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Murata K, Fujiki M, Ooba H, Kubo T, Morishige M, Abe T, Ishii K, Kobayashi H, Kiyosue H, Mori H. Cognitive alteration after carotid revascularization is correlated with cortical GABAB-ergic modulations. Neurosci Lett 2011; 500:151-6. [DOI: 10.1016/j.neulet.2011.04.052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 04/08/2011] [Accepted: 04/20/2011] [Indexed: 11/16/2022]
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52
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Maier J, Sebastian I, Weisbrod M, Freitag CM, Resch F, Bender S. Cortical inhibition at rest and under a focused attention challenge in adults with migraine with and without aura. Cephalalgia 2011; 31:914-24. [DOI: 10.1177/0333102411408627] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Objectives: We aimed to further elucidate the functional and attentional regulation of cortical excitability in migraine patients. Methods: We investigated the cortical silent period (CSP) after transcranial magnetic stimulation as a measure of cortical inhibition under three conditions: resting condition, cortical preactivation during reaction preparation, and during the post-processing of a motor response using a visual contingent negative variation paradigm in adults with migraine with aura, migraine without aura and healthy controls. Results: CSP was reduced in individuals with migraine with aura and unaffected in those with migraine without aura under resting conditions. Along with the intensity of transcranial magnetic stimulation, CSP increased equally in all groups (equal slopes). Furthermore, the functional challenge by a contingent negative variation task requiring focused sustained attention led to a comparable reduction of CSP duration in all groups. Discussion: Our data provide further hints towards the conclusion that a specific cortical inhibition deficit in migraine with aura but not migraine without aura is due to a tonic imbalance and not related to increased reactions to phasic stressors. Given that CSP at rest is related to GABA-ergic inhibition whereas the CSP reduction during late contingent negative variation is thought to be related to dopaminergic disinhibition in the basal ganglia, our results point towards reduced GABA-ergic cortical inhibition related to dysfunctional thalamo-cortical loops, especially in migraine with aura.
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Affiliation(s)
| | | | - Matthias Weisbrod
- University of Heidelberg, Germany
- SRH-Klinikum Karlsbad-Langensteinbach, Germany
| | | | | | - Stephan Bender
- Goethe-University, Germany
- University of Heidelberg, Germany
- University of Dresden, Germany
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53
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Shitara H, Shinozaki T, Takagishi K, Honda M, Hanakawa T. Time course and spatial distribution of fMRI signal changes during single-pulse transcranial magnetic stimulation to the primary motor cortex. Neuroimage 2011; 56:1469-79. [PMID: 21396457 DOI: 10.1016/j.neuroimage.2011.03.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 02/27/2011] [Accepted: 03/03/2011] [Indexed: 11/25/2022] Open
Abstract
Simultaneous transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) may advance the understanding of neurophysiological mechanisms of TMS. However, it remains unclear if TMS induces fMRI signal changes consistent with the standard hemodynamic response function (HRF) in both local and remote regions. To address this issue, we delivered single-pulse TMS to the left M1 during simultaneous recoding of electromyography and time-resolved fMRI in 36 healthy participants. First, we examined the time-course of fMRI signals during supra- and subthreshold single-pulse TMS in comparison with those during voluntary right hand movement and electrical stimulation to the right median nerve (MNS). All conditions yielded comparable time-courses of fMRI signals, showing that HRF would generally provide reasonable estimates for TMS-evoked activity in the motor areas. However, a clear undershoot following the signal peak was observed only during subthreshold TMS in the left M1, suggesting a small but meaningful difference between the locally and remotely TMS-evoked activities. Second, we compared the spatial distribution of activity across the conditions. Suprathreshold TMS-evoked activity overlapped not only with voluntary movement-related activity but also partially with MNS-induced activity, yielding overlapped areas of activity around the stimulated M1. The present study has provided the first experimental evidence that motor area activity during suprathreshold TMS likely includes activity for processing of muscle afferents. A method should be developed to control the effects of muscle afferents for fair interpretation of TMS-induced motor area activity during suprathreshold TMS to M1.
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Affiliation(s)
- H Shitara
- Department of Functional Brain Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Japan
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54
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González-García N, Armony JL, Soto J, Trejo D, Alegría MA, Drucker-Colín R. Effects of rTMS on Parkinson’s disease: a longitudinal fMRI study. J Neurol 2011; 258:1268-80. [DOI: 10.1007/s00415-011-5923-2] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 12/25/2010] [Accepted: 01/17/2011] [Indexed: 11/30/2022]
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55
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Long-interval intracortical inhibition in a human hand muscle. Exp Brain Res 2011; 209:287-97. [DOI: 10.1007/s00221-011-2552-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Accepted: 01/06/2011] [Indexed: 10/18/2022]
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56
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Joo EY, Kim HJ, Lim YH, Ji KH, Hong SB. Zonisamide changes unilateral cortical excitability in focal epilepsy patients. J Clin Neurol 2010; 6:189-95. [PMID: 21264199 PMCID: PMC3024523 DOI: 10.3988/jcn.2010.6.4.189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 06/25/2010] [Accepted: 06/25/2010] [Indexed: 11/17/2022] Open
Abstract
Background and Purpose To evaluate changes in cortical excitability induced by zonisamide (ZNS) in focal epilepsy patients. Methods Twenty-four drug-naїve focal epilepsy patients (15 males; overall mean age 29.8 years) were enrolled. The transcranial magnetic stimulation parameters obtained using two Magstim 200 stimulators were the resting motor threshold, amplitude of the motor-evoked potential (MEP), cortical silent period, short intracortical inhibition, and intracortical facilitation. These five transcranial magnetic stimulation parameters were measured before and after ZNS, and the findings were compared. Results All 24 patients were treated with ZNS monotherapy (200-300 mg/day) for 8-12 weeks. After ZNS, MEP amplitudes decreased (-36.9%) significantly in epileptic hemispheres (paired t-test with Bonferroni's correction for multiple comparisons, p<0.05), whereas the mean resting motor threshold, cortical silent period, short intracortical inhibition, and intracortical facilitation were unchanged (p>0.05). ZNS did not affect cortical excitability in nonepileptic hemispheres. Conclusions These findings suggest that ZNS decreases cortical excitability only in the epileptic hemispheres of focal epilepsy patients. MEP amplitudes may be useful for evaluating ZNS-induced changes in cortical excitability.
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Affiliation(s)
- Eun Yeon Joo
- Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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57
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Joo EY, Hong SB, Kim HJ, Lim YH, Koo DL, Ji KH, Tae WS. The effect of modafinil on cortical excitability in patients with narcolepsy: A randomized, placebo-controlled, crossover study. Sleep Med 2010; 11:862-9. [PMID: 20810312 DOI: 10.1016/j.sleep.2010.07.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 07/07/2010] [Accepted: 07/10/2010] [Indexed: 10/19/2022]
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Levinson AJ, Fitzgerald PB, Favalli G, Blumberger DM, Daigle M, Daskalakis ZJ. Evidence of cortical inhibitory deficits in major depressive disorder. Biol Psychiatry 2010; 67:458-64. [PMID: 19922906 DOI: 10.1016/j.biopsych.2009.09.025] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 08/27/2009] [Accepted: 09/12/2009] [Indexed: 01/11/2023]
Abstract
BACKGROUND Several lines of evidence suggest that major depressive disorder is associated with deficits in gamma-aminobutyric acid (GABA) inhibitory neurotransmission. Transcranial magnetic stimulation represents a noninvasive technique to measure cortical inhibition. In this study, we endeavored to measure cortical inhibition in medicated patients with treatment resistant major depressive disorder (TRD), unmedicated patients with major depressive disorder, and medicated euthymic patients with a history of major depressive disorder and compare them with healthy subjects. METHODS Twenty-five patients with TRD, 16 unmedicated patients with major depressive disorder, 19 medicated euthymic patients with previous major depressive disorder (i.e., 17-item Hamilton Rating Scale for Depression < 8), and 25 healthy subjects were enrolled. Cortical inhibition was measured with transcranial magnetic stimulation paradigms known as short-interval cortical inhibition and the cortical silent period, which index GABA(A) and GABA(B) receptor-mediated inhibitory neurotransmission, respectively. RESULTS All major depressive disorder patient groups demonstrated significant cortical silent period deficits compared with healthy subjects. By contrast, only TRD patients demonstrated significant deficits in short-interval cortical inhibition compared with healthy subjects, medicated euthymic major depressive disorder patients, and unmedicated major depressive disorder patients. The TRD patients also demonstrated a significantly greater resting motor threshold compared with all other clinical subgroups and healthy subjects, suggesting that TRD was also associated with hypoexcitability of the frontal cortex. CONCLUSIONS Our findings suggest that GABA(B) neurophysiological deficits are closely related to pathophysiology of major depressive disorder. Our findings also suggest that more severe illness is selectively associated with GABA(A) receptor-mediated inhibitory deficits.
