551
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Bajbouj M, Lisanby SH, Lang UE, Danker-Hopfe H, Heuser I, Neu P. Evidence for impaired cortical inhibition in patients with unipolar major depression. Biol Psychiatry 2006; 59:395-400. [PMID: 16197927 DOI: 10.1016/j.biopsych.2005.07.036] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2004] [Revised: 04/22/2005] [Accepted: 07/25/2005] [Indexed: 11/22/2022]
Abstract
BACKGROUND Several lines of evidence suggest that central cortical inhibitory mechanisms, especially associated with gamma-aminobutyric acid (GABA) neurotransmission, may play a role in the pathophysiology of major depression. Transcranial magnetic stimulation is a useful tool for investigating central cortical inhibitory mechanisms associated with GABAergic neurotransmission in psychiatric and neurological disorders. METHODS By means of transcranial magnetic stimulation, different parameters of cortical excitability, including motor threshold, the cortical silent period, and intracortical inhibition/facilitation, were investigated in 20 medication-free depressed patients and 20 age- and gender-matched healthy volunteers. RESULTS Silent period and intracortical inhibition were reduced in depressed patients, consistent with a reduced GABAergic tone. Moreover, patients showed a significant hemispheric asymmetry in motor threshold. CONCLUSIONS This study provides evidence of reduced GABAergic tone and motor threshold asymmetry in patients with major depression.
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Affiliation(s)
- Malek Bajbouj
- Department of Psychiatry, Charité University Medicine Berlin, Berlin, Germany.
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552
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Boutte C, Vercueil L, Durand M, Vincent F, Alvarez JC. Apport de l'EEG dans le diagnostic d'une intoxication au baclofène. Neurophysiol Clin 2006; 36:85-9. [PMID: 16844547 DOI: 10.1016/j.neucli.2006.03.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In a young woman presenting with severe coma, the EEG helped diagnosing baclofen overdose. In this patient, the first EEG showed continuous multifocal pseudoperiodic sharp waves. The diagnosis was confirmed by the plasma dosage providing an 8-fold increase above normal baclofen therapeutic range. Following symptomatic therapy, the patient improved within a few days and the EEG normalised. Few other drugs may be responsible for such EEG changes, namely lithium, cephalosporin, and bismuth. In such cases, EEG contribution to the diagnosis should not be ignored.
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Affiliation(s)
- C Boutte
- Laboratoire d'Explorations Fonctionnelles du SNC, CHU de Grenoble, 38043 Grenoble cedex 9, France.
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553
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McDonnell MN, Orekhov Y, Ziemann U. The role of GABAB receptors in intracortical inhibition in the human motor cortex. Exp Brain Res 2006; 173:86-93. [PMID: 16489434 DOI: 10.1007/s00221-006-0365-2] [Citation(s) in RCA: 415] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2005] [Accepted: 01/10/2006] [Indexed: 11/24/2022]
Abstract
While GABA(B) receptors are thought to have an important role in mediating long interval intracortical inhibition (LICI) in the human motor cortex, the effect of a selective GABA(B) receptor agonist on this measure has not been directly tested. Nine healthy volunteers ingested either 50 mg baclofen (BAC) or placebo (PBO) in a randomized, double blind crossover design, with the second session one week later. We used transcranial magnetic stimulation to assess motor threshold, motor evoked potential (MEP) amplitude, cortical silent period (CSP) duration, short interval intracortical inhibition (SICI) and LICI before and 90 min following drug intake. There was no specific effect of drug on motor threshold, MEP amplitude or CSP duration. BAC resulted in a significant increase in LICI (P=0.002) and a significant decrease in SICI (P=0.046) while PBO had no effect. Our findings demonstrate that the enhanced GABA(B) receptor activation results in differential effects on these two measures of intracortical inhibition in the human motor cortex. The increase in LICI is likely to be a result of increased GABA(B) receptor mediated inhibitory post-synaptic potentials, while the reduction in SICI may relate to the activation of pre-synaptic GABA(B) receptors reducing GABA release.
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Affiliation(s)
- Michelle N McDonnell
- Research Centre for Human Movement Control, The University of Adelaide, Adelaide, Australia
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554
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Morgante F, Espay AJ, Gunraj C, Lang AE, Chen R. Motor cortex plasticity in Parkinson's disease and levodopa-induced dyskinesias. Brain 2006; 129:1059-69. [PMID: 16476674 DOI: 10.1093/brain/awl031] [Citation(s) in RCA: 249] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Experimental models of Parkinson's disease have demonstrated abnormal synaptic plasticity in the corticostriatal system, possibly related to the development of levodopa-induced dyskinesias (LID). We tested the hypothesis that LID in Parkinson's disease is associated with aberrant plasticity in the human motor cortex (M1). We employed the paired associative stimulation (PAS) protocol, an experimental intervention involving transcranial magnetic stimulation (TMS) and median nerve stimulation capable of producing long-term potentiation (LTP) like changes in the sensorimotor system in humans. We studied the more affected side of 16 moderately affected patients with Parkinson's disease (9 dyskinetic, 7 non-dyskinetic) and the dominant side of 9 age-matched healthy controls. Motor-evoked potential (MEP) amplitudes and cortical silent period (CSP) duration were measured at baseline before PAS and for up to 60 min (T0, T30 and T60) after PAS in abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles. PAS significantly increased MEP size in controls (+74.8% of baseline at T30) but not in patients off medication (T30: +0.07% of baseline in the non-dyskinetic, +27% in the dyskinetic group). Levodopa restored the potentiation of MEP amplitudes by PAS in the non-dyskinetic group (T30: +64.9% of baseline MEP) but not in the dyskinetic group (T30: -9.2% of baseline). PAS prolonged CSP duration in controls. There was a trend towards prolongation of CSP in the non-dyskinetic group off medications but not in the dyskinetic group. Levodopa did not restore CSP prolongation by PAS in the dyskinetic group. Our findings suggest that LTP-like plasticity is deficient in Parkinson's disease off medications and is restored by levodopa in non-dyskinetic but not in dyskinetic patients. Abnormal synaptic plasticity in the motor cortex may play a role in the development of LID.
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Affiliation(s)
- Francesca Morgante
- Division of Neurology and Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada
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555
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Lefaucheur JP, Ménard-Lefaucheur I, Maison P, Baudic S, Cesaro P, Peschanski M, Bachoud-Lévi AC. Electrophysiological deterioration over time in patients with Huntington's disease. Mov Disord 2006; 21:1350-4. [PMID: 16721731 DOI: 10.1002/mds.20966] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
In recent studies aimed at assessing the effects of original therapeutic strategies applied to patients with Huntington's disease (HD), we observed informative changes in electrophysiological results that recovered normal values in coherence with clinical improvement. However, longitudinal studies were lacking for determining whether electrophysiological test results evolve in parallel with clinical markers of the natural course of the disease and could consequently provide objective quantifiable markers of disease progression. For this purpose, electrophysiological testing was performed annually in a cohort of 20 patients with HD over a 2-year period (three examinations). The study included the recording of sympathetic skin responses and blink reflexes (BRs) to supraorbital nerve stimulation, long latency reflexes (LLRs) and somatosensory evoked potentials (SEPs) to median nerve stimulation, and cortical silent periods (CSPs) to transcranial magnetic stimulation. Clinical evaluation was based on the Total Functional Capacity scale (TFC) and the Motor part of the Unified Huntington's Disease Rating Scale (UHDRS). A significant deterioration with time was found for BR latency, LLR presence, various SEP parameters (parietal N20 peak amplitude and frontal N30 presence) and CSP duration. Attenuation of the N20 peak and CSP shortening correlated with functional decline, as assessed by the TFC score, whereas delayed BR and LLR abolition correlated with UHDRS Motor score deterioration. This study shows that several electrophysiological parameters are closely associated with dysfunction of various neural circuits in HD and could be useful markers of disease progression.
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Affiliation(s)
- Jean-Pascal Lefaucheur
- Service de Physiologie - Explorations Fonctionnelles, Hôpital Henri Mondor, AP-HP, Créteil, France.
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556
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Khedr EM, Ahmed MA, Mohamed KA. Motor and visual cortical excitability in migraineurs patients with or without aura: transcranial magnetic stimulation. Neurophysiol Clin 2006; 36:13-8. [PMID: 16530139 DOI: 10.1016/j.neucli.2006.01.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
BACKGROUND AND PURPOSE OF STUDY Controversy surrounds measures of visual and motor cortical excitability in migraineurs: some authors report that interictal excitability is increased, others decreased. The aim of this work was to provide further evidence about motor and visual cortical excitability in migraineurs between attacks. PATIENTS AND METHODS Twenty-eight migraineurs patients, 18 with aura and 10 patients without aura and 20 healthy right-handed, age and sex matched volunteers were included in the study. Each subject underwent transcranial magnetic stimulation and was submitted to the following: determination of resting motor threshold (rMT), silent period (SP), MEP input-output curves, phosphene threshold (PT). RESULTS Patients had lower rMT, shorter SP, and increased MEP recruitment compared with control group. There was an increased prevalence of phosphene (85%) as well as lower PT (63% of the stimulator output) in migraineurs compared with control group (75%, and 72%, respectively). There was a significant negative correlation between duration of attacks and PT (P = 0.02). No significant differences between patients with aura and without aura in different parameters of cortical excitability. CONCLUSION Our findings confirm that the motor and visual cortexes are hyperexcitable and this appears partly to be consequent upon a failure of inhibitory circuits.
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Affiliation(s)
- Eman M Khedr
- Neuropsychiatry Department, Assiut University Hospital, Assiut, Egypt.
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557
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Attarian S, Pouget J, Schmied A. Covariation of corticospinal efficiency and silent period in motoneuron diseases. Muscle Nerve 2006; 34:178-88. [PMID: 16691593 DOI: 10.1002/mus.20570] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
For a better understanding of the changes affecting the cortically induced silent period (SP) in motoneuron disease, the excitatory and inhibitory effects of transcranial magnetic stimulation were explored repeatedly in 8 patients with amyotrophic lateral sclerosis (ALS), 3 patients with Kennedy's disease (KD), and 10 healthy subjects. In KD, the background electromyogram (EMG) and the motor evoked potential (MEP) area were both enhanced. However, neither the corticospinal efficiency (MEP gain, the ratio between MEP and background EMG) nor the duration of the SP differed from healthy subjects. In ALS patients, the MEP gain and the SP duration decreased conspicuously with time. We conclude that use of the MEP gain improves detection of corticospinal dysfunction in ALS patients. Part of the SP shortening in ALS seems to reflect the reduced activation of cortical or spinal inhibitory networks by the abnormal corticospinal pathway.
