1,721,192 research outputs found
Comparative assessment of best conventional with best theta burst repetitive transcranial magnetic stimulation protocols on human motor cortex excitability
No full textObjective: Comparative assessment of best conventional with best theta burst repetitive transcranial magnetic stimulation (rTMS) protocols on human motor cortex excitability. Methods: Stimulation of dominant hand abductor digiti minimi muscle representation of motor cortex in nine healthy right-handed subjects utilising two different MagPro stimulators to generate TMS pulses of distinct monophasic, half sine and biphasic shape with anteriorly or posteriorly directed current flow, measuring resting and active motor threshold and motor-evoked potential (MEP) amplitude. Comparison of two different conventional rTMSs and eight different theta burst stimulation (TBS) protocols. Results: Continuous TBS (cTBS) yielded an inhibition, and intermittent TBS (iTBS) a facilitation of MEP amplitudes. These effects were not significantly influenced by waveform or current orientation. Compared to conventional rTMS paradigms, neither cTBS nor iTBS showed significantly stronger effects. In addition and confirming earlier findings, the asymmetric monophasic pulse and a posteriorly directed current flow yielded a higher threshold than all other TMS types. The less asymmetric half-sine pulse had a lower threshold for postero-anterior current than in the opposite direction. The biphasic stimuli yielded the lowest motor threshold particularly with an antero-posterior current direction. Conclusions: TBS did not depend on current direction or on pulse configuration in this sample of healthy subjects. In addition, TBS effect size was not clearly superior to conventional rTMS protocols. Significance: This systematic comparison of three waveforms, two current directions and two different interventional protocols allows a better understanding of the mechanisms of TMS on human motor cortex. (c) 2008 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved
Strength-Duration Relationship in Paired-pulse Transcranial Magnetic Stimulation (TMS) and Its Implications for Repetitive TMS
No full textBackground: Paired-pulse protocols have played a pivotal role in neuroscience research using transcranial magnetic stimulation (TMS). Stimulus parameters have been optimized over the years. More recently, pulse width (PW) has been introduced to this field as a new parameter, which may further fine-tune paired-pulse protocols. The relationship between the PW and effectiveness of a stimulus is known as the "strength-duration relationship". Objective: To test the "strength-duration relationship", so as to improve paired-pulse TMS protocols, and to apply the results to develop new repetitive TMS (rTMS) methods. Methods: Four protocols were investigated separately: short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), short-interval intracortical facilitation (SICF) and long-interval intracortical inhibition (LICI). First, various stimulus parameters were tested to identify those yielding the largest facilitation or inhibition of the motor evoked potential (MEP) in each participant. Using these parameters, paired-pulse stimulations were repeated every five seconds for 30 minutes (repetitive paired-pulse stimulation, rPPS). The after-effects of rPPS were measured using MEP amplitude as an index of motor-cortical excitability. Results: Altogether, the effect of changing PW was similar to that of changing the stimulus intensity in the conventional settings. The best parameters were different for each participant. When these parameters were used, rPPS based on either SICF or ICF induced an increase in MEP amplitude. Conclusions: PW was introduced as a new parameter in paired-pulse TMS. Modulation of PW influenced the results of paired-pulse protocols. rPPS using facilitatory protocols can be a good candidate to induce enhancement of motor-cortical excitability. (C) 2016 Elsevier Inc. All rights reserved
Training effects outweigh effects of single-session conventional rTMS and theta burst stimulation in PD patients
No full textBackground. Focal single-session repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex has been claimed to be capable of improving motor function in Parkinson's disease. Objective. The authors sought to determine which type of rTMS protocol holds the highest potential for future therapeutic application. Methods. Twenty-two patients with Parkinson's disease received 5 different rTMS protocols on 5 consecutive days in a pseudorandomized and counterbalanced order either in the defined OFF condition or with their usual medication. The protocols tested in the present study included 2 conventional rTMS protocols (0.5 and 10 Hz) as well as the recently introduced theta burst stimulation (cTBS, iTBS) and a sham condition. Cortical excitability, motor performance (pointing movement, pronation-supination, Purdue Pegboard Test, walking), and mood were assessed before and after each session. Results. The authors observed motor training from days 1 to 4, particularly in the group on dopaminergic medication. None of the rTMS paradigms excelled placebo stimulation. The only exception was the Purdue Pegboard Test, in which all active stimulation paradigms yielded slightly stronger effects than sham stimulation. Conclusions. Within a single session, no clinically relevant difference in the rTMS protocols could be detected. Training effects outweigh and may have masked rTMS effects, particularly in the group on dopaminergic mediation
The effect of current flow direction on motor hot spot allocation by transcranial magnetic stimulation.
No full textThe objective of this study was to investigate the significance of pulse configurations and current direction for corticospinal activation using transcranial magnetic stimulation (TMS). In 11 healthy subjects (8 female), a motor map for the motor evoked potentials (MEPs) recorded from the first dorsal interosseus (FDI), abductor digiti minimi (ADM), extensor carpi radialis, and biceps brachii (BB) muscles of the dominant side was established. Starting from a manually determined hot spot of the FDI representation, we measured MEPs at equal oriented points on an hexagonal grid, with 7 MEPs recorded at each point, using the following pulse configurations: posteriorly directed monophasic (Mo-P), anteriorly directed monophasic (Mo-A), biphasic with the more relevant second cycle oriented posteriorly (Bi-P) as well as a reversed biphasic condition (Bi-A). For each pulse configuration, a hot spot was determined and a center of gravity (CoG) was calculated. We found that the factor current direction had an effect on location of the CoG-adjusted hot spot in the cranio-caudal axis but not in the latero-medial direction with anteriorly directed pulses locating the CoG more anteriorly and vice versa. In addition, the CoG for the FDI was more laterally than the cortical representations for the abductor digiti minimi (ADM) and extensor carpi radialis (ECR) which were registered as well. The results indicate that direction of the current pulse should be taken into account for determination of the motor representation of a muscle by TMS
An unexpected iron in the fire of speech production
No full textThis scientific commentary refers to \‘Elevated iron concentration in putamen and cortical speech motor network in developmental stuttering\’, by Cler et al. (doi:10.1093/brain/awab283).This scientific commentary refers to ‘Elevated iron concentration in putamen and cortical speech motor network in developmental stuttering’, by Cler et al. (doi:10.1093/brain/awab283)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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