The impact of maternal smoking on fast auditory brainstem responses

What risk factors for Developmental Language Disorder can tell us about the neurobiological mechanisms of language development

Language is a complex multidimensional cognitive system that is connected to many neurocognitive capacities. The development of language is therefore strongly intertwined with the development of these capacities and their neurobiological substrates. Consequently, language problems, for example those of children with Developmental Language Disorder (DLD), are explained by a variety of etiological pathways and each of these pathways will be associated with specific risk factors. In this review, we attempt to link previously described factors that may interfere with language development to putative underlying neurobiological mechanisms of language development, hoping to uncover openings for future therapeutical approaches or interventions that can help children to optimally develop their language skills.

DNA methylome perturbations: an epigenetic basis for the emergingly heritable neurodevelopmental abnormalities associated with maternal smoking and maternal nicotine exposure†

Maternal smoking during pregnancy is associated with an ensemble of neurodevelopmental consequences in children and therefore constitutes a pressing public health concern. Adding to this burden, contemporary epidemiological and especially animal model research suggests that grandmaternal smoking is similarly associated with neurodevelopmental abnormalities in grandchildren, indicative of intergenerational transmission of the neurodevelopmental impacts of maternal smoking. Probing the mechanistic bases of neurodevelopmental anomalies in the children of maternal smokers and the intergenerational transmission thereof, emerging research intimates that epigenetic changes, namely DNA methylome perturbations, are key factors. Altogether, these findings warrant future research to fully elucidate the etiology of neurodevelopmental impairments in the children and grandchildren of maternal smokers and underscore the clear potential thereof to benefit public health by informing the development and implementation of preventative measures, prophylactics, and treatments. To this end, the present review aims to encapsulate the burgeoning evidence linking maternal smoking to intergenerational epigenetic inheritance of neurodevelopmental abnormalities, to identify the strengths and weaknesses thereof, and to highlight areas of emphasis for future human and animal model research therein.

Prenatal Exposure to Tobacco and Alcohol Alters Development of the Neonatal Auditory System

Prenatal exposures to alcohol (PAE) and tobacco (PTE) are known to produce adverse neonatal and childhood outcomes including damage to the developing auditory system. Knowledge of the timing, extent, and combinations of these exposures on effects on the developing system is limited. As part of the physiological measurements from the Safe Passage Study, Auditory Brainstem Responses (ABRs) and Transient Otoacoustic Emissions (TEOAEs) were acquired on infants at birth and one-month of age. Research sites were in South Africa and the Northern Plains of the U.S. Prenatal information on alcohol and tobacco exposure was gathered prospectively on mother/infant dyads. Cluster analysis was used to characterize three levels of PAE and three levels of PTE. Repeated-measures ANOVAs were conducted for newborn and one-month-old infants for ABR peak latencies and amplitudes and TEOAE levels and signal-to-noise ratios. Analyses controlled for hours of life at test, gestational age at birth, sex, site, and other exposure. Significant main effects of PTE included reduced newborn ABR latencies from both ears. PTE also resulted in a significant reduction of ABR peak amplitudes elicited in infants at 1-month of age. PAE led to a reduction of TEOAE amplitude for 1-month-old infants but only in the left ear. Results indicate that PAE and PTE lead to early disruption of peripheral, brainstem, and cortical development and neuronal pathways of the auditory system, including the olivocochlear pathway.

A sibling-comparison study of smoking during pregnancy and risk for reading-related problems

This research examines the relationship between smoking during pregnancy (SDP) and risk for reading related problems in siblings discordant for exposure to SDP. Data (N = 173 families) were drawn from the Missouri Mothers and Their Children study, a sample, identified using birth records (years 1998-2005), in which mothers changed her smoking behavior between two pregnancies (Child 1 [older sibling]: M = 12.99; Child 2 [younger sibling]: M = 10.19). A sibling comparison approach was used, providing a robust test for the association between SDP and reading related outcomes in school-aged children. Results suggested within-family (i.e., potentially causal) associations between SDP and reading and language/comprehension factor scores, as well as between SDP and specific reading-related skills, including reading accuracy and receptive language, with increased exposure to SDP associated with decreased performance. SDP was not associated with spelling, reading rate, or receptive vocabulary. Initial within-family associations between SDP and word-letter identification, phonetic/decoding skills, and reading comprehension were fully attenuated following partial control for genetic and environmental confounding of the associations. These findings indicate that exposure to SDP is associated with poorer performance on some, but not all skills assessed.

Fifty Years of Research on Prenatal Substances: Lessons Learned for the Opioid Epidemic

Current efforts to design research on developmental effects of prenatal opioid exposure can benefit from knowledge gained from 50 years of studies of fetal alcohol and prenatal drug exposures such as cocaine. Scientific advances in neurobiology, developmental psychopathology, infant assessments, genetics, and imaging support the principles of developmental neurotoxicology that guide research in prenatal exposures. Important to research design is accurate assessment of amount, frequency, and timing of exposure which benefits from accurate self-report and biomarkers of exposure. Identifying and control of pre- and postnatal factors that impact development are difficult and dependent on appropriate research design and selection of comparison groups and measurement of confounding, mediating, and moderating variables. Polysubstance exposure has increased due to the number of prescribed and nonprescribed substances used by pregnant women and varying combinations of drugs may have differential effects on the outcome. Multiple experimental and clinical assessments of infant behavior have been developed but predicting outcome before 18-24 months of age remains difficult. With some exceptions, prenatal substance exposure effect sizes have been small, and cognitive and behavioral effects tend to be specific rather than global. Studies require large sample sizes, adequate retention, and support for social services in at-risk samples. The ethical and legal contexts and stigma associated with drug/alcohol use disorder should be considered in order to prevent harm to families in research programs. Recognition of the pervasive use of addictive substances in this nation should lead to broad scientific efforts to understand how substances affect child outcomes and to initiate prevention and intervention where needed.

