When is it possible to record from inside the human brain?
The goal of cognitive neuroscience is to understand how brain activity gives rise to cognition. However, researchers cannot measure activity inside the brain without performing neurosurgery, which would not be ethical or safe to do in healthy human volunteers. So, researchers are often limited to measuring brain activity indirectly from outside the head. However, in special situations, we do have the opportunity to directly record activity from a human brain. The procedure is known as intracranial recording, in which electrodes are placed inside of a hospital patient’s brain. These electrodes measure brain activity while the patient rests, sleeps, talks, or performs a behavioral experiment.
Why would someone undergo such an invasive procedure? These patients have intractable epilepsy, meaning that they have severe seizures which cannot be controlled by medications. Seizures often arise from one area of the brain, after which activity spreads and causes symptoms such as uncontrolled body movements or loss of consciousness. When all other medical treatments have failed, the best remaining option is sometimes to remove the part of the brain where seizures start.
To help determine which part of the brain to remove, neurosurgeons implant electrodes inside the patient’s brain and wait for seizures to happen. This can take 1-2 weeks, while the patient lies in their hospital bed. We as researchers visit the patients during this time and ask if they want to participate in experiments. They are often restless or bored, so are happy to be distracted with fun tasks. These epileptic patients provide an incredible and rare opportunity to directly measure human brain activity and allow us to ask new questions about the relationship between brain and behavior.