Diffusion tensor imaging of frontal white matter and executive functioning in cocaine-exposed children

What does diffusion tensor imaging reveal about the brain and cognition in fetal alcohol spectrum disorders?

Over the past 5 years, Diffusion Tensor Imaging (DTI) has begun to provide new evidence about the effects of prenatal alcohol exposure on white matter development. DTI, which examines microstructural tissue integrity, is sensitive to more subtle white matter abnormalities than traditional volumetric MRI methods. Thus far, the available DTI data suggest that white matter microstructural abnormalities fall on a continuum of severity in Fetal Alcohol Spectrum Disorder (FASD). Abnormalities are prominent in the corpus callosum, but also evident in major anterior-posterior fiber bundles, corticospinal tracts, and cerebellum. These subtle abnormalities are correlated with neurocognitive deficits, especially in processing speed, non-verbal ability, and executive functioning. Future studies using larger samples, increasingly sophisticated DTI methods, and additional functional MRI connectivity measures will better characterize the full range of abnormalities in FASD. Ultimately, these measures may serve as indices of change in future longitudinal studies and in studies of interventions for FASD.

The effects of prenatal cocaine exposure and gender on inhibitory control and attention

Children exposed prenatally to cocaine show deficits in emotion regulation and inhibitory control. While controlling for the measures of medical complication in the perinatal period, environmental risk, and prenatal polydrug exposure (alcohol, tobacco, and marijuana), we examined the effects of prenatal cocaine exposure and gender on attention and inhibitory control in 203 children at ages 6, 9, and 11. Cocaine exposure affected the performance of males, but not females. Heavily exposed males showed deficits in the attention and the inhibition tasks. In addition, a significantly greater proportion of heavily exposed males (21%) than unexposed males (7%) or heavily exposed females (7%) failed to complete the task (p<0.01). Even without those poorest performing subjects, the overall accuracy for heavily exposed males (81%) was significantly reduced (p<0.05) compared to lightly exposed males (87%) and unexposed males (89%). The findings highlight the importance of considering gender specificity in cocaine exposure effects. Processes by which cocaine effects may be specific to males are discussed.

Structural, metabolic, and functional brain abnormalities as a result of prenatal exposure to drugs of abuse: evidence from neuroimaging

Prenatal exposure to alcohol and stimulants negatively affects the developing trajectory of the central nervous system in many ways. Recent advances in neuroimaging methods have allowed researchers to study the structural, metabolic, and functional abnormalities resulting from prenatal exposure to drugs of abuse in living human subjects. Here we review the neuroimaging literature of prenatal exposure to alcohol, cocaine, and methamphetamine. Neuroimaging studies of prenatal alcohol exposure have reported differences in the structure and metabolism of many brain systems, including in frontal, parietal, and temporal regions, in the cerebellum and basal ganglia, as well as in the white matter tracts that connect these brain regions. Functional imaging studies have identified significant differences in brain activation related to various cognitive domains as a result of prenatal alcohol exposure. The published literature of prenatal exposure to cocaine and methamphetamine is much smaller, but evidence is beginning to emerge suggesting that exposure to stimulant drugs in utero may be particularly toxic to dopamine-rich basal ganglia regions. Although the interpretation of such findings is somewhat limited by the problem of polysubstance abuse and by the difficulty of obtaining precise exposure histories in retrospective studies, such investigations provide important insights into the effects of drugs of abuse on the structure, function, and metabolism of the developing human brain. These insights may ultimately help clinicians develop better diagnostic tools and devise appropriate therapeutic interventions to improve the condition of children with prenatal exposure to drugs of abuse.

Preadolescent behavior problems after prenatal cocaine exposure: Relationship between teacher and caretaker ratings (Maternal Lifestyle Study)

BACKGROUND

We previously reported an association between prenatal cocaine exposure (PCE) and childhood behavior problems as observed by the parent or caretaker. However, these behavior problems may not manifest in a structured environment, such as a school setting.

