Prenatal Alcohol Exposure: Developmental Abnormalities in the Brain

C H A P T E R

8 Prenatal Alcohol Exposure: Developmental Abnormalities in the Brain David J. Rohac1, Charles W. Abbott2 and Kelly J. Huffman3 1

Department of Psychology, University of California, Riverside, CA, United States 2Interdepartmental Neuroscience Program, University of California, Riverside, CA, United States 3Department of Psychology and Interdepartmental Neuroscience Program, University of California, Riverside, CA, United States

LIST OF ABBREVIATIONS ARND CDC DNA DTI FA FAS FASD fMRI INCs MD MRI P(0, 20, 50) pFAS PrEE S1 SWM V1

changes associated with prenatal alcohol, or ethanol exposure (PrEE) is discussed by exploring human brain imaging studies of individuals with FASD, as well as data generated from animal models. Additionally, it argues for the need for further investigation into potential mechanisms beginning with PrEE and leading to the FASD phenotype. This is important from both basic and translational science perspectives; we need to understand how PrEE alters brain development in such profound ways, and use that information to generate viable methods to effectively prevent and treat FASD. Before the broad term FASD was adopted, fetal alcohol syndrome (FAS) was first used to describe the effects of PrEE in children (Lemoine, Harousseau, Borteyru, & Menuet, 1968; Jones, Smith, Ulleland, & Streissguth, 1973). Today, this classification is reserved for the most severe PrEE-related phenotypes. Children with FAS often have prenatal and postnatal growth deficiencies, microcephaly, characteristic craniofacial dysmorphologies, and varying degrees of central nervous system dysfunction (Lemoine, et al., 1968; Jones et al., 1973; Chudley et al., 2005). Soon after the initial definition of FAS, it became apparent that lower levels of maternal drinking in pregnancy could impact the child in a less severe, yet still significant, way. Thus, the encompassing classification FASD was created to describe the range of phenotypes observed in PrEE children (Streissguth & O’Malley, 2000). Besides FAS, two additional diagnostic classifications within FASD describe the extent of damage due to PrEE. These include alcohol-related neurodevelopmental disorder (ARND) and partial FAS (pFAS). ARND, pFAS, and

alcohol-related neurodevelopmental disorder Centers for Disease Control and Prevention deoxyribonucleic acid diffusion tensor imaging fractional anisotropy fetal alcohol syndrome fetal alcohol spectrum disorders functional magnetic resonance imaging intraneocortical connections mean diffusivity magnetic resonance imaging postnatal day (#) partial fetal alcohol syndrome prenatal ethanol exposure primary somatosensory cortex spatial working memory primary visual cortex

INTRODUCTION Alcohol consumption during pregnancy is the leading known cause of preventable developmental delay and intellectual disability in the United States (Stratton, Howe, & Battaglia, 1996; Williams, Smith, & Committee on Substance Abuse, 2015). Fetal alcohol spectrum disorders (FASD) is an umbrella term used to describe a range of developmental defects that occur in an individual whose mother consumed alcohol during her pregnancy. These defects can include physical abnormalities, cognitive behavioral deficits, and learning disabilities that may impact the child throughout life. In this chapter, a range of developmental brain

Neuroscience of Alcohol. DOI: https://doi.org/10.1016/B978-0-12-813125-1.00008-8

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TABLE 8.1 Summary of FASD Phenotypes Diagnosis

FAS

pFAS

ARND

Facial phenotype

Smooth philtrum

Smooth philtrum

Not observed

and

or

Thin vermillion order

Thin vermillion order

and

or

Small palpebral Fissures

Small palpebral Fissures

and

and/or

Low birth weight for gestational age

Low birth weight for gestational age

or

or

Decelerating weight over time

Decelerating weight over time

or

or

Low weight to height

Low weight to height

and

or

Growth retardation

CNS Decreased cranial size at birth dysfunction or

Decreased cranial size at birth

Decreased cranial size at birth

or

or

Structural brain abnormalities

Structural brain abnormalities

Structural brain abnormalities

or

or

or

Neurological signs (ex. poor motor skills, hearing loss, poor hand eye coordination, etc.)

Neurological signs (ex. poor motor skills, hearing loss, poor hand eye coordination, etc.)