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Affiliation(s)
- Andrea J Levinson
- Centre for Addiction and Mental Health, University of Toronto, Toronto, ON ONM5T 1R8, Canada
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59
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Filipović SR, Papathanasiou I, Whurr R, Rothwell JC, Jahanshahi M. Differential effect of linguistic and non-linguistic pen-holding tasks on motor cortex excitability. Exp Brain Res 2008; 191:237-46. [PMID: 18712373 DOI: 10.1007/s00221-008-1517-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2007] [Accepted: 07/21/2008] [Indexed: 10/21/2022]
Abstract
Writing and drawing are unique human activities. They are complex high-precision actions, which involve not only the motor system but also various cognitive systems, such as attention, short-term memory, action control, and language. In relation to motor control, the study of writing and drawing is of great interest as they provide insight in the interaction between motor control processes and the concurrent non-motor processes. Although sharing similar motor and mechanical demands, writing and drawing involve different levels of linguistic/semantic load and thus may be associated with different modulation of motor cortical excitability. Here, we have used transcranial magnetic stimulation to study separately activation of excitatory and inhibitory mechanisms of the motor cortex during performance of writing and drawing acts as well as during simple pen-squeezing task. While cortical excitatory mechanisms appeared to be saturated by the pure motor demands of the tasks, and thus not amenable to modulation by the tasks' linguistic load, variation in cortical inhibitory activity was the main vehicle for differential modulation of motor cortical excitability by linguistic demands of the tasks. The results of this study highlight the importance of cortical inhibitory mechanisms in the physiology of higher cognitive activities. They also provide further evidence that the task specific modulation of the excitability of the motor cortex goes beyond motor complexity of the task and is also dependant on associated cognitive components.
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Affiliation(s)
- Sasa R Filipović
- Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
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60
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Clark BC, Issac LC, Lane JL, Damron LA, Hoffman RL. Neuromuscular plasticity during and following 3 wk of human forearm cast immobilization. J Appl Physiol (1985) 2008; 105:868-78. [PMID: 18635877 DOI: 10.1152/japplphysiol.90530.2008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Prolonged reductions in muscle activity results in alterations in neuromuscular properties; however, the time course of adaptations is not fully understood, and many of the specific adaptations have not been identified. This study evaluated the temporal evolution of adaptations in neuromuscular properties during and following 3 wk of immobilization. We utilized a combination of techniques involving nerve stimulation and transcranial magnetic stimulation to assess changes in central activation of muscle, along with spinal (H reflex) and corticospinal excitability [i.e., motor-evoked potential (MEP) amplitude, silent period (SP)] and contractile properties in 10 healthy humans undergoing 3 wk of forearm immobilization and 9 control subjects. Immobilization induced deficits in central activation (85 +/- 3 to 67 +/- 7% ) that returned to baseline levels 1 wk after cast removal. The flexor carpii radialis MEP amplitude increased greater than twofold after the first week of immobilization and remained elevated throughout immobilization and 1 wk after cast removal. Additionally, we observed a prolongation of the SP 1 wk after cast removal compared with baseline (78.5 +/- 7.1 to 98.2 +/- 8.7 ms). The contractile properties were also altered, since the rate of evoked force relaxation was slower following immobilization (-14.5 +/- 1.4 to -11.3 +/- 1.0% peak force/ms), and remained depressed 1 wk after cast removal (-10.5 +/- 0.8% peak force/ms). These observations detail the time course of adaptations in corticospinal and contractile properties associated with disuse and illustrate the profound effect of immobilization on the human neuromuscular system as evidenced by the alterations in corticospinal excitability persisting 1 wk following cast removal.
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Affiliation(s)
- Brian C Clark
- Dept. of Biomedical Sciences, Ohio Univ. College of Osteopathic Medicine, Athens, OH 45701, USA.
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61
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Heise CA, Wanschura V, Albrecht B, Uebel H, Roessner V, Himpel S, Paulus W, Rothenberger A, Tergau F. Voluntary motor drive: possible reduction in Tourette syndrome. J Neural Transm (Vienna) 2008; 115:857-61. [PMID: 18196201 PMCID: PMC2440945 DOI: 10.1007/s00702-007-0010-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Accepted: 11/15/2007] [Indexed: 11/03/2022]
Abstract
Electrophysiologically, Tourette syndrome (TS) is characterized by shortened cortical silent period (CSP), reflecting decreased motor inhibition. However, voluntary versus involuntary aspects of inhibitory functions in TS are not well understood. Hence, investigating voluntary motor drive (VMD) could help to elucidate this issue. A group of 14 healthy adolescents was compared with subjects of same age suffering from TS with (N = 6) and without (N = 6) presence of distal tics. Basic resting and active motor thresholds (RMT and AMT, respectively) as well as suprathreshold transcranial magnetic stimulation-conditioned RMT and AMT were determined during the CSP. The difference between AMT and RMT was considered as VMD quantum. No group-differences were found in RMT or AMT. Subjects with distal tics showed reduced VMD compared to healthy controls while patients without distal tics did not differ from controls. In the second half of CSP, patients with distal tics showed also diminished VMD compared to tic-patients without distal tics. The findings support the notion, that TS shows possible reduction of VMD and is associated with central motor threshold alterations confined to the very motor networks related to the tics observed.
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Affiliation(s)
- C A Heise
- Child and Adolescent Psychiatry, University of Göttingen, Göttingen, Germany.
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62
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Joo EY, Kim SH, Seo DW, Hong SB. Zonisamide decreases cortical excitability in patients with idiopathic generalized epilepsy. Clin Neurophysiol 2008; 119:1385-92. [DOI: 10.1016/j.clinph.2008.02.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2007] [Revised: 01/22/2008] [Accepted: 02/12/2008] [Indexed: 11/24/2022]
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63
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Taylor HH, Murphy B. Altered sensorimotor integration with cervical spine manipulation. J Manipulative Physiol Ther 2008; 31:115-26. [PMID: 18328937 DOI: 10.1016/j.jmpt.2007.12.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2007] [Revised: 10/29/2007] [Indexed: 01/15/2023]
Abstract
OBJECTIVE This study investigates changes in the intrinsic inhibitory and facilitatory interactions within the sensorimotor cortex subsequent to a single session of cervical spine manipulation using single- and paired-pulse transcranial magnetic stimulation protocols. METHOD Twelve subjects with a history of reoccurring neck pain participated in this study. Short interval intracortical inhibition, short interval intracortical facilitation (SICF), motor evoked potentials, and cortical silent periods (CSPs) were recorded from the abductor pollicis brevis and the extensor indices proprios muscles of the dominant limb after single- and paired-pulse transcranial magnetic stimulation of the contralateral motor cortex. The experimental measures were recorded before and after spinal manipulation of dysfunctional cervical joints, and on a different day after passive head movement. To assess spinal excitability, F wave persistence and amplitudes were recorded after median nerve stimulation at the wrist. RESULTS After cervical manipulations, there was an increase in SICF, a decrease in short interval intracortical inhibition, and a shortening of the CSP in abductor pollicis brevis. The opposite effect was observed in extensor indices proprios, with a decrease in SICF and a lengthening of the CSP. No motor evoked potentials or F wave response alterations were observed, and no changes were observed after the control condition. CONCLUSION Spinal manipulation of dysfunctional cervical joints may alter specific central corticomotor facilitatory and inhibitory neural processing and cortical motor control of 2 upper limb muscles in a muscle-specific manner. This suggests that spinal manipulation may alter sensorimotor integration. These findings may help elucidate mechanisms responsible for the effective relief of pain and restoration of functional ability documented after spinal manipulation.
