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Results for “Transcranial Magnetic Stimulation”

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At least 19 recordsLinked to original sources
PubMed2004

[Clinical applications of repetitive transcranial magnetic stimulation].

Transcranial magnetic stimulation (TMS), when delivered in trains of pulses is able to induce long-lasting changes of excitability of neuronal networks, not only in the vicinity of the stimulating coil, but also at distant sites. Results of stimulation experiments over the motor cortex indicate that the effects (excitatory or inhibitory) depend on the frequency of stimulation. These data have prompted researchers to use repetitive transcranial magnetic stimulation (rTMS) as a therapeutic tool in various brain disorders, most notably depression. However, as long as large randomized trials have not been conducted, rTMS cannot be recommended as an alternative to validated conventional therapies of such disorders.

Brain↗
PubMed1999

Improvement in Parkinsonian symptoms after repetitive transcranial magnetic stimulation.

Transcranial magnetic stimulation has been used in the diagnosis of neurological lesions, but has also been shown to be useful in the treatment of depression. We have now examined the effect of applying transcranial magnetic stimulation daily for 10 days in a sample of 10 patients with Parkinson's disease in whom maximal benefit was being obtained from drug therapy. The subjects were followed for six months and showed significant improvements over this period when assessed using a range of measures. It is suggested that transcranial magnetic stimulation may be a valuable technique in the treatment or adjunct treatment of Parkinsonism, possibly by inducing changes in brain monoamine levels.

Aged↗
PubMed1997

Temporal aspects of visual search studied by transcranial magnetic stimulation.

Transcranial magnetic stimulation was applied over the parietal visual cortex of subjects while they were performing 'pop-out' or conjunction visual search tasks in arrays containing eight distractors. Magnetic stimulation had no detrimental effect on the performance of pop-out search, but did significantly increase reaction times on conjunction search when stimulation was applied over the right parietal cortex 100 msec after the onset of the visual display for trials when the target was present. Target absent reaction times were elevated when stimulation was applied 160 msec after array onset. Stimulation had no effect on the number of errors made. The results suggest that a sub-region of the right parietal lobe is important for conjunction search but not for pre-attentive pop-out. The result from target present trials is consistent with timing data from studies of single cells in monkeys and the hypothesis that parietal areas generate a signal that projects back to extrastriate visual areas to enhance the processing of features in a restricted part of the visual field. The timing of the effect indicates that transcranial stimulation disrupts the mechanisms underlying the focal attention necessary for feature binding in conjunction search. The effects of TMS on target absent trials are interpreted in terms of fronto-parietal connections and the role of frontal cortex in decision-making. The results also highlight the efficacy of transcranial magnetic stimulation as a complement to other spatial and temporal imaging techniques.

Humans↗
PubMed2000

Coil design for real and sham transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) can be used to excite the human cortex noninvasively. TMS also activates scalp muscles and sensory receptors; additionally, the loud sound from the stimulating coil activates auditory pathways. These side effects complicate the interpretation of the results of TMS studies. For control experiments, we have designed a coil that can produce both real and sham stimulation without moving the coil. The sham TMS is similar to the real TMS, except for the different relative direction of the currents in the two loops of the figure-of-eight coil. While the real TMS elicited activation of hand muscles, sham TMS had no such effect; however, the auditory-evoked potentials were similar.

Electroencephalography↗
PubMed2001

Tickling the brain: studying visual sensation, perception and cognition by transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) is a means of stimulating the brain from outside the skull with little, and occasionally no discomfort for the subject. A single TMS pulse, lasting less than 1 ms, can briefly disrupt the normal activity of a targeted region of the brain for tens of milliseconds, allowing the effects of disruption on specific perceptual and cognitive tasks to be measured behaviorally. Rapid, repeated pulses can disrupt activity for correspondingly longer periods. The reversibility of the effects make it possible to create 'virtual patients' who can be tested in the same way as actual patients with real brain damage in order to explore regional functional specialization. Although several aspects of TMS continue to be evaluated, such as its safety, the extent and localization of the effective region of induced electrical current, the importance of the waveform of the pulse, the configuration and positioning of the coil, its productivity has been firmly established in little more than 10 years of systematic use. Examples of the latter are given from investigations of the nature of visual phosphenes produced by TMS applied to different regions of the visual cortex in normal subjects and subjects with occipital or ocular damage in an attempt to reveal the role of visual cortex in visual awareness.