Neurological signs (ex. poor motor skills, hearing loss, poor hand eye coordination, etc.)

or

or

Behavior or cognitive abnormalities and confirm alcohol exposed

Behavior or cognitive abnormalities

Other

FASD diagnosis summary. Overview of diagnostic criteria commonly used to classify FASD cases in children.

FAS range in severity from mild to most severe, and represent a set of recognizable phenotypes in three primary areas: (1) prenatal and/or postnatal growth deficiency; (2) central nervous system dysfunction; and (3) pattern of facial malformations (Riley & McGee, 2005). A summary of the common features of these classifications can be seen in Table 8.1. FASD prevalence rates in the United States are high with approximately 2% 5% of newborns impacted by prenatal alcohol exposure. Although less common, estimates of FAS births hover just below 1% (Williams et al., 2015). Recently, after years of debate on medical recommendations regarding drinking during pregnancy, the American Academy of Pediatrics stated that there is “no known safe amount of alcohol for a pregnant women to drink” (Williams et al., 2015). Unfortunately, despite this strong language, and similar statements by the Centers for Disease Control and Prevention (CDC), 18.6% of pregnant women age 35 44 continue to drink alcohol during their pregnancies (Tan, Denny, Cheal, Sniezek, & Kanny, 2015).

STUDIES IN HUMANS WITH FETAL ALCOHOL SPECTRUM DISORDER Decades ago, autopsy data revealed distinct alterations of the corpus callosum, enlarged ventricles, a reduced cerebellum, and other brain anomalies including neuronal and glial development as well as microcephaly and microencephaly in people with FASD (Clarren, Alvord, Sumi, Streissguth, & Smith, 1978: Jones et al., 1973; Peiffer, Majewski, Fischbach, Bierich, & Volk, 1979). Since these early works, human brain imaging studies have shown reduced overall brain volume and altered neuroanatomical development of brains structures, such as the corpus callosum (Bookstein, Sampson, Connor, & Streissguth, 2002; Bookstein, Streissguth, Sampson, Connor, & Barr, 2002). These results suggest that changes to brain morphology may underlie the often complex cognitive and behavioral phenotypes observed in people with FASD. The development of in vivo imaging techniques has transformed our ability to diagnose, explore, and track

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STUDIES IN HUMANS WITH FETAL ALCOHOL SPECTRUM DISORDER

changes in the brain. Magnetic resonance imaging (MRI) is a safe, noninvasive technique that can be used to study brain structure and function. Using different contrast techniques, several types of diagnostic tools have been developed, including structural MRI, functional MRI (fMRI), and diffusion tensor imaging (DTI).

Structural Brain Imaging Consistent with early autopsies, structural MRI studies repeatedly demonstrate significantly reduced overall brain volume in patients with FASD. Some studies have shown volumetric differences in white matter and gray matter, or both (Table 8.2). Structural imaging studies also confirm PrEE’s ability to disrupt normal development of the corpus callosum. Bookstein et al. (2002) found a high level of variance in the shape of the corpus callosum of FASD cases and concluded that it is a distinguishing characteristic useful for diagnosis. The neocortex is strongly implicated in FASD, as complex regulation of cognition, learning, behavior, sensorimotor integration, and sophisticated skills are often attributed to cortical function. Within the neocortex, the frontal, parietal, and temporal lobes show PrEE-related defects in cortical thickness, with either increases or decreases found in different cortical areas (Sowell et al., 2002, 2008b). In these studies, Sowell and colleagues found a reduced volume of the ventral frontal lobes of the left hemisphere of children with FASD (Sowell et al., 2002). Subsequent studies by Sowell found increased cortical thickness in both FAS cases and children with less severe diagnoses (Sowell et al., 2008b). MRI studies also demonstrate that PrEE can impact the development of the cerebellum, hippocampus, caudate nucleus, basal ganglia, and other subcortical structures (Table 8.2). Commonly observed motor and learning deficits presented in subjects with FASD suggest possible cerebellar dysfunction in response to PrEE. Imaging studies confirm this and demonstrate a significant volumetric reduction in FAS cases (Archibald et al., 2001). Additional exploration of the cerebellum reveals site-specific reductions within the anterior vermis, whereas the posterior vermis is unaffected (Sowell et al., 1996). The effects of PrEE on developing hippocampal volume in late childhood were investigated by Willoughby, Sheard, Nash, and Rovet (2008). Here, researchers found that PrEE resulted in reduced left hippocampal volume, with volume not significantly increasing with age as it did in normal, healthy subjects. Further investigation into PrEE-derived changes within developing subcortical structures revealed volumetric reductions in both the caudate nucleus and basal ganglia (Cortese et al., 2006; Archibald et al., 2001).

