MRI can help choose where to stimulate, measure what changes afterwards, or capture BOLD responses while stimulation is delivered. These designs answer different questions.
Martin Tik · Imaging Transcranial Magnetic Stimulation (2019), Chapter 4, pp. 34–35
Combining MRI and TMS
MRI and TMS have both immense potential in the field of neuroscience. While structural and functional MRI allow for mapping cognitive functions to spatial and temporal features of brain activation, TMS holds the potential to infer on causal relationships between brain areas and cognitive functions. Here, we examine the combination of both techniques and show how they can support each other based on their respective advantages in order to advance the field of cognitive and clinical neuroscience.
01 · Before TMS
When is fMRI used before TMS?
Anatomical images acquired before TMS can be fed into the neuronavigation software to define the actual stimulation site.
fMRI acquired before TMS allows for functional definition of a stimulation target.
In our language study, task fMRI guided the search for each participant’s stimulation site. We then used concurrent TMS-fMRI to measure the network response to stimulation of that site.
02 · After TMS
Measuring effects after stimulation
Offline imaging (e.g. fMRI during a task or at rest) allows for evaluating effects that persist after TMS.
03 · During TMS
Measuring the response to stimulation
fMRI during TMS, i.e. concurrent TMS-fMRI, measures stimulation-associated BOLD responses during the experiment.
Why combine stimulation with imaging?
Methods for concurrent use of imaging and TMS were developed to examine TMS evoked responses in detail. This combination allows for the investigation of direct and localized neural effects as well as network effects due to TMS stimulation, yielding studies that go beyond simple observation of behavioural changes.
Neuroimaging has proven to be very useful in mapping the effects of TMS on brain activity at the systems level. It complements the knowledge, which can be gained from peripheral electrophysiology and behavioral measures.
Where chronometric TMS-fMRI fits
Chronometric TMS-fMRI adds a further question to the “during TMS” approach: when, relative to a task, is the pulse delivered? Comparing stimulation at defined task timings helps investigate how the response depends on the brain’s ongoing activity.
Explore chronometric TMS-fMRI → · Structural, functional and effective connectivity →
Further reading
The 2019 doctoral thesis → · Download original page 34 (PDF) →