Impact of prenatal exposure to cocaine and tobacco on diffusion tensor imaging and sensation seeking in adolescents

Prenatal influences on postnatal neuroplasticity: Integrating DOHaD and sensitive/critical period frameworks to understand biological embedding in early development

Early environments can have significant and lasting effects on brain, body, and behavior across the lifecourse. Here, we address current research efforts to understand how experiences impact neurodevelopment with a new perspective integrating two well-known conceptual frameworks - the Developmental Origins of Health and Disease (DOHaD) and sensitive/critical period frameworks. Specifically, we consider how prenatal experiences characterized in the DOHaD model impact two key neurobiological mechanisms of sensitive/critical periods for adapting to and learning from the postnatal environment. We draw from both animal and human research to summarize the current state of knowledge on how particular prenatal substance exposures (psychoactive substances and heavy metals) and nutritional profiles (protein-energy malnutrition and iron deficiency) each differentially impact brain circuits' excitation/GABAergic inhibition balance and myelination. Finally, we highlight new research directions that emerge from this integrated framework, including testing how prenatal environments alter sensitive/critical period timing and learning and identifying potential promotional/buffering prenatal exposures to impact postnatal sensitive/critical periods. We hope this integrative framework considering prenatal influences on postnatal neuroplasticity will stimulate new research to understand how early environments have lasting consequences on our brains, behavior, and health.

Relationships Between Prenatal Cocaine Exposure, Cannabis-Use Onset and Emotional and Related Characteristics in Young/Emerging Adults

Background: Exposure to substances in utero may have significant early-life consequences. Less is known about the effects in emerging adulthood, particularly regarding patterns of substance use and related characteristics.Objectives: In this study, we recruited emerging adults, followed since birth, who had been prenatally exposed, or not, to cocaine. Individuals reported on their cannabis, alcohol, and tobacco use, and measures of impulsivity, anhedonia, emotional regulation, and mental health were obtained. Comparisons were made between emerging adults with prenatal cocaine exposure and those without. Correlations were performed between psychological measures and substance use, and regression analyses were conducted to determine potential pathways by which such measures may relate to prenatal exposure or substance use.Results: Individuals with prenatal cocaine exposure (vs. those without) used cannabis at younger ages, reported greater cannabis-use severity, and demonstrated higher impulsivity, state anxiety, and alexithymia. Earlier age of onset of cannabis use was associated with higher impulsivity, state anxiety, alexithymia, and social and physical anhedonia. Cannabis-use age-of-onset mediated the relationship between prenatal cocaine-exposure status and state anxiety and between prenatal cocaine-exposure status and cannabis-use severity in emerging adulthood but not relationships between prenatal cocaine-exposure status and impulsivity or alexithymia in emerging adulthood. Findings suggest that adults with prenatal cocaine exposure may use cannabis at younger ages, which may relate to increased anxiety and more severe use.Conclusions: These findings suggest both mechanisms and possible intervention targets to improve mental health in emerging adults with prenatal cocaine exposure.

The effects of maternal smoking on fetal cranial development. Findings from routine midtrimester sonographic anomaly screening

