Your first Transcranial Magnetic Stimulation (TMS) appointment will be the longest during your treatment series. Before your first treatment session, your TMS psychiatrist will conduct a brain mapping procedure to determine the location of your treatment and the power or “dose” appropriate for you.
Brain mapping, also known as cortical mapping, is the process of pinpointing the left dorsolateral prefrontal cortex (DLPFC), a spot located above the left temple where TMS treatment is applied.
This part of the brain processes a variety of cognitive functions. In addition to working or short-term memory, this area governs a person’s emotional response to people, places and events. It also jumps into action when risky and moral decisions are made.
In people suffering from depression, the DLPFC tends to be underactive, the level of which directly correlates to the severity of their symptoms. This area is intricately linked to the limbic system, which is located deep within the brain and is tasked with behavioral and emotional response.
To identify the DLPFC treatment area, the TMS psychiatrist must first locate your primary motor cortex. Also known as the motor pathway, this area of the brain lies across the top of your head from ear to ear. Different areas along this strip control movement in various parts of the body.
Doctors will use the TMS device to deliver short electromagnetic pulses to the area of the motor strip that controls movement in your right hand. When the TMS psychiatrist has located the correct spot, your hand or thumb may twitch. Moving the device about two inches closer to your forehead will land directly on the DLPFC treatment area.
Doctors will also use that thumb twitch or electromyography (EMG) response to determine your motor threshold, the lowest level of stimulation needed to cause movement in the hand. This helps establish your treatment dose.
TMS is most effective at 120 percent of a patient’s motor threshold. Over the course of treatment, technicians will slowly increase up to this level according to your individual comfort level.
Halfway through your TMS treatment series, a second brain mapping will be performed by the attending psychiatrist and technician to reassess your dosage and to maintain the accuracy of the treatment location.