How does rTMS work? Magnetic pulses, neurons, and brain circuits
How rTMS's magnetic pulses influence brain regions and networks related to mood.
Repetitive transcranial magnetic stimulation (rTMS) acts on the brain through magnetic pulses delivered from a coil placed near the scalp. To understand how it works, it helps to think in terms of three levels: a target region, the neurons that receive the stimulus, and the networks that connect that region to other parts of the brain.
From magnetic field to neuronal activity
The coil generates a brief magnetic field. As it passes through the skull, this field induces a small electrical current in the brain tissue beneath it. That current influences the activity of neurons in the selected area.
The effect depends on several parameters: intensity, frequency, number of pulses, the interval between sessions, and location. Together, these elements make up the stimulation protocol.
The target region in depression
Many depression protocols target the dorsolateral prefrontal cortex. This region is involved in functions such as emotional regulation, attention, decision-making, and cognitive control.
Depression is not located in a single spot. The stimulated region is part of circuits that communicate with other areas. This is why an intervention in one zone can influence a broader network.
Networks rather than isolated points
The brain works as a system of networks. Some are involved in internal reflection; others, in the ability to focus and act; still others help detect which stimuli deserve attention.
In depression, there can be patterns of activity associated with rumination, lack of motivation, and difficulty regulating emotions. rTMS aims to modify the activity and communication within these circuits.
Repetition and neuroplasticity
A single pulse can produce a momentary response. Organized repetition seeks to produce changes that last beyond the session itself. This is where the concept of neuroplasticity comes in: the brain's capacity to change the strength of its connections and reorganize how it functions.
Repetitive protocols make use of that capacity through series of stimuli. The frequency can be designed to increase or decrease the excitability of a region, depending on the therapeutic goal.
Personalizing the treatment
Not every brain has exactly the same anatomy or the same connectivity patterns. Some protocols locate the target area using anatomical landmarks; others incorporate brain imaging and neuronavigation techniques.
The motor threshold is also determined, a measure used to adjust stimulus intensity to each person's individual response. This calibration helps tailor the treatment to the patient.
A mechanism still under investigation
Our understanding of rTMS continues to evolve. Research is studying which parameters work best, how to identify the most suitable target, and why some people respond differently than others.
Understanding these principles makes it clear that rTMS is an intervention on brain circuits. The coil, the pulses, and the repetition together form a technology designed to influence neuronal communication in a targeted way.
“New Hope for Treatment-Resistant Depression Without Medication” develops these concepts in accessible language and connects them to the protocols used in treatment-resistant depression.
