The effect of magnetic coil orientation on the latency of surface EMG and single motor unit responses in the first dorsal interosseous muscle

Werhahn, Konrad J.; Fong, Jky; Meyer, Bernd‐Ulrich; Rothwell, John C.; Day, Brian L.; Thompson, P. D.

doi:10.1016/0168-5597(94)90077-9

Cited by 306 publications

(174 citation statements)

References 14 publications

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“…The spatial resolution of TMS is estimated to be approximately 1 cm within the primary motor hand area (Brasil-Neto et al, 1992;PascualLeone et al, 1994;Werhahn et al, 1994). It has been speculated that electrical stimulation methods directly stimulate the Betz cells in the motor cortex, whereas TMS methods have the Betz cells indirectly stimulated via interneuronal networks (Pascual-Leone et al, 1994).…”

Section: Evidence From Stimulation Studiesmentioning

confidence: 99%

“…It has been speculated that electrical stimulation methods directly stimulate the Betz cells in the motor cortex, whereas TMS methods have the Betz cells indirectly stimulated via interneuronal networks (Pascual-Leone et al, 1994). Previous TMS studies of healthy adult volunteers demonstrated that the TMS-induced current flowing across the central sulcus not in an 'anterior-to-posterior' but 'posterior-to-anterior' direction optimally activated the motor cortex (Brasil-Neto et al, 1992;Werhahn et al, 1994); this well-replicated observation seems to be consistent with the observation in the present study that stimulation of the postcentral gyrus preferably elicited a contralateral hand motor response in a substantial number of young patients with focal epilepsy.…”

Section: Evidence From Stimulation Studiesmentioning

confidence: 99%

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Young patients with focal seizures may have the primary motor area for the hand in the postcentral gyrus

Haseeb¹,

Asano²,

Juhász³

et al. 2007

Epilepsy Research

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SummaryObjective: We determined whether the primary motor hand area was most frequently located in the precentral gyrus in young patients with intractable focal seizures. Methods:Sixty-five patients with focal seizures aged between 5 months and 20 years who underwent a two-stage epilepsy surgery using chronic subdural-EEG monitoring were studied. Pairs of subdural electrodes were electrically stimulated, and the brain region with contralateral hand movement induced by the lowest-intense stimulus was defined as the primary motor hand area.Results: Contralateral hand movement was induced without afterdischarges in 50 children but not in the remaining 15 children. The unpaired t-test revealed that failure to induce contralateral hand motor movement was associated with younger age of subjects. Among the 50 patients with a positive motor response, the primary motor hand area was confined to the precentral gyrus in 9 patients, confined to the postcentral gyrus in 24, and located in both the pre-and post-central gyri in the remaining 17. The McNemar's test revealed that the observed frequency of 24 patients showing the primary motor hand area confined to the postcentral gyrus was larger than chance frequency. Logistic regression analysis failed to demonstrate that the observation of the primary motor hand area confined to the postcentral gyrus was associated with the age, the presence of dysplastic lesion or the seizure onset involving the frontal lobe. Conclusion:Our study failed to support the traditionally-accepted notion that the primary motor hand area is most frequently located in the precentral gyrus but rather demonstrated that a substantial proportion of young patients had the primary motor hand area in the postcentral gyrus.

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Section: Evidence From Stimulation Studiesmentioning

confidence: 99%

Section: Evidence From Stimulation Studiesmentioning

confidence: 99%

Young patients with focal seizures may have the primary motor area for the hand in the postcentral gyrus

Haseeb¹,

Asano²,

Juhász³

et al. 2007

Epilepsy Research

View full text Add to dashboard Cite

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“…The current direction in the circular coil was anticlockwise when viewed from above (side A) for preferential left motor cortex activation and clockwise (side B) for the right motor cortex. The handle of the figure-of-eight focal coil was pointed occipitally so that the current in the brain flowed in a posterior to anterior direction so as to activate corticospinal neurons mainly transsynaptically (Werhahn et al, 1994). The coil position was marked on the scalp and its consistency was continuously monitored throughout the experiment.…”

