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      Functional magnetic resonance imaging of autism spectrum disorders

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          Abstract

          This review presents an overview of functional magnetic resonance imaging findings in autism spectrum disorders (ASDs), Although there is considerable heterogeneity with respect to results across studies, common themes have emerged, including: (i) hypoactivation in nodes of the “social brain” during social processing tasks, including regions within the prefrontal cortex, the posterior superior temporal sulcus, the amygdala, and the fusiform gyrus; (ii) aberrant frontostriatal activation during cognitive control tasks relevant to restricted and repetitive behaviors and interests, including regions within the dorsal prefrontal cortex and the basal ganglia; (iii) differential lateralization and activation of language processing and production regions during communication tasks; (iv) anomalous mesolimbic responses to social and nonsocial rewards; (v) task-based long-range functional hypoconnectivity and short-range hyper-connectivity; and (vi) decreased anterior-posterior functional connectivity during resting states. These findings provide mechanistic accounts of ASD pathophysiology and suggest directions for future research aimed at elucidating etiologic models and developing rationally derived and targeted treatments.

          Translated abstract

          Esta revisión entrega una panoráinica acerca de los hallazgos de la resonancia magnética funcional en los trastornos del espectro autista (TEA), Aunque existe bastante heterogeneidad en los resuliados de los estudios han aparecido aspectos comunes que incluyen: 1) hipoactivación en los nodos del “cerebro social” durante las tareas de procesamiento social, que incluyen regiones dentro de la corteza prefrontal, el sulcus temporal superior posterior, la amígdala y el giro fusiforme, 2) activación frontoestriatal aberrante durante las tareas de control cognitivo, relacionadas con los intereses y las conductas restringidas y repetitivas, y que incluyen regiones dentro de la corteza prefrontal dorsal y los ganglios basales, 3) lateralizatión y activación diferencial de las regiones relacionadas con el procesamiento y la produccion del lenguaje durante las tareas de comunicación, 4) respuestas mesolímbicas anómalas a las recompensas sociales y no sociales, 5) hipoconectividad funcional a largo plazo e hiperconectividad a corto plazo frente a tareas y 6) disminución de la conectividad funcional antero-posterior durante los estados de reposo, Estos hallazgos aportan razones mecanicistas para la fisiopatología de los TEA y sugieren orientaciones para las futuras investigaciones encaminadas a aclarar los modelos etiólogicos y desarrollar tratamientos que puedan ser específicos y obtenerse rationalmente.

          Translated abstract

          Cet article présente une synthèse des résultats de l'imagerie par résonance magnétique fonctionnelle dans les troubles autistiques (TA), En dépit d'une grande hétérogénéité due aux résultais des études, des thèmes communs ressortent comme: 1) une hypoactivation des nœuds du « cerveau social » au cours des tâches sociales, qui concerne les régions du cortex préfrontal, du sillon temporal postérosupérieur, de l'amygdale, et du gyrus fusiforme ; 2) une activation froniostriaiale aberrante du cortex dorsal préfrontal et des noyaux gris centraux lors des tâches de contrôle cognitif se rapportant à des intérêts et à des comportements restreints et répétitifs ; 3) une activation et une latéralisation différentielles des régions de production et de traitement du langage au cours des tâches de communication ; 4) des réponses mésolimbiques anormales aux récompenses sociales et non sociales ; 5) une hypoconnectivité fonctionnelle à longue distance et une hyperconnectivité de courte distance basées sur les tâches ; 6) une connectivité fonctionnelle antéropostérieure diminuée pendant les états de repos. Ces résultais donnent un aperçu mécanisie de la physiopathologie des TA et suggèrent des directions pour la recherche future afin d'élaborer des modèles étiologiques et de développer de façon rationnelle des traitements ciblés et dérivés.

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          The activation of attentional networks.

          Alerting, orienting, and executive control are widely thought to be relatively independent aspects of attention that are linked to separable brain regions. However, neuroimaging studies have yet to examine evidence for the anatomical separability of these three aspects of attention in the same subjects performing the same task. The attention network test (ANT) examines the effects of cues and targets within a single reaction time task to provide a means of exploring the efficiency of the alerting, orienting, and executive control networks involved in attention. It also provides an opportunity to examine the brain activity of these three networks as they operate in a single integrated task. We used event-related functional magnetic resonance imaging (fMRI) to explore the brain areas involved in the three attention systems targeted by the ANT. The alerting contrast showed strong thalamic involvement and activation of anterior and posterior cortical sites. As expected, the orienting contrast activated parietal sites and frontal eye fields. The executive control network contrast showed activation of the anterior cingulate along with several other brain areas. With some exceptions, activation patterns of these three networks within this single task are consistent with previous fMRI studies that have been studied in separate tasks. Overall, the fMRI results suggest that the functional contrasts within this single task differentially activate three separable anatomical networks related to the components of attention.
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            Autism spectrum disorders: developmental disconnection syndromes.

            Autism is a common and heterogeneous childhood neurodevelopmental disorder. Analogous to broad syndromes such as mental retardation, autism has many etiologies and should be considered not as a single disorder but, rather, as 'the autisms'. However, recent genetic findings, coupled with emerging anatomical and functional imaging studies, suggest a potential unifying model in which higher-order association areas of the brain that normally connect to the frontal lobe are partially disconnected during development. This concept of developmental disconnection can accommodate the specific neurobehavioral features that are observed in autism, their emergence during development, and the heterogeneity of autism etiology, behaviors and cognition.
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              Cortical activation and synchronization during sentence comprehension in high-functioning autism: evidence of underconnectivity.

              The brain activation of a group of high-functioning autistic participants was measured using functional MRI during sentence comprehension and the results compared with those of a Verbal IQ-matched control group. The groups differed in the distribution of activation in two of the key language areas. The autism group produced reliably more activation than the control group in Wernicke's (left laterosuperior temporal) area and reliably less activation than the control group in Broca's (left inferior frontal gyrus) area. Furthermore, the functional connectivity, i.e. the degree of synchronization or correlation of the time series of the activation, between the various participating cortical areas was consistently lower for the autistic than the control participants. These findings suggest that the neural basis of disordered language in autism entails a lower degree of information integration and synchronization across the large-scale cortical network for language processing. The article presents a theoretical account of the findings, related to neurobiological foundations of underconnectivity in autism.
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                Author and article information

                Contributors
                Departments of Psychiatry and Psychology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA; Carolina Institute for Developmental Disabilities, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, USA; Duke-UNC Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, USA
                Journal
                Dialogues Clin Neurosci
                Dialogues Clin Neurosci
                Dialogues Clin Neurosci
                Dialogues in Clinical Neuroscience
                Les Laboratoires Servier (France )
                1294-8322
                1958-5969
                September 2012
                September 2012
                : 14
                : 3
                : 319-351
                Affiliations
                Departments of Psychiatry and Psychology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA; Carolina Institute for Developmental Disabilities, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina, USA; Duke-UNC Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, USA
                Author notes
                Article
                10.31887/dcns.2012.14.3/gdichter
                3513685
                23226956
                fc629e23-9b51-450a-a97b-9667ecfbea65
                Copyright: © 2012 LLS

                This is an open-access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by-nc-nd/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                Categories
                Clinical Research

                Neurosciences
                repetitive behavior,connectivity,reward,cognitive control,language,functional magnetic resonance imaging,autism spectrum disorder,fmri

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