OBJECTIVE

We determined whether there is an association between PCE and school behavior problems and whether ratings of behavior problems from the teacher differ from those noted by the parent or caretaker.

METHODS

The Maternal Lifestyle Study, a multicenter study, enrolled 1388 children with and without PCE at one month of age for longitudinal assessment. Teachers masked to prenatal drug exposure status completed the Teacher Report Form (TRF/6-18) when children were 7, 9, and 11 years old. We also administered the Child Behavior Checklist-parent report (CBCL) to the parent/caretaker at same ages and then at 13 years. We performed latent growth curve modeling to determine whether high PCE will predict externalizing, internalizing, total behavior, and attention problems at 7 years of age and whether changes in problems' scores over time differ between those exposed and non-exposed from both teacher and parent report. Besides levels of PCE as predictors, we controlled for the following covariates, namely: site, child characteristics (gender and other prenatal drug exposures), family level influences (maternal age, depression and psychological symptomatology, continuing drug use, exposure to domestic violence, home environment, and socioeconomic status), and community level factors (neighborhood and community violence).

RESULTS

The mean behavior problem T scores from the teacher report were significantly higher than ratings by the parent or caretaker. Latent growth curve modeling revealed a significant relationship between intercepts of problem T scores from teacher and parent ratings; i.e., children that were rated poorly by teachers were also rated poorly by their parent/caretaker or vice versa. After controlling for covariates, we found high PCE to be a significant predictor of higher externalizing behavior problem T scores from both parent and teacher report at 7 years (p=0.034 and p=0.021, respectively) in comparison to non-PCE children. These differences in scores from either teacher or caregiver were stable through subsequent years or did not change significantly over time. Boys had higher T scores than girls on internalizing and total problems by caretaker report; they also had significantly higher T scores for internalizing, total, and attention problems by teacher ratings; the difference was marginally significant for externalizing behavior (p=0.070). Caretaker postnatal use of tobacco, depression, and community violence were significant predictors of all behavior problems rated by parent/caretaker, while lower scores on the home environment predicted all behavior outcomes by the teacher report.

CONCLUSIONS

Children with high PCE are likely to manifest externalizing behavior problems; their behavior problem scores at 7 years from either report of teacher or parent remained higher than scores of non-exposed children on subsequent years. Screening and identification of behavior problems at earlier ages could make possible initiation of intervention, while considering the likely effects of other confounders.

Children of addicted women

The purpose of this article was to review follow up studies of children with prenatal drug exposure from preschool through adolescence. Specifically, the authors focus on the effects of prenatal exposure to cocaine, methamphetamine, and opiates on behavior and development. The largest number of studies have examined cocaine-exposed children. The authors identified 42 studies that suggest that there are unique effects of prenatal cocaine exposure on 4- to 13-year-old children, particularly in the areas of behavior problems, attention, language, and cognition. In addition, studies make reasonable attempts to control for possible confounding factors. Systematic research on the long-term effects of prenatal methamphetamine exposure is just beginning but seems to be showing similar effects to that of cocaine. The literature on the on the long-term effects of children with prenatal opiate exposure is more substantial than the methamphetamine literature but it is still relatively sparse and surprising in that there is little recent work. Thus, there are no studies on the current concerns with opiates used for prescription mediation. There is a growing literature using neuroimaging techniques to study the effects of prenatal drug exposure that holds promise for understanding brain/behavior relationships. In addition to pharmacological and teratogenic effects, drugs can also be viewed from a prenatal stressor model. The author discuss this "fetal origins" approach that involves fetal programming and the neuroendocrine system and the potential implications for adolescent brain and behavioral development.

A review of the effects of prenatal cocaine exposure among school-aged children

CONTEXT

Studies through 6 years have shown no long-term direct effects of prenatal cocaine exposure (PCE) on children's physical growth, developmental test scores, or language outcomes. Little is known about the effects of PCE among school-aged children aged 6 years and older.

