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

Although many functional magnetic resonance imaging(f MRI) 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(Re Ho) of spontaneous neural activities in ADHD, the current study used resting-state f MRI to explore the Re Ho 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 Re Ho in the default mode network(DMN) including the medial prefrontal cortex and precuneus, middle frontal gyrus and angular gyrus. ADHD patients also showed increased Re Ho 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.

Change in EEG-EMG synchronization reflecting abnormal functional corticomuscular coupling following stroke: A pilot study

Stroke is a common clinical cardiovascular and cerebrovascular disease,which can cause severe motor dysfunction.Therefore,it is an important topic to investigate the abnormality mechanism of the cerebral cortex and the corresponding muscles after stroke.In this study,we investigated the functional corticomuscular coupling(FCMC)at specific frequencies by analyzing differences between stroke patients and healthy controls in hand movements.The transfer spectral entropy(TSE)method was used to analyze simultaneous electroencephalography(EEG)and electromyography(EMG)in the right-hand steady state force task.The results illustrated that healthy subjects had the highest TSE values at the beta band in the EMG→EEG and EEG→EMG directions,and the TSE value in the EEG→EMG direction was higher than that in the EMG→EEG direction.In contrast,for stroke patients,beta band coupling was weakened,and there was a notably higher enhancement of alpha and gamma bands in the EMG→EEG direction relative to the EEG→EMG direction.Further analysis found significant correlations between TSE area values at beta2 and gamma2 bands and clinical rating scales.This study demonstrates the frequency specificity properties of FCMC estimated by TSE can assess the rehabilitation status of stroke patients and contribute to our comprehension of the potential mechanism of motor control systems.