22486
Structural Connectivity of the Accumbofrontal Tract in Youth with and without Autism: Associations with Behavioral Phenotypes
Objectives: 1) Compare accumbofrontal structural connectivity in youth with and without ASD. 2) Investigate how accumbofrontal connectivity relates to measures of ASD symptomatology.
Methods: DTI data was acquired in high functioning youth with ASD (N=44) and typically developing youth (N=44) ages 8-17. Data analysis consisted of quality control and removal of volumes with artifacts using DTIPrep (Oguz 2015), eddy current correction, brain extraction, calculation of diffusion parameters (BEDPOSTX), registration to standard space, and probabilistic tractography (PROBTRACKX; Behrens 2007). Binary masks of the left and right NAcc (defined using the Havard-Oxford Atlas) were used as seed regions for probabilistic tractography. For each subject, 5,000 streamlines were initiated from the seed voxels using the contralateral hemisphere as an exclusionary mask; a minimum threshold of 50 streamlines was applied for inclusion in subsequent analyses. The resulting map was binarized and used as a mask to extract FA values for the left and right accumbofrontal tract for each subject, which were compared between diagnostic groups and correlated with behavioral measures of intelligence and social functioning.
Results: In both TD and ASD participants, the left and right NAcc showed structural connectivity with the ipsilateral orbital frontal cortex. There were no significant differences in FA for either the left or right accumbofrontal track when comparing TD and ASD participants (p>0.05). In ASD youth, left (r=0.40, p=0.007) and right (r=0.50, p=0.0005) accumbofrontal FA was associated with higher scores of verbal intelligence. Higher right accumbofrontal connectivity was also associated with less severe scores on the Autism Diagnostic Observation Schedule (ADOS; Lord 2000) social (r=-0.36, p=0.02) and social/communication (r=-0.32, p=0.03) subscales in youth with ASD. There were no significant behavioral correlations in TD youth.
Conclusions: These findings indicate that structural connectivity between the NAcc and orbital frontal cortex is intact in youth with ASD, and that higher levels of FA is associated with less severe verbal and social/communication impairment. This work suggests that structural connectivity of the reward network may be an important biomarker, helping to explain variability of symptomatology in youth with ASD.
See more of: Brain Structure (MRI, neuropathology)