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Biomedical subjects

E R Sowell

Publications and source records attributed to E R Sowell.

12 recordsLinked to original sources
PubMed2001

Mapping continued brain growth and gray matter density reduction in dorsal frontal cortex: Inverse relationships during postadolescent brain maturation.

Recent in vivo structural imaging studies have shown spatial and temporal patterns of brain maturation between childhood, adolescence, and young adulthood that are generally consistent with postmortem studies of cellular maturational events such as increased myelination and synaptic pruning. In this study, we conducted detailed spatial and temporal analyses of growth and gray matter density at the cortical surface of the brain in a group of 35 normally developing children, adolescents, and young adults. To accomplish this, we used high-resolution magnetic resonance imaging and novel computational image analysis techniques. For the first time, in this report we have mapped the continued postadolescent brain growth that occurs primarily in the dorsal aspects of the frontal lobe bilaterally and in the posterior temporo-occipital junction bilaterally. Notably, maps of the spatial distribution of postadolescent cortical gray matter density reduction are highly consistent with maps of the spatial distribution of postadolescent brain growth, showing an inverse relationship between cortical gray matter density reduction and brain growth primarily in the superior frontal regions that control executive cognitive functioning. Inverse relationships are not as robust in the posterior temporo-occipital junction where gray matter density reduction is much less prominent despite late brain growth in these regions between adolescence and adulthood. Overall brain growth is not significant between childhood and adolescence, but close spatial relationships between gray matter density reduction and brain growth are observed in the dorsal parietal and frontal cortex. These results suggest that progressive cellular maturational events, such as increased myelination, may play as prominent a role during the postadolescent years as regressive events, such as synaptic pruning, in determining the ultimate density of mature frontal lobe cortical gray matter.

Adolescent↗
PubMed2001

Mapping callosal morphology and cognitive correlates: effects of heavy prenatal alcohol exposure.

BACKGROUND: Abnormalities of the corpus callosum (CC) have been documented in fetal alcohol syndrome (FAS), ranging from subtle decrements in its size to partial and even complete agenesis. Prenatal exposure to alcohol is also known to result in neurocognitive deficits. OBJECTIVE: To 1) investigate abnormalities in size, shape, and location of the CC within the brain in individuals with FAS and in those exposed to high amounts of alcohol prenatally but without FAS (PEA group); and 2) determine if there is a relationship between callosal dysmorphology and cognitive test performance. METHODS: MRI and novel surface-based image analytic methods were used. Twenty alcohol-exposed subjects (8 to 22 years) along with 21 normal controls (8 to 25 years) were studied with high-resolution MRI and measures of verbal learning and visuospatial abilities. RESULTS: In addition to callosal area reductions, most severe in the splenium, the CC is significantly displaced in patients exposed to alcohol prenatally. In the alcohol-exposed group, this structure lies more anterior and inferior in posterior regions with relatively normal localization of anterior regions. These findings are significant in the FAS group, and a similar but less severe pattern is observed in the PEA patients. The authors show that the amount of CC displacement is correlated with impairment in verbal learning ability and that CC displacement is a better predictor of verbal learning than regional CC area. The brain-behavior relationship is only significant within the alcohol-exposed group, and the effect is not solely mediated by overall impaired verbal intellectual functioning. CONCLUSIONS: These results further emphasize the vulnerability of midline brain structures to prenatal alcohol exposure.

Adolescent↗
PubMed2001

Voxel-based morphometric analyses of the brain in children and adolescents prenatally exposed to alcohol.

Children of mothers who abuse alcohol during pregnancy can suffer varying degrees of neurological abnormality, cognitive impairment, and behavioral problems, and in the worst case, are diagnosed with fetal alcohol syndrome (FAS). The purpose of the present study was to localize brain abnormalities in a group of children and adolescents prenatally exposed to alcohol using high resolution, 3D structural MRI data and whole-brain voxel-based morphometry (VBM). Data were collected for 21 children and adolescents with histories of prenatal alcohol exposure (ALC) and 21 normally developing individuals. Statistical parametric maps revealed abnormalities most prominent in the left hemisphere perisylvian cortices of the temporal and parietal lobes where the ALC patients tended to have too much gray matter and not enough white matter. These results provide further support for dysmorphology in temporo-parietal cortices above and beyond the overall microcephaly that results from severe prenatal alcohol exposure.

Adolescent↗
PubMed2001

Improved memory functioning and frontal lobe maturation between childhood and adolescence: a structural MRI study.