The aim of this study was to assess the effect of continued smoking before and during pregnancy on mid-trimester fetal head development. A total of 250 pregnant women enrolled in the study. All participants were confirmed to be smokers or non-smokers by verifying breath carbon monoxide readings. Biparietal diameter (BPD), head circumference (HC), lateral ventricle (LV), and cisterna magna (CM) were evaluated by ultrasound between 20-22 weeks of pregnancy. Gender and gestational age-adjusted BPD z- scores were not statistically different between smokers and non-smokers (-0.75 ± 1.6 vs -0.51 ± 1, p = .3). HC measurements and z- scores were significantly lower in the smoking group than in the non-smoking groups (183.38 ± 14.56 vs. 189.28 ± 12.53, p = .003, 0.18 ± 1.39 multiple of median (MoM) vs. 0.56 ± 0.92, respectively, p = .023). At linear regression analysis, maternal smoking was the only independent factor associated with fetal HC z score (p = .041). In conclusion, continued smoking during pregnancy reduces fetal HC and has no effect on BPD, LV, or CM measurements at mid-gestation.IMPACT STATEMENTWhat is already known on this subject? Smoking during pregnancy is one of the most common environmental factors affecting fetal and neonatal growth and well-being. Despite the well-known effects of smoking on somatic growth, current studies have shown that it selectively affects some parts of the fetal brain, even in appropriately growing fetuses.What do the results of this study add? Continued smoking during pregnancy reduces fetal HC and has no effect on BPD, LV or CM measurements at mid-gestation. Since smoking is well known for its early and late childhood behavioral and neurological consequences, smaller mid-trimester fetal HC measurements should bring maternal smoking to mind as one of the potentially reversible causes.What are the implications of these findings for clinical practice and/or further research? The harmful effects of smoking start before the third trimester and antenatal counseling should be started early in the gestation. Every effort should be made to quit smoking before or early in pregnancy.

Neuroimaging in infants with prenatal opioid exposure: Current evidence, recent developments and targets for future research

Prenatal opioid exposure (POE) has shown to be a risk factor for adverse long-term cognitive and behavioral outcomes in offspring. However, the neural mechanisms of these outcomes remain poorly understood. While preclinical and human studies suggest that these outcomes may be due to opioid-mediated changes in the fetal and early postnatal brain, other maternal, social, and environmental factors are also shown to play a role. Recent neuroimaging studies reveal brain alterations in children with POE. Early neuroimaging and novel methodology could provide an in vivo mechanistic understanding of opioid mediated alterations in developing brain. However, this is an area of ongoing research. In this review we explore recent imaging developments in POE, with emphasis on the neonatal and infant brain, and highlight some of the challenges of imaging the developing brain in this population. We also highlight evidence from animal models and imaging in older children and youth to understand areas where future research may be targeted in infants with POE.

Prenatal exposure to maternal cigarette smoking and structural properties of the human corpus callosum

Alterations induced by prenatal exposure to nicotine have been observed in experimental (rodent) studies. While numerous developmental outcomes have been associated with prenatal exposure to maternal cigarette smoking (PEMCS) in humans, the possible relation with brain structure is less clear. Here we sought to elucidate the relation between PEMCS and structural properties of human corpus callosum in adolescence and early adulthood in a total of 1,747 youth. We deployed three community-based cohorts of 446 (age 25-27 years, 46% exposed), 934 (age 12-18 years, 47% exposed) and 367 individuals (age 18-21 years, 9% exposed). A mega-analysis revealed lower mean diffusivity in the callosal segments of exposed males. We speculate that prenatal exposure to maternal cigarette smoking disrupts the early programming of callosal structure and increases the relative portion of small-diameter fibres.

Does early maternal responsiveness buffer prenatal tobacco exposure effects on young children's behavioral disinhibition?

Children with prenatal tobacco exposure (PTE) exhibit early self-regulatory impairments, reflecting a life-course persistent propensity toward behavioral disinhibition. Previously, we demonstrated the protective role of parental responsiveness for reducing the risk of exposure-related disruptive behavior in adolescence. Here, we expanded this line of inquiry, examining whether responsiveness moderates the relation of PTE to a broader set of behavioral disinhibition features in early childhood and testing alternative diathesis-stress versus differential susceptibility explanatory models. PTE was assessed prospectively using interviews and bioassays in the Midwestern Infant Development Study (MIDS). Mother-child dyads (N = 276) were re-assessed at approximately 5 years of age in a preschool follow-up. We quantified maternal responsiveness and child behavioral disinhibition using a combination of directly observed activities in the lab and developmentally sensitive questionnaires. Results supported a diathesis-stress pattern. Children with PTE and less responsive mothers showed increased disruptive behavior and lower effortful control compared with children without PTE. In contrast, exposed children with more responsive mothers had self-regulatory profiles similar to their non-exposed peers. We did not observe sex differences. Findings provide greater specification of the protective role of maternal responsiveness for self-regulation in children with PTE and help clarify mechanisms that may underscore trajectories of exposure-related behavioral disinhibition.

