Functional abnormalities of the default network during self- and other-reflection in autism

Abstract

Recent studies of autism have identified functional abnormalities of the default network during a passive resting state. Since the default network is also typically engaged during social, emotional and introspective processing, dysfunction of this network may underlie some of the difficulties individuals with autism exhibit in these broad domains. In the present experiment, we attempted to further delineate the nature of default network abnormality in autism using experimentally constrained social and introspective tasks. Thirteen autism and 12 control participants were scanned while making true/false judgments for various statements about themselves (SELF condition) or a close other person (OTHER), and pertaining to either psychological personality traits (INTERNAL) or observable characteristics and behaviors (EXTERNAL). In the ventral medial prefrontal cortex/ventral anterior cingulate cortex, activity was reduced in the autism group across all judgment conditions and also during a resting condition, suggestive of task-independent dysfunction of this region. In other default network regions, overall levels of activity were not different between groups. Furthermore, in several of these regions, we found group by condition interactions only for INTERNAL/EXTERNAL judgments, and not SELF/OTHER judgments, suggestive of task-specific dysfunction. Overall, these results provide a more detailed view of default network functionality and abnormality in autism.

Fig. 1

Functional activity in control and autism groups for (A) the MENTAL vs MATH contrast (P < 0.001, uncorrected) and (B) the REST vs MATH contrast (P < 0.01, uncorrected); and (C) the regions of overlap between these two contrasts (minimum cluster volume = 1152 mm³). These regions of overlap in the control group were used as ROIs for further analysis (red cluster = vMPFC/vACC; blue cluster = RSC/PCC; green cluster = left ANG). The dMPFC ROI (open circle) is also shown. In the autism group, the left ANG just missed the minimum cluster volume threshold (1139 mm³).

Fig. 2

Functional activity in control and autism groups for (A) INTERNAL vs MATH, EXTERNAL vs MATH, and INTERNAL vs EXTERNAL contrasts; and (B) SELF vs MATH, OTHER vs MATH, and SELF vs OTHER contrasts (all P < 0.001, volume-corrected). The same mid-sagittal slice location is shown for each image. Regions with greater activity in the MATH condition relative to the other conditions are not shown. In the bottom panel, red/yellow represents regions with greater activity in the INTERNAL (A) or SELF (B) conditions, while blue represents regions with greater activity in the EXTERNAL (A) or OTHER (B) conditions.

Fig. 3

Bar graphs depicting percent signal change in control and autism groups in MENTAL vs MATH and REST vs MATH contrasts, shown separately for each ROI. **P ≤ 0.01.

Fig. 4

Bar graphs depicting percent signal change in control and autism groups during INTERNAL and EXTERNAL judgments and SELF and OTHER judgments (each relative to the MATH baseline condition), shown separately for each ROI. For main effects of group collapsed across all person judgment conditions, see Figure 3. *P ≤ 0.05; **P ≤ 0.01.