Transcranial Magnetic Stimulation, or TMS, is widely used to treat major depressive disorder, especially when medications fail. While clinicians know that TMS can improve symptoms, the exact brain mechanisms behind different stimulation styles have been less clear. A new study examining TMS EEG mechanisms helps clarify how various protocols influence brain activity and connectivity in distinct ways.
TMS can be delivered using rhythmic pulses such as standard 10 Hz stimulation or patterned bursts such as intermittent theta burst stimulation, also known as iTBS. These approaches differ in speed, session length, and patient experience. Until recently, it was unclear whether these protocols affected the brain in similar or fundamentally different ways.
How EEG Helps Decode TMS Effects
Electroencephalography, or EEG, measures the brain’s electrical activity in real time. When combined with TMS, EEG allows researchers to see how stimulation changes brain rhythms and communication between regions. In this study, individuals with depression received multiple types of TMS to the left dorsolateral prefrontal cortex, a key region involved in mood regulation.
Researchers analyzed changes in brain oscillations such as alpha, beta, and theta waves, along with shifts in connectivity between brain regions. This approach provided a detailed look at how different stimulation frequencies interact with brain networks rather than focusing only on symptom improvement.
Key Differences Between Rhythmic And Patterned Stimulation
The results showed that rhythmic and patterned TMS protocols engage the brain in clearly different ways. Patterned stimulation such as iTBS produced stronger increases in beta band activity, which is often linked to cognitive control and executive function. Rhythmic stimulation increased both alpha and beta power, especially at higher frequencies above 7 Hz.
The two approaches also affected brain connectivity differently. Rhythmic TMS increased local connectivity near the stimulation site, suggesting a more focal effect. Patterned TMS reduced connectivity to the left precuneus, a region associated with self-referential thinking and rumination. Both protocols increased connectivity to the orbitofrontal cortex, an area involved in emotional regulation and reward processing.
These findings suggest that TMS EEG mechanisms depend heavily on how stimulation is delivered, not just where it is applied.
Why These Findings Matter For Depression Treatment
Understanding protocol specific brain effects could help explain why some patients respond better to one TMS approach than another. Depression is not a single brain disorder, and different symptom profiles may involve different networks. A patient with prominent rumination may benefit from protocols that reduce overactive self focused networks, while another may need stimulation that strengthens cognitive control circuits.
These insights also support the growing movement toward precision psychiatry. Instead of a one size fits all approach, clinicians may eventually use EEG markers to guide protocol selection, frequency choice, or treatment intensity.
The Future Of Personalized TMS
This research adds to a broader trend of using brain based measurements to refine neuromodulation therapies. As EEG guided TMS becomes more accessible, clinicians may be able to track how a patient’s brain responds early in treatment and adjust protocols accordingly. That could shorten treatment courses, reduce non response, and improve long term outcomes.
While more research is needed to link these neural changes directly to clinical improvement, the study represents an important step toward understanding how TMS truly works inside the brain.
Citations
Valles TE et al. Differential neural responses to rhythmic and patterned TMS protocols insights from EEG spectral analysis. Neuropsychopharmacology. 2025. https://pubmed.ncbi.nlm.nih.gov/41501538/
van Rooij SJH et al. Accelerated TMS moving quickly into the future of depression treatment. Neuropsychopharmacology. 2024. https://pubmed.ncbi.nlm.nih.gov/38104647/