QPS
Quadripulse Stimulation

Quadripulse transcranial magnetic stimulation (QPS) is a novel repetitive transcranial magnetic stimulation (rTMS) technique that can be used to increase or decrease cortical excitability1. Four bursts of monophasic TMS, originating from four separate magnetic stimulators, are administered, with each QPS burst being separated by an inter-burst interval (IBI) of five seconds.

In a comprehensive investigation of the inter-stimulus interval (SI) which separates each TMS pulse within a QPS burst, shorter ISIs were found to increase the amplitude of motor evoked potentials (MEPs) for up to at least 75 minutes while, in contrast, quadripulse stimulation at longer ISIs of 50ms suppressed MEPs for at least 75 minutes. The success of QPS at modulating cortical excitability appears to be determined by the IBI, with an IBI of around 5 seconds appearing to be optimal2.

The variability of QPS after-eFFects are smaller relative to other non-invasive brain stimulation protocols, with 80% of younger participants showing effects of QPS-50ms and 69% of participants showing a response as measured by a change in MEP3,4. The success of QPS as a reliable means of altering cortical excitability appears to be due to the use of repetitive monophasic pulses instead of biphasic pulses. 

A systematic comparison of monophasic and biphasic QPS protocols that were otherwise identical revealed that QPS-5ms-induced increases and QPS-50ms-induced decreases in MEP amplitude were greater when monophasic pulses were used compared to biphasic pulses5. 

Not only do monophasic pulses produce larger effects on the MEP, but the monophasic pulses also produce effects that do not return to baseline within an hour. The use of monophasic pulses may be a potential reason for the reduced variability of QPS compared to other biphasic rTMS protocols, and for a high number of responders after the application of QPS6.

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Associated Products

The following products from our catalogue are associated with this technique. To find out more about these supported devices, follow the links below or get in touch via email or phone.

QPS

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