Biomedical subjects

Shelli R Kesler

Publications and source records attributed to Shelli R Kesler.

11 recordsLinked to original sources

PubMed2006

Selective alterations of white matter associated with visuospatial and sensorimotor dysfunction in turner syndrome.

Turner syndrome (TS) is a neurogenetic disorder characterized by impaired spatial, numerical, and motor functioning but relatively spared verbal ability. Results from previous neuroimaging studies suggest that gray matter alterations in parietal and frontal regions may contribute to atypical visuospatial and executive functioning in TS. Recent findings in TS also indicate variations in the shape of parietal gyri and white matter microstructural anomalies of the temporal lobe. Diffusion tensor imaging and structural imaging methods were used to determine whether 10 females with TS and 10 age- and gender-matched control subjects exhibited differences in fractional anisotropy, white matter density, and local brain shape. Relative to controls, females with TS had lower fractional anisotropy (FA) values in the deep white matter of the left parietal-occipital region extending anteriorly along the superior longitudinal fasciculus into the deep white matter of the frontal lobe. In addition, decreased FA values were located bilaterally in the internal capsule extending into the globus pallidus and in the right prefrontal region. Voxel-based morphometry (VBM) analysis showed corresponding white matter density differences in the internal capsules and left centrum semiovale. Tensor-based morphometry analysis indicated that the FA and VBM results were not attributable to differences in the local shape of brain structures. Compared with controls, females with TS had increases in FA values and white matter density in language-related areas of the inferior parietal and temporal lobes. These complementary analyses provide evidence for alterations in white matter pathways that subserve affected and preserved cognitive functions in TS.

Adolescent↗

PubMed2005

Neuro-functional differences associated with arithmetic processing in Turner syndrome.

Turner syndrome (TS) is a neurogenetic disorder characterized by the absence of one X chromosome in a phenotypic female. Individuals with TS are at risk for impairments in mathematics. We investigated the neural mechanisms underlying arithmetic processing in TS. Fifteen subjects with TS and 15 age-matched typically developing controls were scanned using functional MRI while they performed easy (two-operand) and difficult (three-operand) versions of an arithmetic processing task. Both groups activated fronto-parietal regions involved in arithmetic processing during the math tasks. Compared with controls, the TS group recruited additional neural resources in frontal and parietal regions during the easier, two-operand math task. During the more difficult three-operand task, individuals with TS demonstrated significantly less activation in frontal, parietal and subcortical regions than controls. However, the TS group's performance on both math tasks was comparable to controls. Individuals with TS demonstrate activation differences in fronto-parietal areas during arithmetic tasks compared with controls. They must recruit additional brain regions during a relatively easy task and demonstrate a potentially inefficient response to increased task difficulty compared with controls.

Adolescent↗

PubMed2005

Increased temporal lobe gyrification in preterm children.

Preterm birth often results in significant learning disability, and previous magnetic resonance imaging (MRI) studies of preterm children have demonstrated reduction in overall cortical tissue with particular vulnerability in the temporal lobe. We measured cortical gyrification in 73 preterm and 33 term control children at 8 years of age and correlated these findings with tests of language ability to determine the associations among preterm birth, neurodevelopment and functional outcome. Preterm children demonstrated significantly increased bilateral temporal lobe gyrification index compared to term controls. Left temporal gyrification index was significantly negatively correlated with left temporal lobe gray matter volume as well as reading recognition scores in the preterm group. Cortical development in the temporal lobe appears to be differentially vulnerable to preterm birth.

Cerebral Cortex↗

PubMed2004

Sex differences in cerebral volumes of 8-year-olds born preterm.

We investigate sex-associated effects of preterm birth on cerebral gray matter (GM) and white matter (WM) volumes. Preterm children (n=65) and 31 healthy, term control children had usable magnetic resonance imaging (MRI) data acquired at 8 years of age. Both GM and WM volumes were significantly reduced in the preterm group compared with controls. However, only males with preterm birth had significantly reduced WM compared with term males (P=.021), whereas WM volumes were equivalent in the female groups. Lower birth weight was associated with reduced WM in both boys and girls with preterm birth, whereas intraventricular hemorrhage (IVH) was associated with reduced GM in girls only. Positive correlations between GM and cognitive outcome were observed in girls with preterm birth but not boys. We conclude that preterm birth has a significant impact on brain development with increased risk for smaller GM and WM cerebral volumes. Males appear particularly vulnerable to adverse effects of preterm birth on WM development. However, girls with preterm birth show stronger correlations between neuro-anatomical variables and both neonatal risk factors and cognitive outcome, compared with boys. These findings indicate that the sex of the very preterm newborn influences the mechanisms by which the developing brain is affected.

