Brain stimulation could be more invasive than we think

But is it? In the survey by Bluhm and his colleagues, the answers varied. Some thought treatments that involve multiple doctor visits are invasive because they eat into a person’s time. Others believed that device-based treatments are less invasive than traditional talk-based therapies because they don’t require regaling a stranger with their life story. But others said what made TMS invasive was its impact on the brain.

The effects can spread throughout the brain. In theory, noninvasive forms of brain stimulation are designed to target specific regions, such as those involved in mood. But it’s impossible to identify tiny areas when you stimulate the brain through the skull, as Nick Davis of Manchester Metropolitan University points out.

And if TMS can help treat symptoms of chronic pain, depression, or Parkinson’s disease, it must cause some sort of change in the brain. This may be due to how signaling molecules are produced, or how brain circuits connect or fire, or perhaps some other mechanism.

And given that we still don’t really understand how TMS works, it’s hard to know how, if at all, these changes might affect the brain in the long run.

Is a treatment invasive if it changes how a person’s brain works? It may depend on the impact of these changes. We know that “non-invasive” forms of brain stimulation can cause headaches, twitching and potentially seizures. Electroconvulsive therapy, which delivers a higher dose of electrical stimulation, is designed to trigger a seizure and may cause memory loss.

This can be extremely distressing for some people. After all, our memories make us who we are. And that ties in with one of the other concerns about brain-modifying 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. They might become more impulsive or more irritable, for example.

The effects of noninvasive stimulation are unlikely to be as dramatic as this. But where do we draw the line? What is considered “invasive”?

This is an important question. Treatments considered invasive are usually reserved for people who have no other options. They are considered riskier. And treatments deemed too invasive may never be used, or even researched, according to Nir Lipsman, a neurosurgeon based at the University of Toronto, and his colleagues.