Transient Otoacoustic Emissions and Auditory Brainstem Responses in Low-Risk Cohort of Newborn and One-Month-Old Infants: Assessment of Infant Auditory System Physiology in the Prenatal Alcohol in SIDS and Stillbirth Network Safe Passage Study

BACKGROUND

The Prenatal Alcohol and Sudden Infant Death Syndrome and Stillbirth Network, known as the "Safe Passage Study," enrolled approximately 12,000 pregnant women from the United States and South Africa and followed the development of their babies through pregnancy and the infant's first year of life to investigate the role of prenatal alcohol exposure in the risk for sudden infant death syndrome (SIDS) and adverse pregnancy outcomes, such as stillbirth and fetal alcohol spectrum disorders.

PURPOSE

Auditory system tests were included in the physiologic test battery used to study the effects of prenatal alcohol exposure on neurophysiology and neurodevelopment, as well as potential causal relationships between neurodevelopmental disorders and SIDS and/or stillbirth. The purpose of this manuscript is to describe normative results when using the auditory test battery applied.

RESEARCH DESIGN

The test battery included the auditory brainstem response (ABR) and transient-evoked otoacoustic emissions (TEOAEs). Data were collected on individual ears of newborns and 1-month-old infants.

STUDY SAMPLE

From a cohort of 6,070 with auditory system exams, a normative subsample of 325 infants were selected who were not exposed prenatally to alcohol, cigarette smoke, or drugs nor were they preterm or low birthweight. The subsample is small relative to the overall study because of strict criteria for no exposure to substances known to be associated with SIDS or stillbirth and the exclusion of preterm and low birthweight infants. Expectant mothers were recruited from general maternity at two comprehensive clinical sites, in the northern plains in the United States and in Cape Town, South Africa. These populations were selected for study because both were known to be at high-risk for SIDS and stillbirth.

DATA COLLECTION AND ANALYSIS

ABR and TEOAE recordings were stored electronically. Peak latency and amplitude analysis of ABRs were determined by study personnel, and results were evaluated for differences by age, sex, test site, race, and ear (left versus right).

RESULTS

TEOAE findings were consistent with existing literature including the increase in signal-to-noise (SNR) over the first month of life. The SNR increase is due to an increase in amplitude of the emission. TEOAE amplitude asymmetry favoring the right ear was found, whereas SNR asymmetry was not, perhaps because of the small sample size. A nonsignificant trend toward larger responses in female babies was found; a result that is generally statistically significant in studies with larger samples. Latencies were found to be shorter in ABRs elicited in the right ear with amplitudes that were slightly bigger on average. An expected decrease in wave V latency was observed from birth to 1-month of age, but the finding was of borderline significance (p = 0.058).

CONCLUSIONS

One month is a short time to judge development of the auditory system; however, the ABR and TEOAE findings were consistent with current literature. We conclude that the auditory system data acquired for the Safe Passage Study, as reflected in the data obtained from this cohort of "unexposed" infants, is consistent with published reports of these auditory system measures in the general population.

Exposure to tobacco smoke prenatally and during infancy and risk of hearing impairment among children in Japan: A retrospective cohort study

BACKGROUND

Previous studies of the association between tobacco smoke and hearing loss in children are limited, involve small samples and are cross-sectional. We investigated the association of maternal smoking during pregnancy and exposure to tobacco smoke at age 4 months with hearing impairment at age 3 years in children.

METHODS

This population-based retrospective cohort study included 50 734 children born between 2004 and 2010 in Kobe City, Japan. Smoking during pregnancy and exposure to tobacco smoke at 4 months was measured using parent-reported questionnaires. Hearing impairment was determined by the whispered voice test.

RESULTS

Of the included children, 3.8% were exposed to smoking only during pregnancy; 3.9% were exposed only to second-hand smoke at 4 months; and 0.9% were exposed to tobacco smoke during pregnancy and at 4 months. The prevalence of hearing impairment at age 3 years was 4.6%. Compared with children not exposed to tobacco smoke prenatally and at 4 months, the risk of hearing impairment was elevated in children exposed to only maternal past smoking during pregnancy (RR 1.26, 95% CI 1.13, 1.40), only second-hand smoke at 4 months (RR 1.30, 95% CI 1.07, 1.56), only smoking during pregnancy (RR 1.68, 95% CI 1.42, 2.00) and smoking during pregnancy and second-hand smoke at 4 months (RR 2.35, 95% CI 1.79, 3.10).

CONCLUSIONS

Exposure to tobacco smoke prenatally and postnatally was associated with hearing impairment in children. A prevention of smoking before and during pregnancy and exposure to second-hand smoke postnatally may reduce hearing impairment risk in children.

Effect of passive smoking on auditory temporal resolution in children

OBJECTIVE

To determine the effect of passive smoking on auditory temporal resolution in primary school children, based on the hypothesis that individuals who are exposed to smoking exhibit impaired performance.

DESIGN

Auditory temporal resolution was evaluated using the Gaps In Noise (GIN) test. Exposure to passive smoking was assessed by measuring nicotine metabolite (cotinine) excreted in the first urine of the day.

STUDY SAMPLE

The study included 90 children with mean age of 10.2 ± 0.1 years old from a public school in São Paulo. Participants were divided into two groups: a study group, comprising 45 children exposed to passive smoking (cotinine > 5 ng/mL); and a control group, constituting 45 children who were not exposed to passive smoking. All participants had normal audiometry and immittance test results.

