A Distinct Face-Processing Style In the Broad Autism Phenotype Revealed with fMRI

Background:  The genetic liability for autism is expressed in first-degree relatives who do not meet diagnostic criteria for an autism spectrum disorder, but show milder characteristics resembling autism. This so-called Broad Autism Phenotype (BAP) exhibits many of the patterns of abnormal social cognition observed in autism, only milder.

Objectives:  The aim of this study was to investigate the neural substrates of face processing in parents who have a child with autism using functional magnetic resonance imaging (fMRI), with a particular focus on the fusiform gyrus (FG) and amygdala (AMG), two structures known to exhibit abnormal activation to faces in autism.  We further examined the association between fMRI activation and the presence of specific deficits in social-emotional processing domains by classifying the BAP parents as having “aloof personality” (BAP+), or “non-aloof personality” (BAP-).

Methods: BAP- (N = 19) and BAP+ (N=13) were defined on the basis of their scores from extensive interviews.  A healthy control group consisted of parents of neurotypical children (N=14).  Imaging was done on a GE 3T MRI scanner (TR: 2000 ms; TE: 27ms; FOV: 256; image matrix: 64 × 64; Flip angle 60; Voxel size: 4 ×4 × 3.8 mm; 34 axial slices). Subjects viewed alternating blocks of a face-matching and object-matching task, and responded with a button press.  Data were analyzed with a focus on specific regions of interest in FSL.

Results: Analysis of the main effect of face and object stimuli revealed that faces evoked activation in fusiform gyrus (FG) and amygdala (AMG) for all groups. However, the BAP group (BAP+ and BAP- pooled) showed significantly greater activation in FG during face and object matching compared to the control parents. Moreover, FG and AMG showed greater responses during face matching in the BAP+ compared to the BAP- groups.

 Conclusions: The pattern of face processing seen in parents of autistic children differed from that seen in parents of neurotypical children.  Moreover, amongst the parents of autistic children, those with aloof phenotype (BAP+) showed differences from those who were not aloof (BAP-).  In each case, the differences resembled those between people with autism and neurotypical individuals.  These findings provide insights into the neural circuitry underlying the genetic liability for autism and suggest a neural signature for a forme fruste of this condition.