[Effective connectivity within the default mode network modulated by methylphenidate using dynamic causal modeling on resting-state functional magnetic resonance imaging].

The effective connectivity of default mode network (DMN) and its change after taking methylphenidate (MPH) were investigated in this study based on resting-state functional magnetic resonance imaging. Dynamic causal modeling (DCM) was applied to compare the effective connectivity between the conditions of taking MPH and placebo for 18 healthy male volunteers. Started with the network structural basis provided by a recent literature, endogenous low frequency fluctuation signals (0.01-0.08 Hz) of each node of DMN were taken as the driving input, and thirty-two possible models were designed according to the modulation effect of MPH on different connections between nodes. Model fitting and Bayesian model selection were performed to find the winning model and corresponding parameters. Our results indicated that the effective connectivity from medial prefrontal cortex (MPFC) to posterior cingulated cortex (PCC), from left/right inferior parietal lobule (L/RIPL) to MPFC, and from RIPL to PCC were excitatory, whereas the connectivity from LIPL to PCC was inhibitory. Further t-test statistics on connectivity parameters found that MPH significantly reduced the link from RIPL to MPFC in DMN (t = 2.724, P = 0.016) and changed the weak excitatory state to inhibitory state. However, it had no significant effect on other connections. In all, our results demonstrated that MPH modulates the effective connectivity within DMN in resting state.

[Functional magnetic resonance imaging of whole brain related to motor preparation and execution].

OBJECTIVE: To investigate the roles the different functional activation areas in whole human brain related to movement play during motor preparation (CUE) and execution (GO). METHODS: Event-related functional MRI technique was used on 12 right-handed healthy subjects to record the brain activation in a manner of delayed sequential finger movement. Activation maps and time-signal intensity curves were generated. RESULTS: Bilateral anterior parts of supplementary motor area (Pre-SMA), bilateral posterior parietal cortex (PPC), and bilateral anterior premotor cortex (PMC) were strongly activated during the preparation period, while bilateral SMA proper, and contralateral primary motor cortex (M1) were strongly activated during the execution period, Cerebellar cortex was activated during both periods. The time-signal intensity curves based on single voxel indicated that above-mentioned brain areas were activated during both periods to different degrees; however, the characteristics of distribution in every area were different. CONCLUSION: The brain areas related to movement are activated differently during preparation period and execution period, areas close to M1 participate in the motor execution process mainly, and the areas away from M1 are concerned with motor preparation process chiefly.

[Study of paroxysmal kinesigenic dyskinesia with fMRI].

OBJECTIVE: To detect the differences in subcortical structures between patients with paroxysmal kinesigenic dyskinesia (PKD) and normal subjects during movement preparation and execution. METHODS: The PKD patients performed a movement task, in which a CUE signal (preparation) indicated the movement sequence prior to the appearance of an imperative GO signal (execution). Event-related functional magnetic resonance imaging (fMRI) and 3dDeconvolve program of AFNI were used to estimate the hemodynamic response function and to generate activation maps. RESULT: During movement preparation, the activated brain areas in PKD patients were less than those of normal subject, and there was no activation in basal ganglia in PKD patients. During execution, the activation was also less in PKD patients except in bilateral M1. CONCLUSION: During intermission, abnormalities of the brain still exist in PKD patients when during preparing or performing movement. The movement circuit in the brain displays an unusual state. The attack may be caused by reducing of inhibition in brain areas.

[Lateralized distribution of motor areas involved in voluntary movement].

OBJECTIVE: To investigate the brain functional laterality in motor areas during motor execution systematically. METHODS: Functional magnetic resonance imaging (fMRI) was employed combined with right hand sequential finger movement task to investigate brain activation pattern and laterality in 8 right-handed subjects. 3dDeconvolve program of AFNI was used to estimate the hemodynamic response function and to generate activation maps. Then the laterality index (LI) was calculated and tested statistically. RESULT: All motor areas including the areas which were previously considered to be engage in movement preparation only were activated in movement execution. In the activation map, it appeared left lateralization in cerebra and right lateralization in cerebella. After further statistical test, it was found that in primary motor area (M1), supplementary motor area (SMA) and posterior parietal cortex (PPC), there were left lateralization. While in premotor cortex (PMC), cingulate gyrus and basal ganglia (BG), the lateralization tendency was not obvious. The activation in cerebella is characterized with right lateralization. CONCLUSION: Though there are tiny differences among subjects, most of the motor areas appear lateralized activation. Past studies only observed laterality in several motor areas. It may be due to the difficulty of the task or the experimental design.

[Functional MRI of human brain in musicians and non-musicians].

OBJECTIVE: To explore the differences in brain activation between musicians and non-musicians by use of functional MRI. METHODS: Twelve right-handed musicians and twelve right-handed non-musicians were recruited in the study. During a listening task, they were scanned on the Sigma 1.5T scanner (GE) while they were passively listening to several segments of music of "the Butterfly Love" and the white noise with same physical energy. RESULT: Both musicians and non-musicians demonstrated bilateral transverse gyrus weak activated while listening to the white noise. But when listening to music, they showed bilateral temporal areas strongly activated including superior temporal gyrus, transverse gyrus and some middle temporal areas. Moreover, musicians showed relative left dominance (10/12), whereas non-musicians demonstrated right dominance(11/12). Furthermore,besides bilateral temporal areas, more and stronger activated areas were found in musicians such as cuneus, precuneus,medial frontal and left middle occipital gyrus. CONCLUSION: There are different neuro-patterns between musicians and non-musicians.