Contrary to the name, transcranial magnetic stimulation, or TMS is actually a type of neuromodulation rather than stimulation. That is, when TMS therapy is administered, the goal is to change, or modulate brain function by either stimulating or inhibiting brain cells (neurons).
You may be wondering why stimulating or inhibiting parts of the brain would be helpful. While healthcare providers and scientists are still trying to uncover answers to that question, it is believed that brain stimulation can help manage symptoms of depression, and other psychiatric conditions. For example, someone with depression may have lower or higher activity in his/her brain, particularly in areas such as the frontal lobes and the amygdala, where emotions are processed. This altered activity may be contributing to symptoms of depression. Therefore, using TMS to stimulate areas of the brain that are underactive, or inhibiting areas that are overactive, may help reduce symptoms of depression.
Let’s take a closer look at how TMS actually works on the brain. TMS involves a magnetic coil, (often in the shape of a figure eight), which is placed against the scalp. The coil acts as a conductor for an electrical current, where a magnetic field is created. When pulses of electricity are administered, the pulses use the coil to generate a magnetic field that easily travels across the skull and is able to generate a small current on underlying brain cortex (neurons).
The electrical pulses, although lower in intensity (1-50 Hz is a common range), are strong enough to activate or inhibit the activity of neurons. Recall that neurons communicate with each other via electrical and chemical signals. During TMS, neurons do just that – they “communicate” in response to the electrical pulses. In fact, the input the neurons receive from the TMS pulses is the same scenario as when neurons within the brain receive input from each other. The only difference is TMS input is an external source of input to neurons, whereas neuron-to-neuron input within the brain is an internal source of input. Also recall that when neuron communication occurs, it is this communication that allows the neurons to perform their basic functions. Thus, input from TMS provides input to neurons that influences their function.
The amount, or intensity of pulse administration will differ for each patient, and your physician will determine the amount that is therapeutic for you. Although TMS sessions are brief, the effects on the neurons over time are thought to be therapeutic. Researchers and clinicians have reasoned that the input from TMS may help change the neuron activity in helpful ways. As mentioned above, TMS therapy may help regulate neuron activity that has become overactive or underactive in conditions such as depression.