RESULTS

Statistically significant differences (p < 0.005) in performance on the GIN test were found between the two groups, with mean thresholds of 5.3 ms and 68.9% correct responses in the study group versus 4.6 ms and 74.0% in the control group.

CONCLUSION

The children exposed to passive smoking had poorer performance both in terms of thresholds and correct responses percentage on auditory temporal resolution assessment.

Camellia sinensis Prevents Perinatal Nicotine-Induced Neurobehavioral Alterations, Tissue Injury, and Oxidative Stress in Male and Female Mice Newborns

Nicotine exposure during pregnancy induces oxidative stress and leads to behavioral alterations in early childhood and young adulthood. The current study aimed to investigate the possible protective effects of green tea (Camellia sinensis) against perinatal nicotine-induced behavioral alterations and oxidative stress in mice newborns. Pregnant mice received 50 mg/kg C. sinensis on gestational day 1 (PD1) to postnatal day 15 (D15) and were subcutaneously injected with 0.25 mg/kg nicotine from PD12 to D15. Nicotine-exposed newborns showed significant delay in eye opening and hair appearance and declined body weight at birth and at D21. Nicotine induced neuromotor alterations in both male and female newborns evidenced by the suppressed righting, rotating, and cliff avoidance reflexes. Nicotine-exposed newborns exhibited declined memory, learning, and equilibrium capabilities, as well as marked anxiety behavior. C. sinensis significantly improved the physical development, neuromotor maturation, and behavioral performance in nicotine-exposed male and female newborns. In addition, C. sinensis prevented nicotine-induced tissue injury and lipid peroxidation and enhanced antioxidant defenses in the cerebellum and medulla oblongata of male and female newborns. In conclusion, this study shows that C. sinensis confers protective effects against perinatal nicotine-induced neurobehavioral alterations, tissue injury, and oxidative stress in mice newborns.

Plausible Roles for RAGE in Conditions Exacerbated by Direct and Indirect (Secondhand) Smoke Exposure

Approximately 1 billion people smoke worldwide, and the burden placed on society by primary and secondhand smokers is expected to increase. Smoking is the leading risk factor for myriad health complications stemming from diverse pathogenic programs. First- and second-hand cigarette smoke contains thousands of constituents, including several carcinogens and cytotoxic chemicals that orchestrate chronic inflammatory responses and destructive remodeling events. In the current review, we outline details related to compromised pulmonary and systemic conditions related to smoke exposure. Specifically, data are discussed relative to impaired lung physiology, cancer mechanisms, maternal-fetal complications, cardiometabolic, and joint disorders in the context of smoke exposure exacerbations. As a general unifying mechanism, the receptor for advanced glycation end-products (RAGE) and its signaling axis is increasingly considered central to smoke-related pathogenesis. RAGE is a multi-ligand cell surface receptor whose expression increases following cigarette smoke exposure. RAGE signaling participates in the underpinning of inflammatory mechanisms mediated by requisite cytokines, chemokines, and remodeling enzymes. Understanding the biological contributions of RAGE during cigarette smoke-induced inflammation may provide critically important insight into the pathology of lung disease and systemic complications that combine during the demise of those exposed.

Perinatal nicotine exposure impairs the maturation of glutamatergic inputs in the auditory brainstem

KEY POINTS

Chronic perinatal nicotine exposure causes abnormal auditory brainstem responses and auditory processing deficits in children and animal models. The effect of perinatal nicotine exposure on synaptic maturation in the auditory brainstem was investigated in granule cells in the ventral nucleus of the lateral lemniscus, which receive a single calyx-like input from the cochlear nucleus. Perinatal nicotine exposure caused a massive reduction in the amplitude of the excitatory input current. This caused a profound decrease in the number and temporal precision of spikes in these neurons. Perinatal nicotine exposure delayed the developmental downregulation of functional nicotinic acetylcholine receptors on these neurons.

ABSTRACT

Maternal smoking causes chronic nicotine exposure during early development and results in auditory processing deficits including delayed speech development and learning difficulties. Using a mouse model of chronic, perinatal nicotine exposure we explored to what extent synaptic inputs to granule cells in the ventral nucleus of the lateral lemniscus are affected by developmental nicotine treatment. These neurons receive one large calyx-like input from octopus cells in the cochlear nucleus and play a role in sound pattern analysis, including speech sounds. In addition, they exhibit high levels of α7 nicotinic acetylcholine receptors, especially during early development. Our whole-cell patch-clamp experiments show that perinatal nicotine exposure causes a profound reduction in synaptic input amplitude. In contrast, the number of inputs innervating each neuron and synaptic release properties of this calyx-like synapse remained unaltered. Spike number and spiking precision in response to synaptic stimulation were greatly diminished, especially for later stimuli during a stimulus train. Moreover, chronic nicotine exposure delayed the developmental downregulation of functional nicotinic acetylcholine receptors on these neurons, indicating a direct action of nicotine in this brain area. This presumably direct effect of perinatal nicotine exposure on synaptic maturation in the auditory brainstem might be one of the underlying causes for auditory processing difficulties in children of heavy smoking mothers.

