Functional magnetic resonance imaging in idiopathic intellectual impairment and Fragile X Syndrome

Objective - The objective of this study was to explore the neural correlates of emotion processing in individuals with idiopathic intellectual impairment (III) and fragile X syndrome (FXS), and to further examine the mediating effect of co-occurring autism spectrum disorder (ASD) traits. Methods - We conducted an fMRI study using an implicit facial emotion-processing task with 18 individuals with III and 17 with FXS. Prior to undergoing their scan, participants underwent a staged rehearsal procedure to reduce anxiety and facilitate the scans. ASD traits were examined using the Autism Diagnostic Observation Schedule (ADOS).
Results - In the III group, those with significant ASD traits showed regions of significantly greater response to neutral facial stimuli than the non-ASD subgroup, whereas the non-ASD group showed regions of significantly greater activation to the fearful facial stimuli compared to the ASD subgroup. In the FXS group, there were also differences between those with significant ASD traits and those without, however these differences were largely characterised by lower magnitude typical responses in the ASD subgroup, rather than a different pattern of response.
Conclusions - In this study we have demonstrated that it is possible to use functional MRI to examine differential patterns of brain activation in individuals with intellectual impairment and ASD. Further, our results suggest that ASD in idiopathic intellectual impairment may have a different underlying neurobiology than in fragile X syndrome; mirroring the overlapping, but different, clinical phenotypes.