Brain↗
PubMed2000

Studies of human motor physiology with transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) is a safe, noninvasive, and painless way to stimulate the human motor cortex in behaving human subjects. When it is applied as a single-pulse, measurements such as central conduction time, motor threshold, silent-period duration, recruitment curve, and mapping of muscle representation can be determined. Paired-pulse TMS is a useful way to examine cortical excitability. Single and paired-pulse TMS have been applied to study plasticity following amputation and cortical excitability in patients with dystonia. Another form of TMS is repetitive TMS (rTMS), with stimuli delivered repeatedly to a single scalp site. High-frequency rTMS can be used to transiently inactivate different cortical areas to study their functions. rTMS can also modulate cortical excitability. At stimulus frequencies higher than 5 Hz, rTMS increases cortical excitability, and stimulation around 1 Hz reduces cortical excitability. Modulation of cortical excitability by rTMS has therapeutic potential in psychiatric and neurological disorders.

Electric Stimulation↗
PubMed2001

Modification of cortical excitability induced by gabapentin: a study by transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) was employed before and after a single dose of gabapentin to evaluate how this drug affects the activity of excitatory and inhibitory circuits within the motor cortex. Eleven healthy volunteers were studied. For the evaluation of cortical excitability, the following parameters were taken into account: resting and active motor threshold (RMT, AMT); cortical silent period (CSP); and intracortical inhibition (ICI) and facilitation (ICF). Peripheral silent period (PSP) was also detected. All parameters were measured before and 3 and 24 hours after 800 mg gabapentin was administered in a single oral dose. Gabapentin deepened the ICI and suppressed the ICF at 3 h but not at 5 h after dosing. We conclude that, in the normal human brain, gabapentin may act on intracortical excitability by shifting the balance towards less excitation and more inhibition.

Acetates↗
PubMed2003

Transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) is a noninvasive and painless method of stimulating the cerebral cortex that allows the study of cortical excitability and inhibition. This article describes the technique, the parameters most commonly studied, the clinical applications of TMS, and potential research applications.

Brain Mapping↗
PubMed2003

Increased cortical excitability with longer duration of Parkinson's disease as evaluated by transcranial magnetic stimulation.

Transcranial Magnetic Stimulation (TMS) was used to evaluate the cortical excitability and central motor pathways in Parkinson's disease (PD) and correlate with severity and duration of disease. 19 cases of PD and 13 controls were enrolled. The threshold intensity (TI), cortical latency (CL), central conduction time (CCT), motor evoked potential amplitude (MEP) obtained with TMS were correlated with Hoehn and Yahr and duration of disease. The threshold intensity (TI) was significantly lower in patients of PD than controls. The TI in patients with PD was 53.16-/+8.4% patients and 67.1-/+21.6% in controls (p<0.05). This strongly correlated with duration of disease, TI being lower in patients with disease duration more than 5 years. There was no difference in the other TMS parameters - CL, CCT, MEP between patients and controls. Our study revealed increased excitability in PD which was related to longer duration of disease.

Aged↗
PubMedDate not supplied

[The new technique of studying cranial nerves VII, XI and XII: electroneurography by transcranial magnetic stimulation].

Transcranial magnetic stimulation (TMS) technique has been applied to the study of VII, XI and XII cranial nerves in 5 normal subjects, comparing the results with those obtained by conventional electrical stimulation. This technique allows us to study in a painless way the nerve function in all its pathway (motor cortex-motoneurone-muscle). In some cases, TMS yields potentials of a greater amplitude than those obtained by electrical stimulation, due to its capacity to penetrate deeply and stimulate all the fibers of the nerve.

Cranial Nerves↗
PubMed2002

Iron-core coils for transcranial magnetic stimulation.