Developmental toxicity of nicotine: A transdisciplinary synthesis and implications for emerging tobacco products

While the health risks associated with adult cigarette smoking have been well described, effects of nicotine exposure during periods of developmental vulnerability are often overlooked. Using MEDLINE and PubMed literature searches, books, reports and expert opinion, a transdisciplinary group of scientists reviewed human and animal research on the health effects of exposure to nicotine during pregnancy and adolescence. A synthesis of this research supports that nicotine contributes critically to adverse effects of gestational tobacco exposure, including reduced pulmonary function, auditory processing defects, impaired infant cardiorespiratory function, and may contribute to cognitive and behavioral deficits in later life. Nicotine exposure during adolescence is associated with deficits in working memory, attention, and auditory processing, as well as increased impulsivity and anxiety. Finally, recent animal studies suggest that nicotine has a priming effect that increases addiction liability for other drugs. The evidence that nicotine adversely affects fetal and adolescent development is sufficient to warrant public health measures to protect pregnant women, children, and adolescents from nicotine exposure.

Maternal Smoking during Pregnancy and DNA-Methylation in Children at Age 5.5 Years: Epigenome-Wide-Analysis in the European Childhood Obesity Project (CHOP)-Study

Mounting evidence links prenatal exposure to maternal tobacco smoking with disruption of DNA methylation (DNAm) profile in the blood of infants. However, data on the postnatal stability of such DNAm signatures in childhood, as assessed by Epigenome Wide Association Studies (EWAS), are scarce. Objectives of this study were to investigate DNAm signatures associated with in utero tobacco smoke exposure beyond the 12th week of gestation in whole blood of children at age 5.5 years, to replicate previous findings in young European and American children and to assess their biological role by exploring databases and enrichment analysis. DNA methylation was measured in blood of 366 children of the multicentre European Childhood Obesity Project Study using the Illumina Infinium HM450 Beadchip (HM450K). An EWAS was conducted using linear regression of methylation values at each CpG site against in utero smoke exposure, adjusted for study characteristics, biological and technical effects. Methylation levels at five HM450K probes in MYO1G (cg12803068, cg22132788, cg19089201), CNTNAP2 (cg25949550), and FRMD4A (cg11813497) showed differential methylation that reached epigenome-wide significance according to the false-discovery-rate (FDR) criteria (q-value<0.05). Whereas cg25949550 showed decreased methylation (-2% DNAm ß-value), increased methylation was observed for the other probes (9%: cg12803068; 5%: cg22132788; 4%: cg19089201 and 4%: cg11813497) in exposed relative to non-exposed subjects. This study thus replicates previous findings in children ages 3 to 5, 7 and 17 and confirms the postnatal stability of MYO1G, CNTNAP2 and FRMD4A differential methylation. The role of this differential methylation in mediating childhood phenotypes, previously associated with maternal smoking, requires further investigation.

Prenatal Second-Hand Smoke Exposure Measured with Urine Cotinine May Reduce Gross Motor Development at 18 Months of Age

OBJECTIVE

To evaluate the association of second-hand smoke exposure of pregnant mothers using urine cotinine with the neurodevelopment of their children at 18 months of age in the mother-child cohort in Crete (Rhea Study).

STUDY DESIGN

Selected participants were Greek mothers with singleton pregnancies, had never smoked, and had available urine cotinine measurements in pregnancy, and their children for whom a neurodevelopmental assessment was completed. We performed face-to-face interviews twice during pregnancy and postnatally, and assessed children's neurodevelopment at 18 months of age using the Bayley Scales of Infant and Toddler Development, Third Edition. We used linear regression and generalized additive models.

RESULTS

Of 599 mothers, 175 (29%) met the inclusion criteria. Maternal urine cotinine levels were low (mean: 10.3 ng/mL, SD: 11.7 ng/mL). Reported passive smoking from different sources was strongly associated with urine cotinine levels. A negative association was observed between cotinine levels in pregnancy and child's gross motor function (beta = -3.22 per 10 ng/mL, 95% CI -5.09 to -1.34) after adjusting for factors potentially associated with neurodevelopment; results were similar in both sexes. A negative association was also observed for cognitive and receptive communication scales but the effect was small and not statistically significant.

CONCLUSIONS

Maternal exposure during pregnancy to second-hand smoke measured through urine cotinine was associated with a decrease in gross motor function among 18-month-old children, even at low levels of exposure.

Altered placental DNA methylation patterns associated with maternal smoking: current perspectives

The developmental origins of health and disease hypothesis states that adverse early life exposures can have lasting, detrimental effects on lifelong health. Exposure to maternal cigarette smoking during pregnancy is associated with morbidity and mortality in offspring, including increased risks for miscarriage, stillbirth, low birth weight, preterm birth, asthma, obesity, altered neurobehavior, and other conditions. Maternal cigarette smoking during pregnancy interferes with placental growth and functioning, and it has been proposed that this may occur through the disruption of normal and necessary placental epigenetic patterns. Epigenome-wide association studies have identified a number of differentially methylated placental genes that are associated with maternal smoking during pregnancy, including RUNX3, PURA, GTF2H2, GCA, GPR135, and HKR1. The placental methylation status of RUNX3 and NR3C1 has also been linked to adverse infant outcomes, including preterm birth and low birth weight, respectively. Candidate gene analyses have also found maternal smoking-associated placental methylation differences in the NR3C1, CYP1A1, HTR2A, and HSD11B2 genes, as well as in the repetitive elements LINE-1 and AluYb8. The differential methylation patterns of several genes have been confirmed to also exhibit altered gene expression patterns, including CYP1A1, CYP19A1, NR3C1, and HTR2A. Placental methylation patterns associated with maternal smoking during pregnancy may be largely gene-specific and tissue-specific and, to a lesser degree, involve global changes. It is important for future research to investigate the mechanistic roles that these differentially methylated genes may play in mediating the association between maternal smoking during pregnancy and disease in later life, as well as to elucidate the potential influence of emerging tobacco product use during pregnancy, including the use of electronic cigarettes, on placental epigenetics.