Previous studies conducted by our group have provided evidence for age-related reductions in cortical thickness in dorsal frontal and parietal regions between childhood and adulthood, and gray matter volume increases of mesial temporal and anterior diencephalic structures. The purpose of this study was to describe neurobehavioral correlates of these brain maturational changes using morphometric analyses of brain magnetic resonance images (MRI) and two tests of cognitive abilities. Participants were 35 normal children roughly stratified by age (7 to 16 years) and sex (20 boys and 15 girls) and frontal and mesial temporal regions were anatomically defined in each subjects' MRI data. The California Verbal Learning Test-Children's Version and the Rey-Osterrieth Complex Figure test were used as measures of verbal and visuospatial memory and organizational abilities. Analyses designed to show regionally specific relationships between the brain and behavioral measures revealed interesting results. Specifically, frontal lobe gray matter thinning was more strongly predictive of delayed verbal memory functioning than was the mesial temporal lobe gray matter volume, and this relationship did not appear to be mediated by factors indexed in chronological age. Similar, but less regionally specific relationships were observed for measures of visuospatial memory abilities and frontal lobe maturation. Functional imaging studies in the literature consistently report activation in frontal regions in adults during retrieval tasks. The relationship between frontal lobe maturation and delayed recall observed here may be reflective of the children's development towards the more adult-like frontal lobe function revealed in the functional imaging studies.

Adolescent↗
PubMed2000

Brain abnormalities observed in childhood-onset schizophrenia: a review of the structural magnetic resonance imaging literature.

Childhood-onset schizophrenia (COS) is a rare, severe form of schizophrenia in which there are structural brain abnormalities that may be related to the psychotic symptomatology and neurocognitive deficits found in these patients. While there are numerous structural imaging studies of the adult-onset variant of schizophrenia (with many conflicting findings), relatively few brain imaging studies of COS have been conducted. This paper summarizes the extant literature of magnetic resonance imaging (MRI) studies of structural brain abnormalities in COS, and compares findings to similar studies of adult-onset patients. Volumetric MRI studies of COS patients have consistently shown evidence for increased ventricular volume, reduced cerebral gray matter, and increased caudate volume, consistent with findings from adult-onset studies. Other volumetric brain abnormalities are observed in COS patients, such as reduced total brain volume, but not consistently across all studies. Voxel-based morphometric analyses have revealed abnormalities in the shape and spatial location of structures in COS such as the corpus callosum, caudate, and thalamus that could not be observed in the more traditional volumetric assessments. Similar findings also are observed in adult-onset patients. Progressive degenerative changes, such as ventricular enlargement, appear to occur in COS only until young adulthood where there is an apparent asymptote with no further degenerative changes. This is consistent with the lack of progressive changes noted in most longitudinal studies of adult-onset schizophrenia.

Age of Onset↗
PubMed2000

Brain abnormalities in early-onset schizophrenia spectrum disorder observed with statistical parametric mapping of structural magnetic resonance images.

OBJECTIVE: The purpose of this study was to assess neuroanatomic abnormalities in children and adolescents with childhood-onset schizophrenia by using whole-brain voxel-based morphometric analyses. Previous volumetric studies of brain abnormalities in childhood-onset schizophrenia have revealed anomalies similar to those in subjects with adult-onset schizophrenia. Specifically, low cerebral volume, high ventricular volume, and thalamic, basal ganglia, callosal, and temporal lobe abnormalities have been observed in childhood-onset schizophrenia. Relatively few anatomical structures have been delineated and measured in this rare population, partly because of the labor involved in the slice-by-slice region definition required of conventional volumetric image analyses. METHOD: The subjects were 10 normal children and adolescents and nine children and adolescents with early-onset schizophrenia (mean age at diagnosis, 11.0 years; range, 7-16 years). The authors conducted voxel-by-voxel and volumetric statistical analyses of high-resolution structural magnetic resonance images. RESULTS: Statistical parametric maps of gray matter, white matter, and CSF differences between the groups revealed that the subjects with early-onset schizophrenia had larger ventricles, predominantly in the posterior horns of the lateral ventricles, and midcallosal, posterior cingulate, caudate, and thalamic abnormalities. Volumetric analyses of the lateral ventricles in native image data space confirmed significantly higher volume in posterior, but not anterior, regions. Randomization tests confirmed the overall statistical significance of the group differences and validity of the parametric maps. CONCLUSIONS: These findings are generally consistent with the findings of other research groups, but localization of enlarged ventricles specific to the posterior region may be a new finding in the literature on childhood-onset schizophrenia.

Adolescent↗
PubMed1999

Localizing age-related changes in brain structure between childhood and adolescence using statistical parametric mapping.

Volumetric studies have consistently shown reductions in cerebral gray matter volume between childhood and adolescence, with the most dramatic changes occurring in the more dorsal cortices of the frontal and parietal lobes. The purpose of this study was to examine the spatial location of these changes employing methods typical of functional imaging studies. T1-weighted structural MRI data (1.2 mm) were analyzed for nine normally developing children and nine normal adolescents. Validity and reliability of the tissue segmentation protocol were assessed as part of several preprocessing analyses prior to statistical parametric mapping (SPM). Using SPM96, a simple contrast of average gray matter differences between the two age groups revealed 57 significant clusters (SPM[Z] height threshold, P<0.001, extent threshold 50, uncorrected). The pattern and distribution of differences were consistent with earlier findings from the volumetric assessment of the same subjects. Specifically, more differences were observed in dorsal frontal and parietal regions with relatively few differences observed in cortices of the temporal and occipital lobes. Permutation tests were conducted to assess the overall significance of the gray matter differences and validity of the parametric maps. Twenty SPMs were created with subjects randomly assigned to groups. None of the random SPMs approached the number of significant clusters observed in the age difference SPM (mean number of significant clusters = 5.8). The age effects observed appear to result from regions that consistently segment as gray matter in the younger group and consistently segment as white matter in the older group. The utility of these methods for localizing relatively subtle structural changes that occur between childhood and adolescence has not previously been examined.

