Further understanding of the comorbidity between Attention-Deficit/Hyperactivity Disorder and bipolar disorder in adults: an MRI study of cortical thickness.

Although Attention-Deficit/Hyperactivity Disorder (ADHD) and Bipolar Disorder (BPD) frequently co-occur and represent a particularly morbid clinical form of both disorders, neuroimaging research addressing this comorbidity is scarce. Our aim was to evaluate cortical thickness in ADHD and BPD, testing the hypothesis that comorbid subjects (ADHD+BPD) would have neuroanatomical correlates of both disorders. Magnetic Resonance Imaging (MRI) findings were compared between 31 adults with ADHD+BPD, 18 with BPD, 26 with ADHD, and 23 healthy controls. Cortical thickness analysis of regions of interest was estimated as a function of ADHD and BPD status, using linear regression models. BPD was associated with significantly thicker cortices in 13 regions, independently of ADHD status and ADHD was associated with significantly thinner neocortical gray matter in 28 regions, independent of BPD. In the comorbid state of ADHD plus BPD, the profile of cortical abnormalities consisted of structures that are altered in both disorders individually. Results support the hypothesis that ADHD and BPD independently contribute to cortical thickness alterations of selective and distinct brain structures, and that the comorbid state represents a combinatory effect of the two. Attention to comorbidity is necessary to help clarify the heterogeneous neuroanatomy of both BPD and ADHD.

Delineation of the middle longitudinal fascicle in humans: a quantitative, in vivo, DT-MRI study.

Experimental and imaging studies in monkeys have outlined various long association fiber bundles within the temporoparietal region. In the present study the trajectory of the middle longitudinal fascicle (MdLF) has been delineated in 4 human subjects using diffusion tensor magnetic resonance imaging segmentation and tractography. The MdLF seems to extend from the inferior parietal lobule (IPL), specifically the angular gyrus, to the temporal pole remaining within the white matter of the superior temporal gyrus (STG). Comparison of the superior longitudinal fascicle II-arcuate fascicle (SLF II-AF) with the MdLF in the same subjects revealed that MdLF is located in a medial and caudal position relative to SLF II-AF and that it extends more rostrally. Given the location of MdLF between the IPL (angular gyrus) and the STG, it is suggested that MdLF could have a role in language and attention functions.

Cortical thickness abnormalities in cocaine addiction--a reflection of both drug use and a pre-existing disposition to drug abuse?

The structural effects of cocaine on neural systems mediating cognition and motivation are not well known. By comparing the thickness of neocortical and paralimbic brain regions between cocaine-dependent and matched control subjects, we found that four of 18 a priori regions involved with executive regulation of reward and attention were significantly thinner in addicts. Correlations were significant between thinner prefrontal cortex and reduced keypresses during judgment and decision making of relative preference in addicts, suggesting one basis for restricted behavioral repertoires in drug dependence. Reduced effortful attention performance in addicts also correlated with thinner paralimbic cortices. Some thickness differences in addicts were correlated with cocaine use independent of nicotine and alcohol, but addicts also showed diminished thickness heterogeneity and altered hemispheric thickness asymmetry. These observations suggest that brain structure abnormalities in addicts are related in part to drug use and in part to predisposition toward addiction.