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Affiliation(s)
- S Attarian
- Department of Neurology and Neuromuscular Diseases, CHU La Timone, 264 rue Saint-Pierre, 13385 Marseille, France.
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558
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Bajbouj M, Brakemeier EL, Schubert F, Lang UE, Neu P, Schindowski C, Danker-Hopfe H. Repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex and cortical excitability in patients with major depressive disorder. Exp Neurol 2005; 196:332-8. [PMID: 16194530 DOI: 10.1016/j.expneurol.2005.08.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 07/21/2005] [Accepted: 08/15/2005] [Indexed: 10/25/2022]
Abstract
Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex is a relatively non-invasive technique with putative therapeutic effects in major depression. However, the exact neurophysiological basis of these effects needs further clarification. Therefore, we studied the impact of ten daily sessions of left, dorsolateral prefrontal rTMS on motor cortical excitability, as revealed by transcranial magnetic stimulation-elicited motor-evoked potentials in 30 patients. As compared to the non-responders, responders (33%) showed changes in parameters pointing towards a reduced cortical excitability. These results suggest that repetitive transcranial magnetic stimulation of the dorsolateral, prefrontal cortex may have inhibitory effects on motor cortical neuronal excitability in patients with major depressive disorder. Furthermore, measurement of motor cortical excitability may be a useful tool for investigating and monitoring inhibitory brain effects of antidepressant stimulation techniques like rTMS.
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Affiliation(s)
- Malek Bajbouj
- Department of Psychiatry, Charité-University Medicine Berlin, Campus Benjamin Franklin, Eschenallee 3, 14050 Berlin, Germany.
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559
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Begum T, Mima T, Oga T, Hara H, Satow T, Ikeda A, Nagamine T, Fukuyama H, Shibasaki H. Cortical mechanisms of unilateral voluntary motor inhibition in humans. Neurosci Res 2005; 53:428-35. [PMID: 16213048 DOI: 10.1016/j.neures.2005.09.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Revised: 08/25/2005] [Accepted: 09/06/2005] [Indexed: 11/26/2022]
Abstract
While motor control is very often a goal-oriented event, little is known about the mechanisms underlying the termination of motor performance. To investigate what type of cortical activation underlies the muscle relaxation required to terminate the act, we performed single- and double-pulse transcranial magnetic stimulation (TMS) studies during voluntary muscle relaxation in nine normal volunteers. Subjects maintained a weak isometric contraction of the right first dorsal interosseous muscle (FDI), and either increased the level of contraction (Contraction), terminated the contraction (Relaxation), or maintained it (No-go) depending on a visual cue. Motor evoked potentials (MEP) and the silent period (SP) were recorded from the FDI during motor activity. To measure intra-cortical inhibition (ICI), we also performed double-pulse TMS, applying subthreshold conditioning stimuli at interstimulus intervals of 2 ms. When single-pulse TMS was given just prior to muscle relaxation (-21 to -70 ms), the MEP was reduced while the SP was unchanged. Intra-cortical inhibition was smaller just prior to the muscle relaxation. Unilateral voluntary muscle relaxation may not be associated with activation of the intracortical inhibitory system, but rather with the possible excitation of the corticospinal system, which can inhibit motoneurons disynaptically. These findings suggest that multiple inhibitory mechanisms act in diverse ways to achieve motor inhibition.
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Affiliation(s)
- Tahamina Begum
- Human Brain Research Center, Kyoto University Graduate School of Medicine, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
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560
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Benwell NM, Sacco P, Hammond GR, Byrnes ML, Mastaglia FL, Thickbroom GW. Short-interval cortical inhibition and corticomotor excitability with fatiguing hand exercise: a central adaptation to fatigue? Exp Brain Res 2005; 170:191-8. [PMID: 16328285 DOI: 10.1007/s00221-005-0195-7] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Accepted: 08/10/2005] [Indexed: 10/25/2022]
Abstract
The central processes occurring during fatiguing exercise are not well understood, however transcranial magnetic stimulation (TMS) studies have reported increases both in corticomotor excitability, as measured by the motor-evoked potential (MEP) amplitude, and in long-interval intracortical inhibition, as measured by the duration of the post-MEP silent period. To determine whether short-interval cortical inhibition (SICI) is modulated by fatiguing exercise, we used single and paired-pulse TMS to measure MEP amplitude and SICI for the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles of the hand during, and for 20 min after, a 10-min intermittent maximal voluntary abduction of the index finger designed to fatigue the FDI muscle. For the FDI, the index of SICI increased at the onset of exercise (from 0.25+/-0.05 to 0.55+/-0.11, P < 0.05) and then decreased progressively as force declined. At the beginning of recovery, SICI again increased (0.57+/-0.11, P < 0.05) and remained elevated for the 20-min recovery period. In contrast, SICI for ADM did not change during or after exercise. MEP amplitude for both the FDI and ADM increased above baseline during exercise and then decreased below baseline during the recovery period. These results demonstrate that there are significant changes in SICI during and after a fatiguing exercise protocol that are isolated to the representation of the fatigued muscle. The inter-relationship between the changes in excitation and inhibition suggests the presence of a measured and adaptive process of modulation in central excitation and inhibition acting to increase corticomotor drive to the exercising muscle as fatigue is developing.
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Affiliation(s)
- Nicola M Benwell
- Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands, WA, 6009, Australia
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561
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Affiliation(s)
- Robert Chen
- Division of Neurology and Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, ON M5T 2S8, Canada.
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562
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Sofuoglu M, Mouratidis M, Yoo S, Culligan K, Kosten T. Effects of tiagabine in combination with intravenous nicotine in overnight abstinent smokers. Psychopharmacology (Berl) 2005; 181:504-10. [PMID: 15983800 DOI: 10.1007/s00213-005-0010-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2004] [Accepted: 03/28/2005] [Indexed: 11/29/2022]
Abstract
RATIONALE Preclinical studies suggest that medications enhancing the brain gamma amino butyric acid (GABA) system attenuate the rewarding effects of stimulants including nicotine. These preclinical studies have not been followed up in systematic human studies. OBJECTIVES This study was conducted to examine the effects of a GABAergic medication, tiagabine, on acute physiological and subjective effects of intravenous (i.v.) nicotine and on tobacco withdrawal symptoms in overnight abstinent smokers. The proposed mechanism of action for tiagabine is selective inhibition of GABA transporter type I, which leads to increases in synaptic GABA levels. METHODS Eight male and four female smokers participated in a double-blind, placebo-controlled, crossover study. In each of three experimental sessions, participants were treated orally with a single 4- or 8-mg dose of tiagabine or placebo. Two hours following the medication treatment, participants received i.v. saline, followed 30 min later by 1.5 mg/70 kg i.v. nicotine. RESULTS Tiagabine treatment did not affect the heart rate or blood pressure changes induced by nicotine. There was a significant treatment effect for the subjective responses to nicotine, such that tiagabine, compared to placebo, attenuated the ratings of "good effects" and "drug liking." Tiagabine treatment at 8 mg attenuated the craving for cigarettes and enhanced the cognitive performance in the Classical Stoop Tests, compared to placebo or 4 mg tiagabine condition. CONCLUSIONS These results suggest that GABA enhancing medication tiagabine may reduce the rewarding effects of nicotine and improve cognitive performance in abstinent smokers. The utility of GABA medications for smoking cessation needs to be examined further in controlled clinical trials.
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Affiliation(s)
- Mehmet Sofuoglu
- Department of Psychiatry, VA Connecticut Healthcare System, Yale University, 950 Campbell Ave., Bldg. 36/116A4, West Haven, CT 06516, USA.
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563
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Tsai CH, Chang FC, Lu CS, Lee ST, Huang YT, Lu MK, Chen RS, Wu T, Lee JD, Weng YH, Chang HC. Pallidotomy effect on the cortical excitability in patients with severe Parkinson's disease. Mov Disord 2005; 20:463-470. [PMID: 15593137 DOI: 10.1002/mds.20344] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Surgical lesions in the medial pallidum have been shown to ameliorate motor deficits in patients with Parkinson's disease (PD). It is believed that interruption of the pallidothalamocortical projections to the motor cortex is required for the satisfactory results. In this report, we adopt cortico-cortical inhibition as the tool to assess the pallidotomy effect on cortical excitability in PD. Interstimulus interval between 1 and 15 msec were investigated. The average peak-to-peak amplitude was measured and calculated at each delay. A total of 8 patients (M:F = 4:4) 54.9 years of age (SD = 9.6) and 10 controls were recruited for the study. In the controls, the inhibitory phenomenon was observed from the 1-msec to the 4-msec delay points and the maximal inhibition was at the 3-msec delay point (33.69% +/- 6.50% of the control response). Mild facilitation was noticed since the 5-msec delay point and thereafter. In patients before operation, a similar trend of inhibition was also observed in the initial 4 msec with the maximal inhibition also at the 3-msec delay point (64.66 +/- 6.77% of the control response). In the postoperative group, the short interstimulus interval inhibition can no longer be observed and the conditioned response was 95.06 +/- 23.68% of the control at the 3-msec delay point. The suppression was gone at and after the 7-msec delay point. Results of repeated-measures analysis of variance show a significant difference among the controls and PD patients before and 3 months after pallidotomy (F = 3.40, P = 0.05). Post hoc examination revealed a significant difference between the controls and PD patients 3 months after pallidotomy at the 3-msec delay point (P = 0.004). However, no correlation was observed between the 3-msec inhibition and the Unified Parkinson's Disease Rating Scale Motor score or the dyskinesia score. The results suggest that pallidotomy can modulate the cortical inhibitory circuitry in patients with PD.
