 35 weeks' post-conception, were recruited in a single tertiary-level neonatal intensive care unit and well-baby nursery, respectively. Global (i.e., small-worldness) and local (i.e., clustering and strength) connectivity measures were calculated on a single-subject connectivity matrix of EEG data.

RESULTS

Both ELGA and late-preterm infants showed small-worldness organization at 35 weeks' post-conception. The ELGA group had the strength parameter of the theta frequency band lower in the right than in the left hemisphere. This asymmetry did not emerge in the late-preterm group. Moreover, the mean strength parameter was significantly greater in the right hemisphere in the late preterms than in the ELGA group.

CONCLUSION

EEG connectivity measures could represent an index of left-to-right maturation and developmental disadvantage in extremely preterm infants.

Efeito do estado atencional na detecção automática das respostas auditivas corticais em neonatos

RESUMO Objetivo O objetivo desse estudo foi comparar a latência e amplitude do potencial evocado auditivo cortical P1i entre neonatos em estado de alerta e durante o sono leve. Métodos Vinte e cinco neonatos com emissões otoacústicas evocadas transientes presentes foram testados, por meio do potencial evocado auditivo cortical (PEAC), sendo dez em estado de alerta e 15 durante o sono leve. Para pesquisa dos potenciais corticais, utilizou-se o equipamento Hearlab System, de um canal, no módulo Cortical Tone Evaluation (CTE). O potencial P1i foi pesquisado de forma monoaural, na intensidade de 80 dBnNA, para as frequências de 500, 1000, 2000 e 4000Hz. A detecção do P1i foi feita de maneira automática pelo equipamento. A marcação da latência e amplitude foi realizada por três juízes. Resultados Não houve diferença estatisticamente significativa entre os dois grupos de neonatos para os valores de amplitude e latência, nas quatro frequências testadas. Conclusão Não houve influência do estado comportamental dos neonatos na avaliação do potencial cortical P1i.

Immuno-modulator inter-alpha inhibitor proteins ameliorate complex auditory processing deficits in rats with neonatal hypoxic-ischemic brain injury

Hypoxic-ischemic (HI) brain injury is recognized as a significant problem in the perinatal period, contributing to life-long language-learning and other cognitive impairments. Central auditory processing deficits are common in infants with hypoxic-ischemic encephalopathy and have been shown to predict language learning deficits in other at risk infant populations. Inter-alpha inhibitor proteins (IAIPs) are a family of structurally related plasma proteins that modulate the systemic inflammatory response to infection and have been shown to attenuate cell death and improve learning outcomes after neonatal brain injury in rats. Here, we show that systemic administration of IAIPs during the early HI injury cascade ameliorates complex auditory discrimination deficits as compared to untreated HI injured subjects, despite reductions in brain weight. These findings have significant clinical implications for improving central auditory processing deficits linked to language learning in neonates with HI related brain injury.