An examination of the association between prenatal cocaine exposure and brain activation measures of arousal and attention in young adults: An fMRI study using the Attention Network Task

Prenatal drug exposure, including cocaine, alcohol, marijuana, and tobacco, is associated with deficits in behavioral regulation and attention. Using fMRI, the objective of this study was to characterize the association between prenatal cocaine exposure (PCE) and the underlying neural substrates associated with behavioral outcomes of attention. Forty-seven young adults were recruited for this study from the ongoing Maternal Health Practices and Child Development (MHPCD) Project, a longitudinal study of the effects of PCE on growth, behavior, and cognitive function. Three groups were compared: 1) prenatal exposure to cocaine, alcohol, marijuana, and tobacco (CAMT, n = 15), 2) prenatal exposure to alcohol, marijuana, and tobacco (AMT, n = 17), and 3) no prenatal exposure to drugs (Controls, n = 15). Subjects were frequency matched on gender, race, handedness, and 15-year IQ. This study used the theoretical model proposed by Posner and Peterson (1990), which posits three dissociable components of attention: alerting, orienting, and executive attention. Subjects completed a functional MRI (fMRI) scan while performing the Attention Network Task, a validated neuroimaging measure of the 3-network model of attention. Behavioral and fMRI data revealed no associations between PCE and task accuracy, speed of processing, or activation in key brain regions associated with each of the attention networks. The results of this study show that any subtle differences in brain function associated with PCE are not detectable using the ANT task and fMRI. These results should be interpreted in the context of other studies that have found associations between PCE and arousal with emotionally arousing stimuli, compared to this study that found no associations using emotionally neutral stimuli.

Prenatal methamphetamine exposure is associated with corticostriatal white matter changes in neonates

Diffusion tensor imaging (DTI) studies have shown that prenatal exposure to methamphetamine is associated with alterations in white matter microstructure, but to date no tractography studies have been performed in neonates. The striato-thalamo-orbitofrontal circuit and its associated limbic-striatal areas, the primary circuit responsible for reinforcement, has been postulated to be dysfunctional in drug addiction. This study investigated potential white matter changes in the striatal-orbitofrontal circuit in neonates with prenatal methamphetamine exposure. Mothers were recruited antenatally and interviewed regarding methamphetamine use during pregnancy, and DTI sequences were acquired in the first postnatal month. Target regions of interest were manually delineated, white matter bundles connecting pairs of targets were determined using probabilistic tractography in AFNI-FATCAT, and fractional anisotropy (FA) and diffusion measures were determined in white matter connections. Regression analysis showed that increasing methamphetamine exposure was associated with reduced FA in several connections between the striatum and midbrain, orbitofrontal cortex, and associated limbic structures, following adjustment for potential confounding variables. Our results are consistent with previous findings in older children and extend them to show that these changes are already evident in neonates. The observed alterations are likely to play a role in the deficits in attention and inhibitory control frequently seen in children with prenatal methamphetamine exposure.

Long-term effects of prenatal drug exposure on the neural correlates of memory at encoding and retrieval

The objective of the current study was to examine what stage of memory (encoding or retrieval) may be compromised in adolescents with a history of prenatal drug exposure (PDE) and how the effects of PDE on memory ability are substantiated at the neural level. To achieve this goal, we examined memory performance and associated brain activations in adolescents with and without a history of PDE via event-related fMRI during encoding and retrieval. Consistent with previous studies, we found that PDE subjects remembered fewer items than community comparison subjects. However, there were no differences in behavior after adjusting for correct rejections (i.e., d'). Novel extensions of previous work are findings that PDE is associated with changes in brain activation during memory encoding but not during retrieval. These results suggest that less optimal memory performance often observed in adolescents with a history of PDE may result from variations in encoding rather than retrieval processes.