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Affiliation(s)
- Chon-Haw Tsai
- Neuroscience Laboratory, Department of Neurology, China Medical University Hospital, Taichung, Taiwan, Republic of China
- Institute of Medical Science, China Medical University, Taichung, Taiwan, Republic of China
| | - Fang-Chia Chang
- Neuroscience Laboratory, Department of Neurology, China Medical University Hospital, Taichung, Taiwan, Republic of China
| | - Chin-Song Lu
- Movement Disorders Unit, Department of Neurology, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China
| | - Shih-Tseng Lee
- Department of Neurosurgery, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China
| | - Yu-Ting Huang
- Movement Disorders Unit, Department of Neurology, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China
| | - Ming-Kuei Lu
- Neuroscience Laboratory, Department of Neurology, China Medical University Hospital, Taichung, Taiwan, Republic of China
| | - Rou-Shayn Chen
- Movement Disorders Unit, Department of Neurology, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China
| | - Tony Wu
- Movement Disorders Unit, Department of Neurology, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China
| | - Jiann-Der Lee
- Department of Electrical Engineering, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China
| | - Yi-Hsin Weng
- Movement Disorders Unit, Department of Neurology, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China
| | - Hsiu-Chen Chang
- Movement Disorders Unit, Department of Neurology, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China
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564
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King NKK, Kuppuswamy A, Strutton PH, Davey NJ. Estimation of cortical silent period following transcranial magnetic stimulation using a computerised cumulative sum method. J Neurosci Methods 2005; 150:96-104. [PMID: 16105686 DOI: 10.1016/j.jneumeth.2005.06.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 06/06/2005] [Accepted: 06/07/2005] [Indexed: 11/24/2022]
Abstract
The cortical silent period (CSP) following transcranial magnetic stimulation (TMS) of the motor cortex can be used to measure intra-cortical inhibition and changes in a number of important pathologies affecting the central nervous system. The main drawback of this technique has been the difficulty in accurately identifying the onset and offset of the cortical silent period leading to inter-observer variability. We developed an automated method based on the cumulative sum (Cusum) technique to improve the determination of the duration and area of the cortical silent period. This was compared with experienced raters and two other automated methods. We showed that the automated Cusum method reliably correlated with the experienced raters for both duration and area of CSP. Compared with the automated methods, the Cusum also showed the strongest correlation with the experienced raters. Our results show the Cusum method to be a simple, graphical and powerful method of detecting low-intensity CSP that can be easily automated using standard software.
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Affiliation(s)
- Nicolas K K King
- Department of Movement and Balance, Division of Neuroscience, Imperial College, Charing Cross Campus, London W6 8RP, UK.
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565
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Gerdelat-Mas A, Loubinoux I, Tombari D, Rascol O, Chollet F, Simonetta-Moreau M. Chronic administration of selective serotonin reuptake inhibitor (SSRI) paroxetine modulates human motor cortex excitability in healthy subjects. Neuroimage 2005; 27:314-22. [PMID: 16019236 DOI: 10.1016/j.neuroimage.2005.05.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2004] [Revised: 04/12/2005] [Accepted: 05/09/2005] [Indexed: 10/25/2022] Open
Abstract
The aim of the study was to investigate the effect of chronic administration of paroxetine (selective serotonin reuptake inhibitor: SSRI) on motor cortex excitability in healthy subjects by means of transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI) and behavioral motor tests. In a randomized, double-blind, crossover study, twenty-one right-handed subjects received 20 mg daily of either paroxetine or a placebo over a period of 30 days separated by a period of 3 months wash-out. The TMS study is presented here correlated with some results of the motor behavior study (finger tapping test) and the fMRI study (primary sensorimotor cortex (S1M1) volume of activation). TMS was used to test motor threshold (MT), motor evoked potential recruitment curve (RC), cortical silent period (CSP) and paired-pulse intracortical inhibition and facilitation (ICI, ICF). Chronic administration of paroxetine did not modulate ICI or CSP but induced a significant enhancement of mean ICF (ANOVA P=0.04), which significantly correlated with increase of speed in a finger tapping test (P=0.02). This suggests a modulation of cortical interneuronal excitatory pathways without changes in the excitability of cortical inhibitory GABAergic interneurons. A decrease of RC (ANOVA P=0.05) was also observed after 30 days intake of paroxetine in comparison with placebo and was associated with changes of fMRI activation intensity (left S1M1 hypoactivation, ), without changes of S1M1 activation volume. Finally, the different modulation of RC and ICF after chronic administration of paroxetine compared to single dose (opposite effects) emphasizes the different pharmacological action of the drug at cortical level depending on its acute or long-term administration.
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566
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Korchounov A, Ilic TV, Schwinge T, Ziemann U. Modification of motor cortical excitability by an acetylcholinesterase inhibitor. Exp Brain Res 2005; 164:399-405. [PMID: 15991031 DOI: 10.1007/s00221-005-2326-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2004] [Accepted: 02/23/2005] [Indexed: 11/28/2022]
Abstract
Acetylcholine powerfully modulates the excitability of neocortical neurones and networks. This study applied focal transcranial magnetic stimulation (TMS) to eight healthy subjects to test the effects of a single oral dose of 40 mg tacrine, an acetylcholinesterase inhibitor, on motor cortical excitability. It was found that tacrine decreased short-interval intracortical inhibition, and increased intracortical facilitation and short-interval intracortical facilitation. Motor thresholds, motor evoked potential amplitude, cortical silent period (CSP) duration, and measures of spinal and neuromuscular excitability remained unchanged. The effects peaked at 2-6 h and fully reversed after 24 h. All effects can be explained by a reduction of motor cortical GABAergic inhibitory neurotransmission via activation of presynaptic muscarinic M2 receptors, but other more complex mechanisms may also have contributed and are discussed. The findings predict that acetylcholine has the potential to promote plasticity and learning in human motor cortex.
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Affiliation(s)
- Alexei Korchounov
- Motor Cortex Laboratory, Department of Neurology, Johann Wolfgang Goethe-University of Frankfurt, Schleusenweg 2-16, 60528, Frankfurt am Main, Germany
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567
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Abstract
Whether there is a projection from the primary motor cortex (M1) to upper facial muscles and how the facial M1 area is modulated by intracortical inhibitory and facilitatory circuits remains controversial. To assess these issues, we applied transcranial magnetic stimulation (TMS) to the M1 and recorded from resting and active contralateral (C-OOc) and ipsilateral orbicularis oculi (I-OOc), and contralateral (C-Tr) and ipsilateral triangularis (I-Tr) muscles in 12 volunteers. In five subjects, the effects of stimulating at different scalp positions were assessed. Paired TMS at interstimulus intervals (ISIs) of 2 ms were used to elicit short interval intracortical inhibition (SICI) and ISI of 10 ms for intracortical facilitation (ICF). Long interval intracortical inhibition (LICI) was evaluated at ISIs between 50 and 200 ms, both at rest and during muscle activation. The silent period (SP) was also determined. C-OOc and I-OOc responses were recorded in all subjects. The optimal position for eliciting C-OOc responses was lateral to the hand representation in all subjects and MEP amplitude markedly diminished when the coil was placed 2 cm away from the optimal position. For the I-OOc, responses were present in more scalp sites and the latency decreased with more anterior placement of the coil. C-Tr response was recorded in 10 out of 12 subjects and the I-Tr muscle showed either no response or low amplitude response, probably due to volume conduction. SICI and ICF were present in the C-OOc and C-Tr, but not in the I-OOc muscle. Muscle activation attenuated SICI and ICF. LICI at rest showed facilitation at 50 ms ISI in all muscles, but there was no significant inhibition at other ISIs. There was no significant inhibition or facilitation with the LICI protocol during muscle contraction. The SP was present in the C-OOc, C-Tr and I-OOc muscles and the mean durations ranged from 92 to 104 ms. These findings suggest that the I-OOc muscle response is probably related to the first component (R1) of the blink reflex. There is M1 projection to the contralateral upper and lower facial muscles in humans and the facial M1 area is susceptible to cortical inhibition and facilitation, similar to limb muscles.
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Affiliation(s)
- Guillermo O Paradiso
- The Krembil Neuroscience Centre and Toronto Western Research Institute, Ontario M5T 2S8, Canada
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568
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Abstract
When engaged by a stimulus, different nodes of a neural circuit respond in a coordinated fashion. We often ask whether there is a cause and effect in such interregional interactions. This paper proposes that we can infer causality in functional connectivity by employing a 'perturb and measure' approach. In the human brain, this has been achieved by combining transcranial magnetic stimulation (TMS) with positron emission tomography (PET), functional magnetic resonance imaging or electroencephalography. Here, I will illustrate this approach by reviewing some of our TMS/PET work, and will conclude by discussing a few methodological and theoretical challenges facing those studying neural connectivity using a perturbation.
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Affiliation(s)
- Tomás Paus
- Brain & Body Centre, University of Nottingham, UK.
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569
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Ilić TV, Petković S. [Principles and application of transcranial magnetic stimulation]. VOJNOSANIT PREGL 2005; 62:389-402. [PMID: 15913044 DOI: 10.2298/vsp0505389i] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Affiliation(s)
- Tihomir V Ilić
- Vojnomedicinska akademija, Klinika za neurologiju, Crnotravska, Beograd, Srbija i Crna Gora. tihoilic@EUnet
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570
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Boutros NN, Lisanby SH, McClain-Furmanski D, Oliwa G, Gooding D, Kosten TR. Cortical excitability in cocaine-dependent patients: a replication and extension of TMS findings. J Psychiatr Res 2005; 39:295-302. [PMID: 15725428 DOI: 10.1016/j.jpsychires.2004.07.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Accepted: 07/02/2004] [Indexed: 11/23/2022]
Abstract
Cortical excitability can be assessed by transcranial magnetic stimulation (TMS). Previously we observed that TMS motor threshold (MT) was elevated in abstinent cocaine-dependent subjects. In the current study we aimed at replicating our initial finding, exploring other TMS-based measures of excitability, and examining association with personality characteristics. Nineteen cocaine-dependent and 12 healthy control subjects were examined. Resting and activated motor thresholds (RMT and AMT) and duration of the cortical silent period (CSP) were examined. The Cocaine Experience Questionnaire (CEQ) was administered to assess cocaine-induced psychotic symptoms. The relationship between Minnesota Multiphasic Personality Inventory (MMPI) scales and cortical excitability measures was also examined. AMT was significantly elevated in cocaine-dependent subjects on both hemispheres. RMT was also significantly elevated on the right hemisphere. No CSP changes were noted. Patients with cocaine-induced paranoia had longer CSPs on the right hemisphere compared to subjects reporting no paranoid experiences. The patients displayed significantly elevated scores on several MMPI scales, though the scale scores did not correlate with cortical excitability measures. These data support our initial finding of decreased cortical excitability in abstinent cocaine-dependent subjects. We interpret this finding as a compensatory mechanism against the stimulating and epileptogenic effects of cocaine.