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Daskalakis ZJ, Christensen BK, Fitzgerald PB, Moller B, Fountain SI, Chen R. Increased cortical inhibition in persons with schizophrenia treated with clozapine. J Psychopharmacol 2008; 22:203-9. [PMID: 18308816 DOI: 10.1177/0269881107084002] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
It has been previously demonstrated that unmedicated persons with schizophrenia have deficits in cortical inhibition (CI) as indexed with transcranial magnetic stimulation (TMS). This inhibition is largely mediated by cortical GABAergic mechanisms. It has also been demonstrated that these inhibitory deficits may be normalized with the use of atypical antipsychotic medications. The purpose of this study, therefore, was to examine the effects of clozapine on TMS measures of CI and to compare these effects to unmedicated persons with schizophrenia and healthy subjects. We used two TMS inhibitory paradigms: short interval intra-cortical inhibition (SICI) and the cortical silent period (CSP) to evaluate CI in 10 clozapine-treated persons with schizophrenia, 6 unmedicated persons with schizophrenia and 10 healthy subjects. Clozapine-treated persons with schizophrenia had significantly longer CSPs compared with healthy subjects and unmedicated persons with schizophrenia. There were no significant differences in SICI between groups, however, the severity of psychotic symptoms was correlated with reduced SICI across all persons with schizophrenia. Our findings suggest that clozapine treatment is associated with greater CI in persons with schizophrenia and this increase may be related to potentiation of cortical GABAergic receptor mediated inhibitory neurotransmission. Our results also confirm previous findings suggesting that deficits in CI are related to the severity of psychotic symptoms in persons with schizophrenia.
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Affiliation(s)
- Zafiris J Daskalakis
- Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.
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65
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Reis J, Swayne OB, Vandermeeren Y, Camus M, Dimyan MA, Harris-Love M, Perez MA, Ragert P, Rothwell JC, Cohen LG. Contribution of transcranial magnetic stimulation to the understanding of cortical mechanisms involved in motor control. J Physiol 2007; 586:325-51. [PMID: 17974592 DOI: 10.1113/jphysiol.2007.144824] [Citation(s) in RCA: 437] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Transcranial magnetic stimulation (TMS) was initially used to evaluate the integrity of the corticospinal tract in humans non-invasively. Since these early studies, the development of paired-pulse and repetitive TMS protocols allowed investigators to explore inhibitory and excitatory interactions of various motor and non-motor cortical regions within and across cerebral hemispheres. These applications have provided insight into the intracortical physiological processes underlying the functional role of different brain regions in various cognitive processes, motor control in health and disease and neuroplastic changes during recovery of function after brain lesions. Used in combination with neuroimaging tools, TMS provides valuable information on functional connectivity between different brain regions, and on the relationship between physiological processes and the anatomical configuration of specific brain areas and connected pathways. More recently, there has been increasing interest in the extent to which these physiological processes are modulated depending on the behavioural setting. The purpose of this paper is (a) to present an up-to-date review of the available electrophysiological data and the impact on our understanding of human motor behaviour and (b) to discuss some of the gaps in our present knowledge as well as future directions of research in a format accessible to new students and/or investigators. Finally, areas of uncertainty and limitations in the interpretation of TMS studies are discussed in some detail.
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Affiliation(s)
- Janine Reis
- Human Cortical Physiology Section, National Institute of Health, National Institute of Neurological Disorders and Stroke, 10 Center Drive, Bldg 10, Rm 5 N226, Bethesda, MD 20892, USA
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66
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Kang SY, Shin HW, Sohn YH. Different modulation of the cortical silent period by two phases of short interval intracortical inhibition. Yonsei Med J 2007; 48:795-801. [PMID: 17963336 PMCID: PMC2628145 DOI: 10.3349/ymj.2007.48.5.795] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
PURPOSE To investigate the influence of 2 phases of short interval intracortical inhibition (SICI) on the cortical silent period (SP). MATERIALS AND METHODS Single- and paired-pulse transcranial magnetic stimulations (TMSs) at 1 and 2.5ms interstimulus intervals (ISIs) were applied to the left motor cortex in 12 healthy subjects while their right hand muscles were moderately activated. Conditioning stimulation intensity was 90% of the active motor threshold (AMT). Test stimulation intensities were 120, 140, 160, 180, 200, 220, 240, 260% of the AMT and at 100% of the maximal stimulator output, the order of which was arranged randomly. The rectified electromyography area of motor evoked potential (MEP) and duration of the SP were measured off-line using a computerized program. RESULTS At high-test stimulation intensities, MEP areas were saturated in both single- and paired-pulse stimulations, except that saturated MEPs were smaller for the paired-pulse TMS at 1ms ISI than for the other conditions. As the test stimulation intensity increased, SP was progressively prolonged in both single- and paired-pulse stimulations but was shorter in paired-pulse than single-pulse TMS. Overall, the ratio of SP duration/MEP area was comparable between single- and paired-pulse TMS except for the paired-pulse TMS at 1 ms ISI with a test stimulation intensity at 140-180% of the AMT, in which the ratio was significantly higher than in the single pulse TMS. CONCLUSION These results suggest that 2 phases of SICI modulate MEP saturation and SP duration differently and provide additional evidence supporting the view that 2 phases of SICI are mediated by different inhibitory mechanisms.
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Affiliation(s)
- Suk Yun Kang
- Department of Neurology, Yonsei University College of Medicine, Seoul, Korea
| | - Hae-Won Shin
- Department of Neurology, Yonsei University College of Medicine, Seoul, Korea
| | - Young Ho Sohn
- Department of Neurology, Yonsei University College of Medicine, Seoul, Korea
- Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea
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67
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Frantseva MV, Fitzgerald PB, Chen R, Möller B, Daigle M, Daskalakis ZJ. Evidence for impaired long-term potentiation in schizophrenia and its relationship to motor skill learning. Cereb Cortex 2007; 18:990-6. [PMID: 17855721 DOI: 10.1093/cercor/bhm151] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Several lines of evidence suggest that schizophrenia (SCZ) is associated with disrupted plasticity in the cortex. However, there is little direct neurophysiological evidence of aberrant long-term potentiation (LTP)-like plasticity in SCZ and little human evidence to establish a link between LTP to learning and memory. LTP was evaluated using a neurophysiological paradigm referred to as paired associative stimulation (PAS). PAS involves pairing of median nerve electric stimulation with transcranial magnetic stimulation (TMS) over the contralateral motor cortex (for abductor pollicis brevis muscle activation) delivered at 25-ms interstimulus interval. This pairing was delivered at a frequency of 0.1 Hz for 30 min. LTP was reflected by the change in motor evoked potentials (MEPs) before and after PAS. In addition, motor skill learning was assessed using the rotary pursuit task. Compared with healthy subjects, patients with SCZ demonstrated significant MEP facilitation deficits following PAS and impaired rotary-pursuit motor learning. Across all subjects there was a significant association between LTP and motor skill learning. These data provide evidence for disrupted LTP in SCZ, whereas the association between LTP with motor skill learning suggests that the deficits in learning and memory in SCZ may be mediated through disordered LTP.
