Transcranial magnetic stimulation (TMS) is a non-invasive way to perturb activity in the human brain. We use it to ask how a cortical region contributes to a task and how stimulation affects the wider network.
How does TMS work?
A brief current in a coil produces a changing magnetic field, inducing an electric field in the brain. The effect depends on the field reaching the cortex, its orientation and the state of the tissue being stimulated. A target coordinate is therefore only one part of the experiment.
We combine individual MRI with neuronavigation to position stimulation relative to a person’s anatomy. Electric-field modelling provides an additional estimate of how anatomy, position and orientation shape the applied field.
Target, dose, pattern and timing
Where?
Structural anatomy, task responses and functional connectivity help define candidate cortical targets and the networks they may influence.
How?
Intensity and pulse pattern shape the intervention. Single pulses, pulse trains and theta-burst stimulation address different experimental questions.
When?
Pulses delivered at different moments in a task can test when a region contributes to a cognitive process.
Motor threshold is a useful reference for setting intensity, but it does not guarantee equivalent engagement of a prefrontal target across people. Our individual DLPFC dose–response study uses concurrent TMS-fMRI to examine this variability.
Why combine stimulation with fMRI?
A behavioural effect tells us that an intervention changed task performance. Adding fMRI lets us examine associated responses near the target and in distant regions. We can compare candidate targets, doses and task phases within the same methodological framework.
Our language research, for example, asks how stimulation timed to different stages of picture naming changes speech and the response across the language network.
How TMS can interrupt speech → · Chronometric TMS-fMRI →
Why controls matter
TMS also produces a click and scalp sensation. These can affect attention, task performance and the measured brain response. Control sites, timing comparisons or sham conditions help separate the intended intervention from accompanying sensory effects; the right comparison depends on the scientific question.
We study mechanisms and methods in collaboration with clinical partners. Evidence that stimulation engages a network and evidence that a treatment improves symptoms are distinct outcomes.
Methods: Woolgar et al., concurrent TMS-fMRI consensus guidelines (2026); Riddle et al., practical guide to concurrent TMS-fMRI (2022).