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Affiliation(s)
- Nashaat N Boutros
- Department of Psychiatry, c/o VA-Connecticut Healthcare System, Yale University School of Medicine, 950 Campbell Avenue, 116A West Haven, CT 06516, USA.
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571
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Abstract
The aim of this study was to confirm the excitability profile of human cortical circuits on the motor evoked potential (MEP) and the silent period (SP) after paired transcranial magnetic stimulation (TMS) with variable interstimulus intervals (ISI), and to compare the time courses of MEP and SP after paired TMS at variable ISIs. MEPs were elicited at the hypothenar muscles at rest, and during tonic muscle contraction by applying paired TMS to the motor cortex. The authors measured the MEP amplitude during rest and the duration of SP during tonic muscle contraction at various ISIs. The response to paired stimuli was inhibited by an ISI of 15 ms and facilitated by an ISI of 1020 ms. The SP at an ISI of 15 ms was shorter than that at the single suprathreshold stimulus, but the SP at an ISI of 1525 ms was longer than this. A significant correlation was observed between the MEP amplitude and the duration of SP at ISIs of 120 ms and for a CS of 80% of threshold. These results may provide useful data for the study of the function of cortical excitability in disease states and suggest that the neural circuits underlying MEP and SP differ partly.
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Affiliation(s)
- Dai-Youl Kim
- Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Bundang Hospital Seoul, Republic of Korea
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572
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Münchau A, Langosch JM, Gerschlager W, Rothwell JC, Orth M, Trimble MR. Mirtazapine increases cortical excitability in healthy controls and epilepsy patients with major depression. J Neurol Neurosurg Psychiatry 2005; 76:527-33. [PMID: 15774440 PMCID: PMC1739580 DOI: 10.1136/jnnp.2004.037010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Epilepsy is often complicated by depression requiring antidepressant treatment. Such treatment might be proconvulsive. OBJECTIVE To examine the effects of the noradrenergic and specific serotonergic antidepressant mirtazapine on motor cortex excitability in epilepsy patients with depression and in healthy controls, using transcranial magnetic stimulation (TMS). METHODS Seven clinically depressed epilepsy patients treated with anticonvulsant drugs and six healthy volunteers were studied. Before intake of mirtazapine and 24 hours afterwards (and also three weeks afterwards in the patients), the active and resting motor threshold (AMT, RMT), the size of the motor evoked potential (MEP), the cortical silent period (SP), and intracortical inhibition/facilitation and intracortical facilitatory I wave interactions were determined using single and paired pulse TMS. RESULTS At baseline, AMT and RMT were higher (p = 0.049 and p = 0.04, respectively) and the ratio SP duration/MEP area greater in patients (p = 0.041). In patients but not in healthy subjects AMT was lower 24 hours after intake of mirtazapine (p = 0.028). Mirtazapine had no significant effect on the MEP size, duration of the SP, or the ratio of SP duration to MEP size in patients. The duration of the SP was longer (p = 0.037) but the ratio of SP duration to MEP size remained similar in healthy subjects after mirtazapine. There were no significant differences in paired pulse measures between the two groups either at baseline or after mirtazapine. CONCLUSIONS Mirtazapine increased neuronal excitability of pyramidal tract axons in an activated state in both healthy controls and epilepsy patients with major depression.
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Affiliation(s)
- A Münchau
- Sobell Department of Motor Neuroscience and Movement Disorders, Dept. of Clinical and Experimental Epilepsy, Institute of Neurology, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK.
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573
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Inghilleri M, Conte A, Frasca V, Gilio F, Lorenzano C, Berardelli A. Synaptic potentiation induced by rTMS: effect of lidocaine infusion. Exp Brain Res 2005; 163:114-7. [PMID: 15940502 DOI: 10.1007/s00221-005-2225-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Accepted: 12/09/2004] [Indexed: 01/04/2023]
Abstract
Repetitive transcranial magnetic stimulation (rTMS) delivered at various intensities and frequencies excites cortical motor areas. Trains of stimuli (at 5-Hz frequency, and suprathreshold intensity) progressively increase the size of motor evoked potentials (MEPs) and the duration of the cortical silent period (CSP) in normal subjects. Because antiepileptic drugs, acting mainly on sodium channels, depress MEP facilitation during rTMS, we suggested that rTMS trains facilitate the MEP size by inducing synaptic potentiation primarily involving voltage-gated sodium channels. The aim of this study was to evaluate the effect of lidocaine-a drug that acts selectively on sodium channels-on the rTMS-induced changes in cortical excitability. We tested the changes in motor threshold, MEP size, CSP duration evoked by focal rTMS and the M-wave amplitude in healthy subjects before and after lidocaine infusion. Lidocaine abolished the normal rTMS-induced facilitation of MEPs but left the other rTMS variables and the M-wave unchanged. Our results suggest that the MEP facilitation related to rTMS-induced synaptic potentiation results from an increase in cortical excitatory interneuron excitability that involves voltage-gated sodium channels.
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Affiliation(s)
- M Inghilleri
- Department of Neurological Sciences, University of Rome La Sapienza, Viale dell'Università, 30., 00185 Rome, Italy.
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574
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Kimiskidis VK, Papagiannopoulos S, Sotirakoglou K, Kazis DA, Kazis A, Mills KR. Silent period to transcranial magnetic stimulation: construction and properties of stimulus-response curves in healthy volunteers. Exp Brain Res 2005; 163:21-31. [PMID: 15690156 DOI: 10.1007/s00221-004-2134-4] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Accepted: 10/07/2004] [Indexed: 11/28/2022]
Abstract
Silent period (SP) is widely used in transcranial magnetic stimulation studies. Methodologically, SP is usually elicited at stimulus intensities corresponding to a certain percentage of corticomotor threshold. Because this approach might lead to factitious SP changes, the present study was designed to develop, in a stepwise manner, a method for investigating SP independently of corticomotor threshold. First, stimulus-response (S-R) curves of SP against stimulus intensity (SI) were constructed and quantitatively described in healthy volunteers. Second, various methodological issues such as the optimum model for describing the relationship between SP duration and SI and the importance of the type of stimulating coil were addressed. Finally, the proposed method and a commonly used method (eliciting SPs at 130% MT SI) were directly compared for a group of epileptic patients for whom administration of oxcarbazepine resulted in significant corticomotor threshold elevation. Twenty-one subjects (eleven females, median age, 38 years) were studied. SPs were obtained with a figure-of-eight coil using a standardized procedure (recording, FDI). Pilot experiments indicated that at least four trials were required, at each intensity level, to estimate the mean SP duration within 10% of the true mean. Therefore, SPs were determined from the average of four trials with 5% increments from 5 to 100% maximum SI. In a second set of experiments, SPs were obtained for fifteen subjects using a circular coil. In a third set of experiments, eight epileptic patients were studied before and after administration of oxcarbazepine (mean dose 1553 mg, range 900-1800 mg). The S-R curves were fitted to a Boltzman function and to first-order to fourth-order polynomial and sigmoid functions. The Boltzman function described the data accurately (R2=0.947-0.990). In addition, direct comparison of the six models with an F-test proved the superiority of the first. The best-fit parameters of the reference curve, i.e. the maximum and minimum values, the slope, and V50 (the SI at which SP duration is halfway between Min and Max) were 230.8+/-3.31 ms (x+/-SEM), -11.51+/-3.31 ms, 11.56+/-0.65%, and 49.82+/-0.65%, respectively. When the curves obtained with the circular coil were compared with those obtained with the figure-of-eight coil, there were differences between V50 (51.69+/-0.72 vs 47.95+/-0.82, P<0.001) and SP threshold (31.15 vs 24.77, P<0.01) whereas the other best-fit values did not differ significantly. Oxcarbazepine increased corticomotor threshold from 45.3+/-5.8% at baseline to 59.4+/-10.4% (P<0.001). According to the commonly used method, the drug significantly prolonged SP (from 117.6+/-42.4 ms to 143.5+/-46.5 ms, P<0.001) and, consequently, enhanced brain inhibition. In contrast, study of the SP curves led to the conclusion that oxcarbazepine does not affect the Max value and slope but significantly increases V50 and SP threshold (from 54.5+/-4.9% to 59.9+/-7.2% and from 29.1+/-6.4% to 34.6+/-6.8%, respectively, P<0.01). These findings imply that oxcarbazepine does not enhance brain inhibitory mechanisms. Thus, in situations characterized by significant changes in corticomotor threshold the proposed method provides results clearly different from a commonly used approach. It is concluded that S-R curves obtained with a figure-of-eight coil in 5% increments and fitted to a Boltzman function provide an accurate, comprehensive, and clinically applicable method for exploring SP.
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Affiliation(s)
- V K Kimiskidis
- Department of Neurology III, G. Papanikolaou Hospital, Aristotle University of Thessaloniki, 57010 Thessaloniki, Greece.
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575
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Kukaswadia S, Wagle-Shukla A, Morgante F, Gunraj C, Chen R. Interactions between long latency afferent inhibition and interhemispheric inhibitions in the human motor cortex. J Physiol 2005; 563:915-24. [PMID: 15649986 PMCID: PMC1665612 DOI: 10.1113/jphysiol.2004.080010] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Various inhibitory pathways exist in the human brain which are crucial in modulating motor cortex output and they can be investigated non-invasively using transcranial magnetic stimulation. Interhemispheric inhibition (IHI) is one form of cortical inhibition. It can be elicited by stimulation of the opposite motor cortex at interstimulus intervals (ISIs) of 10 ms (IHI10) or 40 ms (IHI40) and inhibitions at these intervals are probably mediated by different mechanisms. Peripheral sensory stimulation can also inhibit the motor cortex. Median nerve stimulation produces long latency afferent inhibition (LAI) at ISI 200 ms. LAI inhibits another form of cortical inhibition known as long interval intracortical inhibition (LICI) and a study that examined the interaction between IHI10 and LICI hypothesized that they are mediated by an overlapping population of inhibitory neurones. We tested this hypothesis by examining the interaction between IHI10, IHI40 and LAI. With increasing test MEP amplitude LAI, IHI10 and IHI40 all decreased. There was no correlation between the strength of LAI, IHI10 and IHI40. In the presence of LAI, IHI10 was slightly but significantly reduced compared to IHI10 alone. There was no correlation between the reduction in IHI10 in the presence of LAI and the strength of LAI or IHI10. In the presence of LAI, IHI40 was significantly reduced compared to IHI40 alone. LAI produced a greater decrease in IHI40 than in IHI10. The decrease in IHI40 in the presence of LAI strongly correlated with the strength of LAI but not with the strength of IHI40. Reducing the strength of LAI, IHI10 and IHI40 still resulted in similar interaction between IHI10 and LAI but markedly decreased the effect of LAI on IHI40. We conclude that LAI and IHI10 do not directly inhibit each other but LAI probably inhibits IHI40. LICI is more likely to be related to IHI40 than to IHI10.