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Affiliation(s)
- Marina V Frantseva
- Schizophrenia Program, Centre for Addiction and Mental Health, Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
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68
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Ni Z, Gunraj C, Chen R. Short interval intracortical inhibition and facilitation during the silent period in human. J Physiol 2007; 583:971-82. [PMID: 17656435 PMCID: PMC2277199 DOI: 10.1113/jphysiol.2007.135749] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Following a suprathreshold transcranial magnetic stimulation (TMS) to the primary motor cortex (M1) during voluntary muscle contraction, a motor evoked potential (MEP) occurs in the target muscle followed by a silent period (SP) in the electromyographic (EMG) activities. The present study investigated how short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) change during the SP. The time course of MEP and motor threshold during the SP were examined in the right first dorsal interosseous muscle. Using a triple-pulse protocol, SICI and ICF were tested at different times during the SP. The effects of different intensities of the conditioning stimulation (CS) for SICI and ICF were also investigated during the SP and at rest. During the SP, MEP was inhibited and motor threshold was increased, whereas MEP latency and background EMG level were same as those at rest. SICI decreased during the SP over a wide range of CS intensities. ICF increased at higher CS intensity. We conclude that SICI is suppressed and ICF is facilitated during the SP and the effects are separate from the interruption of voluntary drive.
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Affiliation(s)
- Zhen Ni
- Division of Neurology, Krembil Neuroscience Centre, University of Toronto, Toronto, Ontario, Canada
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69
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Hattemer K, Knake S, Reis J, Rochon J, Oertel WH, Rosenow F, Hamer HM. Excitability of the motor cortex during ovulatory and anovulatory cycles: a transcranial magnetic stimulation study. Clin Endocrinol (Oxf) 2007; 66:387-93. [PMID: 17302873 DOI: 10.1111/j.1365-2265.2007.02744.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE The pathophysiology of catamenial diseases such as epilepsy is unclear. Therefore, we investigated changes in cortical excitability during anovulatory and ovulatory cycles. PATIENTS AND METHODS Using transcranial magnetic stimulation (TMS), eight healthy women were investigated during anovulatory and 12 during ovulatory cycles. On days 8, -14, -7 and 2 of the cycle, resting motor threshold (RMT), cortical silent period (CSP), intracortical inhibition (ICI) and intracortical facilitation (ICF) were investigated. Repeated-measures analysis of variance (anova) and nonparametric methods were used for statistical analysis. RESULTS A trend was seen for group by phase interaction regarding ICI (F = 2.5, P = 0.10). ICI varied during anovulatory cycles (median: 51.0% on day 8; 45.3% on day -14, 51.0% on day -7, and 28.6% on day 2; P = 0.040), mainly because of an increased inhibition on day 2. ICI was more pronounced in anovulatory cycles on day -14 (P = 0.021), -7 (P = 0.048) and 2 (P = 0.018) compared to ovulatory women who did not show intraindividual changes (P = 0.56). RMT, CSP and ICF showed no significant changes during anovulatory or ovulatory cycles. CONCLUSIONS The results suggest fluctuations in cortical excitability during anovulatory cycles, possibly due to the withdrawal of 'excitatory' oestrogens that initiate menses in anovulatory cycles.
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Affiliation(s)
- Katja Hattemer
- Department of Neurology, University of Marburg, Germany.
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70
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Reis J, John D, Heimeroth A, Mueller HH, Oertel WH, Arndt T, Rosenow F. Modulation of human motor cortex excitability by single doses of amantadine. Neuropsychopharmacology 2006; 31:2758-66. [PMID: 16794570 DOI: 10.1038/sj.npp.1301122] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Amantadine-sulfate has been used for several decades to treat acute influenza A, Parkinson's disease (PD), and acute or chronic drug-induced dyskinesia. Several mechanisms of actions detected in vivo/in vitro including N-methyl-D-aspartate (NMDA)-receptor antagonism, blockage of potassium channels, dopamine receptor agonism, enhancement of noradrenergic release, and anticholinergic effects have been described. We used transcranial magnetic stimulation (TMS) to evaluate the effect of single doses of amantadine on human motor cortex excitability in normal subjects. Using a double-blind, placebo-controlled, crossover study design, motor thresholds, recruitment curves, cortical stimulation-induced silent period (CSP), short intracortical inhibition (ICI), intracortical facilitation (ICF), and late inhibition (L-ICI) in 14 healthy subjects were investigated after oral doses of 50 and 100 mg amantadine with single and paired pulse TMS paradigms. Spinal cord excitability was investigated by distal latencies and M-amplitudes of the abductor digiti minimi muscle. After intake of amantadine, a significant dose-dependent decrease of ICF was noticed as well as a significant increase of L-ICI as compared to placebo. The effect on ICF and L-ICI significantly correlated with amantadine serum levels. ICI was slightly increased after amantadine intake, but the effect failed to be significant. Furthermore, amantadine had no significant effects on motor thresholds, MEP recruitment curves, CSP, or peripheral excitability. In conclusion, a low dose of amantadine is sufficient in modulating human motor cortex excitability. The decrease of ICF and increase of L-ICI may reflect glutamatergic modulation or a polysynaptic interaction of glutamatergic and GABA-ergic circuits. Although amantadine has several mechanisms of action, the NMDA-receptor antagonism seems to be the most relevant effect on cortical excitability. As L-ICI can be influenced by this type of drug, it may be an interesting parameter for studies of motor learning and use-dependent plasticity.
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Affiliation(s)
- Janine Reis
- Department of Neurology, Interdisciplinary Epilepsy Center, Philipps-University, Marburg, Germany
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71
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Benwell NM, Mastaglia FL, Thickbroom GW. Differential changes in long-interval intracortical inhibition and silent period duration during fatiguing hand exercise. Exp Brain Res 2006; 179:255-62. [PMID: 17464523 DOI: 10.1007/s00221-006-0790-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Accepted: 10/30/2006] [Indexed: 11/29/2022]
Abstract
During fatiguing exercise corticomotor excitability increases as force declines, which may serve to increase motor output to the exercising muscle, but paradoxically at the same time there is an increase in silent period (SP) duration which is thought to represent a build-up of intracortical inhibition. Paired-pulse TMS at long interstimulus intervals can also be used to derive an index of long-interval cortical inhibition (LICI), however this has not yet been investigated in fatigue. Our aim was to measure LICI during and after a fatiguing exercise and determine if the changes in the index of LICI parallel the changes in SP duration. To do this, we used single and paired-pulse TMS to measure motor evoked potential (MEP) amplitude, LICI and SP duration during, and for 10 min after, a 10-min intermittent maximal fatiguing exercise of the index finger, designed to fatigue the first dorsal interosseous (FDI) muscle (force after 10-min of exercise 64 +/- 7% of baseline, P < 0.05). Single-pulse MEP amplitude and SP duration were increased during fatiguing exercise (minute 10; 179 +/- 24% and 128 +/- 9% of baseline, respectively, P < 0.05), in contrast the measure of LICI was reduced compared to baseline (minute 10; 0.45 +/- 0.17 vs. baseline; 0.70 +/- 0.10, P < 0.05). These results suggest that SP duration and LICI may reflect processes occurring in different neuronal populations. The increased SP duration may correspond to processes of central fatigue in centres 'upstream' of primary motor cortex (M1), whereas the decrease in LICI, together with increased MEP amplitude, are consistent with an increase in M1 output during fatigue that may serve to compensate for reduced central drive.
