Quadripulse stimulation (QPS)

Abstract

Quadripulse stimulation (QPS) is a newly developed stimulation method to induce neural plasticity in humans. One stimulation burst consisting of four monophasic pulses is given every 5 s for 30 min. A total of 360 bursts (1440 pulses) are given in one session. Short-interval QPS potentiates the target cortical excitability and long-interval QPS depresses it. QPS at an inter-pulse interval of 5 ms (QPS5) induces long-term potentiation (LTP)-like effects most efficiently and QPS50 induces long-term depression (LTD)-like effects most effectively in the primary motor cortex. In this mini-review, we briefly introduce QPS: (i) principle and cortical plasticity (stimulators and protocols, synaptic plasticity, underlying mechanisms, metaplasticity, axonal plasticity, and drug effects), (ii) robust and strong neural plasticity induction (variability, influence of phasic muscle contraction, independency of BDNF polymorphism, sensory cortical plasticity, neural plasticity in the contralateral hemisphere, on-line effects on the brain networks, studies of normal brain physiology, and visuomotor sequence learning), (iii) therapeutic applications to neurological and psychiatric disorders (Parkinson's disease, epilepsy, cerebrovascular disease, and major depression), (iv) safety, and (v) future issues. Based on this evidence, we propose that QPS is currently the most powerful and reliable non-invasive brain stimulation method to induce neural plasticity in humans. Keywords Repetitive transcranial magnetic stimulation (rTMS) • Quadripulse stimulation (QPS) • Synaptic plasticity • Long-term potentiation (LTP) • Long-term depression (LTD) Abbreviations BCM Bienenstock-Cooper-Munro BDNF Brain-derived neurotrophic factor fMRI Functional magnetic resonance imaging LTD Long-term depression LTP Long-term potentiation M1 Primary motor cortex MEP Motor-evoked potential NIBS Non-invasive brain stimulation NIRS Near-infrared spectroscopy QPS Quadripulse stimulation rTMS Repetitive transcranial magnetic stimulation S1 Primary sensory cortex SEP Sensory-evoked potential SMA Supplementary motor cortex TMS Transcranial magnetic stimulation

Programmable Transcranial Magnetic Stimulation: A Modulation Approach for the Generation of Controllable Magnetic Stimuli

“…For example, to produce a train of four monophasic magnetic pulses with a time interval of 1.5-1250 ms (called Quadri-pulse stimulation: QPS), four Magstim TMS devices are connected with a specially designed combining module [38] [39]. Eliminating these costly solutions motivates the design of new circuits for the generation of magnetic stimuli that can provide the ability to generate consecutive pulses required for novel therapies and experiments.…”

“…With a very short time interval, a consistent stimulus can be generated and a stable potential change in the membrane can occur. Using the QPS protocol [39], the proposed system can generate 360 monophasic stimuli in 30 minutes, without a coil heating issue (coil temperature less than 40 ° C).…”

Numerical Modeling of Plasticity Induced by Quadri-Pulse Stimulation

“…One novel paradigm that is showing promising aftereffects is the QPS, which uses monophasic stimuli instead [9] [10]. This method utilizes four monophasic stimuli at predefined inter-stimulus intervals (ISIs) in a burst with an inter-burst interval of 5 s, where modulation of cortical excitability highly depends on the ISIs [11]. According to human experiments, recorded motorevoked potentials (MEPs) are weakened for QPS50 (ISI = 50 ms), whereas they are strengthed for several hours after QPS5 (ISI = 5 ms) [12] .…”

“…QPS1.5, QPS5, and QPS10), while long ISIs have (LTD)-like aftereffects (i.e. QPS30, QPS50, and QPS100) [11] [10].…”

“…Producing short ISIs is one of the main challenges of TMS devices. For example, in the majority of literature, to generate the QPS protocol, four Magstim TMS 200 devices (Magstim, UK) are connected with a specially designed combining module [11]. Therefore, it increases the size and cost of the required QPS system.…”