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Affiliation(s)
- Sadiya Kukaswadia
- Division of Neurology, Krembil Neuroscience Centre and Toronto Western Research Institute, University Health Network, University of Toronto, Ontario, Canada
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576
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Lefaucheur JP. Stimulation du cortex moteur, Parkinson et dystonie : que nous enseigne la stimulation magnétique transcrânienne? revue de la littérature. Rev Neurol (Paris) 2005; 161:27-41. [PMID: 15677999 DOI: 10.1016/s0035-3787(05)84971-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
INTRODUCTION Over the last few years, deep brain stimulation techniques, with targets such as the subthalamic nucleus or the pallidum, have bee found to be beneficial in the treatment of Parkinson's disease and dystonia. Conversely, therapeutic strategies of cortical stimulation have not yet been validated in these diseases, although they are known to be associated with various cortical dysfunctions. Transcranial magnetic stimulation (TMS) is a valuable tool for non-invasive study of the role played by the motor cortex in the pathophysiology of movement disorders, in particular by assessing various cortical excitability determinants using single or paired pulse paradigms. In addition, repetitive TMS (rTMS) trains can be used to study the effects of transient activity changes of a targeted cortical area. BACKGROUND Studies with TMS revealed significant motor cortex excitability changes, particularly regarding intracortical inhibitory pathways, both in Parkinson's disease and in dystonia, and these changes can be distinguished owing to the resting state or to the phases of movement preparation or execution. However, more specific correlation between electrophysiological features and clinical symptoms remains to be established. In addition, the stimulation of various cortical targets by rTMS protocols applied at low or high frequencies have induced some clear clinical effects. PERSPECTIVES The TMS effects are and will remain applied in movement disorders to better understand the role played by the motor cortex, to assess various types of treatment and appraise the therapeutic potential of cortical stimulation. CONCLUSION TMS provides evidence for motor cortex dysfunction in Parkinson's disease or dystonia. Moreover, rTMS results have opened new perspectives for therapeutic strategies of implanted cortical stimulation. By these both aspects, TMS techniques show their usefulness in the assessment of movement disorders.
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Affiliation(s)
- J-P Lefaucheur
- Service de Physiologie, Explorations Fonctionnelles, Hôpital Henri Mondor, Créteil.
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577
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Lefaucheur JP. Motor cortex dysfunction revealed by cortical excitability studies in Parkinson's disease: influence of antiparkinsonian treatment and cortical stimulation. Clin Neurophysiol 2004; 116:244-53. [PMID: 15661100 DOI: 10.1016/j.clinph.2004.11.017] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2004] [Revised: 10/20/2004] [Accepted: 11/18/2004] [Indexed: 11/16/2022]
Abstract
Single or paired pulse paradigms of transcranial magnetic stimulation (TMS) provide several parameters to test motor cortex excitability, such as motor threshold (MT), motor evoked potential (MEP) amplitude, electromyographic silent period to cortical stimulation (CSP) and intracortical facilitation (ICF) or inhibition (ICI). Various changes in TMS parameters, revealing motor cortex dysfunction, were found in patients with Parkinson's disease (PD). For instance, low MT and increased MEP size disclosed an enhanced corticospinal motor output at rest, while reduced ICF and failure of MEP size increase during contraction suggested defective facilitatory cortical inputs, particularly for movement execution. Inhibitory cortical pathways were also found less excitable at rest (reduced ICI) and sometimes during contraction (shortened CSP). By restoring cortical inhibition, dopaminergic drugs and deep brain stimulation probably overcome the difficulty to focus neuronal activity onto the appropriate network required for a specific motor task. The application of repetitive TMS trains over motor cortical areas also showed some effect on cortical excitability, opening perspectives to consider the motor cortex as a target for therapeutic neuromodulation in PD. However, systematic studies of cortical excitability remained to be performed in large series of patients with PD, taking into account disease stage, clinical symptoms and medication influence.
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Affiliation(s)
- Jean-Pascal Lefaucheur
- Service de Physiologie--Explorations Fonctionnelles, Hôpital Henri Mondor, Assistance Publique--Hôpitaux de Paris, 51 avenue de Lattre de Tassigny, 94010 Créteil, France.
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578
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McKay WB, Lee DC, Lim HK, Holmes SA, Sherwood AM. Neurophysiological examination of the corticospinal system and voluntary motor control in motor-incomplete human spinal cord injury. Exp Brain Res 2004; 163:379-87. [PMID: 15616810 DOI: 10.1007/s00221-004-2190-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2004] [Accepted: 10/06/2004] [Indexed: 10/26/2022]
Abstract
This study employed neurophysiological methods to relate the condition of the corticospinal system with the voluntary control of lower-limb muscles in persons with motor-incomplete spinal cord injury. It consisted of two phases. In a group of ten healthy subjects, single and paired transcranial magnetic stimulation (TMS) of the motor cortex was used to study the behavior of the resulting motor evoked potentials (MEP) in lower-limb muscles. Interstimulus intervals (ISIs) of 15-100 ms were examined for augmentation of test MEPs by threshold or subthreshold conditioning stimuli. The second phase of this study examined eight incomplete spinal cord injured (iSCI) subjects, American Spinal Injury Association Impairment Scale C (n = 5) and D (n = 3) in whom voluntary motor control was quantified using the surface EMG (sEMG) based Voluntary Response Index (VRI). The VRI is calculated to characterize relative output patterns across ten lower-limb muscles recorded during a standard protocol of elementary voluntary motor tasks. VRI components were calculated by comparing the distribution of sEMG in iSCI subjects with prototype patterns collected from 15 healthy subjects using the same rigidly administered protocol, The resulting similarity index (SI) and magnitude values provided the measure of voluntary motor control. Corticospinal system connections were characterized by the thresholds for MEPs in key muscles. Key muscles were those that function as the prime-movers, or agonists for the voluntary movements from which the VRI data were calculated. Results include healthy-subject data that showed significant increases in conditioned MEP responses with paired stimuli of 15-50 ms ISI. Stimulus pairs of 75 and 100 ms showed no increase in MEP peak amplitude over that of the single-pulse conditioning stimulus alone, usually no response. For the iSCI subjects, 42% of the agonists responded to single-pulse TMS and 25% required paired-pulse TMS to produce an MEP. American Spinal Injury Association Impairment Scale component motor scores for agonist muscles, Quadriceps, Tibialis Anterior, and Triceps Surae, were significantly lower where MEPs could not be obtained (p < 0.05). VRI values were also significantly lower for motor tasks with agonists that had no resting MEP (p < 0.01). Therefore, the presence of a demonstrable connection between the motor cortex and spinal motor neurons in persons with SCI was related to the quality of post-injury voluntary motor control as assessed by the VRI.
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Affiliation(s)
- W B McKay
- Baylor College of Medicine, Houston, TX, USA
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579
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Oliveri M, Koch G, Torriero S, Caltagirone C. Increased facilitation of the primary motor cortex following 1 Hz repetitive transcranial magnetic stimulation of the contralateral cerebellum in normal humans. Neurosci Lett 2004; 376:188-93. [PMID: 15721219 DOI: 10.1016/j.neulet.2004.11.053] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 10/27/2004] [Accepted: 11/18/2004] [Indexed: 11/27/2022]
Abstract
Connections between the cerebellum and the contralateral motor cortex are dense and important, but their physiological significance is difficult to measure in humans. We have studied a group of 10 healthy subjects to test whether a modulation of the excitability of the left cerebellum can affect the excitability of the contralateral motor cortex. We used repetitive transcranial magnetic stimulation (rTMS) at 1 Hz frequency to transiently depress the excitability of the left cerebellar cortex and paired-pulse TMS testing of intracortical inhibition (ICI) and intracortical facilitation (ICF) to probe the excitability of cortico-cortical connections in the right motor cortex. The cortical silent period was also measured before and after cerebellar rTMS. Motor evoked potentials (MEPs) were significantly larger after than before conditioning rTMS trains (p < 0.01). Moreover, left cerebellar rTMS increased the ICF of the right motor cortex as measured with paired-pulses separated by an interstimulus interval (ISI) of 15 ms. The effect lasted for up to 30 min afterward and was specific for the contralateral (right) motor cortex. The cortical silent period was unaffected by cerebellar rTMS. The implication is that rTMS of the cerebellar cortex can shape the flowing of inhibition from Purkinje cells toward deep nuclei, thereby increasing the excitability of interconnected brain areas.
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Affiliation(s)
- Massimiliano Oliveri
- Laboratorio di Neurologia Clinica e Comportamentale, Unità di Neuropsicologia Sperimentale, Fondazione Santa Lucia IRCCS, Via Ardeatina, 306, 00179 Rome, Italy.