Diffusion MRI of white matter microstructure development in childhood and adolescence: Methods, challenges and progress

Diffusion magnetic resonance imaging (dMRI) continues to grow in popularity as a useful neuroimaging method to study brain development, and longitudinal studies that track the same individuals over time are emerging. Over the last decade, seminal work using dMRI has provided new insights into the development of brain white matter (WM) microstructure, connections and networks throughout childhood and adolescence. This review provides an introduction to dMRI, both diffusion tensor imaging (DTI) and other dMRI models, as well as common acquisition and analysis approaches. We highlight the difficulties associated with ascribing these imaging measurements and their changes over time to specific underlying cellular and molecular events. We also discuss selected methodological challenges that are of particular relevance for studies of development, including critical choices related to image acquisition, image analysis, quality control assessment, and the within-subject and longitudinal reliability of dMRI measurements. Next, we review the exciting progress in the characterization and understanding of brain development that has resulted from dMRI studies in childhood and adolescence, including brief overviews and discussions of studies focusing on sex and individual differences. Finally, we outline future directions that will be beneficial to the field.

White-matter crossing-fiber microstructure in adolescents prenatally exposed to cocaine

BACKGROUND

Prenatal cocaine exposure (PCE) is associated with risk-taking behaviors, including increased initiation of substance use in adolescence. The neurobiological underpinnings of these behaviors in adolescents with PCE are not well understood. The goal of this study was to compare diffusion-weighted imaging data between adolescents with and without PCE using crossing-fiber models, which may provide more comprehensive estimates of white-matter microstructure within regions of multiple (e.g., primary and secondary) fiber orientations.

METHODS

Thirty-nine PCE individuals and 17 comparably aged prenatally non-drug-exposed (NDE) youths were recruited from a longitudinal cohort followed since birth. White matter was examined using tensor-derived and crossing-fiber models. Whole-brain investigations were performed, as were analyses on seven white-matter regions, which included the splenium, body and genu of the corpus callosum, bilateral cingulum, and the right and left superior longitudinal fasciculus (SLF).

RESULTS

Whole-brain analyses revealed no group differences. However, ROI analyses for anisotropy estimates derived from the crossing-fiber model revealed significant group differences for secondary fibers, with reduced anisotropy among PCE adolescents compared to prenatally non-exposed youth in the right cingulum and the left SLF, and increased anisotropy in the genu.

CONCLUSIONS

Our findings suggest that white-matter differences in PCE adolescents are subtle and localized primarily within secondary fiber orientations, perhaps arising from altered white-matter development.

The effects of nicotine on human fetal development

Maternal smoking during pregnancy continues to represent a major public health concern. Nicotine is extremely harmful to the developing fetus through many different mechanisms, and the harms increase with later gestational age at exposure. Pregnancies complicated by maternal nicotine use are more likely to have significant adverse outcomes. Nicotine-exposed children tend to have several health problems throughout their lives, including impaired function of the endocrine, reproductive, respiratory, cardiovascular, and neurologic systems. Poor academic performance and significant behavioral disruptions are also common, including ADHD, aggressive behaviors, and future substance abuse. To diminish the adverse effects from cigarette smoking, some women are turning to electronic cigarettes, a new trend that is increasing in popularity worldwide. They are largely perceived as being safer to use in pregnancy than traditional cigarettes, although there is not adequate evidence to support this claim. At this time, electronic cigarette use during pregnancy cannot be recommended. Birth Defects Research (Part C) 108:181-192, 2016. © 2016 Wiley Periodicals, Inc.

Structural imaging for addiction medicine: From neurostructure to neuroplasticity

Quantitative morphometry and diffusion tensor imaging have provided new insights into structural brain changes associated with drugs of abuse. In this chapter, we review recent studies using these methods to investigate structural brain abnormalities associated with excessive use of marijuana, stimulants, and opiates. Although many brain regions have been associated with structural abnormalities following abuse of these drugs, brain systems underlying inhibition, mood regulation, and reward are particularly involved. Candidate pathological mechanisms underlying these structural abnormalities include the direct toxic effects of the drugs, neuroinflammation, ischemia, hemorrhage, and abnormal brain development. Returning damaged brain areas to neural health would involve enhancing neuroplasticity. Behavioral, environmental, pharmacological, and cell-based therapies have been correlated with enhanced neuroplasticity following brain injury, providing a basis for new treatments of brain changes associated with excessive drug use. When testing new treatments, structural imaging may prove useful in selecting patients, monitoring recovery, and perhaps, tailoring interventions.

