Patients with Asperger’s disorder and pervasive developmental disorder are less able to recognize fearful facial expressions compared with controls, a recently published study shows.
Moreover, the deficit is linked to worse social dysfunction in these patients, reported Shota Uono, Ph.D., and his colleagues in the journal Research in Autism Spectrum Disorders.
Dr. Uono of Kyoto (Japan) University and his colleagues looked at 54 Japanese patients: 18 "typically developing" controls, 18 with Asperger’s disorder, and 18 with pervasive developmental disorder–not otherwise specified (PDD-NOS) (Res. Autism Spectr. Disord. 2013;7:361-8).
Patients with Asperger’s and PDD-NOS were diagnosed at the time of the study, using the DSM-IV-TR, based on extensive patient interviews, and data collected from patients’ families and teachers.
PDD-NOS patients were those who did not satisfy the criteria for Asperger’s in that "they had similar impairments in qualitative social interaction in the absence of apparently restricted interests and stereotyped behaviors, or their impairments in qualitative social interaction were milder than those observed in individuals with Asperger’s," wrote the authors.
The mean age in each group was about 19 years old, and patients were matched with controls according to age and sex.
The researchers then showed the participants 48 photographs of facial expressions depicting anger, disgust, fear, happiness, sadness, and surprise. In half of the images, the models depicting the emotions were Japanese; the other half was white.
The investigators found that the Asperger’s and PDD-NOS patients both performed significantly worse than did controls at correctly identifying fearful faces.
Additionally, the recognition accuracy of the PDD-NOS group was worse than both the controls and the Asperger’s group in response to disgusted facial expressions.
Next, the researchers looked at the relationship between poor facial recognition of these two emotions and social dysfunction, as assessed on several measures of the Childhood Autism Rating Scale (CARS): imitation, nonverbal communication, relationship to people, verbal communication, and visual response.
Here, Dr. Uono and his colleagues found that the correlation between fearful expression recognition and social dysfunction was significant in both the Asperger’s and PDD-NOS groups, "indicating that individuals with Asperger’s and those with PDD-NOS who demonstrated worse recognition of fearful expressions had more severe symptoms in social domains."
The correlation between disgusted expression and social dysfunction, on the other hand, was not significant in either group.
In offering an explanation for the findings, the researchers pointed to studies showing that difficulties with fearful face recognition have been linked to dysfunction in the amygdala, "which is involved in various social behaviors."
They also highlighted another potential target: the basal ganglia.
"It has been reported that individuals with Parkinson’s disease and Huntington’s disease show a specific impairment in disgusted-face recognition," they wrote.
"It is possible that the impairment in disgusted-face recognition in PDD-NOS reflects the existence of more severe motor deficits and functional abnormalities in the basal ganglia than are present in other PDD subtypes."
No matter the mechanism, "Additional research is needed to explore the relationship between this impairment and the clinical manifestations specific to PDD-NOS," they concluded. "These data may prove helpful in attempts at disambiguating specific problems associated with PDD-NOS."
The authors disclosed several grants from nonprofits and corporate foundations. They disclosed no personal conflicts of interest related to this study.