RESUMO
Brain development during childhood and early adolescence is characterized by global changes in brain architecture. Neuroimaging studies have revealed overall decreases in cortical thickness (CT) and increases in fractional anisotropy (FA). Furthermore, previous studies have shown that certain cortical regions display coordinated growth during development. However, there is significant heterogeneity in the timing and speed of these developmental transformations, and it is still unclear whether white and grey matter changes are co-localized. In this multimodal neuroimaging study, we investigated the relationship between grey and white matter developmental changes and asynchronous maturation within brain regions in 249 normally developing children between the ages 7-14. We used structural magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) to analyze CT and FA, respectively, as well as their covariance across development. Consistent with previous studies, we observed overall cortical thinning with age, which was accompanied by increased FA. We then compared the coordinated development of grey and white matter as indexed by covariance measures. Covariance between grey matter regions and the microstructure of white matter tracts connecting those regions were highly similar, suggesting that coordinated changes in the cortex were mirrored by coordinated changes in their respective tracts. Examining within-brain divergent trajectories, we found significant structural decoupling (decreased covariance) between several brain regions and tracts in the 9- to 11-year-old group, particularly involving the forceps minor and the regions that it connects to. We argue that this decoupling could reflect a developmental pattern within the prefrontal region in 9- and 11-year-old children, possibly related to the significant changes in cognitive control observed at this age.
Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/crescimento & desenvolvimento , Substância Cinzenta/diagnóstico por imagem , Substância Cinzenta/crescimento & desenvolvimento , Substância Branca/diagnóstico por imagem , Substância Branca/crescimento & desenvolvimento , Adolescente , Criança , Estudos Transversais , Imagem de Difusão por Ressonância Magnética , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Imagem Multimodal , Tamanho do ÓrgãoRESUMO
BACKGROUND: Attention deficit hyperactivity disorder (ADHD) is frequently associated with poorer reading ability; however, the specific neuropsychological domains linking this co-occurrence remain unclear. This study evaluates information-processing characteristics as possible neuropsychological links between ADHD symptoms and RA in a community-based sample of children and early adolescents with normal IQ (⩾70). METHOD: The participants (n = 1857, aged 6-15 years, 47% female) were evaluated for reading ability (reading single words aloud) and information processing [stimulus discriminability in the two-choice reaction-time task estimated using diffusion models]. ADHD symptoms were ascertained through informant (parent) report using the Development and Well-Being Assessment (DAWBA). Verbal working memory (VWM; digit span backwards), visuospatial working memory (VSWM, Corsi Blocks backwards), sex, socioeconomic status, and IQ were included as covariates. RESULTS: In a moderated mediation model, stimulus discriminability mediated the effect of ADHD on reading ability. This indirect effect was moderated by age such that a larger effect was seen among younger children. CONCLUSION: The findings support the hypothesis that ADHD and reading ability are linked among young children via a neuropsychological deficit related to stimulus discriminability. Early interventions targeting stimulus discriminability might improve symptoms of inattention/hyperactivity and reading ability.
Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Discriminação Psicológica/fisiologia , Dislexia/fisiopatologia , Reconhecimento Visual de Modelos/fisiologia , Leitura , Adolescente , Criança , Feminino , Humanos , MasculinoRESUMO
The anterior cerebral artery (ACA) is a major vessel responsible for the blood supply to the interhemispheric region. The ACA segment after the anterior communicating artery (AComA) origin is called the distal ACA and has central and cortical branches. The cortical branches are distributed in the different regions of the orbital and medial part of the brain. The objects of this study are the anatomical variations found in the distal ACA. In 76 hemispheres the ACA distal branches were injected with latex and dissected under microscope magnification. Vessel diameters and distances between vessel origins and anterior communicating artery were recorded and analyzed. Microsurgical dissection was carried out to demonstrate anatomic variations of these vessels. Average diameter of ACA at origin was 2.61 +/- 0.34 mm and average diameter of cortical branches diameter ranged from 0.79 +/- 0.27 mm to 1.84 +/- 0.3 mm. Distances between vessel origin and AComA ranged from 7.68 +/- 3.91 mm (orbitofrontal) to 112.6 +/- 11.63 mm (inferior internal parietal). This study found anatomical variations: a single (azygos) ACA was present in one case and three in three cases. Crossing branches of the distal ACA to the contralateral hemisphere were present in 26% of the cases. In some cases a single ACA may supply the posterior hemispheric region through crossing branches. This calls attention to potential bilateral brain infarcts due to a single unilateral ACA occlusion.
Assuntos
Artéria Cerebral Anterior/anatomia & histologia , Córtex Cerebral/irrigação sanguínea , Artéria Cerebral Anterior/anormalidades , Cadáver , Dissecação , HumanosRESUMO
In the surgical management of skull base lesions and vascular diseases such as giant aneurysms, involvement of the internal carotid artery may require the resection or the occlusion of the vessel. The anastomosis of the external carotid artery and the middle cerebral artery with venous graft may be indicated to re-establish the blood flow. To determine the best suture site in the middle cerebral artery, an anatomical study was carried out. Fourteen cerebral hemispheres were analysed after the injection of red latex into the internal carotid artery. The superior and inferior trunk of the main division of the middle cerebral artery have more than 2 mm of diameter. They are superficial allowing an anastomosis using a venous graft. The superior trunk has a disadvantage, it gives rise to branches for the precentral and post-central giri. The anastomosis with the inferior trunk presents lower risk of neurological deficit even though the angular artery originates from it.