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580
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Weiss T, Miltner WHR, Liepert J, Meissner W, Taub E. Rapid functional plasticity in the primary somatomotor cortex and perceptual changes after nerve block. Eur J Neurosci 2004; 20:3413-23. [PMID: 15610174 DOI: 10.1111/j.1460-9568.2004.03790.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mature human primary somatosensory cortex displays a striking plastic capacity to reorganize itself in response to changes in sensory input. Following the elimination of afferent return, produced by either amputation, deafferentation by dorsal rhizotomy, or nerve block, there is a well-known but little-understood 'invasion' of the deafferented region of the brain by the cortical representation zones of still-intact portions of the brain adjacent to it. We report here that within an hour of abolishing sensation from the radial and medial three-quarters of the hand by pharmacological blockade of the radial and median nerves, magnetic source imaging showed that the cortical representation of the little finger and the skin beneath the lower lip, whose intact cortical representation zones are adjacent to the deafferented region, had moved closer together, presumably because of their expansion across the deafferented area. A paired-pulse transcranial magnetic stimulation procedure revealed a motor cortex disinhibition for two muscles supplied by the unaffected ulnar nerve. In addition, two notable perceptual changes were observed: increased two-point discrimination ability near the lip and mislocalization of touch of the intact ulnar portion of the fourth finger to the neighbouring third finger whose nerve supply was blocked. We suggest that disinhibition within the somatosensory system as a functional correlate for the known enlargement of cortical representation zones might account for not only the 'invasion' phenomenon, but also for the observed behavioural correlates of the nerve block.
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Affiliation(s)
- Thomas Weiss
- Department of Biological and Clinical Psychology, Friedrich-Schiller-University Jena, Am Steiger 3 Haus 1, D-07743 Jena, Germany.
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581
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Rosenkranz K, Rothwell JC. The effect of sensory input and attention on the sensorimotor organization of the hand area of the human motor cortex. J Physiol 2004; 561:307-20. [PMID: 15388776 PMCID: PMC1665339 DOI: 10.1113/jphysiol.2004.069328] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Accepted: 09/15/2004] [Indexed: 12/18/2022] Open
Abstract
Sensory input can remodel representations in the sensory cortex, and this effect is heavily influenced by attention to the stimulus. Here we ask whether pure sensory input can also influence the spatial distribution of sensory effects on motor cortical hand area (sensorimotor organization) and whether this is modulated by attention. Sensorimotor organization was tested by applying short (1.5 s) periods of low amplitude vibration to single intrinsic hand muscles and measuring motor cortex excitability with transcranial magnetic stimulation (TMS). In healthy subjects, sensorimotor organization in the hand is focal, with input from one hand muscle increasing motor-evoked potentials (MEPs), decreasing short and increasing long-interval intracortical inhibition (SICI and LICI) in the vibrated muscle ('homotopic' effects) and having opposite effects on neighbouring muscles ('heterotopic' effects). Here we show that a 15 min intervention of vibration applied simultaneously to two hand muscles can lead to long-term (> 30 min) changes in the spatial pattern of sensorimotor interaction. The amount and direction of the effects depended on the subject's attention during the intervention: if subjects attended to both muscles when they were receiving simultaneous vibration, subsequent short-term vibration applied to one of them produced 'homotopic' effects on both muscles. 'Heterotopic' effects on a muscle not vibrated during the intervention were unaffected. If subjects did not attend to simultaneous vibration, subsequent short-term vibration of the muscles involved in the intervention no longer had any effect on them although the 'heterotopic' effects on a muscle not involved in the intervention were unchanged. We conclude that a 15 min period of pure sensory input can remodel the way that subsequent sensory inputs interact with motor output, that the effects are specific for the motor output to muscles involved in the intervention and that they are modulated by the subject's attention.
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Affiliation(s)
- Karin Rosenkranz
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, 8-11 Queen Square, London WC1N 3BG, UK.
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582
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Abstract
Plasticity of ligand-gated ion channels plays a critical role in nervous system development, circuit formation and refinement, and pathological processes. Recent advances have mainly focused on the plasticity of channels gated by excitatory amino acids, including their acclaimed role in learning and memory. These receptors, together with voltage-gated ion channels, have also been known to be subjected to a homeostatic form of plasticity that prevents destabilization of the neurone's function and that of the network during various physiological processes. To date, the plasticity of GABA(A) receptors has been examined mainly from a developmental and a pathological point of view. Little is known about homeostatic mechanisms governing their plasticity. This review summarizes some of the findings on the homeostatic plasticity of tonic and phasic inhibitory activity.
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Affiliation(s)
- Istvan Mody
- Department of Neurology, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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583
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Reis J, Wentrup A, Hamer HM, Mueller HH, Knake S, Tergau F, Oertel WH, Rosenow F. Levetiracetam influences human motor cortex excitability mainly by modulation of ion channel function—a TMS study. Epilepsy Res 2004; 62:41-51. [PMID: 15519131 DOI: 10.1016/j.eplepsyres.2004.08.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Revised: 06/24/2004] [Accepted: 08/03/2004] [Indexed: 11/29/2022]
Abstract
PURPOSE Levetiracetam (LEV) is a new compound with anticonvulsive efficacy in focal and generalized epilepsies. Recent in vitro studies suggest LEV to act as a selective N-type-calcium-channel blocker. METHODS We used transcranial magnetic stimulation (TMS) in order to investigate if ion-channel blockade is relevant to the inhibitory CNS effects of LEV in vivo and if motor thresholds (MTs) are a valid TMS parameter to detect this mode of action. In a double blind, placebo-controlled, crossover study, the effects of single oral doses of 500 and 2000 mg LEV on motor thresholds, recruitment curves (REC), cortical induced silent period (CSP) and on intracortical inhibition (ICI) and facilitation (ICF) were studied in 10 healthy subjects. RESULTS A significant increase of motor thresholds was noticed after 2000 mg LEV as compared to placebo. The recruitment curve showed a trend towards motor evoked potential (MEP) amplitude reduction after LEV. LEV had no significant effect on CSP or on intracortical excitability as measured by inhibition and facilitation. CONCLUSIONS We conclude that the modulation of ion-channel function, reflected by motor threshold elevation and a trend towards recruitment curve suppression, is relevant to the inhibitory CNS effects of LEV in vivo, and therefore, may contribute to the anticonvulsive efficacy of LEV. GABAergic or glutamatergic mechanisms seem to be less important in vivo as measured by TMS.
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Affiliation(s)
- Janine Reis
- Interdisciplinary Epilepsy-Center, Department of Neurology, Philipps-University, 35033 Marburg, Germany
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584
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Hoy KE, Fitzgerald PB, Bradshaw JL, Armatas CA, Georgiou-Karistianis N. Investigating the cortical origins of motor overflow. ACTA ACUST UNITED AC 2004; 46:315-27. [PMID: 15571773 DOI: 10.1016/j.brainresrev.2004.07.013] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2004] [Indexed: 11/22/2022]
Abstract
Motor overflow refers to the involuntary movements which may accompany the production of voluntary movements. While overflow is not usually seen in the normal population, it does present in children and the elderly, as well as those suffering certain neurological dysfunctions. Advancements in methodology over the last decade have allowed for more convincing conclusions regarding the cortical origins of motor overflow. However, despite significant research, the exact mechanism underlying the production of motor overflow is still unclear. This review presents a more comprehensive conceptualization of the theories of motor overflow, which have often been only vaguely defined. Further, the major findings are explored in an attempt to differentiate the competing theories of motor overflow production. This exploration is done in the context of a range of neurological and psychiatric disorders, in order to elucidate the possible underlying mechanisms of overflow.
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Affiliation(s)
- Kate E Hoy
- Experimental Neuropsychology Research Unit, Psychology Department, Monash University, Clayton 3800, Victoria, Australia.
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585
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Pierantozzi M, Marciani MG, Palmieri MG, Brusa L, Galati S, Caramia MD, Bernardi G, Stanzione P. Effect of Vigabatrin on motor responses to transcranial magnetic stimulation. Brain Res 2004; 1028:1-8. [PMID: 15518635 DOI: 10.1016/j.brainres.2004.06.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/09/2004] [Indexed: 11/23/2022]
Abstract
In this study, transcranial magnetic stimulation (TMS) of the hand primary motor area was used to test possible excitability changes induced by the administration of Vigabatrin (Gamma-Vinyl-gamma-aminobutryic acid;4-amino-hex-5-enoic acid; GVG), a selective GABAergic drug, on cortical inhibitory mechanisms in healthy subjects. In a group of 15 healthy volunteers, the level of motor cortical excitability was studied by means of paired-pulse TMS (p-TMS) protocols exploring the early (1-6 ms of interstimulus intervals, ISI) and the late cortical inhibition (20-250 ms ISI), and by evaluating the cortical silent period (CSP) duration obtained in response to single pulse stimulation of cortical motor area. In all participants TMS procedures were carried out before and after administering GVG for three consecutive days at a daily dosage of 50 mg/kg. Three months later, a third TMS recording session was repeated to investigate possible long-lasting GVG effects on cortical excitability. GVG induces relevant changes of cortical excitability consisting in an increase of late cortical inhibition in response to the long ISI p-TMS and in a prolonged duration of the CSP. No significant change in the early cortical inhibition was observed in response to the short ISI p-TMS. The analysis of peripheral motor excitability was also assessed, with no effects. The present electrophysiological data show that GVG is able to induce a significant increase of the late cortical inhibition, whereas it does not affect the early cortical inhibition. These data suggest that the great availability of synaptic GABA differently acts on the inhibitory circuitries controlled by different GABA-receptor subtypes.
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586
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Abstract
The application of a single dose of a CNS active drug with a well-defined mode of action on a neurotransmitter or neuromodulator system may be used for testing pharmaco-physiological properties of transcranial magnetic stimulation (TMS) measures of cortical excitability. Conversely, a physiologically well-defined single TMS measure of cortical excitability may be used as a biological marker of acute drug effects at the systems level of the cerebral cortex. An array of defined TMS measures may be used to study the pattern of effects of a drug with unknown or multiple modes of action. Acute drug effects may be rather different from chronic drug effects. These differences can also be studied by TMS measures. Finally, TMS or repetitive TMS by themselves may induce changes in endogenous neurotransmitters or neuromodulators. All these possible interactions are the focus of this in-depth review on TMS and drugs.
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Affiliation(s)
- Ulf Ziemann
- Motor Cortex Laboratory, Clinic of Neurology, Johann Wolfgang Goethe University Frankfurt, Schleusenweg 2-16, D-60528 Frankfurt am Main, Germany.
