Hannah, R;
Rothwell, JC;
(2016)
Pulse Duration as Well as Current Direction Determines the Specificity of Transcranial Magnetic Stimulation of Motor Cortex during Contraction.
Brain Stimulation
, 10
(1)
pp. 106-115.
10.1016/j.brs.2016.09.008.
Preview |
Text
1-s2.0-S1935861X16302601-main.pdf Download (1MB) | Preview |
Abstract
BACKGROUND: Previous research suggested that anterior-posterior (AP) directed currents induced by TMS in motor cortex (M1) activate different interneuron circuits than posterior-anterior currents (PA). The present experiments provide evidence that pulse duration also determines the activation of specific interneuron circuits. OBJECTIVE: To use single motor unit (SMU) recordings to confirm the difference in onset latencies of motor-evoked potentials (MEPs) evoked by different current directions and pulse durations: AP30, AP120, PA30 and PA120. To test whether the amplitude of the MEPs is differentially influenced by somatosensory inputs from the hand (short-latency afferent inhibition, SAI), and examine the sensitivity of SAI to changes in cerebellar excitability produced by direct current stimulation (tDCSCb). METHODS: Surface electromyograms and SMUs were recorded from the first dorsal interosseous muscle. SAI was tested with an electrical stimulus to median or digital nerves ~20-25ms prior to TMS delivered over the M1 hand area via a controllable pulse parameter TMS (cTMS) device. SAI was also tested during the application of anodal or sham tDCSCb. Because TMS pulse specificity is greatest at low stimulus intensities, most experiments were conducted with weak voluntary contraction to reduce stimulus threshold. RESULTS: AP30 currents recruited the longest latency SMU and surface MEP responses. During contraction SAI was greater for AP30 responses versus all other pulses. Online anodal tDCSCb reduced SAI for the AP30 currents only. CONCUSIONS: AP30 currents activate an interneuron circuit with different functional properties to those activated by other pulse types. Pulse duration and current direction determine what is activated in M1 with TMS.
| Type: | Article |
|---|---|
| Title: | Pulse Duration as Well as Current Direction Determines the Specificity of Transcranial Magnetic Stimulation of Motor Cortex during Contraction |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.brs.2016.09.008 |
| Publisher version: | http://dx.doi.org/10.1016/j.brs.2016.09.008 |
| Language: | English |
| Additional information: | Copyright: © 2016 The authors. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0) (https://creativecommons.org/licenses/by/4.0/) |
| Keywords: | Pulse duration; Current direction; Short latency afferent inhibition; Cerebellum; Transcranial direct current stimulation |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Clinical and Movement Neurosciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/1519736 |
Archive Staff Only
 |
View Item |