Developmental Outcomes of School-Age Children with Duarte Galactosemia: A Pilot Study

Duarte galactosemia (DG) is a mild allelic variant of classic galactosemia that results from partial impairment of galactose-1P uridylyltransferase (GALT). Although infants with DG are detected by newborn screening in some US states at close to 1/4,000 live births, most are discharged from follow-up very early in life and there is no consensus on whether these children are at increased risk for any of the long-term developmental delays seen in classic galactosemia. There is also no consensus on whether infants with DG benefit from dietary restriction of galactose. Reflecting the current uncertainty, some states choose to identify infants with DG by newborn screening and others do not. As a first step toward characterizing the developmental outcomes of school-age children with DG, we conducted a pilot study, testing 10 children with DG and 5 unaffected siblings from the same group of families. All children tested were between 6 and 11 years old. We used standardized direct assessments and parent-response surveys to collect information regarding cognition, communication, socio-emotional, adaptive behavior, and physical development for each child. Despite the small sample size, our data demonstrated some notable differences between cases and controls in socio-emotional development, in delayed recall, and in auditory processing speed. These results confirm that direct assessment of school-age children with DG can detect subtle but potentially problematic developmental deficits, and underscore the need for a larger study which has sufficient power to evaluate these outcomes while controlling for potentially confounding factors.

Smoking during pregnancy affects foetal brain development

Environmental factors such as maternal smoking can significantly modulate genetically programmed brain development during foetal life. This review looks at how prenatal smoking exposure modulates brain development, including new evidence on the effects of smoking on foetal brain development and function.

CONCLUSION

Smoking during pregnancy exposes the foetus to thousands of health-threatening chemicals, restricting foetal body and head growth. Alterations in brain structure and function have been seen in children exposed to prenatal smoking.

Developmental consequences of fetal exposure to drugs: what we know and what we still must learn

Most drugs of abuse easily cross the placenta and can affect fetal brain development. In utero exposures to drugs thus can have long-lasting implications for brain structure and function. These effects on the developing nervous system, before homeostatic regulatory mechanisms are properly calibrated, often differ from their effects on mature systems. In this review, we describe current knowledge on how alcohol, nicotine, cocaine, amphetamine, Ecstasy, and opiates (among other drugs) produce alterations in neurodevelopmental trajectory. We focus both on animal models and available clinical and imaging data from cross-sectional and longitudinal human studies. Early studies of fetal exposures focused on classic teratological methods that are insufficient for revealing more subtle effects that are nevertheless very behaviorally relevant. Modern mechanistic approaches have informed us greatly as to how to potentially ameliorate the induced deficits in brain formation and function, but conclude that better delineation of sensitive periods, dose-response relationships, and long-term longitudinal studies assessing future risk of offspring to exhibit learning disabilities, mental health disorders, and limited neural adaptations are crucial to limit the societal impact of these exposures.

Level of intrauterine cocaine exposure and neuropsychological test scores in preadolescence: subtle effects on auditory attention and narrative memory

Neuropsychological processes such as attention and memory contribute to children's higher-level cognitive and language functioning and predict academic achievement. The goal of this analysis was to evaluate whether level of intrauterine cocaine exposure (IUCE) alters multiple aspects of preadolescents' neuropsychological functioning assessed using a single age-referenced instrument, the NEPSY: A Developmental Neuropsychological Assessment (NEPSY) (Korkman et al., 1998), after controlling for relevant covariates. Participants included 137 term 9.5-year-old children from low-income urban backgrounds (51% male, 90% African American/Caribbean) from an ongoing prospective longitudinal study. Level of IUCE was assessed in the newborn period using infant meconium and maternal report. 52% of the children had IUCE (65% with lighter IUCE, and 35% with heavier IUCE), and 48% were unexposed. Infants with Fetal Alcohol Syndrome, HIV seropositivity, or intrauterine exposure to illicit substances other than cocaine and marijuana were excluded. At the 9.5-year follow-up visit, trained examiners masked to IUCE and background variables evaluated children's neuropsychological functioning using the NEPSY. The association between level of IUCE and NEPSY outcomes was evaluated in a series of linear regressions controlling for intrauterine exposure to other substances and relevant child, caregiver, and demographic variables. Results indicated that level of IUCE was associated with lower scores on the Auditory Attention and Narrative Memory tasks, both of which require auditory information processing and sustained attention for successful performance. However, results did not follow the expected ordinal, dose-dependent pattern. Children's neuropsychological test scores were also altered by a variety of other biological and psychosocial factors.

Neuropathology of cigarette smoking

It is well established that cigarette smoking is hazardous to health and is a risk factor for many chronic diseases. However, its impact on the brain, whether it be from prenatal exposure to maternal cigarette smoking, cerebrovascular disease, Alzheimer's disease (AD) or Parkinson's disease, is still not very clear. Neuroimaging and neuropathological investigations suggest that there are heterogeneous effects of cigarette smoking on the brain. On the one hand, it is quite clear that cigarette smoking causes damage to endothelial cells, resulting in increased risk of cerebrovascular disease. On the other hand, it seems to be associated with different Alzheimer's pathologies in post-mortem brains and experimental models, despite the fact that epidemiological studies clearly indicate a positive correlation between cigarette smoking and increased risk for AD. Interestingly, cigarette smoking appears to be associated with reduced Parkinson's pathology in post-mortem brains. However, although nicotine in cigarettes may have some neuroprotective actions, the effects of all the other toxic compounds in cigarettes cannot be ignored. It is, therefore, our aim to summarize what is known about the neuropathology of cigarette smoking and, in particular, its implications for neurodegenerative diseases.

