![]() ![]() This strong denunciation received pushback, with some accusing the Australian team of mischaracterizing studies and of comparing apples and oranges. Modern brain zapping began to be studied with great interest at the turn of this century, and fifteen years later a team in Melbourne, Australia published a review of the field arguing that this sparkly technique had no reliable effect on our nervous system and questioning the very foundation of this nascent discipline. So, does tDCS actually do anything concrete? For example, massages, as pleasant as they can be, often fail to deliver on specific health promises. But it is possible to have an intervention that plausibly interacts with the human body but does not actually fix a specific problem in a predictable way. So far, we have a broad mechanism of action that makes sense given our knowledge of the brain. The effects from a single session can last up to five hours (although multiple sessions might have a cumulative effect, at least based on work done in animals). It turns a mountain that needs to be climbed into a much smaller hill. Transcranial direct current stimulation is not thought to make nerve cells fire rather, it is believed that it makes them more or less likely to fire. ![]() This is the binary language of our brain: either a nerve cell is firing or it’s not. This burst of electricity is triggered by a very quick change in voltage on either side of their membrane, making the cell “fire” a signal. ![]() We know that nerve cells conduct electricity along their length and they do so at breakneck speed, up to 100 metres per second. Exactly how this impacts the brain remains to be fully understood, but there is a leading theory. When it meets the skull, some of it manages to trickle through and it flows inside the brain tissue, generating an electric field along the way. You can think of this mild current as water: it follows the path of least resistance. The entire session lasts twenty to thirty minutes. This current enters the head from the positive electrode and exits it from the negative electrode. The electrodes are connected to a battery which is turned on, providing a mild, steady electrical current somewhere between 1 and 2 milliamps. In between the electrode and the skin is a sponge soaked in saltwater. The other is attached to a different region of the scalp or somewhere else on the head. There are usually two electrodes, with at least one of them placed on a specific part of the scalp. It sounds like a neurological panacea, but a deep dive into the scientific literature on tDCS reveals a big problem with an equally big name: heterogeneity. A mild current is allowed to run through your head in between two electrodes, and this bit of electrical stimulation is claimed to help with everything tied to the brain, from depression to tinnitus, from epilepsy to anxiety, from migraines to stroke rehabilitation. The most studied of them is transcranial direct current stimulation or tDCS for short. Today, the idea has been refined into a suite of non-invasive brain stimulation methods. I hesitate to ask which part of the body the fish was supposed to touch in this case. He recommended this therapy for many painful conditions, including hemorrhoids. In the year 153, a Roman physician realized that the shock caused by touching an electric ray could dull someone’s pain. But given that our brain cells use electricity to allow us to think, speak, and move, might there not be some way to tweak our brain’s electricity to solve our many health problems? Shocking the brain with electricity may bring to mind electroconvulsive therapy or James Whale’s seminal black-and-white adaptation of Frankenstein. ![]()
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