OBJECTIVE

We reviewed articles from studies that examined the effects of PCE on growth, cognitive ability, academic functioning, and brain structure and function among school-aged children.

METHODS

Articles were obtained by searching PubMed, Medline, TOXNET, and PsycInfo databases from January 1980 to December 2008 with the terms "prenatal cocaine exposure," "cocaine," "drug exposure," "substance exposure," "maternal drug use," "polysubstance," "children," "adolescent," "in utero," "pregnancy," "development," and "behavior." Criteria for inclusion were (1) empirical research on children aged 6 years and older prenatally exposed to cocaine, (2) peer-reviewed English-language journal, (3) comparison group, (4) longitudinal follow-up or historical prospective design, (5) masked assessment, (6) exclusion of subjects with serious medical disabilities, and (7) studies that reported nonredundant findings for samples used in multiple investigations. Thirty-two unique studies met the criteria. Each article was independently abstracted by 2 authors to obtain sample composition, methods of PCE assessment, study design, comparison groups, dependent variables, covariates, and results.

RESULTS

Associations between PCE and growth, cognitive ability, academic achievement, and language functioning were small and attenuated by environmental variables. PCE had significant negative associations with sustained attention and behavioral self-regulation, even with covariate control. Although emerging evidence suggests PCE-related alterations in brain structure and function, interpretation is limited by methodologic inconsistencies.

CONCLUSIONS

Consistent with findings among preschool-aged children, environmental variables play a key role in moderating and explaining the effects of PCE on school-aged children's functioning. After controlling for these effects, PCE-related impairments are reliably reported in sustained attention and behavioral self-regulation among school-aged children.

Specific metabolites in the medial prefrontal cortex are associated with the neurocognitive deficits in schizophrenia: a preliminary study

We measured brain metabolites in the medial prefrontal cortex of 19 schizophrenic patients and 18 healthy controls by 3 T proton magnetic resonance spectroscopy ((1)H MRS), and examined the relationship between prefrontal cortex-related neurocognitive functions and brain metabolites in the medial prefrontal cortex. The patients with schizophrenia exhibited deficits on the verbal fluency, Wisconsin card sorting test (WCST), trail making test, Stroop test and digit span distraction test (DSDT), but not on the Iowa gambling test. The patients showed statistical significant changes in the ratio of glutamine/glutamate, the ratio of N-acetyl-l-aspartate (NAA)/glycerophosphorylcholine plus phosphorylcholine (GPC+PC) and the levels of taurine in the medial prefrontal cortex compared with normal controls. Furthermore, we found significant correlations of the ratio of glutamine/glutamate with WCST and DSDT scores, the ratio of NAA/(GPC+PC) with verbal fluency and WCST scores, and the levels of taurine with scores on the Stroop test and Trail making test A among the participants. The ratios of NAA/(GPC+PC) and (GPC+PC)/(Cr+PCr) had significant relationships with the duration of untreated psychosis of the schizophrenic patients. The glutamine/glutamate ratio and levels of taurine were significantly related to the duration of illness of the patients. These data suggest that specific metabolites of the medial prefrontal cortex are associated with the neurocognitive deficits in schizophrenia.

Sex-specific attention problems in long-term survivors of pediatric acute lymphoblastic leukemia

BACKGROUND

Neurocognitive problems are a frequent outcome of chemotherapy for pediatric leukemia, although individual differences exist in patient outcome. Sex of the patient and age at diagnosis are 2 characteristics that have been associated with differential outcomes. The relation between these patient characteristics and specific attention deficits (ie, initiating, inhibiting, shifting, focusing, sustaining attention, and working memory) has not been well researched. The purpose of this study was to evaluate the pattern of attention problems in male and female long-term survivors of pediatric acute lymphoblastic leukemia (ALL).

