Friday, May 21, 2010
Franklin Hall B Level 4 (Philadelphia Marriott Downtown)
3:00 PM
Background: The high degree of inter-individual heterogeneity found in autism spectrum disorder (ASD) is a well-recognized major impediment to effective study and treatment. Variation in the severity of features of other psychiatric disorders often but not always associated with autism, including attention-deficit hyperactivity (ADHD), is a relevant but understudied contributor to this heterogeneity. Research associating structural brain changes, including changes in caudate volume and asymmetry, with ADHD and, separately, with ASD suggest in combination that variation in ADHD severity may contribute to the heterogeneity in structural brain changes present in ASD.
Objectives: The goal of this study was to investigate changes in regional brain volume and asymmetry in young persons with ASD and ADHD. Our primary hypotheses were that caudate volume is increased in ASD and that this volumetric increase is negatively correlated with ADHD severity. We studied other regional and global volumes to determine whether any findings supporting our hypotheses were specific to the caudate nucleus and to support hypothesis generation for future research.
Methods: Structural MRI scans and the Conners’ ADHD/DSM-IV Scales (CADS) were completed for N = 36 high-functioning males with ASD 6-15 years of age and N = 20 typically developing aged-matched males. Regional brain volumes by hemisphere were extracted using FreeSurfer software, including total cortex, gray matter, white matter, the head of the caudate nucleus, putamen, globus pallidus, thalamus, hippocampus, and amygdala; total brain volume, intracranial brain volume, and volumes of the posterior, mid-posterior, central, mid-anterior and anterior corpus callosum were also extracted. These volumes and their asymmetries were compared between the groups and associated with CADS total score among those individuals with ASD.
Results: We observed a highly significant increase in CADS total score in our ASD sample (p<0.001). We also found a significant association between ASD and reduced rightward caudate asymmetry (p =0.006). No association was found, however, between hemispheric asymmetries and CADS total score in our ASD sample. Neither the volumes nor asymmetries of any of the other brain structures we examined were associated with ASD or ADHD severity.
Conclusions: Our preliminary findings suggest that the development of typical rightward asymmetry of caudate volume is disrupted in autism independently of ADHD severity. Our findings also suggest that the volumetric correlates of ADHD in autism are different from correlates reported in non-autistic individuals with ADHD. Similar clinical ADHD phenotypes may have different underlying neurobiological mechanisms in individuals with and without autism. Longitudinal volumetric, diffusion tensor imaging, and fMRI studies are needed to identify unique signatures of brain development in autism with and without ADHD, and in ADHD with and without autism.
Disclaimer: The project described was supported by grant numbers RO1 MH080826 and RO1 MH084795 from the National Institute of Mental Health and the Corneel Fellowship at McLean Hospital. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Mental Health or the National Institutes of Health.
Objectives: The goal of this study was to investigate changes in regional brain volume and asymmetry in young persons with ASD and ADHD. Our primary hypotheses were that caudate volume is increased in ASD and that this volumetric increase is negatively correlated with ADHD severity. We studied other regional and global volumes to determine whether any findings supporting our hypotheses were specific to the caudate nucleus and to support hypothesis generation for future research.
Methods: Structural MRI scans and the Conners’ ADHD/DSM-IV Scales (CADS) were completed for N = 36 high-functioning males with ASD 6-15 years of age and N = 20 typically developing aged-matched males. Regional brain volumes by hemisphere were extracted using FreeSurfer software, including total cortex, gray matter, white matter, the head of the caudate nucleus, putamen, globus pallidus, thalamus, hippocampus, and amygdala; total brain volume, intracranial brain volume, and volumes of the posterior, mid-posterior, central, mid-anterior and anterior corpus callosum were also extracted. These volumes and their asymmetries were compared between the groups and associated with CADS total score among those individuals with ASD.
Results: We observed a highly significant increase in CADS total score in our ASD sample (p<0.001). We also found a significant association between ASD and reduced rightward caudate asymmetry (p =0.006). No association was found, however, between hemispheric asymmetries and CADS total score in our ASD sample. Neither the volumes nor asymmetries of any of the other brain structures we examined were associated with ASD or ADHD severity.
Conclusions: Our preliminary findings suggest that the development of typical rightward asymmetry of caudate volume is disrupted in autism independently of ADHD severity. Our findings also suggest that the volumetric correlates of ADHD in autism are different from correlates reported in non-autistic individuals with ADHD. Similar clinical ADHD phenotypes may have different underlying neurobiological mechanisms in individuals with and without autism. Longitudinal volumetric, diffusion tensor imaging, and fMRI studies are needed to identify unique signatures of brain development in autism with and without ADHD, and in ADHD with and without autism.
Disclaimer: The project described was supported by grant numbers RO1 MH080826 and RO1 MH084795 from the National Institute of Mental Health and the Corneel Fellowship at McLean Hospital. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Mental Health or the National Institutes of Health.