Transcranial magnetic stimulation requires a great deal of power, which mandates bulky power supplies and produces rapid coil heating. The authors describe the construction, modeling, and testing of an iron-core TMS coil that reduces power requirements and heat generation substantially, while improving the penetration of the magnetic field. Experimental measurements and numeric boundary element analysis show that the iron-core stimulation coil induces much stronger electrical fields, allows greater charge recovery, and generates less heat than air-core counterparts when excited on a constant-energy basis. These advantages are magnified in constant-effect comparisons. Examples are given in which the iron-core coil allows more effective operation in research and clinical applications.

Brain↗
PubMed1997

Ontogeny of ipsilateral corticospinal projections: a developmental study with transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) has been used to describe the maturation of the corticospinal tract in children. Ipsilateral corticospinal connections have been demonstrated with TMS in patients with congenital mirror movements, in patients after hemispherectomy, and in children with hemiplegic cerebral palsy. The goal of the study was to find out whether corticospinal ipsilateral projections in children can be demonstrated during the first decade of life as part of normal ontogeny. For this purpose, we examined 50 normal children (age range, 3-11 years) with focal TMS over the left and right hemispheres to target muscles in proximal and distal parts of the upper extremity (first dorsal interosseus, biceps brachii, and brachioradialis). To lower the stimulation threshold, we stimulated under voluntary preinnervation. In two-thirds of the children we elicited ipsilateral motor evoked potentials (MEPs). This occurred more often in proximal than in distal muscles. The latency of the ipsilateral MEPs was about 12 to 14 msec longer than the usual contralateral response. From the age of 10, and in adults, ipsilateral MEPs could not be detected. Also considering lesion data from adult patients, the most likely explanation for the disappearance of ipsilateral corticospinal connections after the age of 10 years is an increasing transcallosal inhibitory influence during development. The presence of ipsilateral corticospinal connections appears to be a normal state in ontogeny.

Adult↗
PubMed2002

Responses of ankle extensor and flexor motoneurons to transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) of the motor cortex excites limb muscles of the contralateral side of the body. Reports of poorly defined, or a complete lack of systematic excitatory responses of soleus motoneurons compared with those of tibialis anterior (TA) motoneurons has led to the proposal that while all ankle flexor motoneurons receive strong corticomotoneuronal connections, very few soleus motoneurons do. In addition, the connections to these few motoneurons are weak. The nature of corticomotoneuronal connections onto these two motoneuron pools was re-evaluated in the following experiments. The leg area of the left motor cortex was stimulated with a large double-cone coil using Magstim 200, while surface electromyographic (EMG) and single motor unit (SMU) responses were recorded from soleus and TA muscles of healthy adult subjects. Under resting conditions, the onset (25-30 ms) and duration of concomitantly recorded short latency motor evoked potentials (MEPs) in surface EMG from both muscles were similar. The input-output relationships of the simultaneously recorded soleus and TA EMG responses showed much greater increases in TA MEPs compared with soleus MEPs with identical increases in stimulus intensity. Under resting and nonisometric conditions, a later peak with onset latency of approximately 100 ms was observed in soleus. During isometric conditions or with vibration of the TA tendon, the second soleus peak was abolished indicating reflex origin of this peak. Recordings from 42 soleus and 39 TA motor units showed clear response peaks in the peristimulus time histograms (PSTHs) of every unit. Two statistical tests were done to determine the onset and duration of response peaks in the PSTHs. With chi(2) test, the duration was 6.9 +/- 4.2 ms (mean +/- SD) for soleus and 5.1 +/- 2.1 ms for TA. Using the criterion of discerning a peak by bin counts being three SDs above background, the duration was 10.0 +/- 4.4 ms for soleus and 7.8 +/- 2.6 ms for TA. Results of these experiments do not suggest a lack of systematic corticomotoneuronal connections on soleus motoneurons when compared with those on TA, though some differences in the strengths of corticomotoneuronal connections onto the two pools do exist.

