Impact of methodological variables on functional connectivity findings in autism spectrum disorders.

Growing evidence suggests that Autism Spectrum Disorder (ASD) involves abnormalities of multiple functional networks. Neuroimaging studies of ASD have therefore increasingly focused on connectivity. Many functional connectivity (fcMRI) studies have reported network underconnectivity in children and adults with ASD.

Local functional overconnectivity in posterior brain regions is associated with symptom severity in autism spectrum disorders.

Although growing evidence indicates atypical long-distance connectivity in autism spectrum disorder (ASD), much less is known about local connectivity, despite conjectures that local overconnectivity may be causally involved in the disorder. Using functional connectivity MRI and graph theory, we found that local functional connectivity was atypically increased in adolescents with ASD in temporo-occipital regions bilaterally. Posterior overconnectivity was found to be associated with higher ASD symptom severity, whereas an ASD subsample with low severity showed frontal underconnectivity.

Pervasive rightward asymmetry shifts of functional networks in autism spectrum disorder.

Importance: Autism spectrum disorder (ASD) is a brain-based pervasive developmental disorder, which-by growing consensus-is associated with abnormal organization of functional networks. Several previous studies of ASD have indicated atypical hemispheric asymmetries for language.

Objective: To examine the asymmetry of functional networks using a data-driven approach for a comprehensive investigation of hemispheric asymmetry in ASD.

Impaired thalamocortical connectivity in autism spectrum disorder: a study of functional and anatomical connectivity.

The thalamus plays crucial roles in the development and mature functioning of numerous sensorimotor, cognitive and attentional circuits. Currently limited evidence suggests that autism spectrum disorder may be associated with thalamic abnormalities, potentially related to sociocommunicative and other impairments in this disorder. We used functional connectivity magnetic resonance imaging and diffusion tensor imaging probabilistic tractography to study the functional and anatomical integrity of thalamo-cortical connectivity in children and adolescents with autism spectrum disorder and matched typically developing children.

Atypical lexicosemantic function of extrastriate cortex in autism spectrum disorder: evidence from functional and effective connectivity.

Previous studies have suggested atypically enhanced activity of visual cortex during language processing in autism spectrum disorder (ASD). However, it remains unclear whether visual cortical participation reflects isolated processing within posterior regions or functional cooperation with distal brain regions, such as left inferior frontal gyrus (LIFG). We addressed this question using functional connectivity MRI (fcMRI) and structural equation modeling in 14 adolescents and adults with ASD and 14 matched typically developing (TD) participants.

Functional connectivity for an "island of sparing" in autism spectrum disorder: an fMRI study of visual search.

Although autism is usually characterized with respect to sociocommunicative impairments, visual search is known as a domain of relative performance strength in this disorder. This study used functional MRI during visual search in children with autism spectrum disorder (n = 19; mean age = 13;10) and matched typically developing children (n = 19; mean age = 14;0). We selected regions of interest within two attentional networks known to play a crucial role in visual search processes, such as goal-directed selective attention, filtering of irrelevant distractors, and detection of behaviorally-relevant information, and examined activation and connectivity within and between these attentional networks.

Functional differentiation of posterior superior temporal sulcus in autism: a functional connectivity magnetic resonance imaging study.

Background: Socio-communicative impairments are salient features of autism spectrum disorder (ASD). Abnormal development of posterior superior temporal sulcus (pSTS)--a key processing area for language, biological motion, and social context--could play a role in these deficits.

Methods: Functional connectivity magnetic resonance imaging was used to examine the synchronization of low-frequency blood oxygen level-dependent fluctuations during continuous performance on a visual search task.

Underconnected, but how? A survey of functional connectivity MRI studies in autism spectrum disorders.

Growing consensus suggests that autism spectrum disorders (ASD) are associated with atypical brain networks, thus shifting the focus to the study of connectivity. Many functional connectivity studies have reported underconnectivity in ASD, but results in others have been divergent. We conducted a survey of 32 functional connectivity magnetic resonance imaging studies of ASD for numerous methodological variables to distinguish studies supporting general underconnectivity (GU) from those not consistent with this hypothesis (NGU).

Atypical network connectivity for imitation in autism spectrum disorder.

Imitation has been considered as one of the precursors for sociocommunicative development. Impairments of imitation in autism spectrum disorder (ASD) could be indicative of dysfunctional underlying neural processes. Neuroimaging studies have found reduced activation in areas associated with imitation, but a functional connectivity MRI network perspective of these regions in autism is unavailable.