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INTERAZIONE TRA cTBS CEREBELLARE E MOVIMENTI VOLONTARI SEMPLICI E COMPLESSI DELL’ARTO SUPERIORE: NUOVE ACQUISIZIONI SUI PROCESSI DI PLASTICITÀ OMEOSTATICA E DI FORMAZIONE DELLA MEMORIA MOTORIA
Full text linkThe aim of the present study was to investigate in healthy subjects whether continuous theta-burst stimulation (cTBS) applied over the lateral cerebellum alters motor learning (acquisition and retention phases) during ipsilateral simple and complex movements.
Eighteen healthy subjects participated in the study. We delivered cTBS over the lateral cerebellum immediately before a motor learning task involving repeated simple (i.e. index finger-abductions) and complex (i.e. reaching) movements. As motor learning measures we evaluated kinematic variables for simple and complex movements during the task. To see whether cerebellar cTBS-induced changes in motor learning take place through changes in primary motor cortex (M1) activity we used single-pulse transcranial magnetic stimulation (TMS) and evaluated changes in motor evoked potential (MEP) amplitude throughout the experiment.
Cerebellar cTBS left the practice-related increase in peak acceleration unchanged but decreased peak acceleration for index finger and reaching movements during motor retention. The smoothness and straightness for trajectories related to reaching movements remained unchanged. When subjects repeated simple and complex movements performed alone, M1 excitability, as measured by the TMS-induced MEP facilitation, increased and MEP amplitudes increased more during simple movements than during complex movements. Cerebellar cTBS given before simple and complex movement tasks decreased the MEP facilitation induced by simple movements, whereas it increased the MEP facilitation induced by complex movements.
During simple and complex movement tasks testing motor learning, no matter how complicated the motor task, cerebellar cTBS interferes with motor memory formation. cTBS induces changes in cerebellar activity thus altering motor-learning-related synaptic activity in M1
Effetti della zonisamide sull’EEG: uno studio quantitativo ed ispettivo in pazienti epilettici.
No full textEarly visuomotor integration processes induce LTP/LTD-like plasticity in the human motor cortex
No full textTo investigate whether visuomotor integration processes induce long-term potentiation (LTP) and depression (LTD)-like plasticity in the primary motor cortex (M1), we designed a new paired associative stimulation (PAS) protocol coupling left primary visual area (V1) activation achieved by hemifield visual evoked potentials (VEPs) and transcranial magnetic stimulation (TMS) over the left M1, at specific interstimulus intervals (ISIs), delivered at 1 Hz (V-PAS). Before and after V-PAS, we measured motor evoked potentials (MEPs). To clarify the mechanisms underlying V-PAS, we tested the effect of 1-Hz repetitive TMS (rTMS), 0.25-Hz V-PAS and rTMS, and a shorter 0.25-Hz V-PAS protocol. To examine V-PAS with contralateral V1 activation, we delivered V-PAS activating the right V1. To clarify whether V-PAS increases V1 activity or parieto- and premotor-to-M1 connectivity, before and after V-PAS, we examined VEPs and MEPs evoked by paired-pulse techniques. V-PAS increased, decreased, or left MEPs unchanged according to the ISI used. After 1-Hz rTMS MEPs decreased. Although 0.25-Hz rTMS elicited no aftereffect, 0.25-Hz V-PAS modulated MEPs according to the ISI used. The short 0.25-Hz V-PAS protocol left MEPs unchanged. Contralateral V-PAS inhibited MEPs. After V-PAS, VEPs remained unchanged and the premotor-to-M1 inhibitory connections decreased. V-PAS induces M1 LTP/LTD-like plasticity by activating premotor-to-motor connections
Primary somatosensory cortical plasticity and tactile temporal discrimination in focal hand dystonia
