, 2009): MEK inhibitor MD was significantly higher in patients with ADHD in these regions, but no difference was observed for FA values (Pavuluri et al., 2009). Moreover, decreased FA in the SLF and in the corticospinal tract in children and adolescents with ADHD has been demonstrated (Hamilton et al., 2008). Our

findings of increased FA bilaterally in frontotemporal WM connections point to an involvement of widespread brain areas in the pathophysiology of ADHD. While temporal structural abnormalities have not yet been described in previous MRI and DTI studies, a recent functional MRI study demonstrated bilateral temporal lobe dysfunction in boys with ADHD (Rubia et al., 2007). Possible reasons for the discrepancy with respect to the results of DTI studies in childhood and adolescence could be the sample heterogeneity between studies, the medication status of the investigated patients and the different diffusion imaging parameters between studies. In contrast to the majority of imaging studies in ADHD, we only included never-medicated patients in our study. Particularly, none of the patients had received any ADHD-specific treatment before such as psychostimulant medication. We are therefore able to exclude potential medication effects on imaging results as well as on neuropsychological findings.

In addition, we have excluded patients with ADHD with acute psychiatric comorbidity. Although Selleck Palbociclib we did not include medicated patients and patients with acute psychiatric comorbidity, symptom

severeness of our patients as measured with the BADDS was quite high (Brown, 1996; Table 1). For completeness, it also needs to be mentioned Tangeritin that the possibility of false positive results in our study cannot be entirely excluded. In fact, taking into account the relatively weak group differences in our study, which would not survive a correction for multiple comparisons, and also the findings in DTI studies conducted by other groups in (adult) ADHD (Casey et al., 2007; Makris et al., 2008), replication studies would be desirable to confirm these findings. To our knowledge, this is the first study demonstrating a direct association between microstructural integrity and measures of attention in adult patients with ADHD. The correlation analyses between diffusion parameters and the ADHD score, which reflects the ability to focus attention (Greenberg & Kindschi, 1996), demonstrated significant findings in the right SLF. This specific fibre pathway together with the cingulum bundle connects frontal areas and cortical regions at the right temporo-occipito-parietal junction, which are considered to play a key role in processing information related to attentional functions (Makris et al., 2008).