Adolescent↗
PubMed1996

Abnormal development of the cerebellar vermis in children prenatally exposed to alcohol: size reduction in lobules I-V.

Abnormalities of the cerebellar vermis have been well documented in animal models of fetal alcohol syndrome. At this point, it is not known if the same brain region is affected in humans prenatally exposed to alcohol. In this study, the area of the cerebellar vermis was measured from brain magnetic resonance images of 9 children and young adults with prenatal alcohol exposure and 24 control subjects in the same age range. Six of the exposed children met standard criteria for fetal alcohol syndrome. The remaining three subjects had significant histories of prenatal exposure to alcohol, but did not have enough of the classic facial features for the diagnosis. For each subject with a suitable midsagittal section, three vermal areas were circumscribed: anterior vermis (vermal lobules I-V), posterior vermis (vermal lobules VI and VII), and the remaining vermal area (including lobules VIII-X). Statistical analyses revealed that the anterior region of the vermis was significantly smaller in subjects with prenatal alcohol exposure, whereas the posterior region and the remaining vermal area did not differ between groups. Previous findings from an animal model of neonatal alcohol exposure have documented Purkinje cell loss in vermal lobules I-V and IX-X, with notable sparing in lobules VI-VII. Thus, the results of both studies indicate similar patterns of abnormal brain development in the anterior vermal region, with apparent sparing in the posterior vermal region. Our findings, for the first time, suggest that regionally specific Purkinje cell death may also occur in humans prenatally exposed to alcohol.

Adolescent↗
PubMed1996

A decrease in the size of the basal ganglia in children with fetal alcohol syndrome.

Magnetic resonance imaging was conducted on six children and adolescents with fetal alcohol syndrome and seven matched normal controls. Detailed volumetric analyses demonstrated significant reductions in the cerebral vault, basal ganglia, and diencephalon in the children with fetal alcohol syndrome, compared with control children. In addition, the volume of the cerebellar vault was smaller than controls in 4 of the 6 children with fetal alcohol syndrome, although the group difference did not reach significance. When the basal ganglia were divided into the caudate and lenticular nuclei, both of these regions were significantly reduced in the children with fetal alcohol syndrome. Finally, when the overall reduction in brain size was controlled, the proportional volume of the basal ganglia and, more specifically, the caudate nucleus was reduced in the children with fetal alcohol syndrome. These results may relate to behavioral findings in both humans and animals exposed to alcohol prenatally.

Adolescent↗
PubMed1995

Abnormalities of the corpus callosum in children prenatally exposed to alcohol.

For 20 years, it has been known that fetal alcohol syndrome (FAS) is associated with abnormal brain development. Early autopsy studies point to the corpus callosum as one area affected by heavy alcohol exposure. Little is known, however, about the integrity of the brain in alcohol-exposed children who survive the perinatal period. This study was designed to assess the corpus callosum in living children exposed to high doses of alcohol prenatally. Thirteen children with histories of significant prenatal alcohol exposure and 12 normal control children were evaluated using magnetic resonance imaging. Using the midsagittal section, images were measured for the area of the corpus callosum using a computer-assisted measurement technique. In addition to the overall area, five equiangular regions were determined for each corpus callosum. Of the 13 alcohol-exposed children assessed, two had agenesis of the corpus callosum. The remaining alcohol-exposed children had significantly smaller overall callosal areas, as well as smaller regional areas of four of the five callosal regions, when compared with the normal control children. Importantly, when corrected for brain size, three of the five callosal regions were still smaller in the alcohol-exposed children, although overall area of the corpus callosum was no longer significantly different. These results suggest that prenatal exposure to high levels of alcohol is associated with abnormalities of the corpus callosum. They verify callosal agenesis in children with FAS, which previously had only been noted in autopsy reports.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Cerebral structure on MRI, Part I: Localization of age-related changes.

In this report, earlier findings of age-related changes in brain morphology on magnetic resonance (MR) images are extended to include measurements of individual cerebral grey matter structures and an index of white matter degeneration. Volumes of caudate, lenticular, and diencephalic structures are estimated, as are grey matter volumes in eight separate cortical regions. Results suggest that between 30 and 79 years significant decreases occur in the volume of the caudate nucleus, in anterior diencephalic structures, and in the grey matter of most cortical regions. The data suggest that the volumes of the thalamus and the anterior cingulate cortex may be unchanged. Among those cortical regions found to be affected in aging, some evidence is present for greater change in association cortices and mesial temporal lobe structures. There are also dramatic age-related changes in the white matter, manifest as lengthened T2 values on MR images.

Adult↗