Pathophysiology of unilateral asterixis due to thalamic lesion.

[Objective]:Unilateral asterixis has been reported in patients with thalamic lesion. This study aims at elucidating the pathophysiology of the thalamic asterixis. [Methods]:Two cases with unilateral asterixis caused by an infarction in the lateral thalamus were studied by analysing the asterixis-related cortical activities, transcranial magnetic stimulation (TMS) for motor cortex excitability and probabilistic diffusion tractography for the thalamo-cortical connectivity. [Results]:Averaging of electroencephalogram (EEG) time-locked to the asterixis revealed rhythmic oscillations of a beta band at the central area contralateral to the affected hand. TMS revealed a decrease in the motor evoked potential (MEP) amplitude and a prolongation of the silent period (SP). The anatomical mapping of connections between the thalamus and cortical areas using a diffusion-weighted image (DWI) showed that the lateral thalamus involved by the infarction was connected to the premotor cortex, the primary motor cortex (M1) and the primary somatosensory cortex (S1) of the corresponding hemisphere. [Conclusions]:The thalamic asterixis is mediated by the sensorimotor cortex, which is subjected to excessive inhibition as a result of the thalamic lesion involving the ventral lateral nucleus. [Significance]:This is the first demonstration of participation of the sensorimotor cortex in the generation of asterixis due to the lateral thalamic lesion

Neural Sources of Vagus Nerve Stimulation–Induced Slow Cortical Potentials

[Objectives] This study investigated neuronal sources of slow cortical potentials (SCPs) evoked during vagus nerve stimulation (VNS) in patients with epilepsy who underwent routine electroencephalography (EEG) after implantation of the device. [Materials and Methods] We analyzed routine clinical EEG from 24 patients. There were 5 to 26 trains of VNS during EEG. To extract SCPs from the EEG, a high-frequency filter of 0.2 Hz was applied. These EEG epochs were averaged and used for source analyses. The averaged waveforms for each patient and their grand average were subjected to multidipole analysis. Patients with at least 50% seizure frequency reduction were considered responders. Findings from EEG analysis dipole were compared with VNS responses. [Results] VNS-induced focal SCPs whose dipoles were estimated to be located in several cortical areas including the medial prefrontal cortex, postcentral gyrus, and insula, with a significantly higher frequency in patients with a good VNS response than in those with a poor response. [Conclusions] This study suggested that some VNS-induced SCPs originating from the so-called vagus afferent network are related to the suppression of epileptic seizures

The role of cortical sensorimotor oscillations in action anticipation.

The human mirror neuron system is believed to play an important role in facilitating the ability of athletes to anticipate the actions of an opponent. This system is often assessed with EEG by measuring event-related changes in mu (8-13Hz) sensorimotor oscillations. However, traditional channel-based analyses of this measure are flawed in that due to volume conduction effects mu and non-mu alpha activity can become mixed. This flaw means it is unclear the extent to which mu activity indexes the mirror system, as opposed to other processes such as attentional demand. As a solution to this problem, we use independent component analysis to separate out the underlying brain processes during a tennis-related action observation and anticipation task. We investigated expertise-related differences in independent component activity. Experienced tennis players (N = 18) were significantly more accurate than unexperienced novices (N = 21) on the anticipation task. EEG results found significant group differences in both the mu and beta (15-25Hz) frequency bands in sensorimotor components, with earlier and greater desynchronization in the experienced tennis players. In particular, only experienced players showed desynchronization in the high mu (11-13Hz) band. No group differences were found in posterior alpha components. These results show for the first time that expertise differences during action observation and anticipation are unique to sensorimotor sources, and that no expertise-related differences exist in attention modulated, posterior alpha sources. As such, this paper provides a much cleaner measure of the human mirror system during action observation, and its modulation by motor expertise, than has been possible in previous work

パーキンソン病患者における神経フィードバック法の訓練を用いた運動準備電位の増強

京都大学0048新制・課程博士博士(医科学)甲第17467号医科博第43号新制||医科||3(附属図書館)30233京都大学大学院医学研究科医科学専攻(主査)教授 福山 秀直, 教授 村井 俊哉, 教授 松原 和夫学位規則第4条第1項該当Doctor of Medical ScienceKyoto UniversityDA