What is TMS?
TMS stands for transcranial magnetic stimulation, which is one of several types of non-invasive brain stimulation methods. TMS uses a powerful magnetic coil to induce currents that interact with the cells in your brain. TMS can be useful in many different contexts, such as changing how the brain functions or used as a way to assess if other interventions made changes to brain activity.
There are many different ways to administer TMS, here’s just a few:
Single Pulse TMS: One of the most common TMS applications uses a single pulse to specific parts of the brain, usually in the motor or occipital cortex. In either case, single pulse TMS is incredibly effective for determining appropriate stimulation intensity for each person.
Paired Pulse TMS (ppTMS): This method uses two pulses, each at different time points. This can be helpful for seeing how the brain responds to stimuli at different times, which can help determine if an intervention produced any meaningful changes in brain activity.
Repetitive TMS (rTMS): This method is uses continuous “trains” of stimulation for a specified duration of time in efforts to produce lasting effects to brain function by either selectively increasing or decreasing the activity of the brain. Low frequency rTMS (less than 1Hz) is believed to inhibit brain activity whereas high frequency rTMS (greater than 1Hz) is believed to facilitate the activity.
Types of Coils
There are many different types of coils that are used for administering TMS. A round or circular shaped coil was the original coil design until the figure-of-eight design was developed. The iconic figure-of-eight coil (top photo) is one of the most commonly used coils for single and paired pulse. There are also modified versions of the figure-of-eight coil design that have a built-in vacuum for cooling the device during repetitive TMS sessions. These coils produce focal pulses that can only penetrate about 2-3 cm into the brain. Other coils, such as the Double-Cone Coil or our custom built Angled Airfilm Coil, are able to reach deeper structures in the brain, but these pulses can be less direct for a specific location.