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.

The long-term effects of prenatal nicotine exposure on verbal working memory: an fMRI study of young adults

BACKGROUND

Using functional magnetic resonance imaging (fMRI), the long-term effects of prenatal nicotine exposure on verbal working memory were investigated in young adults. Participants were members of the Ottawa Prenatal Prospective Study, a longitudinal study that collected a unique body of information on participants from infancy to young adulthood. This allowed for the measurement of an unprecedented number of potentially confounding drug exposure variables including: prenatal marijuana and alcohol exposure and current marijuana, nicotine and alcohol use.

METHODS

Twelve young adults with prenatal nicotine exposure and 13 non-exposed controls performed a 2-Back working memory task while fMRI blood oxygen level-dependent responses were examined. Despite similar task performance, participants with more prenatal nicotine exposure demonstrated significantly greater activity in several regions of the brain that typically subserve verbal working memory including the middle frontal gyrus, precentral gyrus, the inferior parietal lobe and the cingulate gyrus.

RESULTS

These results suggest that prenatal nicotine exposure contributes to altered neural functioning during verbal working memory that continues into adulthood. Working memory is critical for a wide range of cognitive skills such as language comprehension, learning and reasoning.

CONCLUSION

Thus, these findings highlight the need for continued educational programs and public awareness campaigns to reduce tobacco use among pregnant women.

Environmental tobacco smoke in the early postnatal period induces impairment in brain myelination

Environmental tobacco smoke (ETS) is associated with high morbidity and mortality, mainly in children. However, few studies focus on the brain development effects of ETS exposure. Myelination mainly occurs in the early years of life in humans and the first three postnatal weeks in rodents and is sensitive to xenobiotics exposure. This study investigated the effects of early postnatal ETS exposure on myelination. BALB/c mice were exposed to ETS generated from 3R4F reference research cigarettes from the third to the fourteenth days of life. The myelination of nerve fibers in the optic nerve by morphometric analysis and the levels of Olig1 and myelin basic protein (MBP) were evaluated in the cerebellum, diencephalon, telencephalon, and brainstem in infancy, adolescence, and adulthood. Infant mice exposed to ETS showed a decrease in the percentage of myelinated fibers in the optic nerve, compared with controls. ETS induced a decrease in Olig1 protein levels in the cerebellum and brainstem and an increase in MBP levels in the cerebellum at infant. It was also found a decrease in MBP levels in the telencephalon and brainstem at adolescence and in the cerebellum and diencephalon at adulthood. The present study demonstrates that exposure to ETS, in a critical phase of development, affects the percentage of myelinated fibers and myelin-specific proteins in infant mice. Although we did not observe differences in the morphological analysis in adolescence and adulthood, there was a decrease in MBP levels in distinctive brain regions suggesting a delayed effect in adolescence and adulthood.

Structural brain imaging in children and adolescents following prenatal cocaine exposure: preliminary longitudinal findings

