rTMS: How Frequency Affects Our Brain

Repetitive Transcranial Magnetic Stimulation (rTMS) is a non-invasive technique that uses magnetic fields to stimulate parts of the brain. It is increasingly used in psychiatric and neurological settings. One of the crucial parameters in rTMS is the stimulation frequency — that is, how many magnetic pulses are delivered per second. In this article, we will explore how different frequencies of rTMS influence the brain: what “low” and “high” frequencies mean, what effects they tend to produce, how those effects relate to brain rhythms and neuroplastic change, and where the current evidence supports or limits these claims.

Basics of rTMS and Brain Excitability

Before diving into frequencies, let’s clarify in simple terms how rTMS works. A magnetic coil is placed against the scalp, and it generates brief magnetic pulses that pass through the skull and induce small electric currents in the underlying brain tissue. These currents alter the excitability of neurons in the targeted region — making them more or less likely to fire.

When pulses are applied repeatedly (rather than singly), the stimulation is called repetitive TMS (rTMS). Over time, this repeated stimulation can encourage longer-term changes in neural responsiveness, which is often linked to the concept of neuroplasticity — the brain’s ability to reorganize and adapt.

Importantly, the frequency — how fast we send pulses — is one of the key knobs we can turn to push the brain toward either increased excitability or inhibition.

Low vs. High Frequency: What Do They Do?

Low-frequency rTMS (≤ 1 Hz)

Low-frequency rTMS typically means delivering pulses at 1 hertz or less. This mode is generally considered to have an inhibitory effect — it tends to reduce the excitability of the stimulated brain area.

In clinical practice, low-frequency rTMS is often used to dampen overactive brain regions. For example, in depression treatment, clinicians may apply low-frequency stimulation to the right dorsolateral prefrontal cortex to reduce hyperactivity there.

High-frequency rTMS (≥ 5 or 10 Hz)

By contrast, high-frequency rTMS means delivering many pulses per second. This mode is viewed as excitatory — it tends to increase the excitability of the stimulated region.

For example, in depression, high-frequency stimulation is commonly applied to the left dorsolateral prefrontal cortex to boost its activity.

Sometimes, more exotic patterns like theta burst stimulation (TBS) are used. TBS delivers bursts at a theta rhythm (around 5 Hz) but grouped at high frequency — enabling shorter sessions while achieving similar effects to high-frequency rTMS.

How Frequencies Interact with Brain Rhythms

The brain naturally exhibits rhythmic electrical activity in various frequency bands. Some researchers propose that applying external stimulation at certain frequencies might “entrain” or guide the brain’s oscillations to align with those frequencies. However, evidence for clean entrainment is inconsistent; rTMS likely affects connectivity and plasticity more than simple rhythm matching.

Functional imaging studies (using fMRI) have shown that excitatory (high-frequency) rTMS over the left dorsolateral prefrontal cortex can strengthen connectivity between that stimulated area and other brain networks involved in cognition. In Alzheimer’s and mild cognitive impairment, rTMS has been found to alter default mode network connectivity and other large-scale networks, helping to restore more normal patterns of activity.

One animal study using high-frequency rTMS observed modest improvements in spatial memory, along with increased synchronization in hippocampal and thalamic networks. Altogether, the frequency we choose interacts with ongoing brain rhythms and circuits to guide neural reorganization.

Evidence from Clinical and Cognitive Studies

Depression and Psychiatric Disorders

Meta-analyses show that rTMS (both high and low frequency) outperforms sham in improving depressive symptoms. In treatment-resistant depression, rTMS significantly increases response and remission rates. In less treatment-resistant patients, rTMS tends to produce even better outcomes. Real-world data from UCLA found that about 54% of patients achieved a clinical response.

Cognition, Memory, and Dementia

Beyond mood, many studies examine whether rTMS can enhance cognitive function in mild cognitive impairment and Alzheimer’s disease. Meta-analyses report medium-to-large effect sizes on improving cognition compared to sham. High-frequency rTMS over the left DLPFC (10–20 Hz) is often recommended for cognitive enhancement, improving memory, language, and executive function. In mild cognitive impairment, rTMS was found to be safe and effective, with functional connectivity changes serving as potential markers of benefit.

How Frequency Choices Are Made — What Matters

If the goal is to increase activity in a region, a high-frequency protocol is preferred. If the goal is to suppress excessive activity, low-frequency is used. High-frequency rTMS sessions tend to last longer, but protocols like theta burst stimulation deliver the same benefit in minutes.

Not everyone responds equally — baseline brain state and plasticity limits play a role. Some may reach a ceiling where further stimulation adds little benefit.

Conclusion

Frequency is a key factor in rTMS. Low-frequency tends to inhibit brain regions, while high-frequency stimulates them. These effects can enhance brain plasticity, improve mood, and boost cognition. Evidence supports rTMS as safe and beneficial when used with clear therapeutic goals — though frequency optimization remains a growing area of study.

References

Carpenter, L. L., Janicak, P. G., et al. (2012). Transcranial magnetic stimulation (TMS) for major depression: A multisite, naturalistic, observational study of acute treatment outcomes in clinical practice. Depression and Anxiety, 29(7), 587–596. DOI: 10.1002/da.21969

Chervyakov, A. V., et al. (2015). Possible mechanisms underlying the therapeutic effects of rTMS. Frontiers in Human Neuroscience, 9, 303. DOI: 10.3389/fnhum.2015.00303

George, M. S., et al. (2010). Daily left prefrontal transcranial magnetic stimulation therapy for major depressive disorder: A sham-controlled randomized trial. Archives of General Psychiatry, 67(5), 507–516. DOI: 10.1001/archgenpsychiatry.2010.46

Hallett, M. (2007). Transcranial magnetic stimulation: A primer. Neuron, 55(2), 187–199. DOI: 10.1016/j.neuron.2007.06.026

Dalhuisen I., et al. A comparison between rTMS and antidepressant medication on depressive symptom clusters in treatment-resistant depression. Eur Arch Psychiatry Clin Neurosci. 2025 Sep;275(6):1799-1807. doi: 10.1007/s00406-025-02012-0. Epub 2025 Apr 23. PMID: 40266345; PMCID: PMC12500816.

McClintock SM., et al. National Network of Depression Centers rTMS Task Group; American Psychiatric Association Council on Research Task Force on Novel Biomarkers and Treatments. Consensus Recommendations for the Clinical Application of Repetitive Transcranial Magnetic Stimulation (rTMS) in the Treatment of Depression. J Clin Psychiatry. 2018 Jan/Feb;79(1):16cs10905. doi: 10.4088/JCP.16cs10905. PMID: 28541649; PMCID: PMC5846193.