Brain↗

PubMed2004

Amygdala and hippocampal volumes in Turner syndrome: a high-resolution MRI study of X-monosomy.

Turner syndrome (TS) results from partial or complete X-monosomy and is characterized by deficits in visuospatial functioning as well as social cognition and memory. Neuroimaging studies have demonstrated volumetric differences in the parietal region of females with TS compared to controls. The present study examined amygdala and hippocampus morphology in an attempt to further understand the neural correlates of psychosocial and memory functioning in TS. Thirty females with TS age 7.6-33.3 years (mean = 14.7 +/- 6.4) and 29 age-matched controls (mean age = 14.8 +/- 5.9; range = 6.4-32.7) were scanned using high resolution MRI. Volumetric analyses of the MRI scans included whole brain segmentation and manual delineation of the amygdala and hippocampus. Compared to controls, participants with TS demonstrated significantly larger left amygdala gray matter volumes, irrespective of total cerebral tissue and age. Participants with TS also showed disproportionately reduced right hippocampal volumes, involving both gray and white matter. Amygdala and hippocampal volumes appear to be impacted by X-monosomy. Aberrant morphology in these regions may be related to the social cognition and memory deficits often experienced by individuals with TS. Further investigations of changes in medial temporal morphology associated with TS are warranted.

Adolescent↗

PubMed2004

Volumetric analysis of regional cerebral development in preterm children.

Preterm birth is frequently associated with both neuropathologic and cognitive sequelae. This study examined cortical lobe, subcortical, and lateral ventricle development in association with perinatal variables and cognitive outcome. High-resolution volumetric magnetic resonance imaging scans were acquired and quantified using advanced image processing techniques. Seventy-three preterm and 33 term control children ages 7.3-11.4 years were included in the study. Results indicated disproportionately enlarged parietal and frontal gray matter, occipital horn, and ventricular body, as well as reduced temporal and subcortical gray volumes in preterm children compared with control subjects. Birth weight was negatively correlated with parietal and frontal gray, as well as occipital horn volumes. Intraventricular hemorrhage was associated with reduced subcortical gray matter. Ventricular cerebrospinal fluid was negatively correlated with subcortical gray matter volumes but not with white matter volumes. Maternal education was the strongest predictor of cognitive function in the preterm group. Preterm birth appears to be associated with disorganized cortical development, possibly involving disrupted synaptic pruning and neural migration. Lower birth weight and the presence of intraventricular hemorrhage may increase the risk for neuroanatomic abnormality.

Cerebral Cortex↗

PubMed2004

A volumetric study of parietal lobe subregions in Turner syndrome.

Turner syndrome, a genetic disorder that results from the complete or partial absence of an X chromosome in females, has been associated with specific impairment in visuospatial cognition. Previous studies have demonstrated a relationship between parietal lobe abnormalities and visuospatial deficits in Turner syndrome. We used high-resolution magnetic resonance imaging to measure parietal lobe subdivisions in 14 participants with Turner syndrome (mean age 13 years 5 months, SD 5 years) and 14 age-matched controls (mean age 13 years 5 months, SD 4 years 7 months) to localize neuroanatomical variations more closely. Scans were acquired and analyzed for 14 females with Turner syndrome. Analyses of variance were used to investigate differences in regional parietal lobes. Females with Turner syndrome showed a bilateral parietal lobe reduction, specifically in the superior parietal and postcentral gyri. Full-scale IQ scores were significantly positively correlated with postcentral tissue volume in the Turner syndrome group. Structural differences in the parietal lobe are localized specifically to the anterior and superior parietal lobe and might be related to the visuospatial and visuomotor deficits associated with Turner syndrome.

Adolescent↗

PubMed2004

Functional neuroanatomy of spatial orientation processing in Turner syndrome.