Neurobehavioral, neurologic, and neuroimaging characteristics of fetal alcohol spectrum disorders

Alcohol consumption during pregnancy can have deleterious consequences for the fetus, including changes in central nervous system development leading to permanent neurologic alterations and cognitive and behavioral deficits. Individuals affected by prenatal alcohol exposure, including those with and without fetal alcohol syndrome, are identified under the umbrella of fetal alcohol spectrum disorders (FASD). While studies of humans and animal models confirm that even low to moderate levels of exposure can have detrimental effects, critical doses of such exposure have yet to be specified and the most clinically significant and consistent consequences occur following heavy exposure. These consequences are pervasive, devastating, and can result in long-term dysfunction. This chapter summarizes the neurobehavioral, neurologic, and neuroimaging characteristics of FASD, focusing primarily on clinical research of individuals with histories of heavy prenatal alcohol exposure, although studies of lower levels of exposure, particularly prospective, longitudinal studies, will be discussed where relevant.

Tobacco smoke exposure during childhood: effect on cochlear physiology

The rate of smoking in Brazil is about 18.8%. Exposure to environmental tobacco smoke is one of the major factors predisposing children to several hazardous health problems. The objective of the present research was to analyze the effect of tobacco smoke exposure during childhood on cochlear physiology by measuring the transient evoked otoacoustic emissions (TEOAE) response levels. Cotinine, the main metabolite of nicotine, was measured in 145 students’ (8–10 years old) urine. Sixty students indicated tobacco smoke exposure (TSE) (cotinine urine levels ≥ 5.0 ng/mL) and 85 did not. The evaluation of TEOAE of TSE students showed lower response levels, mainly on frequencies of 2.8 kHz on the right and left ears and 2.0 kHz on left ear and lower signal noise response levels, mainly on the 1.0 kHz and 1.4 kHz frequencies, when compared to controls that were not exposed to tobacco. The mean hearing loss in tobacco smoke exposure children was 2.1 dB SPL. These results have important implications on the damage to the cochlear structures and indicate a possible loss in hearing and hearing ability development.

Prenatal smoke exposure: effects on infant auditory system and placental gene expression

Prenatal smoke exposure has been shown to change cochlear echo response amplitudes and auditory brainstem response (ABR) wave latencies in newborns. Since gene expression changes are often synchronized in different tissue types, the goal of the present work was to determine the relationships between prenatal smoke exposure induced changes in hearing responses with changes in placental gene expression. Results showed significant cotinine level elevations in mothers who smoked ≥10cigarettes/day during their pregnancy compared to no detectable cotinine in nonsmoking mothers. Cochlear echo response amplitudes in the 2-8kHz range and ABR wave latencies, specifically wave V and interpeak interval I-V, were also significantly reduced in newborns of smoking mothers. Functional pathway analysis of upregulated placental genes using the Database for Annotation, Visualization and Integrated Discovery (DAVID) online software showed significant enrichment of terms associated with neurodevelopmental processes including glutamatergic and cholinergic systems and a number of wingless type proteins in the top two tiers with corrected enrichment p-values of ≤0.05. Other relevant functional pathways were significant at unadjusted enrichment p-values of 0.001-0.11 and included calcium signaling, neurotransmission/neurological processes and oxidative stress. The neurological process clusters included 7 genes (EML2, OTOR, SLC26A5, TBL1X, TECTA, USH1C and USH1G) known to modulate cochlear outer hair cell motility. We localized proteins encoded by the top two regulated genes, TBL1X and USH1C, using immunohistochemistry to placental stem and anchoring villi associated with active contractile function. These placental genes may mediate active contraction and relaxation in the placental villi, for example, during maternal-fetal perfusion matching, similar to the active lengthening and shortening of the cochlear outer hair cells during sensory transduction. Thus, the functional consequence of their alteration in the cochlea would be reflected as a decline in cochlear echoes as shown in this study. Such parallel changes suggest the potential utility of placental gene expression as a surrogate for evaluating changes in the developing cochlea related to potential aberrant cochlear function in newborns with prenatal smoke exposure.

The epigenetics of maternal cigarette smoking during pregnancy and effects on child development

The period of in utero development is one of the most critical windows during which adverse intrauterine conditions and exposures can influence the growth and development of the fetus as well as the child's future postnatal health and behavior. Maternal cigarette smoking during pregnancy remains a relatively common but nonetheless hazardous in utero exposure. Previous studies have associated prenatal smoke exposure with reduced birth weight, poor developmental and psychological outcomes, and increased risk for diseases and behavioral disorders later in life. Researchers are now learning that many of the mechanisms whereby maternal smoke exposure may affect key pathways crucial for proper fetal growth and development are epigenetic in nature. Maternal cigarette smoking during pregnancy has been associated with altered DNA methylation and dysregulated expression of microRNA, but a deeper understanding of the epigenetics of maternal cigarette smoking during pregnancy as well as how these epigenetic changes may affect later health and behavior remain to be elucidated. This article seeks to explore many of the previously described epigenetic alterations associated with maternal cigarette smoking during pregnancy and assess how such changes may have consequences for both fetal growth and development, as well as later child health, behavior, and well-being. We also outline future directions for this new and exciting field of research.

Research review: maternal prenatal distress and poor nutrition - mutually influencing risk factors affecting infant neurocognitive development

BACKGROUND

Accumulating data from animal and human studies indicate that the prenatal environment plays a significant role in shaping children's neurocognitive development. Clinical, epidemiologic, and basic science research suggests that two experiences relatively common in pregnancy - an unhealthy maternal diet and psychosocial distress - significantly affect children's future neurodevelopment. These prenatal experiences exert their influence in the context of one another and yet, almost uniformly, are studied independently.