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587
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Sharshar T, Ross ET, Hopkinson NS, Porcher R, Nickol AH, Jonville S, Dayer MJ, Hart N, Moxham J, Lofaso F, Polkey MI. Depression of diaphragm motor cortex excitability during mechanical ventilation. J Appl Physiol (1985) 2004; 97:3-10. [PMID: 15020575 DOI: 10.1152/japplphysiol.01099.2003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effect of mechanical ventilation on the diaphragm motor cortex remains unknown. We assessed the effect of mechanical ventilation on diaphragm motor cortex excitability by measuring the costal and crural diaphragm motor-evoked potential (MEP) elicited by single and paired transcranial magnetic stimulation. In six healthy subjects, MEP recruitment curves of the costal and crural diaphragms were assessed at relaxed end expiration during spontaneous breathing [baseline tidal volume (Vtbaseline)] and isocapnic volume cycled ventilation delivered noninvasively (NIV) at three different levels of tidal volume (Vtbaseline, Vtbaseline + 5 ml/kg liters, and Vtbaseline + 10 ml/kg liters). The costal and crural diaphragm response to peripheral stimulation of the right phrenic nerve was not reduced by NIV. NIV reduced the costal and crural MEP amplitude during NIV ( P < 0.0001) with the maximal reduction at Vtbaseline + 5 ml/kg. Response to paired TMS showed that NIV (Vtbaseline + 5 ml/kg) significantly increased the sensitivity of the cortical motoneurons to facilitatory (>9 ms) interstimulus intervals ( P = 0.002), suggesting that the diaphragm MEP amplitude depression during NIV is related to neuromechanical inhibition at the level of motor cortex. Our results demonstrate that mechanical ventilation directly inhibits central projections to the diaphragm.
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Affiliation(s)
- Tarek Sharshar
- Respiratory Muscle Laboratory, Royal Brompton Hospital, Sydney St, London SW3 6NP UK
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588
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Paus T, Barrett J. Transcranial magnetic stimulation (TMS) of the human frontal cortex: implications for repetitive TMS treatment of depression. J Psychiatry Neurosci 2004; 29:268-79. [PMID: 15309043 PMCID: PMC446221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/01/2023] Open
Abstract
Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive tool used to manipulate activity in specific neural circuits of the human brain. Clinical studies suggest that, in some patients with major depression, rTMS has the potential to alleviate symptoms that may be related to functional abnormalities in a frontocingulate circuit. This paper reviews the rationale for the use of rTMS in this context. The following topics are discussed: symptoms and cognition in major depression, with special emphasis on the initiation of speech; neuroimaging studies of depression; rTMS as treatment for depression; structure and function of the mid-dorsolateral frontal and anterior cingulate cortices; and combined TMS/positron emission tomography studies of frontocortical connectivity.
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Affiliation(s)
- Tomás Paus
- Neuropsychology Department, Montreal Neurological Institute, McGill University, Montréal, Que.
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589
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Peinemann A, Reimer B, Löer C, Quartarone A, Münchau A, Conrad B, Siebner HR. Long-lasting increase in corticospinal excitability after 1800 pulses of subthreshold 5 Hz repetitive TMS to the primary motor cortex. Clin Neurophysiol 2004; 115:1519-26. [PMID: 15203053 DOI: 10.1016/j.clinph.2004.02.005] [Citation(s) in RCA: 218] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/03/2004] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To study the after effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) on corticospinal excitability. METHODS Eight healthy volunteers received either 150 or 1800 stimuli of 5 Hz rTMS on two separate days in a counterbalanced order. rTMS was given over the 'motor hot spot' of the right first dorsal interosseus (FDI) muscle using an intensity of 90% of resting motor threshold (referred to as subthreshold rTMS). We evaluated the amplitude of the motor-evoked potential (MEP), short-latency intracortical inhibition (SICI), short-latency intracortical facilitation (SICF), and cortical silent period (CSP) before and for about 30 min after rTMS. MEPs were recorded from the right FDI muscle and abductor digiti minimi (ADM) muscle. RESULTS 1800 stimuli induced an increase in MEP amplitude in the relaxed FDI muscle, but not in the relaxed ADM muscle. This facilitatory after effect was stable for at least 30 min. Prolonged 5 Hz rTMS had no effect on the relative magnitude of SICI and SICF. 150 stimuli caused no lasting modulation of MEP amplitudes in either muscle. In a subgroup of 5 subjects, 900 conditioning stimuli caused only a short-lived MEP facilitation. 5 Hz rTMS did not modify the duration of the CSP during tonic contraction. CONCLUSIONS A single session of subthreshold 5 Hz rTMS to the M1 can induce a long-lasting and muscle-specific increase in resting corticospinal excitability. However, a sufficient number of conditioning stimuli is necessary to produce persistent corticospinal facilitation.
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Affiliation(s)
- Alexander Peinemann
- Department of Neurology, Technische Universität München, Möhlstrasse 28, D-81675 Munich, Germany
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590
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Stefan K, Wycislo M, Classen J. Modulation of Associative Human Motor Cortical Plasticity by Attention. J Neurophysiol 2004; 92:66-72. [PMID: 14724259 DOI: 10.1152/jn.00383.2003] [Citation(s) in RCA: 358] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of attention in generating motor memories remains controversial principally because it is difficult to separate the effects of attention from changes in kinematics of motor performance. We attempted to disentangle attention from performance effects by varying attention while plasticity was induced in human primary motor cortex by external stimulation in the absence of voluntary movement. A paired associative stimulation (PAS) protocol was employed consisting of repetitive application of single afferent electric stimuli, delivered to the right median nerve, paired with single-pulse transcranial magnetic stimulation (TMS) over the optimal site for activation of the right abductor pollicis brevis muscle (APB) to generate near-synchronous events in the left primary motor cortex. In experiment 1, the spatial location of attention was varied. PAS failed to induce plasticity when the subject's attention was directed to their left hand, away from the right target hand the cortical representation of which was being stimulated by PAS. In experiment 2, the grade of attention to the target hand was manipulated. PAS-induced plasticity was maximal when the subject viewed their target hand, and its magnitude was slightly reduced when the subject could only feel their hand. Conversely, plasticity was completely blocked when the subject's attention was diverted from the target hand by a competing cognitive task. A similar modulation by attention was observed for PAS-induced changes in the duration of the silent period evoked by TMS in voluntarily contracted muscle. Associative plasticity in the human motor cortex depends decisively on attention.
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Affiliation(s)
- Katja Stefan
- Human Cortical Physiology and Motor Control Laboratory, Department of Neurology, University of Würzburg, Germany
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591
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Robol E, Fiaschi A, Manganotti P. Effects of citalopram on the excitability of the human motor cortex: a paired magnetic stimulation study. J Neurol Sci 2004; 221:41-6. [PMID: 15178212 DOI: 10.1016/j.jns.2004.03.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2003] [Revised: 02/18/2004] [Accepted: 03/08/2004] [Indexed: 11/29/2022]
Abstract
Several recent reports suggest the possibility of monitoring pharmacological effects on brain excitability through transcranial magnetic stimulation (TMS). Different drugs have been studied using paired magnetic stimulation in normal subjects and patients. In particular, it has been suggested that antidepressant drugs may have an appreciable effect on motor excitability. The aim of the present study was to investigate motor area excitability in normal subjects after oral administration of a single dose of citalopram, a selective serotonin reuptake inhibitor (SSRI) antidepressant. Motor cortex excitability was studied by single and paired transcranial magnetic stimulation before and 2.5 and 36 (t1/2=36 h) h after oral administration of 30 mg of citalopram. Cortical excitability was measured using different transcranial magnetic stimulation parameters: motor threshold (MT), motor-evoked potential (MEP) amplitude and latency, motor recruitment, duration of cortical silent period (CSP), intracortical inhibition and intracortical facilitation. Spinal excitability and peripheral nerve conduction were measured by F response and M wave. Temporary but significant increases in motor threshold, motor-evoked potentials, silent period and intracortical inhibition were observed 2.5 h after drug administration, without any significant changes in motor-evoked potential amplitude and latency and spinal excitability parameters. Our findings suggest that a single oral dose of citalopram can induce significant but transitory suppression of motor cortex excitability in normal subjects.
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Affiliation(s)
- Elisa Robol
- Dipartimento di Scienze Neurologiche e della Visione, Sezione Neurologia Riabilitativa, Policlinico Giambattista Rossi, Università di Verona, Via delle Menegone, 10-Verona 37134, Italy.
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592
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Sohn YH, Dang N, Hallett M. Suppression of corticospinal excitability during negative motor imagery. J Neurophysiol 2004; 90:2303-9. [PMID: 14534268 DOI: 10.1152/jn.00206.2003] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To investigate the effect of negative motor imagery on corticospinal excitability, we performed transcranial magnetic stimulation (TMS) studies in seven healthy subjects during imagination of suppressing movements. Subjects were asked to imagine suppression of TMS-induced twitching movement of their nondominant left hands by attempting to increase the amount of relaxation after receiving an auditory NoGo cue (negative motor imagery), but to imagine squeezing hands after a Go cue (positive motor imagery). Single- and paired-pulse TMS were triggered at 2 s after Go or NoGo cues. Motor-evoked potentials (MEPs) were recorded in the first dorsal interosseus (FDI), abductor pollicis brevis (APB), and abductor digiti minimi (ADM) muscles of the left hand. Paired-pulse TMS with subthreshold conditioning stimuli at interstimulus intervals of 2 (short intracortical inhibition) and 15 ms (intracortical facilitation) and that with suprathreshold conditioning stimuli at interstimulus interval of 80 ms (long intracortical inhibition) were performed in both negative motor imagery and control conditions. Compared with the control state (no imagination), MEP amplitudes of FDI (but not APB and ADM) were significantly suppressed in negative motor imagery, but those from all three muscles were unchanged during positive motor imagery. F-wave responses (amplitudes and persistence) were unchanged during both negative and positive motor imagery. During negative motor imagery, resting motor threshold was significantly increased, but short and long intracortical inhibition and intracortical facilitation were unchanged. The present results demonstrate that excitatory corticospinal drive is suppressed during imagination of suppressing movements.
