Transcranial Magnetic Stimulation (TMS) has become very popular for treatment resistant depression, especially for individuals who have not found success with traditional medications or psychotherapy. But how exactly does TMS influence the brain to alleviate symptoms of depression? Recent research has begun to uncover the mechanisms underlying this non-invasive therapy, shedding light on its role in modulating brain circuits involved in mood regulation.
How TMS Works
TMS works by using electromagnetic fields to stimulate specific areas of the brain. In the treatment of depression, the target is usually the dorsolateral prefrontal cortex (DLPFC), a region implicated in mood regulation and cognitive function. By delivering pulses of magnetic energy, TMS alters the activity of neurons in this area, effectively resetting dysfunctional neural circuits. The stimulation can enhance or suppress neural activity depending on the frequency and pattern of the magnetic pulses used.
Modulating Mood-Related Brain Circuits
Depression is linked to disruptions in the brain’s mood-regulating circuits, including areas such as the prefrontal cortex, limbic system, and other regions responsible for emotional processing. Research has shown that individuals with depression often exhibit hyperactivity in certain brain regions, while others may be under-active.
TMS influences these circuits by increasing connectivity between the DLPFC and deeper brain regions involved in emotion regulation, such as the amygdala and hippocampus. Studies suggest that high-frequency stimulation of the left DLPFC boosts neural activity in areas linked to positive emotions, while lower-frequency stimulation on the right side can dampen overactive regions that contribute to negative emotional states.
Another key mechanism through which TMS exerts its therapeutic effects is neuroplasticity—the brain’s ability to reorganise itself by forming new neural connections. Depression can lead to reduced neuroplasticity, but TMS helps reverse this by promoting the growth of new synapses and strengthening existing ones. This increased plasticity allows the brain to adapt more easily to positive changes, improving mood regulation and cognitive function.
Targeted Treatment Protocols
While traditional TMS protocols focus on specific areas of the brain, newer research suggests that individualising treatment may yield even better results. For example, combining high-frequency TMS with intermittent theta-burst stimulation (iTBS) has been shown to improve outcomes in patients with treatment-resistant depression. This combination targets multiple neural circuits simultaneously, enhancing the overall efficacy of the treatment.
Furthermore, studies are underway to identify biomarkers, such as pupil response to light, that could help predict how well a patient will respond to TMS. This personalised approach could pave the way for more targeted and effective treatment protocols, ensuring that each patient receives the most appropriate stimulation for their unique brain activity patterns.
As research continues to uncover the intricate ways TMS interacts with brain circuits, the potential for refining this therapy grows. From understanding how to optimise stimulation frequencies to identifying specific brain regions that influence mood, the future of TMS holds great promise. The ultimate goal is to develop personalised treatment plans that maximise benefits and minimise side effects for patients suffering from depression.
