Hysteresis effects on the input–output curve of motor evoked potentials

Section: Methodssupporting

confidence: 90%

Corticospinal excitability during preparation for an anticipatory action is modulated by the availability of visual information

Marinovic

Reid²,

Plooy³

et al. 2011

“…First, Tinazzi et al (2003) used a nonfocal circular coil and measured SP duration at only one stimulus intensity. In our study stimuli were delivered with a focal figure-of-eight coil and we measured complete SP duration I/O curves, which provide more complete and accurate estimates of SP durations (Kimiskidis et al 2005;Möller et al 2009). Kimiskidis et al (2005) compared the classical SP measurement method at one stimulus intensity to measurements of plateau value, S 50 , and slope of I/O duration curves in epileptic patients.…”

Section: Discussionmentioning

confidence: 99%

Task-dependent changes of motor cortical network excitability during precision grip compared to isolated finger contraction

Kouchtir-Devanne

Capaday

Cassim

et al. 2012

The purpose of this study was to determine whether task-dependent differences in corticospinal pathway excitability occur in going from isolated contractions of the index finger to its coordinated activity with the thumb. Focal transcranial magnetic stimulation (TMS) was used to measure input-output (I/O) curves--a measure of corticospinal pathway excitability--of the contralateral first dorsal interosseus (FDI) muscle in 21 healthy subjects performing two isometric motor tasks: index abduction and precision grip. The level of FDI electromyographic (EMG) activity was kept constant across tasks. The amplitude of the FDI motor evoked potentials (MEPs) and the duration of FDI silent period (SP) were plotted against TMS stimulus intensity and fitted, respectively, to a Boltzmann sigmoidal function. The plateau level of the FDI MEP amplitude I/O curve increased by an average of 40% during the precision grip compared with index abduction. Likewise, the steepness of the curve, as measured by the value of the maximum slope, increased by nearly 70%. By contrast, all I/O curve parameters [plateau, stimulus intensity required to obtain 50% of maximum response (S(50)), and slope] of SP duration were similar between the two tasks. Short- and long-latency intracortical inhibitions (SICI and LICI, respectively) were also measured in each task. Both measures of inhibition decreased during precision grip compared with the isolated contraction. The results demonstrate that the motor cortical circuits controlling index and thumb muscles become functionally coupled when the muscles are used synergistically and this may be due, at least in part, to a decrease of intracortical inhibition and an increase of recurrent excitation.

“…Therefore, it is possible that there is an order effect for these two conditions with subjects having a modified response to subsequent exposures to the water flow condition. Third, in EX 2 and 3, the interstimulus interval might be too short and lead to hysteresis effects on MEPs recruitment curve (Moller et al 2009). …”

Section: Primary Motor Cortex Excitability At Rest (Tms Study)mentioning

confidence: 99%

Whole-hand water flow stimulation increases motor cortical excitability: a study of transcranial magnetic stimulation and movement-related cortical potentials

Sato

Yamashiro

Onishi

et al. 2015

Maruyama A. Whole-hand water flow stimulation increases motor cortical excitability: a study of transcranial magnetic stimulation and movement-related cortical potentials. J Neurophysiol 113: 822-833, 2015. First published November 5, 2014 doi:10.1152/jn.00161.2014.-Previous studies examining the influence of afferent stimulation on corticospinal excitability have demonstrated that the intensity of afferent stimulation and the nature of the afferents targeted (cutaneous/proprioceptive) determine the effects. In this study, we assessed the effects of whole-hand water immersion (WI) and water flow stimulation (WF) on corticospinal excitability and intracortical circuits by measuring motor evoked potential (MEP) recruitment curves and conditioned MEP amplitudes. We further investigated whether whole-hand WF modulated movement-related cortical activity. Ten healthy subjects participated in three experiments, comprising the immersion of participants' right hands with (whole-hand WF) or without (whole-hand WI) water flow, and no immersion (control). We evaluated MEP recruitment curves produced by a single transcranial magnetic stimulation (TMS) pulse at increasing stimulus intensities, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) using the paired TMS technique before and after 15 min of intervention. Movement-related cortical potentials (MRCPs) were evaluated to examine primary motor cortex, supplementary motor area, and somatosensory cortex excitability upon movement before and after whole-hand WF. After wholehand WF, the slope of the MEP recruitment curve significantly increased, whereas SICI decreased and ICF increased in the contralateral motor cortex. The amplitude of the Bereitschaftspotential, negative slope, and motor potential of MRCPs significantly increased after whole-hand WF. We demonstrated that whole-hand WF increased corticospinal excitability, decreased SICI, and increased ICF, although whole-hand WI did not change corticospinal excitability and intracortical circuits. Whole-hand WF modulated movement-related cortical activity, increasing motor cortex activation for the planning and execution of voluntary movements.whole-hand water flow stimulation; primary motor cortex; corticospinal excitability; intracortical circuit; movement-related cortical potentials