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Affiliation(s)
- Young H Sohn
- Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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593
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Gilbert DL, Bansal AS, Sethuraman G, Sallee FR, Zhang J, Lipps T, Wassermann EM. Association of cortical disinhibition with tic, ADHD, and OCD severity in Tourette syndrome. Mov Disord 2004; 19:416-25. [PMID: 15077239 DOI: 10.1002/mds.20044] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hyperkinetic disorders may involve excess excitatory output from thalamus to cerebral cortex. Case-control, neurophysiological studies in persons with Tourette Syndrome (TS), Attention Deficit Hyperactivity Disorder (ADHD), and Obsessive-Compulsive Disorder (OCD) support this model. To compare the strength of association between motor cortex inhibition and tic, ADHD, and OCD severity in TS, we used transcranial magnetic stimulation to measure motor cortex inhibition in 36 children and adults with TS. Current symptom severity was assessed with standard clinical rating scales and compared with neurophysiological measures using correlational and multivariate regression analyses. Severity of ADHD symptoms and motor tics were associated significantly and independently with short interval intracortical inhibition (SICI) (r(2) = 0.50; F[2,27] = 13.7; P < 0.001), particularly in subjects not taking neuroleptics (r(2) = 0.68; F[2,17] = 17.8; P < 0.0001). The correlation of cortical disinhibition was greater with ADHD symptoms severity (r = 0.53; P = 0.003) than with tic severity (r = 0.42; P = 0.02), suggesting that in TS, the association between SICI and ADHD symptoms may be more consistent or direct than the association between SICI and tics.
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Affiliation(s)
- Donald L Gilbert
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
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594
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Cortical threshold and excitability measurements. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s1567-4231(04)04017-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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595
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Nardone R, Buffone E, Covi M, Lochner PG, Tezzon F. Changes in motor cortical excitability in humans following orally administered theophylline. Neurosci Lett 2004; 355:65-8. [PMID: 14729236 DOI: 10.1016/j.neulet.2003.10.055] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The effects of theophylline on human corticospinal excitability were studied using transcranial magnetic stimulation (TMS) before and after double-blind oral administration of theophylline or placebo in 20 healthy volunteers. TMS measurements included resting and active motor threshold, silent period, intracortical inhibition (ICI), and intracortical facilitation. F-wave and compound muscle action potential (CMAP) were also measured. Theophylline produces a reduction in ICI, while other parameters of corticospinal excitability remained unaffected. Since ICI is thought to depend on GABAA intracortical inhibitory mechanisms, our data suggest that the increase of human motor cortex excitability is the result of a decrease in GABAergic transmission. Our results further support the hypothesis that theophylline might induce convulsions by inhibiting GABAA receptor binding.
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Affiliation(s)
- R Nardone
- Department of Neurology, F. Tappeiner Hospital, Via Rossini 5, 39012 Merano (BZ), Italy.
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596
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Schubert M, Kretzschmar E, Waldmann G, Hummelsheim H. Influence of repetitive hand movements on intracortical inhibition. Muscle Nerve 2004; 29:804-11. [PMID: 15170613 DOI: 10.1002/mus.20035] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Repetitive movements have been reported to induce task-specific changes of intracortical inhibition and facilitation, but the mechanism operating shortly after hand movement is unclear. Transcranial magnetic single and paired stimuli (2 ms) were applied to 15 healthy subjects at rest and 1 s after repetitive (every 6 s) active and passive hand extensions. Motor evoked potentials (MEPs) were recorded from hand extensors (agonists) and flexors (antagonists). A strong overall inhibitory effect was observed after applying paired stimuli. In agonists only, active movements produced significantly larger MEPs. Inhibition, however, did not differ between active or passive movements and rest. This suggests that MEP increases produced by active movements in agonists are not caused by disinhibition, but are rather due to excitation (facilitation). This finding may also have implications for future studies evaluating the preferential activation of target muscles in physiotherapy.
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Affiliation(s)
- Margot Schubert
- NRZ Neurological Rehabilitation Clinic, Department of Neurology, University of Leipzig, Muldentalweg 1, D-04828 Bennewitz, Germany.
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597
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Wolters A, Classen J, Kunesch E, Grossmann A, Benecke R. Measurements of transcallosally mediated cortical inhibition for differentiating parkinsonian syndromes. Mov Disord 2004; 19:518-28. [PMID: 15133815 DOI: 10.1002/mds.20064] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Clinicopathologic evidence suggests differential involvement of cortex and corpus callosum (CC) in various disorders presenting with a parkinsonian syndrome. We tested the hypothesis of whether neurophysiologic and morphometric assessments of CC as surrogate parameters of cortical involvement could be helpful in differential diagnosis of parkinsonian disorders. The integrity of CC was assessed neurophysiologically by measuring the ipsilateral silent period (iSP) evoked by transcranial magnetic stimulation (TMS) in a total of 25 patients with idiopathic parkinsonian syndromes (IPS), corticobasal ganglionic degeneration (CBD), progressive supranuclear palsy (PSP), or multiple system atrophy (MSA). Additionally, morphometric analyses of magnetic resonance imaging (MRI) measurements of CC was carried out in all patients. iSP was abnormal in all 5 CBD and all 5 PSP patients, whereas it was intact in all 10 IPS patients and all 5 MSA patients. Among various MRI parameters of CC, testing between different groups revealed a significant difference only for measurements of the middle part of the truncus. CBD and PSP patients exhibited a significant atrophy as compared with control subjects. These data suggest impairment of callosal integrity in patients with CBD and PSP. iSP measurements may be a useful clinical neurophysiologic test in differential diagnosis of patients with parkinsonian syndromes.
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Affiliation(s)
- Alexander Wolters
- Human Cortical Physiology Laboratory, Department of Neurology, University of Rostock, Germany
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598
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Chen R, Anastakis DJ, Haywood CT, Mikulis DJ, Manktelow RT. Plasticity of the human motor system following muscle reconstruction: a magnetic stimulation and functional magnetic resonance imaging study. Clin Neurophysiol 2003; 114:2434-46. [PMID: 14652104 DOI: 10.1016/s1388-2457(03)00283-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
OBJECTIVE Although motor system plasticity in response to neuromuscular injury has been documented, few studies have examined recovered and functioning muscles in the human. We examined brain changes in a group of patients who had a muscle transfer. METHODS Transcranial magnetic stimulation (TMS) was used to study a unique group of 9 patients who had upper extremity motor function restored using microneurovascular transfer of the gracilis muscle. The findings from the reconstructed muscle were compared to the homologous muscle of the intact arm. One patient was also studied with functional magnetic resonance imaging (fMRI). RESULTS TMS showed that the motor threshold and short interval intracortical inhibition was reduced on the transplanted side while at rest but not during muscle activation. The difference in motor threshold decreased with the time since surgery. TMS mapping showed no significant difference in the location and size of the representation of the reconstructed muscle in the motor cortex compared to the intact side. In one patient with reconstructed biceps muscle innervated by the intercostal nerves, both TMS mapping and fMRI showed that the upper limb area rather than the trunk area of the motor cortex controlled the reconstructed muscle. CONCLUSIONS Plasticity occurs in cortical areas projecting to functionally relevant muscles. Changes in the neuronal level are not necessarily accompanied by changes in motor representation. Brain reorganization may involve multiple processes mediated by different mechanisms and continues to evolve long after the initial injury. SIGNIFICANCE Central nervous system plasticity following neuromuscular injury may have functional relevance.
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Affiliation(s)
- Robert Chen
- Division of Neurology, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ont., Canada.
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599
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Cincotta M, Borgheresi A, Gambetti C, Balestrieri F, Rossi L, Zaccara G, Ulivelli M, Rossi S, Civardi C, Cantello R. Suprathreshold 0.3 Hz repetitive TMS prolongs the cortical silent period: potential implications for therapeutic trials in epilepsy. Clin Neurophysiol 2003; 114:1827-33. [PMID: 14499744 DOI: 10.1016/s1388-2457(03)00181-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
OBJECTIVE To investigate the after-effects of 0.3 Hz repetitive transcranial magnetic stimulation (rTMS) on excitatory and inhibitory mechanisms at the primary motor cortex level, as tested by single-pulse TMS variables. METHODS In 9 healthy subjects, we studied a wide set of neurophysiological and behavioral variables from the first dorsal interosseous before (Baseline), immediately after (Post 1), and 90 min after (Post 2) the end of a 30 min long train of 0.3 Hz rTMS delivered at an intensity of 115% resting motor threshold (RMT). Variables under investigation were: maximal M wave, F wave, and peripheral silent period after ulnar nerve stimulation; RMT, amplitude and stimulus-response curve of the motor evoked potential (MEP), and cortical silent period (CSP) following TMS; finger-tapping speed. RESULTS The CSP was consistently lengthened at both Post 1 and Post 2 compared with Baseline. The other variables did not change significantly. CONCLUSIONS These findings suggest that suprathreshold 0.3 Hz rTMS produces a relatively long-lasting enhancement of the inhibitory mechanisms responsible for the CSP. These effects differ from those, previously reported, of 0.9-1 Hz rTMS, which reduces the excitability of the circuits underlying the MEP and does not affect the CSP. This provides rationale for sham-controlled trials aiming to assess the therapeutic potential of 0.3 Hz rTMS in epilepsy.
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Affiliation(s)
- M Cincotta
- Unita' Operativa di Neurologia, Azienda Sanitaria di Firenze, Ospedale S. Maria Nuova, Piazza S. Maria Nuova, 1 50122, Florence, Italy.
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600
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Hammond G, Faulkner D, Byrnes M, Mastaglia F, Thickbroom G. Transcranial magnetic stimulation reveals asymmetrical efficacy of intracortical circuits in primary motor cortex. Exp Brain Res 2003; 155:19-23. [PMID: 15064880 DOI: 10.1007/s00221-003-1696-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2003] [Accepted: 08/08/2003] [Indexed: 10/26/2022]
Abstract
The efficacy of inhibitory and excitatory intracortical circuits acting on the representation of an intrinsic hand muscle in the primary motor cortex of both hemispheres was measured with paired transcranial magnetic stimuli in right-handed subjects. Both intracortical inhibition (measured with an interstimulus interval of 3 ms) and intracortical facilitation (measured with an interstimulus interval of 16 ms) developed more rapidly with increasing conditioning stimulus intensity in the dominant than the non-dominant hand. We conclude that the intracortical circuits in the primary motor cortex are more potent in the dominant than the non-dominant hemisphere, and hypothesize that this difference is a factor in the asymmetrical dexterity associated with hand preference.
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Affiliation(s)
- Geoff Hammond
- School of Psychology, The University of Western Australia, Crawley, WA 6009, Australia.
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