Human brain mapping
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Human brain mapping · Aug 2009
Meta AnalysisFunctional brain imaging of swallowing: an activation likelihood estimation meta-analysis.
A quantitative, voxel-wise meta-analysis was performed to investigate the cortical control of water and saliva swallowing. Studies that were included in the meta-analysis (1) examined water swallowing, saliva swallowing, or both, and (2) reported brain activation as coordinates in standard space. Using these criteria, a systematic literature search identified seven studies that examined water swallowing and five studies of saliva swallowing. ⋯ This meta-analysis emphasizes the distributed and partly overlapping cortical networks involved in the control of water and saliva swallowing. Water swallowing is associated with right inferior parietal activation, likely reflecting the sensory processing of intraoral water stimulation. Saliva swallowing more strongly involves premotor areas, which are crucial for the initiation and control of movements.
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Human brain mapping · Aug 2009
Neural substrates of low-frequency repetitive transcranial magnetic stimulation during movement in healthy subjects and acute stroke patients. A PET study.
The aim of the study was to investigate, with an rTMS/PET protocol, the after-effects induced by 1-Hz repetitive transcranial magnetic stimulation (rTMS) in the regional cerebral blood flow (rCBF) of the primary motor cortex (M1) contralateral to that stimulated during a movement. Eighteen healthy subjects underwent a baseline PET scan followed, in randomized order, by a session of Real/Sham low-frequency (1 Hz) subthreshold rTMS over the right M1 for 23 min. The site of stimulation was fMRI-guided. ⋯ Commissural connectivity between right dorsal premotor cortex and left M1 after real-rTMS was observed with a psychophysiological interaction analysis in healthy subjects. No major changes were found for the left hand. These results give further arguments in favor of a plastic commissural connectivity between M1 both in healthy subjects and in stroke patients, and reinforce the potential for therapeutic benefit of low-frequency rTMS in stroke rehabilitation.
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Human brain mapping · Aug 2009
Defective inhibition and inter-regional phase synchronization in pianists with musician's dystonia: an EEG study.
Recent neurophysiological studies have associated focal-task specific dystonia (FTSD) with impaired inhibitory function. However, it remains unknown whether FTSD also affects the inhibition (INH) of long-term overlearned motor programs. Consequently, we investigated in a Go/NoGo paradigm the neural correlates associated with the activation (ACT) and inhibition of long-term overlearned motor memory traces in pianists with musician's dystonia (MD), a form of FTSD, during a relevant motor task under constraint timing conditions with multichannel EEG. ⋯ This effect was due to a weaker phase synchronization between the supplementary motor cortex and left premotor and sensorimotor electrodes in patients. Thus, our findings support the hypothesis of a deficient phase coupling between the neuronal assemblies required to inhibit motor memory traces in patients with MD. EMG recorded from the right flexor pollicis longus muscle confirmed that patients with MD had a disrupted INH in NoGo trials.
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Human brain mapping · Jul 2009
Regional brain activation changes and abnormal functional connectivity of the ventrolateral prefrontal cortex during working memory processing in adults with attention-deficit/hyperactivity disorder.
Previous studies on working memory (WM) function in adults with attention-deficit/hyperactivity disorder (ADHD) suggested aberrant activation of the prefrontal cortex and the cerebellum. Although it has been hypothesized that activation differences in these regions most likely reflect aberrant frontocerebellar circuits, the functional coupling of these brain networks during cognitive performance has not been investigated so far. In this study, functional magnetic resonance imaging (fMRI) and both univariate and multivariate analytic techniques were used to investigate regional activation changes and functional connectivity differences during cognitive processing in healthy controls (n = 12) and ADHD adults (n = 12). ⋯ ADHD adults had significantly lower connectivity in the bilateral VLPFC, the anterior cingulate cortex, the superior parietal lobule, and the cerebellum compared with healthy controls. Increased connectivity in ADHD adults was found in right prefrontal regions, the left dorsal cingulate cortex and the left cuneus. These findings suggest both regional brain activation deficits and functional connectivity changes of the VLPFC and the cerebellum as well as functional connectivity abnormalities of the anterior cingulate and the parietal cortex in ADHD adults during WM processing.
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Human brain mapping · Jul 2009
Stability of tactile- and pain-related fMRI brain activations: an examination of threshold-dependent and threshold-independent methods.
Functional MRI can be used to assess brain plasticity over time. To confidently attribute changes in activation patterns to cortical plasticity, it is important to establish the stability of cortical activation patterns. Because little is known concerning the stability of somatosensory-evoked brain responses, we assessed the reproducibility of within-subject responses in key somatosensory regions [thalamus, primary and secondary cortex (S1, S2)] to tactile and painful stimuli using threshold-dependent and threshold-independent analyses. ⋯ Deactivations within ipsilateral S1 occurred 48% of the time with tactile stimuli, and 90% of the time with painful stimuli. Within contralaterally activated regions intraclass correlations (ICCs) were very high using the unthresholded method regardless of the type of stimulation, whereas much lower ICCs arose from the thresholded analyses. These data indicate that a threshold-independent analysis can produce more reproducible outcomes than a standard threshold-dependent analysis.