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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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72
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Daskalakis ZJ, Möller B, Christensen BK, Fitzgerald PB, Gunraj C, Chen R. The effects of repetitive transcranial magnetic stimulation on cortical inhibition in healthy human subjects. Exp Brain Res 2006; 174:403-12. [PMID: 16683138 DOI: 10.1007/s00221-006-0472-0] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Accepted: 03/24/2006] [Indexed: 02/08/2023]
Abstract
It has been suggested that the therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) are mediated through changes in cortical inhibition (CI). However, in healthy human subjects the effects of rTMS on CI have been inconsistent. Therefore, this study sought to improve on the methodological limitations of previous studies by exploring several different rTMS-stimulus conditions on inhibition in the human motor cortex. In the first experiment, 12 healthy control subjects were randomly assigned to receive regular 1, 10 or 20 Hz rTMS in a counterbalanced order with sessions separated by at least 1 week. In the second experiment, 10 of these 12 subjects received priming rTMS (600 stimuli at 6 Hz followed by 600 stimuli at 1 Hz). Cortical inhibition was indexed using short-interval intracortical inhibition (SICI) and cortical silent period (CSP). Corticospinal excitability was indexed using motor threshold and MEP amplitude. We found no significant overall change in SICI, although there was a significant correlation between changes in SICI with baseline SICI. Subjects with greater SICI at baseline tended to have reduction in SICI post-rTMS, whereas subjects with less SICI tended to have increase in SICI post-rTMS. There was also a significant lengthening of the CSP with higher stimulation frequencies compared to lower stimulation frequencies. These findings suggest that rTMS increases CI, particularly in subjects with reduced baseline inhibition, a finding consistent with the concept of homeostatic plasticity. Baseline physiological characteristics may be further explored as a method to select patients who may benefit from rTMS treatment.
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Affiliation(s)
- Zafiris J Daskalakis
- Centre for Addiction and Mental Health, University of Toronto, Toronto, ON, Canada
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73
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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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74
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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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75
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Mochizuki H, Ugawa Y, Terao Y, Sakai KL. Cortical hemoglobin-concentration changes under the coil induced by single-pulse TMS in humans: a simultaneous recording with near-infrared spectroscopy. Exp Brain Res 2005; 169:302-10. [PMID: 16328307 DOI: 10.1007/s00221-005-0149-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Accepted: 07/21/2005] [Indexed: 11/30/2022]
Abstract
We measured cortical hemoglobin-concentration changes under the coil induced by single-pulse transcranial magnetic stimulation (TMS) using a technique of simultaneous recording with near-infrared spectroscopy (NIRS). Single-pulse TMS was delivered over the hand area of the left primary motor cortex at an intensity of 100, 120, or 140% of the active motor threshold (AMT). NIRS recordings were also made during sham stimulation. These four different stimulation sessions (TMS at three intensities and sham stimulation) were performed both when the subject slightly contracted the right first dorsal interosseous muscle and when relaxed it (active and resting conditions). Under the active condition with TMS at 100% AMT, we observed a transient increase in oxy-hemoglobin (oxy-Hb), which was significantly larger than sham stimulation. Under the resting conditions with TMS at 120 and 140% AMT, we observed significant decreases in both deoxy-hemoglobin (deoxyHb) and total-hemoglobin (total-Hb) as compared to sham stimulation. We suggest that the increase of oxy-Hb concentration at 100% AMT under the active condition reflects an add-on effect by TMS to the active baseline and that decrease of deoxy-Hb and total-Hb concentrations at 120 and 140% AMT under the resting condition are due to reduced baseline firings of the corticospinal tract neurons induced by a lasting inhibition provoked by a higher intensity TMS.
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Affiliation(s)
- Hitoshi Mochizuki
- Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
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76
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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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77
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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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78
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Lefaucheur JP. Excitability of the motor cortical representation of the external anal sphincter. Exp Brain Res 2004; 160:268-72. [PMID: 15565435 DOI: 10.1007/s00221-004-2170-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2004] [Accepted: 09/30/2004] [Indexed: 10/26/2022]
Abstract
This study was designed to assess the excitability of the motor cortical representation of the external anal sphincter by using transcranial magnetic stimulation (TMS). In six healthy volunteers, the rest motor threshold and the duration of the cortical silent period were determined with single TMS pulses, and the intracortical inhibition and facilitation were measured with paired TMS pulses. Values obtained from the anal sphincter were compared with those obtained from a muscle in the right hand. All subjects completed the study. Rest motor threshold and intracortical facilitation were similar in both muscles. In contrast, cortical silent period duration and intra-cortical inhibition were less for the anal sphincter than for hand muscle. This study has opened new perspectives for the investigation of anal sphincter cortical control in humans.
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Affiliation(s)
- Jean-Pascal Lefaucheur
- Club d'Electrophysiologie Périnéale, 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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79
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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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80
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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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81
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Lewis GN, Polych MA, Byblow WD. Proposed cortical and sub-cortical contributions to the long-latency stretch reflex in the forearm. Exp Brain Res 2003; 156:72-9. [PMID: 14689132 DOI: 10.1007/s00221-003-1767-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2003] [Accepted: 10/16/2003] [Indexed: 10/26/2022]
Abstract
The short- and long-latency (SLSR, LLSR) components of the stretch reflex response were investigated in the forearm using a paired transcranial magnetic stimulation (TMS)-stretch reflex protocol. Responses to TMS were recorded in the flexor and extensor carpi radialis muscles (FCR, ECR) after conditioning with a rapid wrist extension movement. The cortical stimuli were timed to elicit a motor-evoked potential (MEP) at either the SLSR or LLSR onset in the FCR muscle. Responses were also collected in TMS-alone and stretch reflex-alone conditions. Six intensities of magnetic stimulation were applied in all conditions. In the FCR muscle, MEP amplitude when timed to arrive at the LLSR onset was significantly greater than the sum of the MEP and stretch reflex responses when given separately. MEP amplitudes at the SLSR onset in the FCR muscle and in the ECR muscle at both SLSR and LLSR onset were not significantly different from that expected from the sum of the two stimuli given separately. This indicates heightened corticospinal excitability at a time corresponding to the passage of an afferent volley induced by the stretch, and raises the possibility of a transcortical loop of the LLSR in the forearm. The extent of MEP facilitation was generally consistent across all stimulus intensities tested. A reduced component of the LLSR was evident when the stretch response was timed to arrive during the silent period following the cortical stimulus, suggesting both cortical and sub-cortical components to the reflex response.
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Affiliation(s)
- Gwyn N Lewis
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60611, USA.
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82
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Daskalakis ZJ, Christensen BK, Chen R, Fitzgerald PB, Zipursky RB, Kapur S. Effect of antipsychotics on cortical inhibition using transcranial magnetic stimulation. Psychopharmacology (Berl) 2003; 170:255-262. [PMID: 12904966 DOI: 10.1007/s00213-003-1548-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2002] [Accepted: 05/20/2003] [Indexed: 12/25/2022]
Abstract
Previous studies suggest that antipsychotic medications may alter cortical inhibition (CI). The current study was designed to determine if typical or atypical antipsychotics indeed alter CI in healthy subjects using three CI paradigms as measured with transcranial magnetic stimulation (TMS): short interval intracortical inhibition (SICI), cortical silent period (CSP) and transcallosal inhibition (TCI). CI was measured before, 6 and 24 h after being randomly assigned to receive a single dose of 2 mg haloperidol (n=8), 10 mg olanzapine (n=10) or placebo (n=9). There was no significant effect on any measure of CI at 6 and 24 h after receiving olanzapine, haloperidol or placebo. Moreover, no significant change in the motor threshold was observed across the three medication groups. Therefore, single administration of an antipsychotic has no effect on CI or resting motor threshold. Whether chronic, repeated administration of antipsychotics has effects on CI requires further investigation.
