90 research outputs found
Timing of Intervention Affects Brain Electrical Activity in Children Exposed to Severe Psychosocial Neglect
Background: Early psychosocial deprivation has profound effects on brain activity in the young child. Previous reports have shown increased power in slow frequencies of the electroencephalogram (EEG), primarily in the theta band, and decreased power in higher alpha and beta band frequencies in infants and children who have experienced institutional care. Methodology/Principal Findings: We assessed the consequences of removing infants from institutions and placing them into a foster care intervention on brain electrical activity when children were 8 years of age. We found the intervention was successful for increasing high frequency EEG alpha power, with effects being most pronounced for children placed into foster care before 24 months of age. Conclusions/Significance: The dependence on age of placement for the effects observed on high frequency EEG alpha power suggests a sensitive period after which brain activity in the face of severe psychosocial deprivation is less amenabl
Meta-analysis of diffusion tensor imaging studies shows altered fractional anisotropy occurring in distinct brain areas in association with depression
Fractional anisotropy anomalies occurring in the white matter tracts in the brains of depressed patients may reflect microstructural changes underlying the pathophysiology of this disorder. We conducted a meta-analysis of fractional anisotropy abnormalities occurring in major depressive disorder using voxel-based diffusion tensor imaging studies. Using the Embase, PubMed and Google Scholar databases, 89 relevant data sets were identified, of which 7 (including 188 patients with major depressive disorder and 221 healthy controls) met our inclusion criteria. Authors were contacted to retrieve any additional data required. Coordinates were extracted from clusters of significant white matter fractional anisotropy differences between patients and controls. Relevant demographic, clinical and methodological variables were extracted from each study or obtained directly from authors. The meta-analysis was carried out using Signed Differential Mapping. Patients with depression showed decreased white matter fractional anisotropy values in the superior longitudinal fasciculus and increased fractional anisotropy values in the fronto-occipital fasciculus compared to controls. Using quartile and jackknife sensitivity analysis, we found that reduced fractional anisotropy in the left superior longitudinal fasciculus was very stable, with increases in the right fronto-occipital fasciculus driven by just one study. In conclusion, our meta-analysis revealed a significant reduction in fractional anisotropy values in the left superior longitudinal fasciculus, which may ultimately play an important role in the pathology of depression
Adolescent Engagement in Dangerous Behaviors Is Associated with Increased White Matter Maturity of Frontal Cortex
Background: Myelination of white matter in the brain continues throughout adolescence and early adulthood. This cortical immaturity has been suggested as a potential cause of dangerous and impulsive behaviors in adolescence. Methodology/Principal Findings: We tested this hypothesis in a group of healthy adolescents, age 12β18 (N = 91), who underwent diffusion tensor imaging (DTI) to delineate cortical white matter tracts. As a measure of real-world risk taking, participants completed the Adolescent Risk Questionnaire (ARQ) which measures engagement in dangerous activities. After adjusting for age-related changes in both DTI and ARQ, engagement in dangerous behaviors was found to be positively correlated with fractional anisotropy and negatively correlated with transverse diffusivity in frontal white matter tracts, indicative of increased myelination and/or density of fibers (ages 14β18, N = 60). Conclusions/Significance: The direction of correlation suggests that rather than having immature cortices, adolescents who engage in dangerous activities have frontal white matter tracts that are more adult in form than their more conservative peers
Development of Large-Scale Functional Brain Networks in Children
Large-scale rewiring of brain circuits in children leads to emergence of hierarchical organization in the mature adult brain
Adolescent Brain Development and the Risk for Alcohol and Other Drug Problems