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Functional Brain Imaging fMRI data has shown differential patterns of cortical activation correlating with spatial memory, verbal learning, verbal working memory, and visual working memory in PrEE subjects. Early fMRI studies examining brain function in subjects with FASD investigated brain activation during a spatial working memory (SWM) task (Malisza, Allman, & Shiloff, 2005). Results from this work indicated that children and adults with FASD had greater activity in the inferior and middle-frontal cortex. These findings were extended by Spadoni et al. (2009), who showed changes in the activation patterns of FASD patients when performing similar SWM tasks, with greater activation within dorsolateral frontalparietal regions of cortex. The prefrontal cortex, which is thought to play a strong role in behavioral inhibition and impulse control, also displays differential activation in subjects with FASD. A study by Fryer in 2007 indicated that participants with FASD showed increased functional activation in the prefrontal cortex and decreased activation in the caudate nucleus during trials that required response inhibition.

Diffusion Tensor Imaging Preliminary DTI studies focused on callosal defects, which persisted into young adulthood of individuals with FAS (Ma et al., 2005). Using fractional anisotropy (FA) and mean diffusivity (MD) measures from select regions of interest in the corpus callosum, researchers were able to identify lower FA and higher MD within the splenium and genu of the corpus callosum of FAS subjects, suggesting microstructural defects. Additional studies by Sowell et al. in 2008 found lower FA in the lateral splenium, posterior cingulate, right temporal lobe, right internal capsule, and brain stem. Sowell also found that white matter density was reduced in the same areas FA was lowered. This suggests that PrEE results in disorganized fiber tracts, signified by lower FA, that may be a consequence of reductions in myelin development.

The Role of Animal Research in Our Understanding of Fetal Alcohol Spectrum Disorder Although human brain imaging studies inform us of the human condition by describing the ways in which the brain can be altered by PrEE, it is difficult to experimentally investigate how these neuroanatomical or functional changes occur. We need controlled experimental methodology to identify the biological mechanisms that generate changes in the brain. Animal models allow researchers to experimentally

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TABLE 8.2 Anatomy and Functional Results of MRI Scans of FASD Patients Structural studies Published by

Overall brain volume

Corpus Cerebellum callosum

Subcortical

Mattson, Schoenfeld, and Riley (2001)

 (Cerebral, cranial)



 Caudate, thalamus, basal ganglia, lenticular

Riley and McGee (2005)



 



Joseph, Warton, and Jacobson (2014) Swayze et al. (1997)

Small brain stem Altered hippocampus and caudate nucleus



 

Clark, Li, Conry, Conry, and Loock (2000) Archibald et al. (2001)



Sowell et al. (2008b)

 (Total vol., intracranial,



 (Intracranial vault)

 Caudate nucleus 

WM, GM, and CSF)

Riikonen, Salonen, Partanen, and Verho (1999)

nucleus, diencephalon enlarged ventricles



Sowell et al. (1996) Johnson, Swayze, Sato, and Andreasen (1996)





Bookstein et al. (2002)

 Caudate, left hippocampus Varied shape

Willoughby et al. (2008)



Autti-Ramo et al. (2002)

 (Cerebral and skull)

Chen, Coles, Lynch, and Hu (2012)



Cortese et al. (2006)



Astley et al. (2009)



Meintjes, Jacobson, and Molteno (2010)



Roussotte, Sulik, and Mattson (2012)

 (Overall vol. and cortical

Rajaprakash, Chavrakarty, Lerch, and Rovet (2014)

 (Overall and GM)

Nardelli, Lebel, Rasmussen, Andrew, and Beaulieu (2011)

