Just down the hall from our MRI suite is our Brain Stimulation lab, complete with multiple transcranial magnetic stimulators, and a Brainsight neuronavigation system for functional and anatomical MRI-guided brain stimulation. Our Brainsight neuronavigation system includes a two-channel EMG module enabling flexible visualisation and recording of motor evoked potentials (MEP). We have a wide range of TMS coils, including the Magstim D11 “cone coil” specialised for stimulation at greater depths, a cooled coil, and multiple “butterfly” coils of differing diameters and handle configurations.
Magstim Rapid Plus This system is specialised for high-frequency repetitive TMS, useful for temporarily changing the functional ‘state’ of a brain area. The number of TMS pulses and how they are timed are the key factors that determine whether the brain area stimulated will become more or less responsive following repetitive TMS. This approach is used, for example, with ‘offline’ TMS experiments, where TMS is applied prior to the participant performing the task that is used to test its predicted effects. That our MRI suite is nearby also makes it possible for our researchers to combine ‘offline’ TMS with functional MRI or magnetic resonance spectroscopy. This can help better understand the mechanisms driving the functional-state-changes caused by high-frequency repetitive TMS and its effects on behaviour.
High-frequency repetitive TMS enabled by this system also enables the use of ‘online burst’ protocols, where quick bursts of TMS are applied during tasks. This is particularly useful when researchers have predictions about the causal role of a given brain area in a task, yet are less certain about when to apply the TMS. Follow-up online TMS experiments involving single-pulse methods can then be used to provide more precise timing information, honing in on when, more precisely, the functions of a particular brain area make critical contributions to behaviour.
Magstim Bi-Stim This system is specialised for paired-pulse TMS applications, and is better suited for estimating TMS-induced physiological changes, such as MEPs. These features complement our Rapid Plus system, enabling, for example, more precise and comprehensive evaluation of predicted high-frequency repetitive TMS on motor physiology. With the participant’s anatomical MRI, TMS-induced MEP data can also be ‘back-projected’ onto the brain-surface reconstruction, for example, showing the hotspots of maximal MEP activity. This represents a different kind of functional brain mapping method, complementary to fMRI.