Section: Transcranial Magnetic Stimulationmentioning

confidence: 99%

Modulation of motor cortex excitability after upper limb immobilization

Zanette

Manganotti

Fiaschi

et al. 2004

Clinical Neurophysiology

102

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Objective: To examine the mechanisms of disuse-induced plasticity following long-term limb immobilization. Methods: We studied 9 subjects, who underwent left upper limb immobilization for unilateral wrist fractures. All subjects were examined immediately after splint removal. Cortical motor maps, resting motor threshold (RMT), motor evoked potential (MEP) latency and MEP recruitment curves were studied from abductor pollicis brevis (APB) and flexor carpi radialis (FCR) muscles with single pulse transcranial magnetic stimulation (TMS). Paired pulse TMS was used to study intracortical inhibition and facilitation. Compound muscle action potentials (CMAPs) and F waves were obtained after median nerve stimulation. In 4/9 subjects the recording was repeated after 35 -41 days.Results: CMAP amplitude and RMT were reduced in APB muscle on the immobilized sides in comparison to the non-immobilized sides and controls after splint removal. CMAP amplitude and RMT were unchanged in FCR muscle. MEP latency and F waves were unchanged. MEP recruitment was significantly greater on the immobilized side at rest, but the asymmetry disappeared during voluntary muscle contraction. Paired pulse TMS showed an imbalance between inhibitory and excitatory networks, with a prevalence of excitation on the immobilized sides. A slight, non-significant change in the strength of corticospinal projections to the non-immobilized sides was found. TMS parameters were not correlated with hand dexterity. These abnormalities were largely normalized at the time of retesting in the four patients who were followed-up.Conclusions: Hyperexcitability occurs within the representation of single muscles, associated with changes in RMT and with an imbalance between intracortical inhibition and facilitation. These findings may be related to changes in the sensory input from the immobilized upper limb and/or in the discharge properties of the motor units.Significance: Different mechanisms may contribute to the reversible neuroplastic changes, which occur in response to long-term immobilization of the upper-limbs.

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“…However, it should be noted that when one is evoking MEPs with the unconditioned pulse it is best to set one of the MagStim units to "0%" and still indicate an interpulse interval (e.g., 100 msec) as opposed to turning the unit off. Reason being is that the BiStim 2 system when one of the units is not on summates the two single pulses provided by the Magstim stimulators to produce a single high power pulse equal to 113% of a single Magstim 200 2 . Thus, when one is using the unconditioned pulse for normalization to potentials elicited with paired-pulse TMS it is critical that the test pulse intensities be held constant in this regard.…”

Section: General Issues To Be Aware Of When Performing Tms As Describmentioning

confidence: 99%

Utilizing Transcranial Magnetic Stimulation to Study the Human Neuromuscular System

Goss

Hoffman

Clark

2012

JoVE

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Transcranial magnetic stimulation (TMS) has been in use for more than 20 years 1 , and has grown exponentially in popularity over the past decade. While the use of TMS has expanded to the study of many systems and processes during this time, the original application and perhaps one of the most common uses of TMS involves studying the physiology, plasticity and function of the human neuromuscular system. Single pulse TMS applied to the motor cortex excites pyramidal neurons transsynaptically 2 ( Figure 1) and results in a measurable electromyographic response that can be used to study and evaluate the integrity and excitability of the corticospinal tract in humans 3 . Additionally, recent advances in magnetic stimulation now allows for partitioning of cortical versus spinal excitability 4,5 . For example, paired-pulse TMS can be used to assess intracortical facilitatory and inhibitory properties by combining a conditioning stimulus and a test stimulus at different interstimulus intervals 3,4,[6][7][8] . In this video article we will demonstrate the methodological and technical aspects of these techniques. Specifically, we will demonstrate singlepulse and paired-pulse TMS techniques as applied to the flexor carpi radialis (FCR) muscle as well as the erector spinae (ES) musculature. Our laboratory studies the FCR muscle as it is of interest to our research on the effects of wrist-hand cast immobilization on reduced muscle performance 6,9 , and we study the ES muscles due to these muscles clinical relevance as it relates to low back pain 8 . With this stated, we should note that TMS has been used to study many muscles of the hand, arm and legs, and should iterate that our demonstrations in the FCR and ES muscle groups are only selected examples of TMS being used to study the human neuromuscular system. Video LinkThe video component of this article can be found at http://www.jove.com/video/3387/ Protocol 1. Single and Paired-Pulse TMS of the FCR and ES Muscles 1. Basic Safety Precautions: Prior to performing TMS on a human subject it is necessary to first screen them for basic safety precautions as it pertains to exposure to a magnetic field. In our laboratory we follow the screening guidelines set forth by the Institute for Magnetic Resonance Safety, Education and Research 10 . In our laboratory we also routinely exclude individuals with a family history of epilepsy seizures. We also require subjects undergoing TMS of the ES muscles to wear earplugs and a mouth guard due to the less focal and stronger stimulation intensities. Electrical Recordings:To examine TMS responses in the motor system it is necessary to record electromyographic (EMG) signals from skeletal muscles. For the FCR muscle we place surface electrodes on the forearm using a bipolar electrode arrangement located longitudinally over the muscle on shaved and abraded skin as we have previously described 7,11 . For the erector spinae muscles we use a similar electrode arrangement located longitudinally over the muscles at the L3-L5 vertebral level...

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The effect of magnetic coil orientation on the latency of surface EMG and single motor unit responses in the first dorsal interosseous muscle

Cited by 306 publications

References 14 publications

Young patients with focal seizures may have the primary motor area for the hand in the postcentral gyrus

Young patients with focal seizures may have the primary motor area for the hand in the postcentral gyrus

Modulation of motor cortex excitability after upper limb immobilization

Utilizing Transcranial Magnetic Stimulation to Study the Human Neuromuscular System

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