Functional Connectivity of Attention Networks In Children and Adolescents with ASD: A Resting State fcMRI Study

Background:  

Individuals with Autism Spectrum Disorder (ASD) experience early and pervasive deficits of attention. Previous research has detected three functionally separate attention networks, each of which is responsible for a separate set of cognitive processes that facilitate attention: the alerting, orienting, and executive control networks. Functional connectivity magnetic resonance imaging (fcMRI) detects the degree of correlation between brain regions of the blood oxygen level dependent (BOLD) response and is considered to be an indicator of brain network organization. Developmental studies of functional connectivity have suggested a dual process model of functional development, involving functional segregation at a local level, and functional integration through long-distance connections. The analysis of functional connectivity during resting state identifies spontaneous low-frequency BOLD signal fluctuations in brain voxels, therefore allowing the identification of correlated regions of neural activity across brain regions that serve similar functions.

Objectives:  

To examine the functional connectivity of the alerting, orienting, and executive control networks of attention using resting state data in individuals with ASD.

Methods:  

Functional images were acquired on a 3T GE scanner for 12 high-functioning children and adolescents with ASD and 13 age-, gender-, and IQ-matched TD individuals. Participants were scanned at rest for a period of six-minutes. Data were preprocessed using AFNI. We applied a low-pass filter to isolate intrinsic low-frequency BOLD fluctuations and included the six motion parameters as nuisance regressors. ROIs were selected using the fMRI activation results from Fan et al. (2005) for the alerting, orienting, and executive control networks. The average time series was extracted from the set of ROIs for each network and correlated with the whole-brain.

Results:  

Within-group connectivity maps were relatively consistent with the activation maps reported by Fan et al, (2005) for the alerting and executive networks. On between-group comparison, the alerting network showed reduced connectivity in bilateral anterior cingulate cortex in the ASD compared to TD group. Reduced connectivity was also seen in the left fusiform gyrus, right superior frontal gyrus, and thalamus. Between-group comparison of the executive network showed reduced connectivity in the anterior cingulate cortex in the ASD group. 

Conclusions:  

Our findings may suggest reduced connectivity for two attention networks, alerting and executive, in ASD. A consistent site of reduced connectivity for both networks was the anterior cingulate gyrus, which has been found to be anatomically and functionally affected in ASD in previous studies. Resting state data are generally considered to be unaffected by confounds of task performance in fcMRI studies. However, as in other resting studies of ASD, it cannot be ruled out that atypical and individually variable response to a task-free scanning condition may have affected the findings.