But is it? In Bluhm and colleagues’ survey, responses varied. Some thought treatments that involve multiple visits to the doctor’s office are invasive as they affect a person’s time. Others felt that device-based treatments were less invasive than traditional speech-based therapies because they didn’t require re-enacting a stranger with a life story. But others said it’s the effect on the brain that makes TMS invasive.
The effects can spread throughout the brain. Theoretically, non-invasive forms of brain stimulation are designed to target specific regions, such as those related to mood. But as Nick Davis of Manchester Metropolitan University points out, it’s impossible to locate small areas when you stimulate the brain through the skull.
And if GMS can help treat symptoms of chronic pain, depression or Parkinson’s disease, then it must be causing some sort of change in the brain. It could be in the way signaling molecules are produced, or the way brain circuits connect or fire, or maybe some other mechanism.
And given that we still don’t really understand how GMS works, it’s hard to know how these changes will affect the brain in the long run.
If it changes the way a person’s brain works, is the treatment invasive? Perhaps it depends on the impact of these changes. We know that “non-invasive” forms of brain stimulation can cause headaches, twitches and potentially seizures. Electroconvulsive therapy, which provides higher doses of electrical stimulation, is designed to trigger a seizure and can cause memory loss.
This can be extremely distressing for some people. After all, it is our memories that make us who we are. And that gets to one of the other concerns about brain-altering technologies: the potential to change our personalities. Doctors have noticed that some people with DBS for Parkinson’s disease experience temporary changes in their behavior. For example, they may become more impulsive or more irritable.
The effects of non-invasive stimulation are unlikely to be that dramatic. But where do we draw the line – what counts as an “invader”?
This is an important question. Treatments that are considered invasive are usually reserved for people who have no other choice. They are seen as more risky. According to Nir Lipsman, a neurosurgeon at the University of Toronto, and colleagues, treatments deemed too invasive may never be used or even investigated.