METHODS

One hundred three long-term survivors (ie, >or=5 years from diagnosis; 51% boys, mean age at diagnosis of 3.9 years, and mean time since diagnosis 7.5 years) completed standardized measures of basic and complex attention skills related to anterior (ie, inhibition, shifting attention, working memory), posterior (ie, focusing), and subcortical brain systems (ie, sustaining).

RESULTS

Treatment intensity was related to sustained attention, with those patients treated on high-risk protocols displaying significantly lower performance. Girls performed worse than boys on measures related to the anterior attention system (ie, shifting attention, P<.042) and the subcortical attention system (ie, sustained attention, P<.001), whereas boys performed worse than girls on different measures of anterior control (ie, inhibition, P<.039; working memory, P<.003).

CONCLUSIONS

The results of this study suggest that children diagnosed with and treated for pediatric ALL perform poorly on select measures of attention and executive control, and that this performance is influenced by sex and treatment intensity.

Prenatal cocaine exposure alters emotional arousal regulation and its effects on working memory

While prenatal cocaine exposure (PCE) has been associated with arousal dysregulation and attentional impairments in both human and animal studies, the neurobiological bases of these teratogenic effects have not been well characterized. In the current study, we report functional neuroimaging observations of these effects in exposed youth. Using functional magnetic resonance imaging (fMRI), we embedded task-irrelevant emotional distracters in a working memory task to examine the interaction of emotional arousal and memory in 33 PCE and 23 non-exposed adolescents. Though with similar behavioral performance, the two groups exhibited different activation patterns associated with emotion-memory interactions. On the one hand, higher memory load attenuated emotion-related amygdala activation in controls but not in the exposed adolescents; on the other hand, prefrontal activation associated with memory load decreased in the presence of emotional distraction in the controls but increased in the exposed group. These group interaction differences suggest neurobiological substrates for arousal-associated neuronal alterations related to prenatal cocaine exposure. Consistent with previous findings in behavioral and physiological studies, the present neuroimaging data provided more in-depth evidence supporting the view that PCE has significant long-term teratogenic effect on arousal regulation system.

Children with and without gestational cocaine exposure: a neurocognitive systems analysis

BACKGROUND

Concern for effects of gestational cocaine exposure (GCE) on human neurocognitive (NC) development is based on effects of cocaine on blood flow to the fetus and impact of cocaine on developing monoaminergic systems. GCE has been shown to affect language, attention and perceptual reasoning skills.

OBJECTIVE

Our objective was to investigate effects of GCE on 7 NC systems, assessed behaviorally in middle school-aged, low socioeconomic status subjects followed prospectively since birth.

METHODS

55 GCE and 65 non-exposed Control subjects were tested with a battery of 14 tasks adapted from neuroimaging and lesion literature designed to tap 3 frontal systems (Cognitive Control, Working Memory, and Reward Processing) and 4 non-frontal systems (Language, Memory, Spatial Cognition, and Visual Cognition). Using multivariate analysis of covariance, we assessed the relation between NC functioning and GCE status with the following covariates: age at testing; gender; gestational exposure to cigarettes, alcohol and marijuana; foster care placement; caregiver current cocaine use; and two indices of childhood environment.

RESULTS

None of the analyses showed an effect of GCE on NC function. In contrast, child characteristics, including age at testing and childhood environment, were associated with NC function.

CONCLUSIONS

In this cohort there is either no effect of GCE on NC function at middle school age, or that effect is less pronounced than the effect of age or childhood environment.