 (Intracranial vault, total

 Hippocampus 

 Left caudate 



 Caudate, putamen, hippocampus

 Basal ganglia, left putamen and right

GM)

palladium

 Caudate, putamen, thalamus, amygdala,

WM and deep cortical GM)

hippocampus, globus pallidus



Yang, Phillips, and Kan (2012) Li et al. (2008)



Zhou, Lebel, and Lepage (2011)



Lebel, Roussotte, and Sowell (2011)

 (GM and WM)

 Caudate, putamen, thalamus, ventral

Treit et al. (2013)



 Basal ganglia, hippocampus, globus pallidus

diencephalon

Functional studies Spadoni et al. (2009) Fryer, Tapert, and Mattson (2007) Malisza et al. (2005)

 Dorsolateral frontal-parietal  Prefrontal cortex   Inferior and middle-frontal

Structural and functional MRI studies of subjects with prenatal alcohol exposure and their findings in select brain areas. CSF, Cerebrospinal fluid; GM, gray matter; WM, white matter.

STUDIES IN HUMANS WITH FETAL ALCOHOL SPECTRUM DISORDER

control or manipulate factors, including dosage, pattern and timing of exposure, nutritional status, maternal factors, and genetics, which aid our understanding of mechanisms of PrEE-related changes and deficits.

Prenatal Ethanol Exposure and Neuroanatomical Development: Alterations in Subcortical Structures PrEE-induced alterations of specific brain structures have been discovered using animal models of FASD. Along with neuroimaging studies in humans, animal models reveal the largest deviations within the basal ganglia, CA3 regions of the hippocampus and the corpus callosum (Abbott, Kozanian, Kanaan, Wendel, & Huffman, 2016; Godin, Dehart, Parnell, O’Leary-Moore, & Sulik, 2011; Norman, Crocker, Mattson, & Riley, 2009). Data suggest that PrEE causes a delay in the development of these structures, possibly from altered gene expression patterning in early development. Studies documenting changes to the corpus callosum confirm results from human imaging studies and show consistent abnormal development from PrEE (Livy & Elberger, 2008). Presented in Fig. 8.1, measures of the basal ganglia show reduced volume at birth, which then recovers to normal volume later in development. Analysis of the CA3 region of the hippocampus showed an initial reduction in thickness at birth with a thickening noted at later developmental stages that persists into adulthood. Finally, measures of the corpus callosum showed a significantly thinner corpus callosum at birth and at 20 days old; however, by adulthood the thickness was greater than control brains (Fig. 8.1). Similar anatomical changes have been observed in humans with FASD and may be associated with deficits in executive function (Bookstein et al., 2002).

Prenatal Ethanol Exposure and Neuroanatomical Development: Alterations in Neocortex When considering how the brain may be damaged in PrEE, we can look to phenotypes in children with FASD. The motor and cognitive behavioral issues observed in children with FASD strongly suggest that the neocortex, the brain structure responsible for complex behavior, language, fine motor skills, and highlevel cognitive processing is particularly susceptible to developmental damage caused by PrEE. During brain development, the neocortex is vulnerable to modification either through intrinsic influences, such as gene expression, or experience-dependent changes from altered sensory input or toxic exposures (El Shawa, Abbott, & Huffman, 2013; Sur & Rubenstein, 2005). Although plasticity still occurs in the adult cortex (Pons

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et al., 1991), the developing neocortex is particularly sensitive to modification from toxic exposures that can have long-lasting behavioral ramifications (Abbott et al., 2016). Indeed, reports from animal models of FASD have shown significant defects in the anatomy of the neocortex and how it is patterned in development.

Prenatal Ethanol Exposure Impacts Thickness of the Neocortex PrEE significantly impacts the developmental trajectory of the cortex in a way that alters the rate of thickening of the cortical sheet. Specifically, thickening of frontal cortex, putative primary somatosensory cortex (S1), and putative primary visual cortex (V1) along with thinning of the prelimbic cortex and putative primary auditory cortex in newborn PrEE mice has been observed (Abbott et al., 2016). During normal development, area and layer-dependent cortical thinning occurs across the neocortex, and PrEE mice show a delay in this pattern of natural cortical thinning (Abbott et al., 2016). The process of cortical thinning and pruning during development proceeds at variable rates dependent on brain region (Sowell et al., 2004), and alcohol exposure during the prenatal period seems to impact these regions differentially. However, for all cortical regions except the visual cortex, the altered cortical thickness is sustained at least until early adulthood in a mouse model of FASD (Abbott et al., 2016).