Adult↗
PubMed2003

Mechanisms and the current state of transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) is unique among the current brain stimulation techniques because it is relatively non-invasive. TMS markedly differs from vagus nerve stimulation, deep brain stimulation and magnetic seizure therapy, all of which require either an implanted prosthesis or general anesthesia, or both. Since its rebirth in its modern form in 1985, TMS has already shown potential usefulness in at least three important domains-as a basic neuroscience research instrument, as a potential clinical diagnostic tool, and as a therapy for several different neuropsychiatric conditions. The TMS scientific literature has now expanded beyond what a single summary article can adequately cover. This review highlights several new developments in combining TMS with functional brain imaging, using TMS as a psychiatric therapy, potentially using TMS to enhance performance, and finally recent advances in the core technology of TMS. TMS' ability to non-invasively and focally stimulate the brain of an awake human is proving to be a most important development for neuroscience in general, and neuropsychiatry in particular.

Animals↗
PubMed1997

Prognostication of Bell's palsy using transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) provides a method to noninvasive excitation of the facial nerve in its intracranial segment close to the internal acoustic meatus. Thus, the site of facial nerve activation with TMS is proximal to or within the site of the lesion in Bell's palsy. To evaluate the prognostic capability of TMS in unilateral Bell's palsy we examined 137 patients with this method, and compared the results with electroneuronography (ENoG). Within 0-4 days from the onset of palsy, the patients with elicitable TMS responses recovered better than those in whom TMS responses were not elicitable. If TMS was performed 5-9 days or 10-28 days after the onset of palsy, it did not provide any prognostic information. Based on amplitude side-to-side differences, ENoG did not contribute prognostic information during the first 9 days from the onset of palsy. Later on, 10-28 days after the onset of palsy, ENoG showed an increased capability to discriminate the patients with poor prognosis. Thus, elicitable facial motor response with TMS predicts good prognosis of Bell's palsy at an early stage whereas poor response with ENoG predicts less favorable prognosis at a later stage.

Electric Stimulation↗
PubMed2001

Impaired motor cortical inhibition in Parkinson's disease: motor unit responses to transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS)-induced corticospinal volleys can be investigated in detail by analysing the firing pattern modulation of active motor units (MUs) at close to threshold stimulation strengths. In amyotropic lateral sclerosis (ALS) these volleys are dispersed and prolonged, attributed to altered motor cortical excitability. Impaired intracortical inhibition, as found in ALS, is not unique to this disease, but is also a well-established finding in Parkinson's disease (PD). The present study explored whether reduced inhibition in the motor cortex in PD is accompanied by similar changes in motor unit firing modulation by TMS as are found in ALS. TMS was applied to the contralateral motor cortex during a low-force voluntary elbow flexion while 126-channel surface electromyography (SEMG) was recorded from the brachial biceps muscle. A recently developed method for SEMG decomposition was used to extract the firing pattern of up to five simultaneously active MUs. Sixteen MUs in 7 PD patients and 17 MUs in 5 healthy control subjects were analysed and peristimulus time histograms (PSTHs) and interspike interval change functions (IICFs) were calculated. The IICF provides an estimate of the modulation of the postsynaptic membrane potential at the spinal motoneuron, evoked by the stimulus. In PD the duration of the PSTH peak was significantly increased and the synchrony was decreased. The excitatory phase at 20-50 ms of the IICF was broader in PD, reflecting a longer duration of the TMS-evoked excitatory postsynaptic potential. It is proposed that these results are due to prolonged corticospinal volleys resulting from impaired intracortical inhibition.

Action Potentials↗
PubMed2006

A flexible infrastructure for delivering augmented reality enabled transcranial magnetic stimulation.

Transcranial Magnetic Stimulation (TMS) is the process in which electrical activity in the brain is influenced by a pulsed magnetic field. Common practice is to align an electromagnetic coil with points of interest identified on the surface of the brain, from an MRI scan of the subject. The coil can be tracked using optical sensors, enabling the targeting information to be calculated and displayed on a local workstation. In this paper we explore the hypothesis that using an Augmented Reality (AR) interface for TMS will improve the efficiency of carrying out the procedure. We also aim to provide a flexible infrastructure that if required, can seamlessly deploy processing power from a remote high performance computing resource.

Computing Methodologies↗