Neuroimaging of children following prenatal drug exposure

Recent advances in MR-based brain imaging methods have provided unprecedented capabilities to visualize the brain. Application of these methods has allowed identification of brain structures and patterns of functional activation altered in offspring of mothers who used licit (e.g., alcohol and tobacco) and illicit (e.g., cocaine, methamphetamine, and marijuana) drugs during pregnancy. Here we review that literature, which though somewhat limited by the complexities of separating the specific effects of each drug from other confounding variables, points to sets of interconnected brain structures as being altered following prenatal exposure to drugs of abuse. In particular, dopamine-rich cortical (e.g., frontal cortex) and subcortical (e.g., basal ganglia) fetal brain structures show evidence of vulnerability to intrauterine drug exposure suggesting that during brain development drugs of abuse share a specific profile of developmental neurotoxicity. Such brain malformations may shed light on mechanisms underlying prenatal drug-induced brain injury, may serve as bio-markers of significant intrauterine drug exposure, and may additionally be predictors of subsequent neuro-developmental compromise. Wider clinical use of these research-based non-invasive methods will allow for improved diagnosis and allocation of therapeutic resources for affected infants, children, and young adults.

Intrauterine cocaine exposure and executive functioning in middle childhood

This longitudinal study evaluated whether the level of intrauterine cocaine exposure (IUCE) or the interaction between IUCE and contextual variables was related during middle childhood to executive functioning, as assessed with the Stroop Color-Word and Rey Osterrieth Complex Figure tests. The Stroop Interference score measures verbal inhibitory control while the Rey Osterrieth Organizational score evaluates skills such as planning, organization and perception. Masked examiners assessed 143 children at 9.5 and 11 years of age (74 with IUCE and 69 demographically similar children without IUCE). Level of IUCE (Unexposed; Lighter, and Heavier) was documented by positive postpartum maternal reports and infant meconium assays. In covariate-controlled regressions, level of IUCE was not significantly associated with Stroop Interference or Rey Osterrieth Organization scores. However, in covariate controlled post-hoc tests comparing the Heavier exposed group to the combined Lighter/Unexposed group, children in the Heavier group had significantly poorer Stroop Interference scores, but there was no significant group difference for Rey Osterrieth Organizational scores. Children's average Organization scores in Unexposed, Lighter, and Heavier exposed groups were well below the test norm means. Results of this study indicate that heavier IUCE may be associated with mild compromise on school-aged children's ability to inhibit prepotent verbal responses.

Functional MRI and response inhibition in children exposed to cocaine in utero. Preliminary findings

This study investigated the potential long-term effects of cocaine exposure on brain functioning using fMRI in school-aged children. The sample included 12 children with prenatal cocaine exposure and 12 non-exposed children (8-9 years old). Groups did not differ on IQ, socioeconomic status, or perinatal risk factors. A response inhibition task was administered during an fMRI scan using a 1.5-T MRI system. Task performance did not differentiate groups, but groups were differentiated by patterns of task-related brain activity. Cocaine-exposed children showed greater activation in the right inferior frontal cortex and caudate during response inhibition, whereas non-exposed children showed greater activations in temporal and occipital regions. These preliminary findings suggest that prenatal cocaine may affect the development of brain systems involved in the regulation of attention and response inhibition.

Executive functioning at ages 5 and 7 years in children with prenatal cocaine exposure

This prospective longitudinal study evaluated the effect of prenatal cocaine exposure (PCE) on executive functioning in 5- and 7-year-old children. In total, 154 pregnant cocaine users, identified by urine toxicology and structured interviews, were matched to 154 nonusers. Children were assessed by certified masked evaluators, and caregivers were interviewed by experienced staff during home visits. In approximately 90% of the surviving sample tested at ages 5 and 7 years, structural equation modeling demonstrated that an increased head circumference at birth (adjusted for gestation) significantly predicted better performance on executive functioning, and that PCE was indirectly related to executive functioning through its significant negative effect on head circumference at birth. At age 5 years, quality of environment also predicted executive functioning, and the R(2) for the total model was 0.24. At 7 years, caregiver functioning predicted quality of environment, which in turn was positively related to executive functioning, and girls had better executive functioning. The total model at age 7 years accounted for 30% of the variance in executive functioning.