Turner syndrome (TS), a neurogenetic disorder characterized by the absence of one X chromosome in a phenotypic female, is frequently associated with visuospatial impairments. We investigated the neural mechanisms underlying deficits in spatial orientation processing in TS. Thirteen subjects with TS and 13 age-matched typically developing controls underwent neuropsychological assessments and were scanned using functional MRI while they performed easy and difficult versions of a judgment of line orientation (JLO) task. Controls and subjects with TS activated parietal-occipital regions involved in spatial orientation during the JLO task. However, activation was significantly less in the TS group. Control subjects responded to increased task difficulty by recruiting executive frontal areas whereas subjects with TS did not activate alternate brain regions to meet increased task demands. Subjects with TS demonstrate activation deficits in parietal-occipital and frontal areas during the JLO task. Activation, and possibly deactivation, deficits in these areas may be responsible for the visuospatial deficits observed in females with TS.

Adolescent↗

PubMed2003

Effects of X-monosomy and X-linked imprinting on superior temporal gyrus morphology in Turner syndrome.

BACKGROUND: Turner syndrome (TS) results from complete or partial monosomy X. The cognitive phenotype of TS involves preservation of verbal skills with visuospatial functioning deficits. The superior temporal gyrus (STG), which is involved in language capacities, has not been investigated in TS. METHODS: The STG was measured in 30 female subjects (mean age = 14.73 +/- 6.41; range = 7.56-33.30) with TS and 30 age-matched control subjects (mean age = 14.63 +/- 5.90; range = 6.35-32.65) using volumetric magnetic resonance imaging analyses. RESULTS: -Right STG, including both gray and white matter volumes, was significantly larger in TS compared with control subjects. Overall left STG volume was not significantly different between groups, although left white matter volume was increased in the TS subjects. The TS subgroup with a maternally derived X chromosome (Xm) demonstrated more aberrant STG volumes compared with subjects with a paternally (Xp) derived X and control subjects. The difference in STG volumes between Xm and control subjects involved both white and gray matter. The Xm subjects differed from Xp subjects only in terms of gray matter. CONCLUSIONS: These findings suggest that X-monosomy and X-linked imprinting negatively affect STG development, possibly by disrupting neural pruning mechanisms.

Adolescent↗

PubMed2003

Premorbid intellectual functioning, education, and brain size in traumatic brain injury: an investigation of the cognitive reserve hypothesis.

Cognitive reserve theories have been postulated in an attempt to explain individual differences in functional outcome following cerebral insult or disease. These theories suggest that higher education and psychometric intelligence may preserve functional capacity regardless of injury or disease severity. This study investigated cognitive reserve in 25 participants with traumatic brain injury (TBI) using high-resolution magnetic resonance imaging (MRI) analyses. We examined the relationships between total intracranial volume (TICV), ventricle-tobrain ratio (VBR), education level, and standardized testing obtained prior to injury with post-injury cognitive outcome. Participants with lower post-injury IQ scores had significantly lower TICV values, irrespective of injury severity, and experienced significantly greater change in IQ from pre- to post-injury. TICV and education correctly predicted participants' post-injury IQ category ( Y 90 or < 90). However, premorbid standardized testing (PST) scores did not predict cognitive outcome. The results of this study suggest that larger premorbid brain volume and higher education level may decrease vulnerability to cognitive deficits following TBI, consistent with the notion of a cognitive reserve.

Adult↗

PubMed2002

Brain development in Turner syndrome: a magnetic resonance imaging study.

Turner syndrome (TS) results from the absence of an X chromosome in females. This genetic condition is associated with specific cognitive deficits and variations in brain volumes. The goal of this study was to use high-resolution magnetic resonance imaging (MRI) to determine morphological variations in TS and to investigate the effects of parental origin of the X chromosome on brain development in TS. MRI brain scans were acquired from 26 girls with TS and 26 age- and gender-matched controls. Seventeen of the TS subjects had a maternally inherited X chromosome (Xm), and nine of the subjects had a paternally inherited X chromosome (Xp). Rater-blind morphometric analyses were conducted to compare tissue volume differences between girls with TS and controls. Three-way analyses were used to compare subgroups and controls. Subjects with TS demonstrated bilateral decreases in parietal gray and occipital white matter accompanied by increased cerebellar gray matter. Subjects with Xm showed decreased occipital white matter and increased cerebellar gray matter compared to controls. No differences were found in comparisons between subjects with Xp and controls or between subjects with Xm and Xp. Results suggest that X monosomy affects posterior cerebral and cerebellar anatomy in TS. While differences between comparisons of Xm and Xp to controls might suggest an imprinting effect, no significant differences were found when the two subgroups were directly compared to each other. Further investigation into the possible role of genomic imprinting is therefore warranted.

Adolescent↗