How Can Surgery Help Us Understand Skill Learning?

Doctors help us stay healthy and fix our bodies when something is wrong. Sometimes this means checking to see if we are sick, and other times it means fixing body parts that are hurt or broken. Surgery is when a doctor cuts into the body to repair a part that is hidden under the skin. There are lots of different types of surgery. Some types involve making big cuts in the skin, while others involve making small cuts and inserting a camera and tools into the opening. This type of surgery is called laparoscopic surgery (Figure 1A) and it is very useful because patients can recover much faster from small cuts than from big ones.

If you have ever threaded a needle or painted a portrait, you can probably appreciate how hard it is to make our hands do exactly what our brains want them to do. Surgery is challenging in the same way, because it takes very good coordination between what doctors see and what their hands do (called eye-hand coordination). Surgery is also hard because small mistakes can lead to big problems for patients. For these reasons, doctors must practice before they can operate on real patients, just like you might have practiced riding a bike with training wheels at first, to avoid getting hurt. Because surgery uses some of the same skills we use every day, it can help us understand how we learn how to do new things.

How Do Doctors Practice?

The same way that you might practice drills to get good at sports, doctors spend a lot of time practicing drills on a simulator to get good at surgery. A surgery simulator is a machine that makes doctors feel like they are practicing real surgery but does not involve an actual human body. An example of a drill that a surgeon might practice on a simulator is called the peg transfer task (Figures 1B,C). The goal of this drill is to use pincers to move six small triangles from one peg to another. This task teaches surgeons how to move things quickly with the same tools they use in real surgery.

Doctors know they have practiced enough when they pass a challenging test that requires them to perform the drills they practiced, like the peg transfer task or other tasks, like tying knots or cutting shapes. To pass, the doctor must be very fast and cannot make any mistakes. The test is important because it has been shown that doctors who do better on the test perform better surgeries on their patients [1].

Could Electricity Help Us Learn New Skills Faster?

You probably know that we use electricity every day, to turn on the TV or flip on a light switch, but you may not know that we have electricity inside our bodies, too. Our brains are made of lots of really tiny cells called neurons. Neurons are unlike most of our other body parts because they can use electricity to talk to each other. They help us do things like talk, breathe, and see. One special group of neurons helps us move our bodies, and is called the primary motor cortex, or M1 for short. Without your M1, you could not move your hands to make a sandwich or move your legs to run around. Doctors use their M1s during surgery because they move their hands to operate.

Because the M1 uses electricity to tell the body how to move, it makes sense that adding electricity to the M1 could help a person learn new skills that involve movement. One way that scientists can do this is called transcranial direct current stimulation (tDCS) (Figure 2A). “Transcranial” means, across (trans) the skull (cranium), which is exactly where the electricity is going.

tDCS works by adding tiny amounts of electricity to the brain through wet sponges on the head [2]. Two sponges are needed to guide the flow of electricity. The electricity flows from a negative sponge to a positive sponge, passing through the brain on its way. tDCS does not hurt—it feels like a light tingling. Even though tDCS uses only very weak electricity, some of it gets to the neurons and helps them talk to each other. By making it easier for neurons to communicate, tDCS could help the brain to learn new skills¹.

Can tDCS Help Us Get Better and Faster?

So, you may be wondering whether tDCS can make you better at using your hands to play video games or piano. Past experiments have shown that tDCS can be used to speed up learning of tasks that use just one hand [3], but we decided to test whether tDCS could also help speed up learning for two hands. We tested this by adding electricity to people’s brains while they practiced the peg transfer task on the surgical simulator. While they practiced, we measured how fast they were at moving the triangles and how many mistakes they made. Everybody wore sponges over their M1s, as shown in Figure 2B. One group of people practiced with the electricity turned on to a very low intensity, which they could barely feel. The other group practiced with electricity turned off. This is called sham stimulation. “Sham” means “fake” because people cannot tell that the electricity is off, but it is. A sham stimulation group helps us figure out how fast people learn without any help from electricity, so that we have a baseline to use to judge whether adding electricity actually helps with learning.

We found that the group who practiced with electricity delivered to their M1s learned faster and got higher scores than the sham group (Figure 3). This shows that people practicing with electricity got better at the task, and got better at it faster, than those without electricity.

Why Is This Research Important?

The results of this study tell us that adding electricity to the brain can help people learn eye-hand coordination skills faster. This finding could be used to help doctors while they practice to become surgeons, or may be used to help people learn other types of skills. Because good eye-hand coordination is important for activities like playing sports, music, or video games, it is possible that adding electricity to the brain could also help speed up learning of these activities, too. The tDCS technique may also help other types of learning, like problem solving or memory, but further research is needed to figure out whether this is true. So, stay tuned to discover exactly what kinds of learning can be aided by adding tiny amounts of electricity to the brain!

Funding

Support for the preparation of this article was provided to the authors by the United States Army Research Office award (W911NF-15-1-0390).

Glossary

Laparoscopic Surgery: ↑ A type of surgery in which a tiny camera and instruments are inserted into the patient’s body through small cuts in the skin.

Eye-hand Coordination: ↑ Is the ability to do activities that require the simultaneous use of vision to guide hand movements.

Simulator: ↑ A device that allows people to practice a complex activity in a realistic way, like surgery, driving a vehicle, or flying an airplane.

Neuron: ↑ A specialized cell that carries electrical impulses; a nerve cell.

Primary Motor Cortex: ↑ The part of the brain that is most directly connected to muscles and a major source of the control of movement of the body. Also called “M1” for short.

Transcranial Direct Current Stimulation (tDCS): ↑ When electricity is applied to the brain to help neurons communicate with each other more easily.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

The authors would like to thank Moxy and Layla Appelbaum for providing feedback on drafts of this article.

Footnote

1. ↑WARNING: Do not try this at home! tDCS is always done under careful conditions in a laboratory to make sure that the electricity is not harmful.