Lower diffusion in white matter of children with prenatal methamphetamine exposure

BACKGROUND

Methamphetamine use is a common problem among women of childbearing age, leading to an increasing number of children with prenatal methamphetamine exposure. Whether microstructural brain changes associated with prenatal methamphetamine exposure can be detected with diffusion tensor imaging (DTI) is unknown.

METHOD

Twelve-direction DTI was performed in 29 methamphetamine-exposed and 37 unexposed children ages 3-4 years on a 3-T MRI scanner. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were determined in the corpus callosum (genu and splenium) and bilaterally in the frontal and parietal white matter (WM), basal ganglia (caudate, putamen, globus pallidus), and thalamus.

RESULTS

Children with prenatal methamphetamine exposure had lower ADC in the frontal (right: -2.1%, p = 0.04; left: -2.0%, p = 0.09) and parietal WM (right: -3.9%, p = 0.002; left: -3.3%, p = 0.02) compared to unexposed children. The methamphetamine-exposed children also showed a trend for higher FA in the left frontal WM (+4.9%, p = 0.06) compared to the unexposed children.

CONCLUSION

Since less myelination and higher dendritic or spine density have been reported in animals exposed to methamphetamine, lower diffusion in our children may reflect more compact axons or greater dendritic or spine density associated with prenatal methamphetamine exposure. These findings suggest alterations in white matter maturation in these children exposed to methamphetamine in utero.

Attention in selective mutism--an exploratory case-control study

The aim of the study was to explore the association between selective mutism (SM) and attention. In SM social anxiety seems central but language impairment and motor problems are also reported. Attention problems have been described in parental behavioral ratings, while neuropsychological studies are lacking. A neuropsychological test (the Trail Making Test) and parental ratings of attention- and anxiety problems were administered to a clinical sample of 23 children with SM (aged 7-16 years, 12 boys and 11 girls) and 46 non-referred matched controls. The SM group differed from controls on the Trail Making Test, but the group difference disappeared, when controlling for motor function and IQ. Parental ratings of attention problems were not significantly associated with the neuropsychological attention measure. Neuropsychological studies of attention controlled for IQ and motor function are needed as well as tests that measure different aspects of attention.

Prenatal cocaine exposure: drug and environmental effects at 9 years

OBJECTIVE

To assess school-age cognitive and achievement outcomes in children with prenatal cocaine exposure, controlling for confounding drug and environmental factors.

STUDY DESIGN

At age 9 years, 371 children (192 cocaine exposure [CE]; 179 non-cocaine exposure [NCE]) were assessed for IQ and school achievement in a longitudinal, prospective study from birth. An extensive number of confounding variables were controlled, including quality of caregiving environment, polydrug exposure, blood lead level, iron-deficiency anemia (IDA), and foster/adoptive care.

RESULTS

Prenatal cocaine exposure predicted poorer perceptual reasoning IQ, with a linear relationship of the concentration of the cocaine metabolite benzoylecgonine to the degree of impairment. Effects were mediated through birth head circumference, indicating a relationship with fetal brain growth. Negative effects of alcohol, lead, and marijuana exposure and positive effects of the home environment were additive. The CE children in foster/adoptive care had better home environments and lower lead levels. School achievement was not affected.

CONCLUSIONS

Persistent teratologic effects of CE on specific cognitive functions and additive effects of alcohol, lead, and marijuana exposure; IDA; and the home environment were identified. Documenting environmental factors in behavioral teratology studies is important, because in this sample, CE was associated with better home environment and lower environmental risk in a substantial number of children.

Importance of stability of early living arrangements on behavior outcomes of children with and without prenatal drug exposure

OBJECTIVE

We evaluated whether living arrangements of children with or without prenatal drug exposure would be associated with their behavior outcomes and adaptive functioning.

