Attention Orienting in Autism Spectrum Disorders: Brain Function and Connectivity

Background:  Deficits in attention are consistently reported in Autism Spectrum Disorders (ASDs) and researchers suggest that the behavioural deficits characteristic of ASD may be due to an inability to orient attention to social stimuli. Spatial attention orienting is a cognitive process that facilitates the movement of attentional focus from one location to another in response to a stimulus. Attention orienting is considered important for socio-emotional development, learning and a crucial component of joint attention. Neuroimaging studies support the modulation of two interacting networks in attention orienting, the bilateral dorsal frontoparietal network or the dorsal attention network (DAN) responsible for cognitive selection of sensory stimuli and the right lateralised ventral frontoparietal system or the ventral attention network (VAN) which functions to direct attention to unattended relevant stimuli. 

Objectives:  This study aims to dissociate dorsal and ventral attention networks in an ASD population to determine if the cognitive selection of sensory information (DAN) and/or the function to direct attention to behaviourally relevant stimuli are impaired using functional MRI techniques.

Methods:   21 individuals with high functioning ASD and 21 age and IQ matched control participants performed a Posner style spatial attention paradigm consisting of four trial types; valid, invalid, neutral and cue-only. Reaction time (ms) to target appearance was used to measure behavioural performance. Functional MRI data was acquired in a 3Tesla MRI scanner. Preprocessing and analysis of the data was carried out using AFNI and FSL imaging software. First-level contrasts and second-level t-tests were performed to evaluate within and between groups differences. All data was corrected for multiple comparisons at p < 0.05.   

Results:  ANOVA revealed participants performed significantly better on valid trials than invalid and neutral trials, p < 0.001, however there was no significant difference in behavioural performance between groups, p = 0.436. A t-test of cue-only trial activation revealed a significant difference in the right superior frontal gyrus between the ASD and control group, p < 0.05. In the ASD group, a t-test of invalid-valid trials revealed significant activation in the left temporoparietal junction while in the control group, only right superior orbital gyral activation survived correction. A between group comparison of invalid-valid trial activation yielded significant group differences in the parietal, frontal and temporal regions, p < 0.05.    

Conclusions:  Isolation of the bilateral dorsal attention network was facilitated by the analysis of cue-only trials. Reduced activation observed in superior frontal regions suggests that individuals with ASD are impaired in the ability to process and select cognitive information. Comparison of invalid-valid or ‘reorienting’ trials enabled the investigation of the ventral attention network. While behavioural results indicate that the ASD group performed similarly to the control group, analysis of fMRI images revealed significant differences in a number of regions. Differences observed in frontoparietal regions may be an indication that individuals with ASD use a compensatory mechanism in order to attend to behaviourally relevant stimuli similarly to controls. These observations are in keeping with the theory that functional connectivity may differ in individuals with ASD in comparison to typically developing individuals.