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Affiliation(s)
- Zafiris J Daskalakis
- Schizophrenia Program, Centre for Addiction and Mental Health, Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada.
- Schizophrenia Program, Centre for Addiction and Mental Health, 7th Floor, Clarke Division, 250 College Street, Toronto, Ontario, Canada.
| | - Bruce K Christensen
- Schizophrenia Program, Centre for Addiction and Mental Health, Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
| | - Robert Chen
- Division of Neurology, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Paul B Fitzgerald
- Alfred Psychiatry Research Centre, The Alfred and Monash University Department of Psychological Medicine, Commercial Road, Melbourne, Victoria, Australia
| | - Robert B Zipursky
- Schizophrenia Program, Centre for Addiction and Mental Health, Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
| | - Shitij Kapur
- Schizophrenia Program, Centre for Addiction and Mental Health, Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
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83
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Maeda F, Pascual-Leone A. Transcranial magnetic stimulation: studying motor neurophysiology of psychiatric disorders. Psychopharmacology (Berl) 2003; 168:359-76. [PMID: 12830365 DOI: 10.1007/s00213-002-1216-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2001] [Accepted: 07/12/2002] [Indexed: 10/26/2022]
Abstract
RATIONALE Transcranial magnetic stimulation (TMS) is a noninvasive tool that directly stimulates cortical neurons by inducing magnetic and secondary electric fields. Traditionally TMS has been used to study the motor neurophysiology of healthy subjects and those with neurological disorders. OBJECTIVE Given the known motor dysfunctions in many psychiatric disorders supplemental usage of TMS to study the underlying pathophysiology of certain psychiatric disorders and to assess treatment outcomes is underway. Such studies include examination of motor neuronal membrane, corticospinal and intracortical excitability. Our objective is to overview the past findings. METHODS We review the past literature that used TMS as an assessment tool in psychiatric disorders such as schizophrenia, mood disorders, Tourette's syndrome, obsessive-compulsive disorder, attention-deficit hyperactivity disorder, and substance abuse. RESULTS While the findings are still preliminary due to small sample-size, inconsistent patient population (diagnosis, medication), differences in methodology between research groups, studies restricted to the motor region and possible lack of sensitivity and specificity, the studies are yielding interesting results which could potentially lead to trait- and state-markers of psychiatric disorders. CONCLUSIONS Future studies using TMS alone or in combination with other neuroimaging techniques promise to further expand the application of TMS from studies of motor excitability to higher cognitive functions.
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Affiliation(s)
- Fumiko Maeda
- Department of Psychology, Stanford University, Stanford, Calif, USA
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84
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Murphy BA, Haavik Taylor H, Wilson SA, Knight JA, Mathers KM, Schug S. Changes in median nerve somatosensory transmission and motor output following transient deafferentation of the radial nerve in humans. Clin Neurophysiol 2003; 114:1477-88. [PMID: 12888031 DOI: 10.1016/s1388-2457(03)00131-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To determine if transient anaesthetic deafferentation of the radial nerve would lead to alterations in processing of early somatosensory evoked potentials (SEPs) from the median nerve or alter cortico-motor output to the median nerve innervated abductor pollicis brevis (APB) muscle. METHODS Spinal, brainstem, and cortical SEPs to median nerve stimulation were recorded before, during and after ipsilateral radial nerve block with local anaesthesia. Motor evoked potentials (MEPs) and motor cortex output maps were recorded from the APB muscle. RESULTS There were no significant changes to most early SEP peaks. The N30 peak, however, showed a significant increase in amplitude, which remained elevated throughout the anaesthetic period, returning to baseline once the anaesthetic had completely worn off. MEP amplitude of the median nerve innervated APB muscle was significantly decreased during the radial nerve blockade. There was also a significant alteration in the APB optimal site location, and a small but significant decrease in the silent period during the radial nerve blockade. CONCLUSIONS Transient anaesthetic deafferentation of the radial nerve at the elbow leads to a rapid modulation of cortical processing of median nerve input and output. These changes suggest an overall decrease in motor cortex output to a median nerve innervated muscle not affected by the radial nerve block, occurring concomitantly with an increased amplitude of the median nerve generated N30 SEP peak, thought to represent processing in the supplementary motor area (SMA). Independent subcortical connections to the SMA are thought to contribute to the N30 response observed in this study. Unmasking of pre-existing but latent cortico-cortical and/or thalamo-cortical connections may be the mechanism underlying the cortical SEP increases observed following radial nerve deafferentation. SIGNIFICANCE Transient deafferentation of the radial nerve, which supplies wrist and hand extensor muscles, has been shown to alter sensory processing from and motor output to the median nerve innervated thenar muscles.
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Affiliation(s)
- B A Murphy
- Department of Sport and Exercise Science, Tamaki Campus, University of Auckland, Private Bag 92019, Auckland, New Zealand.
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Tassinari CA, Cincotta M, Zaccara G, Michelucci R. Transcranial magnetic stimulation and epilepsy. Clin Neurophysiol 2003; 114:777-98. [PMID: 12738425 DOI: 10.1016/s1388-2457(03)00004-x] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Epileptic conditions are characterized by an altered balance between excitatory and inhibitory influences at the cortical level. Transcranial magnetic stimulation (TMS) provides a noninvasive evaluation of separate excitatory and inhibitory functions of the cerebral cortex. In addition, repetitive TMS (rTMS) can modulate the excitability of cortical networks. We review the different ways that TMS has been used to investigate pathophysiological mechanisms and effects of antiepileptic drugs in patients with epilepsy and epileptic myoclonus. The safety of different TMS techniques is discussed too. Finally, we discuss the therapeutic prospects of rTMS in this field.
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Affiliation(s)
- Carlo Alberto Tassinari
- Department of Neurosciences, Division of Neurology, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy.
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86
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Daskalakis ZJ, Molnar GF, Christensen BK, Sailer A, Fitzgerald PB, Chen R. An automated method to determine the transcranial magnetic stimulation-induced contralateral silent period. Clin Neurophysiol 2003; 114:938-44. [PMID: 12738441 DOI: 10.1016/s1388-2457(03)00038-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The transcranial magnetic stimulation (TMS)-induced contralateral silent period (CSP) refers to a period of interruption of voluntary muscle activity measured in tonically active muscles. The length of the CSP is generally interpreted to reflect cortical inhibition. The determination of the return of voluntary motor activity is typically accomplished via visual inspection of the electromyography (EMG) waveform and may be subject to inaccuracy on the part of the rater. OBJECTIVE To present and evaluate an automated method (AM) to determine the CSP. METHODS The CSP of 11 healthy controls was recorded using stimulus intensities 20 and 50% above the resting motor threshold (RMT). The mean CSP duration obtained by the two raters using visual inspection and our automated approach were compared. RESULTS The interclass correlation coefficient (ICC) between the two raters and the AM was 0.99 at 150% of RMT and was 0.97 at 120% of RMT. The level of pre-stimulus EMG amplitude and sampling rate did not affect agreement between the AM and more conventional visually guided methods. CONCLUSIONS Our study demonstrates that this AM is a simple, objective and reliable approach for CSP determination. SIGNIFICANCE The CSP is an important neurophysiological measure of cortical inhibition and its determination by our AM provides a more objective and automated approach compared to visually guided methods.