METHODS

A total of 1388 children with or without prenatal cocaine or opiate exposure were enrolled in a longitudinal cohort study at 1 month of age, were seen at intervals, tracked over time for their living situation, and evaluated for behavior problems and adaptive functioning at 3 years of age. The Child Behavior Checklist and Vineland Adaptive Behavior Scales were administered. Using multiple regression models, we determined the factors that would predict behavior problems and adaptive functioning.

RESULTS

Of the children enrolled, 1092 children were evaluated. Total and externalizing behavior problems T scores of children in relative care were lower (better) than those in parental care; externalizing behavior scores were lower than those in nonrelative care (p < .05). Total behavior problem scores increased 2.3 and 1.3 points, respectively, with each move per year and each year of Child Protective Services involvement. Compared to children in nonrelative care, those in parental or relative care had higher (better) scores in the Vineland Adaptive Behavior Scales total composite (p < .023), communication (p < .045), and daily living (p < .001). Each caretaker change was associated with a decrease of 2.65 and 2.19 points, respectively, in communication and daily living scores.

CONCLUSION

Children's living arrangements were significantly associated with childhood behavior problems and adaptive functioning. The instability of living situation was also a significant predictor of these outcomes. While family preservation continues to be the goal of the child welfare system, expediting decision toward permanency remains paramount once children are placed in foster care.

Substantia nigra MR imaging signal changes and cardiomyopathy following prenatal exposure to cocaine and heroin

Exposure to cocaine in utero results in behavioral and neurodevelopmental abnormalities that persist into adulthood. Conventional MR imaging has generally failed to reveal the expected structural lesions to explain these clinical findings. We report a case of focal MR imaging signal-intensity changes in the substantia nigra, locus ceruleus, and other selected nerve tracts and nuclei in a child exposed prenatally to cocaine and other drugs. The patient also had dilated cardiomyopathy.

Volumetric MRI study of brain in children with intrauterine exposure to cocaine, alcohol, tobacco, and marijuana

OBJECTIVE

The objective of this study was to use volumetric MRI to study brain volumes in 10- to 14-year-old children with and without intrauterine exposure to cocaine, alcohol, cigarettes, or marijuana.

METHODS

Volumetric MRI was performed on 35 children (mean age: 12.3 years; 14 with intrauterine exposure to cocaine, 21 with no intrauterine exposure to cocaine) to determine the effect of prenatal drug exposure on volumes of cortical gray matter; white matter; subcortical gray matter; cerebrospinal fluid; and total parenchymal volume. Head circumference was also obtained. Analyses of each individual substance were adjusted for demographic characteristics and the remaining 3 prenatal substance exposures.

RESULTS

Regression analyses adjusted for demographic characteristics showed that children with intrauterine exposure to cocaine had lower mean cortical gray matter and total parenchymal volumes and smaller mean head circumference than comparison children. After adjustment for other prenatal exposures, these volumes remained smaller but lost statistical significance. Similar analyses conducted for prenatal ethanol exposure adjusted for demographics showed significant reduction in mean cortical gray matter; total parenchymal volumes; and head circumference, which remained smaller but lost statistical significance after adjustment for the remaining 3 exposures. Notably, prenatal cigarette exposure was associated with significant reductions in cortical gray matter and total parenchymal volumes and head circumference after adjustment for demographics that retained marginal significance after adjustment for the other 3 exposures. Finally, as the number of exposures to prenatal substances grew, cortical gray matter and total parenchymal volumes and head circumference declined significantly with smallest measures found among children exposed to all 4. CONCLUSIONS; These data suggest that intrauterine exposures to cocaine, alcohol, and cigarettes are individually related to reduced head circumference; cortical gray matter; and total parenchymal volumes as measured by MRI at school age. Adjustment for other substance exposures precludes determination of statistically significant individual substance effect on brain volume in this small sample; however, these substances may act cumulatively during gestation to exert lasting effects on brain size and volume.