The brain morphometry of 21 children, who were followed from birth and underwent structural brain magnetic resonance imaging at 8-10 years, was studied. This cohort included 11 children with prenatal cocaine exposure (CE) and 10 noncocaine-exposed children (NCE). We compared the CE versus NCE groups using FreeSurfer to automatically segment and quantify the volume of individual brain structures. In addition, we created a pediatric atlas specifically for this population and demonstrate the enhanced accuracy of this approach. We found an overall trend towards smaller brain volumes among CE children. The volume differences were significant for cortical gray matter, the thalamus and the putamen. Here, reductions in thalamic and putaminal volumes showed a robust inverse correlation with exposure levels, thus highlighting effects on dopamine-rich brain regions that form key components of brain circuitry known to play important roles in behavior and attention. Interestingly, head circumferences (HCs) at birth as well as at the time of imaging showed a tendency for smaller size among CE children. HCs at the time of imaging correlated well with the cortical volumes for all subjects. In contrast, HCs at birth were predictive of the cortical volume only for the CE group. A subgroup of these subjects (6 CE, 4 NCE) was also scanned at 13-15 years of age. In subjects who were scanned twice, we found that the trend for smaller structures continued into teenage years. We found that the differences in structural volumes between the CE and NCE groups are largely diminished when the HCs are controlled for or matched by study design. Participants in this study were drawn from a unique longitudinal cohort and, while the small sample size precludes strong conclusions regarding the longitudinal findings reported, the results point to reductions in HCs and in specific brain structures that persist through teenage years in children who were exposed to cocaine in utero.

Prenatal tobacco exposure and response inhibition in school-aged children: an event-related potential study

Prenatal cigarette smoke exposure (PCSE) has been linked to problems in behavioral inhibition and attention deficit hyperactivity disorder in children in several epidemiological studies. We used event-related potentials (ERPs) to examine the effects of PCSE on neural correlates of inhibitory control of behavior. In a prospective longitudinal study on child development in the Canadian Arctic, we assessed 186 Inuit children (mean age=11.3years) on a visual Go/No-go response inhibition paradigm. PCSE was assessed through maternal recall. Potential confounders were documented from a maternal interview, and exposure to neurotoxic environmental contaminants was assessed from umbilical cord and child blood samples. PCSE was not related to behavioral performance on this simple response inhibition task. Nevertheless, this exposure was associated with smaller amplitudes of the N2 and P3 components elicited by No-go stimuli, suggesting an impairment in the neural processes underlying response inhibition. Amplitude of the No-go P3 component was also inversely associated with behavioral measures of externalizing problems and hyperactivity/impulsivity in the classroom. This study is the first to report neurophysiological evidence of impaired response inhibition in school-aged children exposed to tobacco smoke in utero. Effects were found on ERP components associated with conflict processing and inhibition of a prepotent response, indicating neurophysiological deficits that may play a critical role in the attention and behavior problems observed in children with PCSE.

Comparison of 12-year-old children with prenatal exposure to cocaine and non-exposed controls on caregiver ratings of executive function

Differences in caregiver reported executive function in 12-year-old children who were prenatally exposed to cocaine (PCE) compared to children who were not prenatally exposed to cocaine (NCE) were assessed. One hundred and sixty-nine PCE and 169 NCE, primarily African-American, low socioeconomic status children participated in a prospective longitudinal study. The Behavior Rating Inventory of Executive Function (BRIEF) Parent Form was administered. Two broadband BRIEF scores (Behavioral Regulation Index (BRI) and Metacognition Index (MI)) and a summary Global Executive Composite (GEC) were computed. Multiple and logistic regression analyses were used to assess the effects of amount of PCE on executive function, controlling for covariates including caregiver (rater) psychological distress, child's gender and other prenatal drug exposure variables. After adjustment for covariates, amount of PCE was associated with the GEC and two MI subscales, Plan/Organize and Monitor, with heavier exposure associated with more problems of executive function. An amount of PCE by gender interaction revealed amount of PCE effects in other remaining subscales of the MI (Initiate, Working Memory, and Organization of Materials) only among girls. Head circumference did not mediate the effects of cocaine on outcomes. Higher current caregiver psychological distress levels were independently associated with poorer ratings on the executive function scales. Assessment and targeted interventions to improve metacognitive processes are recommended for girls who were prenatally exposed to cocaine.

