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Brain is a complex network with an anatomical and functional organization. The differences in brain organization of those with attention-deficit/hyperactivity disorder (ADHD) are still not well understood. Here, we study brain organization in ADHD subjects using a complex network derived from resting-state functional magnetic resonance imaging (fMRI) data of ADHD and normal subjects. Our results reveal that the brain networks of ADHD subjects are reorganized compared to those without ADHD in global and local brain functional networks. We find that the ADHD subjects show decreasing brain network integration and increasing brain network segregation. More interestingly, we find similarities of brain topology properties between local and global brain networks. Our finding indicates that cognitive dysfunction in ADHD is probably associated with disrupted global and local brain network topological properties. Our results can help us understand the pathophysiological mechanism of ADHD and serve as a sensitive and specific biomarker of ADHD.

Neurovascular coupling reflects the close relationship between neuronal activity and cerebral blood flow (CBF), providing a new mechanistic insight into health and disease. Neuromyelitis optica (NMO) is an autoimmune inflammatory demyelinating disease of the central nervous system and shows cognitive decline‐related brain gray matter abnormalities besides the damage of optic nerve and spinal cord. We aimed to investigate neurovascular coupling alteration and its clinical significance in NMO by using regional homogeneity (ReHo) to measure neuronal activity and CBF to measure vascular response. ReHo was calculated from functional MRI and CBF was computed from arterial spin labeling (ASL) in 56 patients with NMO and 63 healthy controls. Global neurovascular coupling was assessed by across‐voxel CBF‐ReHo correlations and regional neurovascular coupling was evaluated by CBF/ReHo ratio. Correlations between CBF/ReHo ratio and clinical variables were explored in patients with NMO. Global CBF‐ReHo coupling was decreased in patients with NMO relative to healthy controls (p = .009). Patients with NMO showed decreased CBF/ReHo ratio (10.9%–17.3% reduction) in the parietal and occipital regions and increased CBF/ReHo ratio (8.0%–13.3% increase) in the insular, sensorimotor, temporal and prefrontal regions. Some of these abnormalities cannot be identified by a single CBF or ReHo analysis. Both abnormally decreased and increased CBF/ReHo ratios were correlated with more severe clinical impairments and cognitive decline in patients with NMO. These findings suggested that patients with NMO show abnormal neurovascular coupling, which is associated with disease severity and cognitive impairments.

Type 2 diabetes mellitus (T2DM) and hypertension are both associated with cognitive impairment and brain function abnormalities. We investigated whether abnormal cerebral blood flow (CBF) patterns exists in T2DM patients and possible relationships between aberrant CBF and cognitive performance. Furthermore, we examined the influence of hypertension on CBF alterations in T2DM patients.T2DM patients (n = 38) and non-T2DM subjects (n = 40) were recruited from clinics, hospitals, and normal community health screenings. Cerebral blood flow images were collected and analyzed using arterial spin labeling perfusion functional magnetic resonance imaging (fMRI). Regions with major CBF differences between T2DM patients and non-T2DM controls were detected via 1-way ANOVA. The interaction effects between hypertension and T2DM for CBF alterations were also examined. Correlation analyses illustrated the association between CBF values and cognitive performance and between CBF and blood pressure.Compared with non-T2DM controls, T2DM patients exhibited decreased CBF, primarily in the visual area and the default mode network (DMN); decreased CBF in these regions was correlated with cognitive performance. There was a significant interaction effect between hypertension and diabetes for CBF in the precuneus and the middle occipital gyrus. Additionally, blood pressure correlated negatively with CBF in T2DM patients.T2DM patients exhibited reduced CBF in the visual area and DMN. Hypertension may facilitate a CBF decrease in the setting of diabetes. T2DM patients may benefit from blood pressure control to maintain their brain perfusion through CBF preservation.