No full textObjective: To investigate whether theta burst stimulation (TBS) applied over primary somatosensory cortex (S1) modulates somatosensory temporal discrimination threshold (STDT) and writing performances in patients with focal hand dystonia (FHD). Methods: Twelve patients with FHD underwent STDT testing and writing tasks before and after intermittent, continuous, or sham TBS (iTBS, cTBS, sham TBS) over S1 contralateral to the affected hand. Twelve healthy subjects underwent iTBS and cTBS over S1 and STDT values were tested on the right hand before and after TBS. Results: Baseline STDT values were higher in patients than in healthy subjects on both the affected and unaffected hand. In patients and healthy subjects iTBS decreased, whereas cTBS increased STDT values and did so to a similar extent in both groups. In patients, although STDT values decreased after iTBS, they did not normalize. S1 modulation did not improve the writing performance. Conclusions: In patients, S1 responds normally to protocols inducing homotopic synaptic plasticity. The inhibitory interneuron activity responsible for STDT is altered. Significance: The pathophysiological mechanisms underlying abnormal temporal discrimination differ from those responsible for motor symptoms in FHD. © 2013 International Federation of Clinical Neurophysiology
Somatosensory temporal discrimination in Parkinson's disease, dystonia and essential tremor: Pathophysiological and clinical implications
No full textObjective: To investigate whether changes in the somatosensory temporal discrimination threshold (STDT) in Parkinson's disease (PD) and dystonia reflect the involvement of specific neural structures or mechanisms related to tremor, and whether the STDT can discriminate patients with PD, dystonia or essential tremor (ET). Methods: We tested STDT in 223 patients with PD, dystonia and ET and compared STDT values in patients with PD and dystonia with tremor with those of PD and CD without tremor. Data were compared with those of age-matched healthy subjects. Results: STDT values were high in patients with dystonia and PD but normal in ET. In PD, STDT values were similar in patients with resting or postural/action tremor and in those without tremor. In dystonia, STDT values were higher in patients with tremor than in those without tremor. The ROC curve showed that STDT discriminates tremor in dystonia from ET. Conclusions: In PD, STDT changes likely reflect basal ganglia abnormalities and are unrelated to tremor mechanisms. In dystonia, the primary somatosensory cortex and cerebellum play an additional role. Significance: STDT provides information on the pathophysiological mechanisms of patients with movement disorders and may be used to differentiate patients with dystonia and tremor from those with tremor due to ET
Short-term and long-term plasticity interaction in human primary motor cortex
No full textRepetitive transcranial magnetic stimulation (rTMS) over primary motor cortex (M1) elicits changes in motor evoked potential (MEP) size thought to reflect short- and long-term forms of synaptic plasticity, resembling short-term potentiation (STP) and long-term potentiation/depression (LTP/LTD) observed in animal experiments. We designed this study in healthy humans to investigate whether STP as elicited by 5-Hz rTMS interferes with LTP/LTD-like plasticity induced by intermittent and continuous theta-burst stimulation (iTBS and cTBS). The effects induced by 5-Hz rTMS and iTBS/cTBS were indexed as changes in MEP size. We separately evaluated changes induced by 5-Hz rTMS, iTBS and cTBS applied alone and those induced by iTBS and cTBS delivered after priming 5-Hz rTMS. Interactions between 5-Hz rTMS and iTBS/cTBS were investigated under several experimental conditions by delivering 5-Hz rTMS at suprathreshold and subthreshold intensity, allowing 1 and 5 min intervals to elapse between 5-Hz rTMS and TBS, and delivering one and ten 5-Hz rTMS trains. We also investigated whether 5-Hz rTMS induces changes in intracortical excitability tested with paired-pulse transcranial magnetic stimulation. When given alone, 5-Hz rTMS induced short-lasting and iTBS/cTBS induced long-lasting changes in MEP amplitudes. When M1 was primed with 10 suprathreshold 5-Hz rTMS trains at 1 min before iTBS or cTBS, the iTBS/cTBS-induced after-effects disappeared. The 5-Hz rTMS left intracortical excitability unchanged. We suggest that STP elicited by suprathreshold 5-Hz rTMS abolishes iTBS/cTBS-induced LTP/LTD-like plasticity through non-homeostatic metaplasticity mechanisms. Our study provides new information on interactions between short-term and long-term rTMS-induced plasticity in human M1
