Numerical Modeling of Plasticity Induced by Quadri-Pulse Stimulation

Abstract

Quadri-pulse stimulation (QPS), a type of repetitive transcranial magnetic stimulation (rTMS), can induce a considerable aftereffect on cortical synapses. Human experiments have shown that the type of effect on synaptic efficiency (in terms of potentiation or depression) depends on the time interval between pulses. The maturation of biophysically-based models, which describe the physiological properties of plasticity mathematically, offers a beneficial framework to explore induced plasticity for new stimulation protocols. To model the QPS paradigm, a phenomenological model based on the knowledge of spike timingdependent plasticity (STDP) mechanisms of synaptic plasticity was utilized where the cortex builds upon the platform of neuronal population modeling. Induced cortical plasticity was modeled for both conventional monophasic pulses and unidirectional pulses generated by the cTMS device, in a total of 117 different scenarios. For the conventional monophasic stimuli, the results of the predictive model broadly follow what is typically seen in human experiments. Unidirectional pulses can produce a similar range of plasticity. Additionally, changing the pulse width had a considerable effect on the plasticity (approximately 20% increase). As the width of the positive phase increases, the size of the potentiation will also increase. The proposed model can generate predictions to guide future plasticity experiments. Estimating the plasticity and optimizing the rTMS protocols might effectively improve the safety implications of TMS experiments by reducing the number of delivered pulses to participants. Finding the optimal stimulation protocol with the maximum potentiation/depression can lead to the design of a new TMS pulse generator device with targeted hardware and control algorithms. INDEX TERMS Transcranial magnetic stimulation, TMS-induced plasticity, QPS, near-rectangular magnetic stimuli, cTMS device.

Non-invasive, non-pharmacological/bio-technological interventions towards neurorestoration upshot after ischemic stroke, in adults—systematic, synthetic, literature review

“…To be added to the above mentioned type of interventions-including as regards their capability to augment functional outcomes after ischemic stroke, (and inserting accordingly, the assertion that "These techniques can enhance the effect of practice and facilitate the retention of tasks that mimic daily life activities", too) [208]-the paired associative stimulation (PAS-see below)-with only the enumeration, hereinafter, of some not (yet ?) frequently availed in practice variants of theirs (alphabetically): quadripulse rTMS-a newer and more complex protocol emerging of "… repetitive biphasic-pulse protocols, such as theta-burst stimulation (TBS) …" [226] (maybe also octa-pulse, too), transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) [47,208].…”

Estimation of the Motor Threshold for Near‐Rectangular Stimuli Using the Hodgkin–Huxley Model

“…Despite the success of the TMS procedure, there are several critical limitations associated with the magnetic pulse shape parameters. Conventional neurostimulators most commonly employ LC resonant circuits, resulting in a constant waveform for the magnetic pulses, depending on the predetermined hardware [ 3 , 4 ].…”

“…More adjustable control of the magnetic field waveform can potentially enable new research and clinical applications that are not realizable with conventional TMS tools, such as changing the waveform of the magnetic pulse [ 4 ]. Addressing this need, Peterchev et al have introduced a controllable-TMS (cTMS) machine to produce flexible near-rectangular stimulus shapes with three different architectural variations [ 5 ].…”