Objectives: In the present study, we assessed cortical functional connectivity using resting-state fMRI, in large samples of young children with and without ASD, and in a number of different networks.
Methods: Twenty-eight TD children (20 male, mean age 12.7±2.8) and twenty-eight children with an ASD (20 male, mean age 12.7±3.0) participated in the study. Furthermore, we acquired resting-state data from 48 TD adults (23 male, mean age 23.4±3.0), for the purposes of defining seed regions for correlation analysis. Diagnoses of ASD were determined using the Autism Diagnostic Observation Schedule, the Autism Diagnostic Interview – Revised, and the judgment of experienced clinicians at the Yale Child Study Center. TD children and adults had no psychiatric or neurological conditions. All children received the Differential Ability Scales – Second Edition to assess general intelligence, and a subset of 26 subjects per group received the Social Responsiveness Scale to assess autistic traits. The TD and ASD groups did not differ significantly in age, verbal/nonverbal intelligence, gender, or mean translational head motion between volumes (P > .05, unpaired, two-tailed two-sample t-test); however, they did differ significantly in SRS score (t = 11.13, P < 5x10-15), as expected. Structural and functional images were acquired on a 3 Tesla Siemens Magnetom Trio scanner, with a 32-channel head coil. Functional data were acquired in the resting state: participants viewed a gray screen with a black crosshair, and were asked to keep their eyes open, remain awake, and stay as still as possible. Resting-state scans lasted 6:40 minutes, or 200 volumes; a single run was acquired per participant.
Results: Patterns of functional connectivity were largely similar in children with and without ASDs. A number of network-specific group differences were found in both directions. In particular, we found reduced functional connectivity in ASD in the default mode network (DMN), most strongly in the ventral DMN subnetwork. Increased functional connectivity was found within the somatomotor and visual networks. In addition, we found reduced functional connectivity between primary visual cortex and the fusiform gyrus and posterior superior temporal sulcus, regions involved in social perception.
Conclusions: This study provides evidence against the hypothesis of broadly decreased functional connectivity in ASD. Instead, they suggest a pattern of network-specific alterations, including increased integration of sensorimotor networks and decreased integration of the DMN.