Neocortical Circuitry Development and Prenatal Ethanol Exposure: Gene Expression and Intraneocortical Connections Proper gene expression within the neocortex during development is critical for accurate targeting of intraneocortical connections (INCs), which form the circuitry that generates complex function in the animal. If gene expression is changed during cortical patterning due to exposure to a toxin such as alcohol, then development of the circuit may be derailed, leading to a disorganized, abnormal neocortex. Previous studies have demonstrated a wide range of gene expression changes due to PrEE. Specifically, work from our laboratory has shown an observable shift in the expression patterns of three specific genes: Rzrß, Cad8, and Id2 (Fig. 8.2). Additional studies, using quantitative polymerase chain reaction methods, demonstrate quantifiable changes to gene expression within rostral and caudal regions of cortex (Abbott, Rohac, Bottom, Patadia, & Huffman, 2017). In that report, our laboratory showed that PrEE can alter the epigenome, generating differential deoxyribonucleic acid (DNA) methylation in the neocortex of mice,

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8. PRENATAL ALCOHOL EXPOSURE: DEVELOPMENTAL ABNORMALITIES IN THE BRAIN

FIGURE 8.1 Select subcortical anatomical measures in PrEE mice at P0, P20, and P50. Nissl-stained coronal sections demonstrate measures of the basal ganglia (BG), CA3 of the hippocampus, and corpus callosum (CC). Measures of the BG show reduced volume at P0 (A1 vs A2), with no differences later in development (A3 A6). Analysis of the CA3 region showed an initial reduction in thickness at P0 (B1 vs B2) with a thickening noted at later developmental stages (B4 and B6 vs B3 and B5) that persists into adulthood. Finally, measures of the corpus callosum showed a significantly thinner corpus callosum at P0 (C2 vs C1) and at P20 (C4 vs C3); however, by adulthood the thickness was greater than control brains (C6 vs C5). Scale bar 5 500 µm, Control n 5 8, PrEE n 5 8 for all ages. Source: Taken with permission from Abbott, C.W., Kozanian, O.O., Kanaan, J., Wendel, K.M., & Huffman, K.J. (2016). The impact of prenatal ethanol exposure on neuroanatomical and behavioral development in mice. Alcoholism: Clinical and Experimental Research, 40(1), 122 133.

concomitant with altered gene expression. It is possible that these changes in DNA methylation perturb gene expression, leading to ectopic development of the neocortical circuit (Abbott et al., 2017). Patterned in early development, INCs form the circuitry that is paramount for proper nervous system function and rely on proper gene expression for correct developmental targeting. These connections enable complex behavior by processing sensory inputs and

motor outputs (Dye, El Shawa, & Huffman, 2011a; Dye, El Shawa, & Huffman, 2011b). PrEE disrupts the normal developmental patterning of connections within sensorimotor regions in the neocortex, as is observed in newborn mice exposed to alcohol prenatally (El Shawa et al., 2013). Connections of sensory and motor areas within neocortex have fairly restricted borders in normal, control mice. For example, the V1 receives input from nearby areas, and its connections

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FIGURE 8.2 Neocortical gene expression of Rzrß, Cad8, and Id2. 100 µm Coronal sections of P0 control and PrEE brain hemispheres following free-floating nonradioactive in situ hybridization. A1 (Control, Rzrß) section of caudal cortex, left arrow denotes lower medial expression and right arrow denotes moderate lateral expression. A2 (PrEE, Rzrß) section of caudal cortex, left arrow denotes moderate medial expression and right arrow denotes high lateral expression. B1 (Control, Rzrß) section through rostral cortex where left black arrow denotes low medial expression, white middle arrow denotes the medial boundary of Rzrß, and right arrow denotes moderate lateral expression. B2 (PrEE, Rzrß) section through rostral cortex where left black arrow denotes moderate medial expression, white middle arrow denotes the shifted medial boundary of Rzrß expression and right arrow denotes high lateral expression. C1 (Control, Cad8) section through rostral cortex where black arrow denotes the lateral boundary of Cad8 expression. C2 (PrEE, Cad8), section through rostral cortex where black arrow denotes a shifted lateral boundary of expression. D1 (Control, Id2) section through rostral cortex where black arrow denotes an absence of expression within cortical layers 3 and 4. D2 (PrEE, Id2) Section through rostral cortex where black arrow denotes an extension of the lateral expression. E1, E2, Patterns of gene expression compressed onto a coronal reconstruction of control (E1) or PrEE (E2) brains. Rzrß, diagonal line area; Cad8, crossed line area; Id2, dotted area. Dark line, cortical outline. Sections oriented dorsal (D) up and lateral (L) right. Scale bar 5 500 µm. Source: Taken with permission from El Shawa, H., Abbott, C.W., & Huffman, K.J. (2013). Prenatal ethanol exposure disrupts intraneocortical circuitry, cortical gene expression, and behavior in a mouse model of FASD. Journal of Neuroscience, 33(48), 18893 18905.

