Abnormalities of intrinsic functional connectivity in autism spectrum disorders,

Abstract

Autism spectrum disorders (ASD) impact social functioning and communication, and individuals with these disorders often have restrictive and repetitive behaviors. Accumulating data indicate that ASD is associated with alterations of neural circuitry. Functional MRI (FMRI) studies have focused on connectivity in the context of psychological tasks. However, even in the absence of a task, the brain exhibits a high degree of functional connectivity, known as intrinsic or resting connectivity. Notably, the default network, which includes the posterior cingulate cortex, retro-splenial, lateral parietal cortex/angular gyrus, medial prefrontal cortex, superior frontal gyrus, temporal lobe, and parahippocampal gyrus, is strongly active when there is no task. Altered intrinsic connectivity within the default network may underlie offline processing that may actuate ASD impairments. Using FMRI, we sought to evaluate intrinsic connectivity within the default network in ASD. Relative to controls, the ASD group showed weaker connectivity between the posterior cingulate cortex and superior frontal gyrus and stronger connectivity between the posterior cingulate cortex and both the right temporal lobe and right parahippocampal gyrus. Moreover, poorer social functioning in the ASD group was correlated with weaker connectivity between the posterior cingulate cortex and the superior frontal gyrus. In addition, more severe restricted and repetitive behaviors in ASD were correlated with stronger connectivity between the posterior cingulate cortex and right parahippocampal gyrus. These findings indicate that ASD subjects show altered intrinsic connectivity within the default network, and connectivity between these structures is associated with specific ASD symptoms.

Atypical Bilateral Brain Synchronization in the Early Stage of Human Voice Auditory Processing in Young Children with Autism

“…As indicated in Fig 6A and 6B, children with ASD tended to exhibit higher Omega complexities than TD children in many time windows (such as time windows from 0 to 600 ms), which suggests that the former children exhibit reduced whole brain synchronization relative to the latter children. Our results are consistent with several recent reports of reduced brain hemodynamic synchronization in young children, adolescents and adults with ASD [55][56][57][58][59]. Two recent studies reported significantly decreased inter-hemispheric synchronization in toddlers with ASD [55] and in adolescents and adults with ASD [56].…”

Functional connectivity-based subtypes of individuals with and without autism spectrum disorder

“…Lee et al (2016) reported overall reduced FC density in ASD, and found that average interhemispheric FC density and contralateral FC density in a lingual/parahippocampal gyrus cluster and default mode network (DMN) regions was negatively correlated with RRBs. On the other hand, hyperconnectivity between the posterior cingulate cortex (PCC), a core region of the DMN, and the right parahippocampal gyrus was associated with more severe RRBs in another study (Monk et al, 2009). These investigators also reported that weaker FC between the PCC and superior frontal gyrus was correlated with reduced social functioning in ASD participants.…”

“…Assaf et al, 2010). Many studies have reported decreased FC between DMN regions in those with ASD (Assaf et al, 2010;Kennedy & Courchesne, 2008;Monk et al, 2009;Weng et al, 2010), although hyperconnectivity within this network has also been reported (Monk et al, 2009;Uddin et al, 2013a). One study found that hypo-or hyperconnectivity of the DMN may be region-specific (Doyle-Thomas et al, 2015).…”

“…Hahamy et al, 2015;Keown et al, 2013;Lee et al, 2016;Monk et al, 2009;Uddin et al, 2013b). Defining subtypes of ASD based on FC metrics has the potential to resolve some of the current discrepancies in the literature regarding the nature of FC abnormalities in individuals with this disorder, as well as to shed light on the complex relationships between FC and behaviour, which may differ between meaningful subtypes.…”

Default mode network in young male adults with autism spectrum disorder: Relationship with autism spectrum traits

“…Several studies of the DMN in individuals with ASD have shown its lower functional connectivities in restingstate functional magnetic resonance imaging (rs-fMRI), using the approaches of both region of interest (ROI) analysis and independent component analysis (ICA), than in individuals with TD [27][28][29][30][31][32]. In addition, these studies also showed negative correlations between the strength of the resting-state functional connectivity (rs-FC) of DMN and autism spectrum traits including social deficits in individuals with ASD.…”