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Affiliation(s)
- Zafiris J Daskalakis
- Centre for Addiction and Mental Health, Schizophrenia and Continuing Care Program, University of Toronto, Ontario, Canada
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87
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Stiasny-Kolster K, Haeske H, Tergau F, Müller HH, Braune HJ, Oertel WH. Chapter 38 Cortical silent period is shortened in restless legs syndrome independently from circadian rhythm. TRANSCRANIAL MAGNETIC STIMULATION AND TRANSCRANIAL DIRECT CURRENT STIMULATION, PROCEEDINGS OF THE 2ND INTERNATIONAL TRANSCRANIAL MAGNETIC STIMULATION (TMS) AND TRANSCRANIAL DIRECT CURRENT STIMULATION (TDCS) SYMPOSIUM 2003; 56:381-9. [PMID: 14677414 DOI: 10.1016/s1567-424x(09)70241-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Affiliation(s)
- K Stiasny-Kolster
- Department of Neurology, Center of Nervous Diseases, Philipps-University of Marburg, Rudolf-Bultmann-Strasse 8, D-35033 Marburg, Germany.
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88
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Reis J, Tergau F, Hamer HM, Müller HH, Knake S, Fritsch B, Oertel WH, Rosenow F. Topiramate selectively decreases intracortical excitability in human motor cortex. Epilepsia 2002; 43:1149-56. [PMID: 12366728 DOI: 10.1046/j.1528-1157.2002.09902.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE Topiramate (TPM) is a novel drug with broad antiepileptic effect in children and adults. In vitro studies suggest activity as sodium-channel blocker, as gamma-aminobutyric acid type A (GABAA)-receptor agonist and as non-N-methyl-D-aspartate (NMDA)-glutamate receptor antagonist. METHODS With transcranial magnetic stimulation (TMS), we evaluated which of the mechanisms of action of TPM detected in vitro are relevant for the modulation of human motor cortex excitability. In a double-blind, placebo-controlled, crossover study design, we investigated the effect of single oral doses of 50 mg and 200 mg TPM on motor thresholds, cortical silent period (CSP), and on intracortical inhibition (ICI) and intracortical facilitation (ICF) in 20 healthy subjects. RESULTS A significant dose-dependent increase of ICI was noticed after 200 mg TPM as compared with placebo at short interstimulus intervals of 2 to 4 ms. TPM had no effect on motor thresholds or the CSP. CONCLUSIONS We conclude that a single dose of TPM selectively increases ICI by GABAAergic and/or glutamatergic mechanisms without a relevant influence on measures, depending on ion-channel blockade or GABAB-receptor activity. The decrease of intracortical excitability (as measured by ICI and ICF) caused by TPM may correlate with its lack of proconvulsive potential in idiopathic generalized epilepsy, because drugs without this action or with less pronounced action may exacerbate seizures in this condition.
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Affiliation(s)
- Janine Reis
- Interdisciplinary Epilepsy Center, Department of Neurology, Philipps-University, Marburg, Germany
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89
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Kimbrell TA, Dunn RT, George MS, Danielson AL, Willis MW, Repella JD, Benson BE, Herscovitch P, Post RM, Wassermann EM. Left prefrontal-repetitive transcranial magnetic stimulation (rTMS) and regional cerebral glucose metabolism in normal volunteers. Psychiatry Res 2002; 115:101-13. [PMID: 12208488 DOI: 10.1016/s0925-4927(02)00041-0] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Repetitive transcranial magnetic stimulation (rTMS) holds promise as a probe into the pathophysiology and possible treatment of neuropsychiatric disorders. To explore its regional effects, we combined rTMS with positron emission tomography (PET). Fourteen healthy volunteers participated in a baseline 18-fluorodeoxyglucose (FDG) PET scan. During a second FDG infusion on the same day, seven subjects received 30 min of 1 Hz rTMS at 80% of motor threshold to left prefrontal cortex, and seven other subjects received sham rTMS under identical conditions. Global and normalized regional cerebral glucose metabolic rates (rCMRglu) from the active and sham conditions were compared to baseline and then to each other. Sham, but not active 1 Hz rTMS, was associated with significantly increased global CMRglu. Compared to baseline, active rTMS induced normalized decreases in rCMRglu in right prefrontal cortex, bilateral anterior cingulate, basal ganglia (L>R), hypothalamus, midbrain, and cerebellum. Increases in rCMRglu were seen in bilateral posterior temporal and occipital cortices. Sham rTMS compared to baseline resulted in isolated normalized decreases in rCMRglu in left dorsal anterior cingulate and left basal ganglia, and increases in posterior association and occiptal regions. Differences between the 1 Hz active versus sham changes from baseline revealed that active rTMS induced relative decrements in rCMRglu in the left superior frontal gyrus and increases in the cuneus (L>R). One Hertz rTMS at 80% motor threshold over the left prefrontal cortex in healthy subjects compared to sham rTMS in another group (each compared to baseline) induced an area of decreased normalized left prefrontal rCMRglu not directly under the stimulation site, as well as increases in occipital cortex. While these results are in the predicted direction, further studies using other designs and higher intensities and frequencies of rTMS are indicated to better describe the local and distant changes induced by rTMS.
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90
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Aoki H, Tsukahara R, Yabe K. Cortical and spinal motor excitability during the premovement EMG silent period prior to rapid voluntary movement in humans. Brain Res 2002; 949:178-87. [PMID: 12213314 DOI: 10.1016/s0006-8993(02)02979-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
(1) To delineate the cortical and spinal excitability during the pre-movement silent period (PMSP), the motor-evoked potentials (MEPs) and H-reflexes were measured for 0-150 ms prior to rapid voluntary movements of 11 healthy subjects. The appearance of PMSP was judged from the electromyogram of the agonist muscle at each rapid movement and the differences of MEPs or H-reflex between the movement which PMSP appeared (PMSP MEPs or PMSP H-reflex) and the movement which did not appear (non-PMSP MEPs or non-PMSP H-reflex) were compared. (2) The mean amplitudes of the PMSP MEPs in the flexor carpi radialis were significantly smaller than the non-PMSP MEPs, whereas the mean amplitude of the PMSP H-reflex was not significantly different from the non-PMSP H-reflex. (3) In the soleus muscle, the change in MEPs and H-reflexes was examined at three periods for 0-150 ms before the rapid movements. The mean amplitudes of PMSP MEPs for the -150- to -100-ms period and for the -50- to -5-ms period were significantly smaller than those of non-PMSP MEPs. On the other hand, the differences of the mean amplitudes between PMSP H-reflex and non-PMSP H-reflex at the three periods were not significant. (4) These findings suggested that the cortical sensitivity to the TMS was decreased during PMSP though the spinal inhibitory mechanisms assess by H-reflex was not altered during the PMSP and that the EMG pause of the PMSP originates not at the spinal level but at the cortical level. The data support the hypothesis that PMSP is preprogrammed in the preparation and initiation process of the voluntary movements aimed at reinforcement of the performance of the subsequent ballistic movements.
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Affiliation(s)
- Hisashi Aoki
- Institute for Developmental Research, Aichi Human Service Center, Kamiya-cho 713-8, Kasugai, Aichi 480-0392, Japan.
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91
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Abbruzzese G, Trompetto C. Clinical and research methods for evaluating cortical excitability. J Clin Neurophysiol 2002; 19:307-21. [PMID: 12436087 DOI: 10.1097/00004691-200208000-00005] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The evaluation of motor cortical output after transcranial magnetic stimulation (TMS) is a means of investigating how the motor cortex reacts to external stimuli (i.e., a method to assess the excitability of the motor cortex). The recording of the descending volleys at the surface of the spinal cord provides a direct measure of the motor cortical output. However, this approach is highly invasive and can be used only during particular conditions. On the other hand, electromyographic recordings of the motor phenomena induced by TMS provide a completely painless, noninvasive, indirect measure of the cortical output, with these phenomena obviously reflecting the excitability of the spinal motoneurons as well as that of the muscle itself. The authors review how the electromyographic activity induced by TMS can provide valuable information about motor cortical excitability for use in clinical practice and research.
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Affiliation(s)
- Giovanni Abbruzzese
- Laboratory of Clinical Neurophysiology, Department of Neurological Sciences & Vision, University of Genoa, Italy.