FIGURE 8.3 Somatosensory and visual INC development in control and PrEE brains at P0. Rostral caudal series of 100 µm coronal sections of P0 hemispheres following DiA (green) or DiI (red) crystal placements in putative somatosensory (B1 and B2, stars) and putative visual cortex (D1and D2, stars) of control and PrEE mouse brains. Sections were counterstained with DAPI. All arrows indicate retrogradely labeled cells. In rostral sections, DiI labeled red cells from visual cortex dye placements are seen in cortex of PrEE brains (A2, B2, C2, red cells, arrows) and other rostral regions but not in controls (A1, B1, C1). DiA-labeled green cells from somatosensory cortex dye placements were seen in abnormally caudal locations in cortex of PrEE mice (D2, E2) and not in corresponding locations in controls (D1, E1). Images oriented dorsal (D) up and lateral (L) to the right. F1 and F2: Flattened, lateral-view, reconstructions of control and PrEE brains at P0. Large red patches are DiI visual dye placements; large green patches are DiA somatosensory dye placements; small red and green dots, retrogradely labeled cell bodies. Reconstructions oriented medial (M) up and rostral (R) left. Scale bars 5 500 µm. Source: Adapted with permission from El Shawa, H., Abbott, C.W., & Huffman, K.J. (2013). Prenatal ethanol exposure disrupts intraneocortical circuitry, cortical gene expression, and behavior in a mouse model of FASD. Journal of Neuroscience, 33(48), 18893 18905.

do not overlap with connections of other primary sensory areas, such as the S1 cortex (Dye et al., 2011a, 2011b). Accordingly, in normal nonexposed mice, we observed the development of an organized cortex (Fig. 8.3, top row) with nonoverlapping connections of

primary sensory regions. However, in the cortices of PrEE mice, we observe a disorganized cortex with labeled cells found in ectopic locations (Fig. 8.3, bottom row). Specifically, somatosensory cortical connections are located in positions far caudal compared to that of

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FIGURE 8.4 Theoretical overview of PrEE’s teratogenic effects. Flowchart of how exposure to ethanol during the prenatal period can cause epigenetic changes (epigenome), resulting in altered gene expression (transcriptome) that can disrupt cortical circuitry (connectome).

normal mice, and visual cortex connections show labeled cells in far rostral positions. This extreme phenotype, where the frontal lobe is connected to the occipital lobe, is a projection pattern not seen in any healthy mammal at any time during development. Also, this development of aberrant INCs does not appear to depend on changes in inputs from the thalamus, as thalamocortical connections appear normal in PrEE mice (El Shawa et al., 2013).

Potential Mechanisms of Prenatal Ethanol Exposure Induced Neocortical Changes As described above, emerging evidence suggests that PrEE can induce epigenetic modifications that

influence features of cortical development. In a recent paper, we have described data supporting the idea that early, prenatal alcohol exposure alters DNA methylation, leading to abnormal gene expression and connections within the cortex. We have shown that the readout of this biological change is atypical animal behavior in late childhood or early adolescence. For example, PrEE leads to increased anxiety-like and depressive-like behaviors as well as poor motor skills and sensorimotor integration in mice (Abbott et al., 2017). Also, in that paper we show how these epigenetic modifications lead to heritable effects on neocortical gene expression, cortical circuitry and behavior (Fig. 8.4). As scientists who study FASD begin to understand more about the

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SUMMARY POINTS

mechanisms underlying alcohol’s teratogenic effects on the developing offspring, we will be able to generate preventative methods and therapeutic treatments for FASD.