Somatosensory temporal discrimination threshold may help to differentiate patients with multiple system atrophy from patients with Parkinson's disease
No full textBackground and purpose Somatosensory temporal discrimination threshold (STDT) is defined as the threshold at which two tactile stimuli applied to the skin are perceived as clearly distinct. The aim of the study was to investigate whether the extent of STDT alterations differs between patients with parkinsonian type multiple system atrophy (MSA-P) and patients with Parkinson's disease (PD). Possible differences between the two groups may help to differentiate MSA-P from PD. Methods STDT was investigated in 20 patients with MSA-P, 21 patients with PD and 18 age-matched healthy subjects. The clinical evaluation included the Mini-Mental State Examination, Hoehn and Yahr Scale, Frontal Assessment Battery, Unified Multiple System Atrophy Rating Scale for patients with MSA-P, and Unified Parkinson's Disease Rating Scale for patients with PD. STDT was investigated by delivering paired electrical stimuli starting with an inter-stimulus interval (ISI) of 0ms (simultaneous pair), and progressively increasing the ISIs in 10-ms steps. Results Between-group anova showed that STDT statistically differed in MSA-P versus patients with PD and healthy subjects. Post hoc showed that STDT values in patients with MSA-P were significantly higher than those in patients with PD and healthy subjects. Receiver operating characteristic curve analysis showed that STDT testing yielded high diagnostic specificity and sensitivity. Conclusions STDT is abnormal in patients with MSA-P and PD. The degree of STDT abnormalities is higher in patients with MSA-P than in patients with PD
The photoparoxysmal response reflects abnormal early visuomotor integration in the human motor cortex
No full textCerebellar continuous theta-burst stimulation affects motor learning of voluntary arm movements in humans
No full textIn this study we investigated in healthy subjects whether continuous theta-burst stimulation (cTBS) over the lateral cerebellum alters motor practice and retention phases during ipsilateral index finger and arm reaching movements. In 12 healthy subjects we delivered cTBS before repeated index finger abductions or arm reaching movements differing in complexity (reaching-to-grasp and reaching-to-point). We evaluated kinematic variables for index finger and arm reaching movements and changes in primary motor cortex (M1) activity tested with transcranial magnetic stimulation. Peak acceleration increased during motor practice for index finger abductions and reaching-to-grasp movements and persisted during motor retention. Peak acceleration decreased during motor practice for reaching-to-point movements and the decrease remained during motor retention. Cerebellar cTBS left the changes in peak acceleration during motor practice for index finger abductions and reaching-to-grasp arm movements unchanged but reduced peak acceleration at motor retention. Cerebellar cTBS prevented the decrease in peak acceleration for reaching-to-point movements during motor practice and at motor retention. Index finger abductions and arm reaching movements increased M1 excitability. Cerebellar cTBS decreased the motor evoked potential (MEP) facilitation induced by index finger movements, but increased the MEP facilitation after reaching-to-grasp and reaching-to-point movements. Cerebellar stimulation prevents motor retention for index finger abductions, reaching-to-grasp and reaching-to-point movements and degrades motor practice only for reaching-to-point movements. Cerebellar cTBS alters practice-related changes in M1 excitability depending on how intensely the cerebellum contributes to the task. Changes in M1 excitability reflect mechanisms of homeostatic plasticity elicited by the interaction of an 'exogenous' (cTBS-induced) and an 'endogenous' (motor practice-induced) plasticity-inducing protocol. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd
Somatosensory temporal discrimination threshold is impaired in patients with multiple sclerosis
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