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To get started, go to audible.com/scishowpsych or text “SciShowPsych” to 500 500. {♫Intro♫}. It's a classic sci-fi plot device: A chip is implanted into someone's brain, and with a jolt of electricity, their brain is suddenly under someone else's control.

As with all good sci-fi, this is mostly fiction. But there is a bit of real science in there. Obviously, you can't just plant a chip in someone's head and start manipulating their thoughts and behavior.

But doctors and scientists can use electricity to activate or inhibit certain parts of the brain, to help treat serious medical conditions or mental disorders. These treatments have changed the lives of many patients--especially those who may not have responded well to other treatments like medications or psychotherapy. Using electricity as a medical treatment is not new: We've known for centuries that electricity can have an effect on brain and nerve function.

But, for a long time, we did not understand why. For example, ancient Romans were known to actually use an electric fish -- a kind of ray known as Torpedo nobiliana -- to treat patients with a variety of symptoms, from headaches to seizures. just put the fish on you. The ray was known to stun anything that came in contact with it, so the medical professionals of the time would just put this ray on the heads of their patients to numb their symptoms.

Put a fish on it! How do we know that they didn't know why this worked? Because they sometimes used the same technique to treat … hemorrhoids.

Just put a fish on it! Fast forward to the nineteenth century, when physicians started experimenting with applying electricity to the exposed human brain. One physician experimented on the exposed cerebral cortices of decapitated prisoners.

He found that by stimulating the surface of the cortex with electricity, he could cause the face to actually grimace. Gruesome as it was, this at least provided some new scientific insights. It proved that the brain could be directly stimulated with electricity.

Scientists were starting to learn a very important truth: the human nervous system relies on electricity to function. Nerve cells use electricity and chemicals to communicate with one another, transmitting information like little messages throughout your body and brain. Your body depends on these electrical signals to do just about everything.

From smiling to walking, processing memories or feelings, it all comes back to electrical signals in the brain. Beginning in the nineteen thirties, physicians built on this knowledge, developing something known as the Montreal Procedure to help treat epilepsy patients. This method used an electrical probe to directly stimulate different parts of a patient's cerebral cortex.

After removing a section of a patient's skull, a physician would use the probe to electrically trigger different sections of the brain. While the patient was awake and providing feedback, the physician would use the probe to stimulate different parts of the brain -- which would produce sensations like flashing lights or smells that the patient could report. Epileptic patients sometimes experience “auras” before the onset of a seizure.

These “auras” might involve very particular sensations or perceptions — like the smell of burnt toast, for example. If the patient reported something similar to their seizure aura as a result of the electrical stimulation, the doctor knew they'd found the part of the brain causing the seizures. And they could remove or destroy a small section of tissue there.

Freaky as it sounds, this often successfully reduced the patient's risk of seizures. And the Montreal Procedure was also used to map out the brain, notably the sensory and motor cortices. By the second half of the twentieth century, physicians were learning that certain types of electrical stimulation were especially useful in treating symptoms related to neurological movement disorders like Parkinson's disease.

Though it's still not fully understood, it's believed that electrical stimulation affects the way nerve cells in the brain, called neurons, communicate with one another. For example, Deep Brain Stimulation, or DBS for short, is often used to treat symptoms associated with Parkinson's disease. Electrodes are planted deep within the patient's brain.

These electrodes release controlled electrical signals, and these messages may encourage the brain to release an energy-carrying molecule we all use, ATP. [adenosine triphosphate] As the brain releases ATP, a chemical called adenosine gradually builds up, initiating a process that helps to slow nerve signals related to uncontrollable movements, like tremors. Though it was originally approved to help treat Parkinson's disease, DBS may also help with treating symptoms related to depression or obsessive-compulsive disorder, since DBS can help with regulating brain activity. By the sixties and seventies, researchers were starting to experiment with electrical implants within the brain to help treat chronic pain, epilepsy and other neurological disorders.

But most of these implants weren't practical, because they needed bulky external power sources. However, the invention of the cardiac pacemaker in the nineteen sixties showed that it was possible to place a mobile power supply into a person's body safely. With DBS currently, for example, the electrodes planted in a patient's brain are controlled by a small power source that's placed in a patient's chest.

Today, a number of different brain-stimulation therapies are used to help treat a variety of disorders. Aside from DBS, there is also electroconvulsive therapy, or ECT. This method is used to treat disorders like depression and schizophrenia.

With ECT, an electric current passes through electrodes on a patient's scalp, triggering the brain to cause a brief seizure. We're still not sure how ECT works in the brain, but it may involve changes in both neurotransmitters like dopamine and the brain's stress response. Likewise, a technique known as vagus nerve stimulation uses electrical pulses to stimulate the parts of the brain that are associated with seizures, to treat epilepsy.

It can also be used in other cases, like severe depression. In this case, the pulses come from a device implanted in the patient's chest and stimulate the left vagus nerve, which passes a signal on to the brain. This nerve is part of the control system that helps to regulate involuntary actions, like heart rate.

It also acts like a freeway of sorts, sharing information from the brain to the heart, abdomen, lungs, and neck and back again. These pulses may help control or limit the effects of seizures by spurring neurons to release neurotransmitters that help to modify the excitability of certain cells, lessening or even stopping seizures. Electrical brain implants might sound like science fiction, but these techniques are grounded in pure reality.

Brain stimulation techniques have radically improved how physicians treat neurological and mental-health conditions. As these technologies improve, neuroscientists will hopefully continue to develop more effective, and less invasive, treatments, truly changing the lives of countless people around the world. Not all of us have medical needs serious enough to warrant electrodes in our brains.

But for those of us who like to manipulate our minds in more conventional ways, we're lucky to have audiobooks. Compelling stories lets us experience new worlds, new ideas, and new people -- and Audible can hook you up. I recently have been listening to the work of Becky Chambers.

The first installment in the series is called The Long Way to a Small, Angry Planet. It's beautiful, it's human, it's peculiar, it's just everything that I want from a story that's going to give me insight into people, but also not be terribly stressful. And, it's just a great sci-fi story!

And yes, they can connect their brains to computers. Audible also makes original content. These are exclusive audio titles created by celebrated storytellers from worlds as diverse as sci-fi, journalism, literature, and more.

And so you can grab titles from Becky Chambers or from just about any author you like in the the largest collection of audiobooks on the planet. You can get your first audiobook for free plus 2 Audible Originals when you try Audible for 30 days. Visit audible.com/scishowpsych or text “SciShowPSYCH” to 500 500 to try it out! {♫Outro♫}.