CONCLUSION In humans, the prenatal period is a particularly sensitive time for brain development. Genetic signals pattern the embryo and input from the environment can modify this development. Alcohol has great potential to disrupt these signals by modifying the function of DNA, leading to abnormal brain development and, ultimately, deficits in cognitive function and behavior. FASD is a preventable condition and measures must be taken to not only understand the underlying biology so that treatments can be created, but increase awareness of moms-to-be and their partners that no amount of drinking in pregnancy is safe.

KEY FACTS Fetal Alcohol Spectrum Disorders Diagnosis • FASD diagnosis is heavily dependent on the admission of maternal consumption of alcohol. • Within FASD, the three main diagnostic classifications describe the extent of damage due to prenatal ethanol exposure including: • Alcohol-related neurodevelopment disorders. • Including an array of additional malformations including: cardiac, skeletal, renal, ocular and auditory symptoms. • Partial fetal alcohol syndrome. • Fetal alcohol syndrome. • Symptoms range in severity and represent a set of recognizable symptoms in three primary areas: • Prenatal and/or postnatal growth deficiency. • Central nervous system dysfunction. • A distinctive pattern of facial malformations including a thin vermillion border, smooth philtrum, and short palpebral fissure length. • The guidelines for diagnosis were developed for fetal alcohol syndrome.

MINI-DICTIONARY OF TERMS Cortical patterning The process of how the functional areas of the cerebral cortex are generated, including determining their size and shape, as well as how their spatial pattern on the surface of the cortex is established. Fractional anisotropy A measurement used in diffuse tensor imaging (DTI) that ranges from 0, isotropic (flow is equally likely in any direction), to 1, anisotropic (flow is restricted to one direction) movement of water molecules (e.g., through a fiber). Seen as a summary measure of structural integrity. Magnetic resonance imaging An imaging technology where scanners generate images of the organs in the body based on the emitted radio waves of specific atomic nuclei when exposed to a strong magnetic field. This is mainly measured through hydrogen atoms found throughout the body in water and fatty tissue. Mean diffusivity An inverse measure of membrane density calculated by generating the average measure of total diffusion within an area using DTI. Microcephaly A neonatal malformation signified by a much smaller head size compared with other babies of the same age and sex. Microencephaly A neonatal malformation producing a much smaller brain compared to other babies of the same age and sex. Quantitative polymerase chain reaction A laboratory method used to detect a specific DNA sequence in a sample and determine the actual number of copies of that sequence compared to a known standard DNA sequence. Sensorimotor integration The ability of the central nervous system to integrate multiple sources of stimuli, process, and transform those inputs into useable neural output. Spatial working memory The ability to keep spatial information active in working memory over a short period of time. Thalamocortical A nerve originating in the thalamus that acts as an input pathway to the cortex.

Epigenetics • Defined as a change in gene activity not associated with a change in gene sequence. • May include changes to DNA methylation/ acetylation, histone modifications, and miRNAmediated changes. • The epigenome is theorized to be one of the substrates, which can be modified by external experience, changing gene activity for an individual and their offspring. • One way alcohol is thought to affect the epigenome is by altering one-carbon metabolism, the primary source of methyl donors in DNA-transmethylation reactions.

SUMMARY POINTS • Alcohol consumption during pregnancy is the leading known cause of preventable developmental delay and intellectual disability in the United States. • FASD was created to describe the range of phenotypes observed in PrEE children and includes ARND, pFAS, and FAS. • Brain imaging studies and functional studies reveal system-wide alterations to anatomy and function as a result of FASD.

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8. PRENATAL ALCOHOL EXPOSURE: DEVELOPMENTAL ABNORMALITIES IN THE BRAIN

• Animal models of FASD allow researchers to experimentally control or manipulate multiple factors in order to study the wide range of effects of FASD. • Studies of animal models of FASD show changes to cortical anatomy, connectivity, gene expression, and subcortical anatomy. • PrEE can induce epigenetic modifications that can influence features of cortical development. • Key words: FASD, prenatal ethanol exposure, epigenetics, alcohol, brain development, and neocortex.

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