Abstract
The default mode network (DMN) is a collection of brain areas found to be consistently deactivated during task performance. Previous neuroimaging studies of resting state have revealed reduced task-related deactivation of this network in autism. We investigated the DMN in 13 high-functioning adults with autism spectrum disorders (ASD) and 14 typically developing control participants during three fMRI studies (two language tasks and a Theory-of-Mind (ToM) task). Each study had separate blocks of fixation/resting baseline. The data from the task blocks and fixation blocks were collated to examine deactivation and functional connectivity. Deficits in the deactivation of the DMN in individuals with ASD were specific only to the ToM task, with no group differences in deactivation during the language tasks or a combined language and self-other discrimination task. During rest blocks following the ToM task, the ASD group showed less deactivation than the control group in a number of DMN regions, including medial prefrontal cortex (MPFC), anterior cingulate cortex, and posterior cingulate gyrus/precuneus. In addition, we found weaker functional connectivity of the MPFC in individuals with ASD compared to controls. Furthermore, we were able to reliably classify participants into ASD or typically developing control groups based on both the whole-brain and seed-based connectivity patterns with accuracy up to 96.3%. These findings indicate that deactivation and connectivity of the DMN were altered in individuals with ASD. In addition, these findings suggest that the deficits in DMN connectivity could be a neural signature that can be used for classifying an individual as belonging to the ASD group.
Highlights
Neuroimaging studies have consistently shown altered patterns of functional brain activation and connectivity during cognitive tasks in individuals with autism spectrum disorders (ASD) (e.g., [1,2,3])
Participants with ASD, showed default mode network (DMN) deactivation limited to the posterior cingulate cortex and precuneus; 2) Between-group analyses revealed that participants with ASD showed lower levels of deactivation in DMN areas during rest; 3) When the tasks were separated to examine rest blocks following social cognitive or linguistic tasks, using a Group (ASD, Control)6Tasks (Fixation, Language, Selfreferential language, theory of mind’ (ToM)) ANOVA, rest blocks following the language tasks and self-other discrimination language task revealed no group difference
Our betweengroup results revealed that the ASD group had significantly reduced DMN connectivity specific to the dorsal medial prefrontal cortex (MPFC) when compared to the control group (p,0.001, cluster-corrected at 32 voxels)
Summary
Neuroimaging studies have consistently shown altered patterns of functional brain activation and connectivity during cognitive tasks in individuals with autism spectrum disorders (ASD) (e.g., [1,2,3]). The DMN has been hypothesized to be involved in internal mentalizations that help individuals navigate their social environment by attributing mental states (beliefs, desires, and thoughts) to oneself and to others, the ability to rehearse social narratives to engage in interactions with others, and in imagining the future [17,16,22] As both behavioral and neuroimaging studies have successfully shown, processes like ToM and self-referential thinking are atypical in autism [23,24,1,2], suggesting that such social deficits in autism may be pervasive even at rest
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