White matter microstructure abnormalities and executive function in adolescents with prenatal cocaine exposure

Children with prenatal exposure to cocaine are at higher risk for negative behavioral function and attention difficulties, and have demonstrated brain diffusion abnormalities in frontal white matter regions. However, brain regions beyond frontal and callosal areas have not been investigated using diffusion tensor imaging (DTI). DTI data were collected on 42 youth aged 14-16 years; subjects were divided into three groups based on detailed exposure histories: those with prenatal exposure to cocaine but not alcohol (prenatal cocaine exposure (PCE), n=12), prenatal exposure to cocaine and alcohol (cocaine and alcohol exposure (CAE), n=17), and controls (n=13). Tractography was performed and along-tract diffusion parameters were examined for group differences and correlations with executive function measures. In the right arcuate fasciculus and cingulum, the CAE group had higher fractional anisotropy (FA) and/or lower mean diffusivity (MD) than the other two groups. The PCE group demonstrated lower FA in the right arcuate and higher MD in the splenium of the corpus callosum than controls. Diffusion parameters in tracts with group differences correlated with measures of executive function. In conclusion, these diffusion differences in adolescents with prenatal cocaine exposure suggest localized, long-term structural brain alterations that may underlie attention and response-inhibition difficulties.

Prenatal and gestational cocaine exposure: Effects on the oxytocin system and social behavior with implications for addiction

Drug abuse during pregnancy is a major public health concern, with negative consequences throughout development. Prenatal cocaine exposure (PCE) in rats produces social behavior deficits with corresponding changes in neuroendocrine and monoaminergic signaling. The relevance of parental care in social behavior maturity cannot be ignored, and gestational exposure to cocaine severely disrupts parental care, thus impacting the early environment of the offspring. Oxytocin (Oxt) is critical in regulating social behaviors and central levels are disrupted following acute and chronic cocaine (CC) treatment in postpartum rat dams, coincident with deficits in maternal care. We will discuss studies aimed to determine the relative contribution of PCE and CC-induced deficits in maternal care to social behaviors and Oxt signaling across development. PCE results in decreased social (including parental) behaviors in adolescence and adulthood. PCE is also associated with increased aggression in adults. Rearing by CC-exposed mothers synergistically increases the behavioral effects of PCE. Rearing by CC-exposed mothers, but not PCE, disrupts Oxt levels and mRNA in regions relevant to social behavior, but does not affect receptors in postpartum adult offspring. Preliminary work indicates that PCE/CC rearing has dynamic effects on Oxt levels and receptors in neonatal rat pups, suggesting very early regulation of Oxt signaling. This work highlights how the interactive role of Oxt signaling and behavioral context throughout development can be derailed by drug abuse during pregnancy. The relevance of disrupted Oxt to intergenerational transmission of addiction is briefly discussed.

Systematic review of prenatal cocaine exposure and adolescent development

BACKGROUND AND OBJECTIVE

Previous research found that prenatal cocaine exposure (PCE) may increase children's vulnerability to behavior and cognition problems. Maturational changes in brain and social development make adolescence an ideal time to reexamine associations. The objective was to conduct a systematic review of published studies examining associations between PCE and adolescent development (behavior, cognition/school outcomes, physiologic responses, and brain morphology/functioning).

METHODS

Articles were obtained from PubMed, PsycInfo, Web of Science, and CINAHL databases through July 2012 with search terms: prenatal drug, substance, or cocaine exposure; adolescence/adolescent; and in utero substance/drug exposure. Criteria for inclusion were nonexposed comparison group, human adolescents aged 11 to 19, peer-reviewed, English-language, and adolescent outcomes.

RESULTS

Twenty-seven studies representing 9 cohorts met the criteria. Four outcome categories were identified: behavior, cognition/school performance, brain structure/function, and physiologic responses. Eleven examined behavior; 7 found small but significant differences favoring nonexposed adolescents, with small effect sizes. Eight examined cognition/school performance; 6 reported significantly lower scores on language and memory tasks among adolescents with PCE, with varying effect sizes varied. Eight examined brain structure/function and reported morphologic differences with few functional differences. Three examined physiologic responses with discordant findings. Most studies controlled for other prenatal exposures, caregiving environment, and violence exposure; few examined mechanisms.

