- Psychiatry, Child and Adolescent
Clinical Associate Professor, Psychiatry and Behavioral Sciences - Vaden Health Center
Fellowship:Stanford University School of Medicine Registrar (2002) CA
Residency:Stanford University School of Medicine Registrar (1999) CA
Internship:Stanford University School of Medicine Registrar (1997) CA
Board Certification: Psychiatry, American Board of Psychiatry and Neurology (2003)
Medical Education:University of Texas Medical School (1996) TX
A volumetric study of parietal lobe subregions in Turner syndrome
DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY
2004; 46 (9): 607-609
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.
View details for DOI 10.1017/S0012162204001021
View details for Web of Science ID 000223720900005
View details for PubMedID 15344520
Functional neuroanatomy of spatial orientation processing in Turner syndrome
2004; 14 (2): 174-180
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.
View details for DOI 10.1093/cercor/bhg116
View details for Web of Science ID 000187975800006
View details for PubMedID 14704214
Brain development in Turner syndrome: a magnetic resonance imaging study
2002; 116 (3): 187-196
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.
View details for Web of Science ID 000180535800005
View details for PubMedID 12477602
Functional neuroanatomy of visuo-spatial working memory in Turner syndrome
HUMAN BRAIN MAPPING
2001; 14 (2): 96-107
Turner syndrome (TS), a genetic disorder characterized by the absence of an X chromosome in females, has been associated with cognitive and visuo-spatial processing impairments. We utilized functional MRI (fMRI) to investigate the neural substrates that underlie observed deficits in executive functioning and visuo-spatial processing. Eleven females with TS and 14 typically developing females (ages 7-20) underwent fMRI scanning while performing 1-back and 2-back versions of a standard visuo-spatial working memory (WM) task. On both tasks, TS subjects performed worse than control subjects. Compared with controls, TS subjects showed increased activation in the left and right supramarginal gyrus (SMG) during the 1-back task and decreased activation in these regions during the 2-back task. In addition, decreased activation in the left and right dorsolateral prefrontal cortex (DLPFC) and caudate nucleus was observed during the 2-back task in TS subjects. Activation differences localized to the SMG, in the inferior parietal lobe, may reflect deficits in visuo-spatial encoding and WM storage mechanisms in TS. In addition, deficits in the DLPFC and caudate may be related to deficits in executive function during WM performance. Together these findings point to deficits in frontal-striatal and frontal-parietal circuits subserving multiple WM functions in TS.
View details for Web of Science ID 000171325100003
View details for PubMedID 11500993
Brain imaging in neurogenetic conditions: Realizing the potential of behavioral neurogenetics research
MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS
2000; 6 (3): 186-197
Behavioral neurogenetics research is a new method of scientific inquiry that focuses on investigation of neurodevelopmental dysfunction associated with specific genetic conditions. This research method provides a powerful tool for scientific inquiry into human gene-brain-behavior linkages that complements more traditional research approaches. In particular, the use of specific genetic conditions as models of common behavioral and cognitive disorders occurring in the general population can reveal insights into neurodevelopmental pathways that might otherwise be obscured or diluted when investigating more heterogeneous, behaviorally defined subject groups. In this paper, we review five genetic conditions that commonly give rise to identifiable neurodevelopmental and neuropsychiatric disability in children: fragile X syndrome, velo-cardio-facial syndrome, Williams syndrome, Turner syndrome, and Klinefelter syndrome. While emphasis is placed on describing the brain morphology associated with these conditions as revealed by neuroimaging studies, we also include information pertaining to molecular genetic, postmortem, and neurobehavioral investigations to illustrate how behavioral neurogenetics research can contribute to an improved understanding of brain disorders in childhood.
View details for Web of Science ID 000089075600006
View details for PubMedID 10982496