Search results for "Transcranial"
showing 10 items of 413 documents
Modulation of excitatory and inhibitory circuits for visual awareness in the human right parietal cortex.
2005
The balance of specific patterns of excitation and inhibition in critical regions of both hemispheres could be relevant in orienting attention over the extrapersonal space. In the present study a group of normal subjects had to detect small rectangular stimuli presented briefly on a computer screen in three different conditions: unilateral presentation either to left or right visual periphery or bilateral simultaneous presentation. Paired transcranial magnetic stimulation (TMS), was applied over the right parietal cortex 150 ms after the presentation of the visual stimuli with different inter-stimulus intervals (ISIs: 1, 3,5 and 10 ms). When paired TMS was applied 150 ms, but not 100 ms, af…
Specific modulation of corticospinal and spinal excitabilities during maximal voluntary isometric, shortening and lengthening contractions in synergi…
2011
Non-technical summary The neural control of muscle activity differs during voluntary shortening and lengthening contractions. In this paper, we show that the relative contribution of both cortical and spinal mechanisms to the modulation of neural activation is specific during lengthening contraction and differs between synergist muscles. Knowledge of spinal and corticospinal excitabilities modulations during shortening and lengthening muscle contraction improves our understanding of the processes that underlies the neural control of muscles during dynamic contractions.
Cerebellar magnetic stimulation decreases levodopa-induced dyskinesias in Parkinson disease
2009
BACKGROUND: The neural mechanisms and the circuitry involved in levodopa-induced dyskinesia (LID) are still partially obscure. LID can be considered the consequence of an abnormal pattern or code of activity that originates and is conveyed from the basal ganglia to the thalamus and the cortical motor areas. However, not only striatothalamocortical motor circuits but also other interconnected pathways could be implicated in its pathogenesis. METHODS: In a series of experiments, we applied repetitive transcranial magnetic stimulation (rTMS) over the lateral cerebellum in a group of patients with advanced Parkinson disease, to investigate whether modulation of cerebellothalamocortical circuits…
Which direction should I go? A quest for understanding the effect of TMS stimulus orientation on evoked responses
2023
The orientation of the electric field (E-field) induced by transcranial magnetic stimulation (TMS) plays a significant role in determining the magnitude of motor evoked potentials (MEP) and TMS-evoked potentials (TEP). However, fundamental mechanisms explaining the interaction of the induced E-field and the underlying neuronal populations are still largely unknown. We recently entered a quest to understand and describe neurophysiological and physical factors affecting the effect of the E-field orientation on the MEP and TEP. We developed a dual-coil TMS transducer capable of fast and accurate electronic control of the induced E-field orientation. With this transducer, we could scan the effe…
Beta Rebound as an Index of Temporal Integration of Somatosensory and Motor Signals
2020
Modulation of cortical beta rhythm (15-30 Hz) is present during preparation for and execution of voluntary movements as well as during somatosensory stimulation. A rebound in beta synchronization is observed after the end of voluntary movements as well as after somatosensory stimulation and is believed to describe the return to baseline of sensorimotor networks. However, the contribution of efferent and afferent signals to the beta rebound remains poorly understood. Here, we applied electrical median nerve stimulation (MNS) to the right side followed by transcranial magnetic stimulation (TMS) on the left primary motor cortex after either 15 or 25 ms. Because the afferent volley reaches the …
Intracranial measurement of current densities induced by transcranial magnetic stimulation in the human brain
2003
Transcranial magnetic stimulation (TMS) is a non-invasive technique that uses the principle of electromagnetic induction to generate currents in the brain via pulsed magnetic fields. The magnitude of such induced currents is unknown. In this study we measured the TMS induced current densities in a patient with implanted depth electrodes for epilepsy monitoring. A maximum current density of 12 microA/cm2 was recorded at a depth of 1 cm from scalp surface with the optimum stimulation orientation used in the experiment and an intensity of 7% of the maximal stimulator output. During TMS we recorded relative current variations under different stimulating coil orientations and at different points…
Progression of adverse effects over consecutive sessions of transcranial direct current stimulation
2017
final draft
Motor and linguistic linking of space and time in the cerebellum
2009
Background: Recent literature documented the presence of spatial-temporal interactions in the human brain. The aim of the present study was to verify whether representation of past and future is also mapped onto spatial representations and whether the cerebellum may be a neural substrate for linking space and time in the linguistic domain. We asked whether processing of the tense of a verb is influenced by the space where response takes place and by the semantics of the verb. Principal Findings: Responses to past tense were facilitated in the left space while responses to future tense were facilitated in the right space. Repetitive transcranial magnetic stimulation (rTMS) of the right cereb…
Aktueller Stand der Hirntoddiagnostik in Deutschland
2000
□ Der Hirntod kann grundsatzlich nur dann diagnostiziert werden, wenn eine schwere akute Hirnschadigung vorliegt und andere Storungen sicher auszuschliesen sind. Primare Hirnschadigungen betreffen das Gehirn direkt (zum Beispiel intrakranielle Blutungen, Raumforderungen, schweres Schadel-Hirn-Trauma), sekundare Hirnschadigungen indirekt (zum Beispiel Hypoxie nach kardiopulmonaler Reanimation). Supratentorielle Hirnschadigungen betreffen das Groshirn, infratentorielle Hirnschadigungen den Hirnstamm und/oder das Kleinhirn. □ Koma, Hirnstammareflexie und Ausfall der Spontanatmung sind die obligaten klinischen Hirntodzeichen. Wenn diese Zeichen im Verlauf unverandert fortbestehen, ist der irrev…
Neurophysiological mechanisms of motor imagery : effects of associated somatosensory stimulation
2018
Mental training, which involves mentally simulating an action without motor output, is an effective stimulus to improve the maximal voluntary contraction. If only the motor pathway is activated, an activation of the somatosensory cortex is observed despite the lack of afferent feedback. Indeed, the motor imagery task efficiency is based in part on an interaction between motor and sensory pathway. Thus, it’s seems reasonable to think that the addition of sensory afferent feedback during motor imagery could potentiate the motor imagery effects and thus improve motor performance. In our first study, we showed that the addition of somatosensory stimulation of Ia-afferents during a motor imagery…