CONCLUSIONS

Consistent with findings among younger children, PCE increases the risk for small but significantly less favorable adolescent functioning. Although the clinical importance of differences is often unknown, the caregiving environment and violence exposure pose additional threats. Future research should investigate mechanisms linking PCE with adolescent functioning.

Prenatal tobacco exposure predicts differential brain function during working memory in early adolescence: a preliminary investigation

Children prenatally exposed to tobacco exhibit higher rates of learning and emotional-behavioral problems related to worse working memory performance. Brain function, however, among tobacco exposed children while performing a working memory task has not previously been examined. This study compared the brain function of tobacco-exposed (n = 7) and unexposed (n = 11) 12-year-olds during a number N-back working memory task using an event-related functional magnetic resonance imaging (fMRI) design. Prenatal alcohol exposure, neonatal medical problems, environmental risk, and sex were statistically controlled. Tobacco-exposed children showed greater activation in inferior parietal regions, whereas unexposed children showed greater activation in inferior frontal regions. These differences were observed in the context of correct responses, suggesting that exposed and unexposed children use different brain regions and approaches to succeed in working memory tasks. Implications for future research and intervention are discussed.

Are there volumetric brain differences associated with the use of cocaine and amphetamine-type stimulants?

While a large number of studies have examined brain volume differences associated with cocaine use, much less is known about structural differences related to amphetamine-type stimulant (ATS) use. What is known about cocaine may help to interpret emerging information on the interaction of brain volume with ATS consumption. To date, volumetric studies on the two types of stimulant have focused almost exclusively on brain differences associated with chronic use. There is considerable variability in the findings between studies which may be explained in part by the wide variety of methodologies employed. Despite this variability, seven recurrent themes are worth noting: (1) loci of lower cortical volume (approximately 10% on average) are consistently reported, (2) almost all studies indicate less volume in all or parts of the frontal cortex, (3) more specifically, a core group of studies implicate the ventromedial prefrontal cortex (including the medial portion of the orbital frontal cortex) and (4) the insula, (5) an enlarged striatal volume has been repeatedly observed, (6) reports on volume differences in the hippocampus and amygdala have been equivocal, (7) evidence supporting differential interaction of brain structure with cocaine vs. ATS is scant but the volume of all or parts of the temporal cortex appear lower in a majority of studies on cocaine but not ATS. Future research should include longitudinal designs on larger sample sizes and examine other stages of exposure to psychostimulants.

Adolescents with prenatal cocaine exposure show subtle alterations in striatal surface morphology and frontal cortical volumes

Background

Published structural neuroimaging studies of prenatal cocaine exposure (PCE) in humans have yielded somewhat inconsistent results, with several studies reporting no significant differences in brain structure between exposed subjects and controls. Here, we sought to clarify some of these discrepancies by applying methodologies that allow for the detection of subtle alterations in brain structure.

Methods

We applied surface-based anatomical modeling methods to magnetic resonance imaging (MRI) data to examine regional changes in the shape and volume of the caudate and putamen in adolescents with prenatal cocaine exposure (n = 40, including 28 exposed participants and 12 unexposed controls, age range 14 to 16 years). We also sought to determine whether changes in regional brain volumes in frontal and subcortical regions occurred in adolescents with PCE compared to control participants.

Results

The overall volumes of the caudate and putamen did not significantly differ between PCE participants and controls. However, we found significant (P <0.05, uncorrected) effects of levels of prenatal exposure to cocaine on regional patterns of striatal morphology. Higher levels of prenatal cocaine exposure were associated with expansion of certain striatal subregions and with contraction in others. Volumetric analyses revealed no significant changes in the volume of any subcortical region of interest, but there were subtle group differences in the volumes of some frontal cortical regions, in particular reduced volumes of caudal middle frontal cortices and left lateral orbitofrontal cortex in exposed participants compared to controls.

Conclusions

Prenatal cocaine exposure may lead to subtle and regionally specific patterns of regional dysmorphology in the striatum and volumetric changes in the frontal lobes. The localized and bidirectional nature of effects may explain in part the contradictions in the existing literature.