SCOPE AND METHOD OF REVIEW

In this review, we suggest that studying neurocognitive development in children in relation to both prenatal exposures is ecologically most relevant, and methodologically most sound. To support this approach, we selectively review two research topics that demonstrate the need for dual exposure studies, including exemplar findings on (a) the associations between pregnant women's inadequate maternal intake of key nutrients - protein, fat, iron, zinc, and choline - as well as distress in relation to overlapping effects on children's neurocognitive development; and (b) cross-talk between the biology of stress and nutrition that can amplify each experience for the mother and fetus,. We also consider obstacles to this kind of study design, such as questions of statistical methods for 'disentangling' the exposure effects, and aim to provide some answers.

CONCLUSION

Studies that specifically include both exposures in their design can begin to determine the relative and/or synergistic impact of these prenatal experiences on developmental trajectories - and thereby contribute most fully to the understanding of the early origins of health and disease.

Enhanced auditory brainstem response and parental bonding style in children with gastrointestinal symptoms

BACKGROUND

The electrophysiological properties of the brain and influence of parental bonding in childhood irritable bowel syndrome (IBS) are unclear. We hypothesized that children with chronic gastrointestinal (GI) symptoms like IBS may show exaggerated brainstem auditory evoked potential (BAEP) responses and receive more inadequate parental bonding.

METHODOLOGY/PRINCIPAL FINDINGS

Children aged seven and their mothers (141 pairs) participated. BAEP was measured by summation of 1,000 waves of the electroencephalogram triggered by 75 dB click sounds. The mothers completed their Children's Somatization Inventory (CSI) and Parental Bonding Instrument (PBI). CSI results revealed 66 (42%) children without GI symptoms (controls) and 75 (58%) children with one or more GI symptoms (GI group). The III wave in the GI group (median 4.10 interquartile range [3.95-4.24] ms right, 4.04 [3.90-4.18] ms left) had a significantly shorter peak latency than controls (4.18 [4.06-4.34] ms right, p = 0.032, 4.13 [4.02-4.24] ms left, p = 0.018). The female GI group showed a significantly shorter peak latency of the III wave (4.00 [3.90-4.18] ms) than controls (4.18 [3.97-4.31] ms, p = 0.034) in the right side. BAEP in the male GI group did not significantly differ from that in controls. GI scores showed a significant correlation with the peak latency of the III wave in the left side (rho = -0.192, p = 0.025). The maternal care PBI scores in the GI group (29 [26]-[33]) were significantly lower than controls (31 [28.5-33], p = 0.010), while the maternal over-protection PBI scores were significantly higher in the GI group (16 [12]-[17]) than controls (13 [10.5-16], p = 0.024). Multiple regression analysis in females also supported these findings.

CONCLUSIONS

It is suggested that children with chronic GI symptoms have exaggerated brainstem responses to environmental stimuli and inadequate parental behaviors aggravate these symptoms.

Impaired auditory discrimination learning following perinatal nicotine exposure or β2 nicotinic acetylcholine receptor subunit deletion

Maternal smoking during pregnancy can impair performance of the exposed offspring in tasks that require auditory stimulus processing and perception; however, the tobacco component(s) responsible for these effects and the underlying neurobiological mechanisms remain uncertain. In this study, we show that administration of nicotine during mouse perinatal development can impair performance in an auditory discrimination paradigm when the exposed animals are mature. This suggests that nicotine disrupts auditory pathways via nicotinic acetylcholine receptors (nAChRs) that are expressed at an early stage of development. We have also determined that mice which lack nAChRs containing the β2 subunit (β2* nAChRs) exhibit similarly compromised performance in this task, suggesting that β2* nAChRs are necessary for normal auditory discrimination or that β2* nAChRs play a critical role in development of the circuitry required for task performance. In contrast, no effect of perinatal nicotine exposure or β2 subunit knockout was found on the acquisition and performance of a differential reinforcement of low rate task. This suggests that the auditory discrimination impairments are not a consequence of a general deficit in learning and memory, but may be the result of compromised auditory stimulus processing in the nicotine-exposed and knockout animals.

Maternal smoking during pregnancy and offspring brain structure and function: review and agenda for future research

INTRODUCTION

Maternal smoking during pregnancy (MSDP) has been associated with long-term neurobehavioral and cognitive deficits in offspring. Animal models demonstrate alterations in brain structure and function following prenatal nicotine exposure. However, few studies have assessed the relationship between MSDP and brain development in humans. Therefore, the aims of this review are (a) to synthesize findings from the small number of human studies investigating effects of MSDP on offspring brain development and (b) to outline an agenda for future research in this nascent area.

METHODS

We searched MEDLINE and Psychinfo databases for human studies of MSDP and offspring brain structure and/or function.

RESULTS

Eleven studies meeting our search criteria were identified; 6 studies investigated effects of MSDP on brain structure; 5 examined effects on brain function. Across studies, MSDP was associated with decreased volume/thickness of the cerebellum and corpus callosum, increased auditory brainstem responses, and lack of coordination across brain regions during information and auditory processing.

CONCLUSIONS

Results from the small number of human studies revealed effects of MSDP on brain structure and function, highlighting potential neural pathways linking MSDP and offspring neurobehavioral and cognitive deficits. Given the limited amount of research in this area, we propose an agenda for future research. Gold standard studies would utilize longitudinal designs, integrated biological and maternal report measures of MSDP, and repeated measures of brain structure/function and neurobehavioral deficits across key developmental periods.

