18995
Behavioral, but Not Neural Differences in Face Recognition in Adults and Elderly with Autism
Perceptual closure refers to the ability to form a global and coherent perceptual representation on the basis of few details. A classical example is provided by two-tone (black and white) images of human faces (Mooney faces). In a Mooney image, the local features become too ambiguous to be recognized individually, and must be disambiguated based on their context within a global configuration. Mooney faces have been used to investigate various aspects of intact and impaired face processing (the ability to recognize a person from their facial appearance). Given that autism is typically associated with a detail-oriented visual processing style and social deficits, the neural mechanisms underlying perceptual closure may be different in patients with autism spectrum disorders (ASD).
Objectives:
Examine the neural mechanisms underlying perceptual closure in face processing in adults and elderly with ASD.
Methods:
Using 3T event-related fMRI we measured BOLD-signal changes in 50 subjects with and 49 without ASD (30-74yrs) to investigate how the brain forms perceptual decisions about complex visual forms. We showed 100 upright Mooney faces and 100 visually similar non-face images for 200ms in a random sequence. To identify closure-related activity contrasts of correctly identified faces minus non-faces were computed. Post-scanning tests included a self-paced shortened version of the same perceptual closure task to examine the overall ability to recognize face stimuli.
Results:
Behavior
Preliminary data suggest that participants with ASD showed significant reduced detection-rates for faces (M=71% vs 77%; Mann-Whittney-U=.027), but not for non-faces (M=85% vs 86%; Mann-Whittney-U=.85). People with ASD were slower on both conditions, irrespective of accuracy (all p’s<.02). Performance on the self-paced task outside the scanner was similar between groups (p’s>.62), with higher accuracy rates for non-faces than for faces in both groups (p’s<.001). In addition, controls were faster in the face-condition with correct responses (p=.01), but there were no reaction time differences for the other conditions.
fMRI
There were no differences in neural responses between the groups for faces>non-faces or the inverse contrast (irrespective of accuracy). In the combined sample, the fMRI data showed increased activation for faces relative to non-faces in the bilateral fusiform face area (FFA), inferior frontal gyri, parietal lobule, amygdala-hippocampal complex and right angular gyrus and left anterior cingulum (FWE-corrected: p<.05; >10 contiguous voxels).
No age-related effects were found for behavioral and neuroimaging data.
Conclusions:
The behavioral data suggest that face recognition is more dependent on holistic processing than non-face recognition in both groups. This finding is further strengthened by the significant difference in detection rates in the self-paced task. The fMRI data showed typical responses in the FFA and inferior frontal gyri and are consistent with other recent studies demonstrating similar activation patterns for faces compared to non-faces in ASD. Overall, these findings suggest a specific face recognition deficit in adults and elderly with ASD independent of age, despite similar brain recruitment.