Disrupted cortical connectivity theory as an explanatory model for autism spectrum disorders.
ABSTRACT Recent findings of neurological functioning in autism spectrum disorder (ASD) point to altered brain connectivity as a key feature of its pathophysiology. The cortical underconnectivity theory of ASD (Just et al., 2004) provides an integrated framework for addressing these new findings. This theory suggests that weaker functional connections among brain areas in those with ASD hamper their ability to accomplish complex cognitive and social tasks successfully. We will discuss this theory, but will modify the term underconnectivity to 'disrupted cortical connectivity' to capture patterns of both under- and over-connectivity in the brain. In this paper, we will review the existing literature on ASD to marshal supporting evidence for hypotheses formulated on the disrupted cortical connectivity theory. These hypotheses are: 1) underconnectivity in ASD is manifested mainly in long-distance cortical as well as subcortical connections rather than in short-distance cortical connections; 2) underconnectivity in ASD is manifested only in complex cognitive and social functions and not in low-level sensory and perceptual tasks; 3) functional underconnectivity in ASD may be the result of underlying anatomical abnormalities, such as problems in the integrity of white matter; 4) the ASD brain adapts to underconnectivity through compensatory strategies such as overconnectivity mainly in frontal and in posterior brain areas. This may be manifested as deficits in tasks that require frontal-parietal integration. While overconnectivity can be tested by examining the cortical minicolumn organization, long-distance underconnectivity can be tested by cognitively demanding tasks; and 5) functional underconnectivity in brain areas in ASD will be seen not only during complex tasks but also during task-free resting states. We will also discuss some empirical predictions that can be tested in future studies, such as: 1) how disrupted connectivity relates to cognitive impairments in skills such as Theory-of-Mind, cognitive flexibility, and information processing; and 2) how connection abnormalities relate to, and may determine, behavioral symptoms hallmarked by the triad of Impairments in ASD. Furthermore, we will relate the disrupted cortical connectivity model to existing cognitive and neural models of ASD.
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ABSTRACT: Co-occurrence of preserved musical function with language and socio-communicative impairments is a common but understudied feature of Autism Spectrum Disorders (ASD). Given the significant overlap in neural organization of these processes, investigating brain mechanisms underlying speech and music may not only help dissociate the nature of these auditory processes in ASD but also provide a neurobiological basis for development of interventions. Using a passive-listening functional magnetic resonance imaging paradigm with spoken words, sung words and piano tones, we found that 22 children with ASD, with varying levels of functioning, activated bilateral temporal brain networks during sung-word perception, similarly to an age and gender-matched control group. In contrast, spoken-word perception was right-lateralized in ASD and elicited reduced inferior frontal gyrus (IFG) activity which varied as a function of language ability. Diffusion tensor imaging analysis reflected reduced integrity of the left hemisphere fronto-temporal tract in the ASD group and further showed that the hypoactivation in IFG was predicted by integrity of this tract. Subsequent psychophysiological interactions revealed that functional fronto-temporal connectivity, disrupted during spoken-word perception, was preserved during sung-word listening in ASD, suggesting alternate mechanisms of speech and music processing in ASD. Our results thus demonstrate the ability of song to overcome the structural deficit for speech across the autism spectrum and provide a mechanistic basis for efficacy of song-based interventions in ASD. Autism Res 2014, ●●: ●●–●●. © 2014 International Society for Autism Research, Wiley Periodicals, Inc.Autism Research 12/2014; · 3.99 Impact Factor
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ABSTRACT: The posterior right temporo-parietal junction (pRTPJ) is a key brain region representing other's mental status. Despite reports of atypical activation at pRTPJ during mentalizing in individuals with autism spectrum disorder (ASD), the intrinsic functional connectivity (iFC) of the pRTPJ remains under-investigated. We examined whether boys with ASD show altered resting-state iFC of the pRTPJ, and whether atypical iFC of the pRTPJ is associated with social defi-cits in ASD in a sample of 40 boys with high-functioning ASD (aged 9–17 years, mean age, 12.38 6 2.17; mean IQ, 105.60 6 16.06) and 42 typically developing (TD) boys (aged 9–17 years, mean age, 11.64 6 2.71; mean IQ, 111.29 6 13.45). Both groups received resting-state fMRI assessment after imaging data quality control for in-scanner head motion and spatial coverage. Seed-based approach was used to investigate iFC of the pRTPJ. TD and ASD boys demonstrated a resting-state pRTPJ iFC pattern comparable to the known spatial involvement of the default-mode network. Boys with ASD showed pRTPJ hyperconnectivity relative to TD boys in the right ventral occipito-temporal cortex. This atypically increased iFC in the ASD group was positively correlated with social deficits assessed by the Chinese version of the Autism Diagnostic Interview-Revised and the Social Responsive Scale. Our findings provide empirical support for functional " dysconnectivity, " that is, atypical functional integration among brain regions, as an integral component of the atypical neurobiology of ASD.Autism Research 01/2015; 00:0-0. · 4.53 Impact Factor
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ABSTRACT: The modification of performance following conflict can be measured using conflict adaptation tasks thought to measure the change in the allocation of cognitive resources in order to reduce conflict interference and improve performance. While previous studies have suggested atypical processing during nonsocial cognitive control tasks, conflict adaptation (i.e. congruency sequence effects) for social-emotional stimuli have not been previously studied in autism spectrum disorder. A total of 32 participants diagnosed with autism spectrum disorder and 27 typically developing matched controls completed an emotional Stroop conflict task that required the classification of facial affect while simultaneously ignoring an overlaid affective word. Both groups showed behavioral evidence for emotional conflict adaptation based on response times and accuracy rates. However, the autism spectrum disorder group demonstrated a speed-accuracy trade-off manifested through significantly faster response times and decreased accuracy rates on trials containing conflict between the emotional face and the overlaid emotional word. Reduced selective attention toward socially relevant information may bias individuals with autism spectrum disorder toward more rapid processing and decision making even when conflict is present. Nonetheless, the loss of important information from the social stimuli reduces decision-making accuracy, negatively affecting the ability to adapt both cognitively and emotionally when conflict arises. © The Author(s) 2014.Autism 12/2014; · 2.27 Impact Factor