PURPOSE: We aimed to determine whether Autism Spectrum Disorder (ASD) would show neural abnormality of the social reward system using functional MRI (fMRI). MATERIALS AND METHODS: 27 ASDs and 12 typically developing controls (TDCs) participated in this study. The social reward task was developed, and all participants performed the task during fMRI scanning. RESULTS: ASDs and TDCs with a social reward learning effect were selected on the basis of behavior data. We found significant differences in brain activation between the ASDs and TDCs showing a social reward learning effect. Compared with the TDCs, the ASDs showed reduced activity in the right dorsolateral prefrontal cortex, right orbitofrontal cortex, right parietal lobe, and occipital lobe; however, they showed increased activity in the right parahippocampal gyrus and superior temporal gyrus. CONCLUSION: These findings suggest that there might be neural abnormality of the social reward learning system of ASDs. Although this study has several potential limitations, it presents novel findings in the different neural mechanisms of social reward learning in children with ASD and a possible useful biomarker of high-functioning ASDs.
Brain/*physiopathology ; Brain Mapping ; Case-Control Studies ; Child ; Child Development Disorders, Pervasive/*physiopathology ; Female ; Functional Neuroimaging/*methods ; Humans ; Magnetic Resonance Imaging/methods ; Male ; Neural Pathways/*physiopathology ; Psychiatric Status Rating Scales ; Republic of Korea ; *Reward ; *Social Behavior

BACKGROUNDAutism spectrum disorders (ASD), which include autism, asperger syndrome (AS) and pervasive developmental disorder-not otherwise specified (PDD-NOS), are devastating neurodevelopmental disorders of childhood resulting in deficits in social interaction, repetitive patterns of behaviors, and restricted interests and activities. Single photon emission computed tomography (SPECT) is a common technique used to measure regional cerebral blood flow (rCBF). Several studies have measured rCBF in children with ASD using SPECT, however, findings are discordant. In addition, the majority of subjects used in these studies were autistic. In this study, we aimed to investigate changes in rCBF in children with ASD using SPECT.

METHODSA Technetium-99m-ethyl cysteinate dimmer (⁹⁹m)Tc-ECD) brain SPECT study was performed on an ASD group consisting of 23 children (3 girls and 20 boys; mean age (7.2 ± 3.0) years) who were diagnosed according to Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) criteria and an age-matched control group with 8 children (1 girl and 7 boys, mean age (5.5 ± 2.4) years). Image data were evaluated with Statistical Parametric Mapping, 5th version (SPM5). A Student's t test for unpaired data was used to compare rCBF and asymmetry in the autism and corresponding control group. The covariance analysis, taking age as covariance, was performed between the ASD and control group.

RESULTSThere was a significant reduction in rCBF in the bilateral frontal lobe (frontal poles, arcula frontal gyrus) and the bilateral basal ganglia in the autism group, and a reduction in the bilateral frontal, temporal, parietal, legumina nucleus and cerebellum in the AS group compared to the control. In addition, asymmetry of hemispheric hypoperfusion in the ASD group was observed. Inner-group comparison analysis revealed that rCBF decreased significantly in the bilateral frontal lobe (42.7%), basal nucleus (24.9%) and temporal lobe (22.8%) in the autism group, and in the bilateral cerebellum (22.8%), basal nucleus (19.3%) and right thalamencephalon (16.6%) in the AS group (P < 0.05).

CONCLUSIONSThe decrease in rCBF in ASD is a global event, which involves the bilateral frontal, temporal, limbic system and basal ganglias. Asymmetry of hemispheric hypoperfusion was more obvious in the AS group than the autism group, which indicates a different neurobiological mechanism from that of autism.

Cerebrovascular Circulation ; physiology ; Child ; Child Development Disorders, Pervasive ; pathology ; physiopathology ; Child, Preschool ; Cysteine ; analogs & derivatives ; Female ; Humans ; Male ; Organotechnetium Compounds ; Regional Blood Flow ; physiology ; Tomography, Emission-Computed, Single-Photon ; methods