Frequency-specific abnormalities in regional homogeneity among children with attention deficit hyperactivity disorder: a resting-state fMRI study

Although many functional magnetic resonance imaging (fMRI) studies have investigated the neurophysiology of attention deficit hyperactivity disorder (ADHD), the existing studies have not yielded consistent findings. This may be related to the different properties of different frequency bands. To investigate the frequency-specific regional homogeneity (ReHo) of spontaneous neural activities in ADHD, the current study used resting-state fMRI to explore the ReHo properties of five frequency bands, slow-5 (0.01-0.027 Hz), slow-4 (0.027-0.073 Hz), slow-3 (0.073-0.198 Hz), slow-2 (0.198-0.25 Hz) and the extra-low frequency (0-0.01 Hz), in 30 drug-naive boys with ADHD and 30 healthy controls. Compared with controls, the ADHD group showed decreased ReHo in the default mode network (DMN) including the medial prefrontal cortex and precuneus, middle frontal gyrus and angular gyrus. ADHD patients also showed increased ReHo in the posterior cerebellum. Significant interactions between frequency band and group were observed predominantly in the dorsolateral prefrontal and parietal cortices, orbital frontal cortex, supplementary motor area, inferior occipital gyrus, thalamus and anterior cerebellum. In particular, we found that the between-group difference in the extra-low frequency band (0-0.01 Hz) seemed to be greater than that in the other frequency bands for most brain regions. The findings suggest that ADHD children display widespread abnormalities in regional brain activity, particularly in the DMN and attention network, and these abnormalities show frequency specificity.