Functional neuroimaging in the examination of effects of prenatal alcohol exposure

Functional neuroimaging offers the opportunity to understand the effect of prenatal alcohol exposure on the activities of the brain as well as providing a window into the relationship between neural activation and the behavioral outcomes that have been described in affected individuals. Several different methodologies have been used to examine the neurophysiological signal changes associated with different brain functions in prenatally exposed individuals and those diagnosed with fetal alcohol syndrome (FAS) or other fetal alcohol spectrum disorders (FASD). These include electroencephalography (EEG), positron emission tomography (PET), single-photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI). These studies demonstrate that it is feasible to use these technologies with this clinical population and that the damage to the central nervous system associated with prenatal alcohol exposure has widespread functional implications; however, currently, the literature in these areas is limited and unsystematic. Functional MRI with this clinical population has just begun to explore the implications of prenatal alcohol exposure with the first paper published in 2005. Other methodologies are similarly limited in scope. Nonetheless, these functional neuroimaging studies suggest that prenatal alcohol exposure, or a diagnosis of FAS, may lead to restrictions in neural efficiency or a global decrement in processing resources.

Smoking in pregnancy and parenting stress: maternal psychological symptoms and socioeconomic status as potential mediating variables

INTRODUCTION

The purpose of this study was to examine the impact of smoking in pregnancy on parenting stress. Maternal psychological symptoms and socioeconomic status (SES) were evaluated as potential mediating factors between prenatal cigarette use and later parenting stress.

METHOD

The sample included 218 mothers who were recruited at the hospital after birth and completed a 6-month visit with their infants at a university laboratory. Based on the mothers' responses to interviews at the hospital on tobacco use during pregnancy, the sample included 77 nonsmokers and 141 smokers. Information on sociodemographic variables, prenatal care, and other substance use during pregnancy was collected at the hospital interview. At the 6-month visit, the mothers completed measures of parenting stress and psychological symptoms. Cotinine levels were assessed at both timepoints.

RESULTS

Regression analysis showed that maternal smoking during pregnancy predicted parenting stress in infancy. Maternal symptoms of psychological distress and SES were evaluated simultaneously to determine whether they functioned as mediating variables between smoking in pregnancy and parenting stress. A multiple mediation analysis (Preacher & Hayes, 2008a) showed that maternal psychological symptoms functioned as a mediating variable but that SES did not.

CONCLUSIONS

Results suggest that mothers who smoke in pregnancy are likely to experience higher levels of psychological symptoms, which, in turn, predict higher levels of parenting stress. Smoking in pregnancy may be a marker for symptoms of psychological distress in mothers.

Neurobehavioral manifestations of developmental impairment of the brain

Individual characteristics of human nature (e.g. introversion, extroversion, mood, activity, adaptability, aggressiveness, social ability, anxiety) do not need to be primarily innate. They can be determined by the action of various influences and their interactions on functional development of the brain. There is ample epidemiological and experimental evidence that chemical and/or physical factors acting during sensitive time windows of the brain development can cause mental, behavioral, emotional and/or cognitive disorders. Environmental pollutants, addictive substances, drugs, malnutrition, excessive stress and/or hypoxia-ischemia were reported to induce functional maldevelopment of the brain with consequent neurobehavioral disorders. The article provides review on most significant neurobehavioral manifestations of developmental impairment of the brain during prenatal, perinatal and early postnatal period. The most known adverse factors causing developmental neurobehavioral dysfunctions in humans as well as in experimental animals are discussed.

Maternal alcohol use during pregnancy causes systemic oxidation of the glutathione redox system

BACKGROUND

Increased systemic oxidant stress contributes to a variety of maternal complications of pregnancy. Although the antioxidant glutathione (GSH) and its oxidized component glutathione disulfide (GSSG) have been demonstrated to be significantly altered in the adult alcoholic, the effects of maternal alcohol use during pregnancy on oxidant stress in the postpartum female remain under investigation. We hypothesized that maternal alcohol use would increase systemic oxidant stress in the pregnant female, evidenced by an oxidized systemic GSH redox potential.

METHODS

As a subset analysis of a larger maternal language study, we evaluated the effects of alcohol consumption during pregnancy on the systemic GSH redox status of the postpartum female. Using an extensive maternal questionnaire, postpartum women where queried regarding their alcohol consumption during pregnancy. Any drinking, the occurrence of drinking >3 drinks/occasion, and heavy drinking of >5 drinks/occasion during pregnancy were noted. Using HPLC, maternal plasma samples were analyzed for GSH, oxidized GSSG and the redox potential of the GSH/GSSG antioxidant pair calculated.

RESULTS

Maternal alcohol use occurred in 25% (83/321) of our study sample. Two in ten women reported consuming >3 drinks/occasion during pregnancy, while 1 in 10 women reported consuming alcohol at >5 drinks/occasion. Any alcohol use during pregnancy significantly decreased plasma GSH (p < 0.05), while alcohol at >3 drinks/occasion or >5 drinks/occasion significantly decreased plasma GSH concentration (p < 0.05), increased the percent of oxidized GSSG (p < 0.05), and substantially oxidized the plasma GSH redox potential (p < 0.05).

CONCLUSIONS

Alcohol use during pregnancy, particularly at levels >3 drinks/occasion, caused significant oxidation of the systemic GSH system in the postpartum women. The clinical ramifications of the observed alcohol-induced oxidation of the GSH redox system on high risk pregnancies or on the exposed offspring require more accurate identification and further investigation.