Functional magnetic resonance imaging and working memory in adolescents with gestational cocaine exposure

OBJECTIVE

To assess the effect of gestational cocaine exposure on the prefrontal cortex (PFC) with functional magnetic resonance imaging (fMRI).

STUDY DESIGN

Using an n-back task, we obtained fMRI with a 3T Siemens scanner on 49 adolescents, 25 who were exposed to cocaine and 24 who were not exposed. The primary outcome was PFC activation during task performance. Five functionally derived regions of interest (ROI) were defined; in addition, 2 a priori anatomical ROIs were generated for Brodmann regions 10 and 46.

RESULTS

Of the 49 adolescents who underwent imaging, data from 17 who were exposed to cocaine and 17 who were not exposed were in the final analysis. Groups had similar performance on the n-back task (P >/= .4), with both showing a fewer number of correct responses on the 2-back than the 1-back (P < .001), indicating increased demands on working memory with greater task difficulty. In functionally derived ROIs, imaging results showed increased activation for both groups in the 2-back versus the 1-back condition. In anatomical ROIs, both groups showed greater activation in the 2-back versus the 1-back condition, with activation in the non-exposed group proportionally greater for the left prefrontal region (P = .05).

CONCLUSION

In this sample of adolescents, participants who were exposed to cocaine and participants who were not exposed were similar in performance on an executive function task and in fMRI activation patterns during task performance.

Alcohol, psychological dysregulation, and adolescent brain development

While adolescent alcohol consumption has been asserted to adversely alter brain development, research in human adolescents has not yet provided us with sufficient evidence to support or refute this position. Brain constituents actively developing during adolescence include the prefrontal cortex, limbic system areas, and white matter myelin. These areas serving cognitive, behavioral, and emotional regulation may be particularly vulnerable to adverse alcohol effects. Alternatively, deficits or developmental delays in these structures and their functions may underlie liability to accelerated alcohol use trajectories in adolescence. This review will describe a conceptual framework for considering these relationships and summarize the available studies on the relationships among risk characteristics, alcohol involvement and brain development during this period. The cross-sectional designs and small samples characterizing available studies hamper definitive conclusions. This article will describe some of the opportunities contemporary neuroimaging techniques offer for advancing understanding of adolescent neurodevelopment and alcohol involvement.

Imaging the addicted human brain

Modern imaging techniques enable researchers to observe drug actions and consequences as they occur and persist in the brains of abusing and addicted individuals. This article presents the five most commonly used techniques, explains how each produces images, and describes how researchers interpret them. The authors give examples of key findings illustrating how each technique has extended and deepened our knowledge of the neurobiological bases of drug abuse and addiction, and they address potential clinical and therapeutic applications.

Clinical applications of diffusion tensor imaging and tractography in children

Diffusion tensor imaging (DTI) is a relatively new addition to routine MR imaging. DTI exploits the preferential movement of water protons within the brain along the axis of the axons. This anisotropic diffusion provides information about the immature brain prior to myelination, during maturation, and in normal and disease states, information that MRI cannot provide. By virtue of sensitivity to anisotropic movement of protons, DTI allows the core of larger individual white matter tracts to be visualized as discreet anatomic structures. DTI can also provide information about the microarchitecture of white matter in the form of metrics referred to as fractional anisotropy and diffusivity. The information contained within the diffusion tensor data can be used to create 3-D mathematical renderings of white matter or tractography. This article is an introduction to DTI for pediatric radiologists interested in exploring potential applications in children.

Administration and interpretation of the Trail Making Test

Measurement of cognitive functions is an increasingly important goal for clinicians and researchers. Many neuropsychological test batteries are comprehensive and require specialized training to administer and interpret. The Trail Making Test is an accessible neuropsychological instrument that provides the examiner with information on a wide range of cognitive skills and can be completed in 5-10 min. Its background, psychometric properties, administration procedures and interpretive guidelines are provided in this protocol.