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92
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Baldissera F, Borroni P, Cavallari P, Cerri G. Excitability changes in human corticospinal projections to forearm muscles during voluntary movement of ipsilateral foot. J Physiol 2002; 539:903-11. [PMID: 11897859 PMCID: PMC2290195 DOI: 10.1113/jphysiol.2001.013282] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Excitability of the H-reflex in the relaxed flexor carpi radialis (FCR) muscle was tested during voluntary oscillations of the ipsilateral foot at five evenly spaced delays during a 600 ms cycle. In some experiments the H-reflex was conditioned by transcranial magnetic stimulation (TMS). With the hand prone, the amplitude of the FCR H-reflex was modulated sinusoidally with the same period as the foot oscillation, the modulation peak occurring in coincidence with contraction of the foot plantar-flexor soleus and the trough during contraction of the extensor tibialis anterior. When the H-reflex was facilitated by TMS at short latency (conditioning-test interval: -2 to -3.5 ms), the modulation was larger than that occurring with an unconditioned reflex of comparable size. This suggests that both the peripheral and the corticospinal components of the facilitated response were modulated in parallel. When the H-reflex was tested 40-60 ms after conditioning, i.e. during the cortical "silent period" induced by TMS, no direct effect was produced on the reflex size but the foot-associated modulation was deeply depressed. These results suggest that the reflex modulation may depend on activity fluctuations in the cortical motor area innervating the forearm motoneurones. It is proposed that when the foot is rhythmically oscillated, along with the full activation of the foot cortical area a simultaneous lesser co-activation of the forearm area produces a subliminal cyclic modulation of cervical motoneurones excitability. Should the two limbs be moved together, the time course of this modulation would favour isodirectional movements of the prone hand and foot, indeed the preferential coupling observed when hand and foot are voluntarily oscillated.
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Affiliation(s)
- Fausto Baldissera
- Istituto di Fisiologia Umana II, Università degli Studi di Milano, Via Mangiagalli 32, I-20133 Milan, Italy.
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93
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Fitzgerald PB, Brown TL, Daskalakis ZJ, Kulkarni J. A transcranial magnetic stimulation study of inhibitory deficits in the motor cortex in patients with schizophrenia. Psychiatry Res 2002; 114:11-22. [PMID: 11864806 DOI: 10.1016/s0925-4927(02)00002-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
It has been proposed that inhibitory deficits play a crucial role in the pathophysiological process of schizophrenia as suggested by post-mortem, neuropsychological and neurophysiological evidence. We hypothesised that patients with schizophrenia would demonstrate abnormalities of cortical inhibition in the motor cortex with single and paired pulse transcranial magnetic stimulation (TMS). Patients with DSM-IV schizophrenia (n=22) and normal volunteers (n=21) participated in the study. Electromyographic recordings from the abductor pollicis brevis (APB) muscle were made during focal TMS stimulation to the contra-lateral motor cortex. The threshold intensity to produce a motor response, the size of the motor evoked potential, the duration of the silent period, and the cortical inhibition and facilitation to paired pulse TMS were measured. The patient group demonstrated a reduction in length of the silent period and a reduction in cortical inhibition with paired stimuli. No changes were found in motor threshold, motor evoked potential size, or cortical facilitation. The study demonstrated deficits of cortical inhibition in the motor cortex of patients with schizophrenia. These deficits appear to be of cortical origin. Their relationship to dysfunction in other cortical networks requires further elucidation.
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Affiliation(s)
- Paul B Fitzgerald
- Dandenong Psychiatric Research Centre, Monash University, Department of Psychological Medicine and Dandenong Area Mental Health Service, P.O. Box 956, Victoria, 3175, Dandenong, Australia.
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94
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Sanger TD, Garg RR, Chen R. Interactions between two different inhibitory systems in the human motor cortex. J Physiol 2001; 530:307-17. [PMID: 11208978 PMCID: PMC2278414 DOI: 10.1111/j.1469-7793.2001.0307l.x] [Citation(s) in RCA: 388] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Intracortical inhibition in the human motor cortex has been previously demonstrated using paired-pulse transcranial magnetic stimulation (TMS) protocols at short intervals (1-6 ms; short interval intracortical inhibition, SICI) with a subthreshold conditioning pulse preceding a suprathreshold test pulse, and at long intervals (50-200 ms; long interval intracortical inhibition, LICI) with suprathreshold conditioning and test pulses. We investigated whether different circuits mediate these inhibitory phenomena and how they interact. In nine healthy volunteers, we applied TMS to the motor cortex and recorded motor evoked potentials from the first dorsal interosseous muscle. With increasing test pulse strength, LICI decreases but SICI tends to increase. There was no correlation between the degree of SICI and LICI. We tested the interactions between SICI and LICI. SICI was reduced or eliminated in the presence of LICI. Loss of SICI was seen even with a conditioning stimulus too weak to induce significant LICI. Our findings demonstrate that different cell populations mediate SICI and LICI. The results are consistent with the hypothesis that LICI inhibits SICI through presynaptic GABAB receptors. Testing of SICI in the presence of LICI may be a non-invasive way of evaluating inhibitory interactions in the human motor cortex.
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Affiliation(s)
- T D Sanger
- Division of Neurology, Toronto Western Hospital and Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada
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95
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Wu T, Sommer M, Tergau F, Paulus W. Modification of the silent period by double transcranial magnetic stimulation. Clin Neurophysiol 2000; 111:1868-72. [PMID: 11018504 DOI: 10.1016/s1388-2457(00)00426-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVES To study the time course of the changes of the inhibitory network of the human motor system, we investigated the silent period (SP) in 7 healthy subjects by double suprathreshold transcranial magnetic stimulation (TMS). METHODS SPs and motor evoked potentials (MEPs) were recorded from the voluntarily activated right abductor digiti minimi muscle. Conditioning and test stimuli were delivered with equal intensity, which was set to yield a baseline SP duration of 130 ms by a single pulse, and with various interstimulus intervals (ISIs). In addition, a control experiment with adjustment of the intensity of single stimuli was performed. RESULTS At ISIs of 20 and 30 ms the test pulse SP duration was prolonged, without increasing the MEP amplitude. The SP duration shortened at longer ISIs and showed a significant depression between ISIs of 60-110 ms. The shortened SP was accompanied by a diminished MEP. The control experiment revealed that the SPs evoked by the adjusted pulses were significantly shorter than the test pulse SPs. CONCLUSIONS A conditioning stimulus can prolong and shorten the test pulse SP duration at different ISIs. The prolongation is probably cortically generated, whereas the shortening is likely to occur at a cortical and spinal level.
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Affiliation(s)
- T Wu
- Department of Clinical Neurophysiology, Georg August University, Robert-Koch-Street 40, D-37075, Göttingen, Germany
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96
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Moll GH, Wischer S, Heinrich H, Tergau F, Paulus W, Rothenberger A. Deficient motor control in children with tic disorder: evidence from transcranial magnetic stimulation. Neurosci Lett 1999; 272:37-40. [PMID: 10507537 DOI: 10.1016/s0304-3940(99)00575-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Decreased motor inhibition was reported in adult patients with tic disorder (TD) using the technique of transcranial magnetic stimulation. Since tics usually begin during childhood, motor threshold, cortical silent period (CSP) and intracortical inhibition/facilitation were measured in 21 TD children and 25 healthy children aged 10-16 years. In TD children motor threshold was normal. The CSP was significantly shortened compared to healthy controls but did not depend on tic localization. Intracortical inhibition and facilitation did not differ between the two groups. This study confirms that the finding of decreased motor control in adult patients also holds true for children wherever the tics in the latter group were located.
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Affiliation(s)
- G H Moll
- Child and Adolescent Psychiatry, University of Göttingen, Germany
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