Dynamic changes in neurochemistry, fiber architecture, and tissue composition occur in the adolescent brain. The course of these maturational processes is being charted with greater specificity, owing to advances in neuroimaging and indicate grey matter volume reductions and protracted development of white matter in regions known to support complex cognition and behavior. Though fronto-subcortical circuitry development is notable during adolescence, asynchronous maturation of prefrontal and limbic systems may render youth more vulnerable to risky behaviors such as substance use. Indeed, binge-pattern alcohol consumption and comorbid marijuana use are common among adolescents, and are associated with neural consequences. This review summarizes the unique characteristics of adolescent brain development, particularly aspects that predispose individuals to reward seeking and risky choices during this phase of life, and discusses the influence of substance use on neuromaturation. Together, findings in this arena underscore the importance of refined research and programming efforts in adolescent health and interventional needs
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Congenital X-linked Stapes Gusher Syndrome in an Infant A Case Report
Congenital X-linked deafness with stapes gusher is a rare, but well-known clinical entity with characteristic radiological features. Recognition of these findings is important as it changes the treatment course and precludes stapedectomy, which if done can lead to stapes gusher in these patients. We present the case of a nine-month-old male infant with hearing loss. CT scan showed typical radiological features of X-linked stapes gusher syndrome. In addition, the superior semicircular canals appeared dehiscent which could be due to immature ossification or less likely due to defective development as part of the disease. To the best of our knowledge this is the youngest patient prospectively identified by imaging in the English medical literature
Novel mechanism for interesting C-C coupling and cleavage reactions and control of thermodynamic stability involving [L<SUB>2</SUB>M(μ-CCR)<SUB>2</SUB>ML<SUB>2</SUB>] and [L<SUB>2</SUB>M(μ-RCC-CCR)ML<SUB>2</SUB>] complexes (M = Ti, Zr; L = η <SUP>5</SUP>-C<SUB>5</SUB>H<SUB>5</SUB>, Cl, H; R = H, F, CN): a theoretical study
Possible reaction mechanisms for C-C coupling and cleavage reactions involving [(η5-C5H5)M(μ-CCR)2M(η5-C5H5)2] and [(η5-C5H5)M(μ-RCC-CCR)M(η5-C5H5)2] (M = Ti, Zr) complexes are discussed on the basis of theoretical studies. A series of realistic and simplified model complexes, [L2M(μ-CCR)2ML2] 8 and [L2M(μ-RCC-CCR)ML2] 9 (M = Ti, Zr; L = η5-C5H5, Cl, H; R = H, F, CN) were calculated using ab initio MO and density functional methods. The formation of the bisacetylide bridging complex starting from either metal acetylides or butadiyne is explained by a mechanistic scheme involving metallacyclocumulenes (5), binuclear complexed metallacyclocumulenes (6), and the M+2-M+4 complexes (7). The latter rather than 6 led to the C-C coupled products 9 via 8. The experimentally observed unusual C-C coupling in the dimeric bis(η5-cyclopentadienyl)phenylethynyltitanium complex and the lack of it in the corresponding zirconium complex are influenced by substituents on the ethynyl group. Theoretical studies demonstrate that the electron-withdrawing substituent R = F drives the thermodynamic equilibrium distinctively towards the C-C coupled product, 9 both for M = Ti and Zr. An unusually short Zr-Zr interatomic distance in [(η5-C5H5)Zr(μ-CCR)2Zr(η5-C5H5)2] compared to Ti-Ti distance in the corresponding Ti complex is observed theoretically and from X-ray crystal structures of related complexes. Substitution of cyclopentadienyls by Cl and even H to obtain computationally viable models does not change the relative energies of the ground and transition states of the binuclear Zr complexes. The Ti complexes are affected somewhat more by these changes but the trends in relative energies between Ti and Zr isomers are retained. Geometric parameters and relative energies obtained at the B3LYP/LANL2DZ level are found to be better than those at the HF level
Organometallic analogs of the cyclobutadiene dication: an ab initio MO and density functional study of the symmetrical planar and puckered [WL<SUB>2</SUB>(μ-CR)]<SUB>2</SUB> complexes (L = H, Me, F, OH; R = H, F, Me)
Ab initio MO and density functional theory calculations are reported for tungsten complexes [WL2(μ-CR)]2 (L = H, Me, F, OH; R = H, F, Me). The general perception that these complexes are always planar is contradicted. The effect of ligand L and substituent R on the puckering of four-membered W2C2 ring are studied. With L = H, the ring puckering is in the order of R = F < H < Me. With R = H, the ring puckering is in the order of L = OH ≈ F < Me < H. The puckering of W2C2 ring depends more on the ligand L than on the substituent R. The analogous nature of these complexes to cyclobutadiene dications is also discussed
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Persistent trigeminal artery and associated vascular variations (vol 51, pg B31, 2007)
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