What is a brain-computer interface (BCI)?

Brain-computer interfaces enable direct communication between the brain and a computer. They work by capturing neural signals, interpreting them and transforming them into commands that computers or machines can understand.

What is meant by a brain-computer interface?

A brain-computer interface (BCI) is an interface between the human brain and a computer that allows direct information transfer between humans and machines. This neurotechnology facilitates the connection without engaging the peripheral nervous system, which means that it operates independently of speech and movement.

Brain-computer interfaces are based on the understanding that merely imagining an action is enough to produce a measurable change in the brain’s electrical activity. For example, imagining moving a finger already triggers a response in the motor cortex, which plans and initiates voluntary movements. Through a training process, the brain-computer interface learns which brain activities correspond to specific thoughts or mental commands. This allows the extracted brain signals to be used as neurotechnological input systems. However, due to numerous technological challenges, BCI development involves significant time and financial investments.

How does a brain-computer interface work?

Brain-computer interfaces capture and analyze brain activity to convert it into control commands for computers. The measurement of electrical brain activity is done using electrodes. Subsequently, specialized algorithms process the captured signals to recognize patterns that correlate with specific thoughts and mental images. In the next step, the brain-computer interface translates these patterns into commands that machines can understand. Researchers use machine learning and artificial intelligence to recognize and analyze signals due to the complexity of the data.

Non-invasive vs. invasive brain-computer interfaces

Brain activity can be recorded either using manually applied and removable BCIs or through surgically implanted BCIs:

• Non-invasive brain-computer interfaces capture brain activity using electroencephalography (EEG). This method measures voltage fluctuations on the surface of the scalp through electrodes placed on the head. These BCIs typically involve a cap fitted with sensors. Alternatively, magnetoencephalography (MEG) is used to record magnetic brain activity, producing a three-dimensional image of various areas.
• Invasive brain-computer interfaces use electrodes implanted directly into the brain to measure electrical impulses via EEG. This observation method offers the highest signal resolution but currently carries the risk of medical complications such as neural damage. There are also semi-invasive methods where electrodes are placed on the cerebral cortex, which is considered less risky.

What is the current state of brain-computer interface development?

Due to intensive research efforts, the quality of the extracted brain signals is continuously improving. This is especially true for implanted BCI systems, which have a high transmission rate and are increasingly the focus of scientific research and studies. Non-invasive BCIs, however, offer limited accuracy because the skull filters the signals. Although the first invasive BCI system was implanted in a human as early as 1998, the high complexity of the procedure has resulted in very few BCI implants since then, with only about 50 worldwide in over 25 years.

Due to recent funding initiatives for fundamental neurological research in the U.S. (BRAIN Initiative) and Europe (Human Brain Project), significant advancements in BCI technologies are expected in the coming years. Research teams are currently working on bidirectional interfaces, capable of transmitting signals from external sources into the brain. Additionally, continuous progress is being made in interpreting brain activity, owing primarily to modern analytical methods like neural networks, big data, and deep learning, which can process large data sets efficiently.

Who is working on BCI technologies?

As of 2024, numerous governmental institutions, universities and private companies are conducting research on BCI technologies. In 2020, researchers at Zhejiang University (China) implanted a brain-computer interface in a paraplegic patient, enabling him to control robotic arms and operate devices with his thoughts. In January 2024, a team from the Massachusetts Institute of Technology (MIT) introduced a non-invasive brain-computer interface that can control Boston Dynamics’ robot dog.

The United States and China are currently leaders in BCI implantation, while German research focuses on non-invasive BCIs due to the lower associated risks. Notable BCI companies include:

• Neuralink develops invasive Brain-Computer Interfaces. The U.S.-based company’s BCI implant contains over 1,000 electrodes attached to hair-thin wires. Besides better treatment for severe brain disorders, Neuralink aims to eventually enhance mental capabilities.
• Blackrock Neurotech is based in Utah and has been active in the brain-computer interface sector since 2008. Blackrock devices are among the most widely used BCI implants, primarily aimed at increasing the independence of people with severe paralysis.
• BrainGate introduced the first-ever human-implantable BCI chip in 2004 and is considered a pioneer in the field. The latest implants consist of two or more units with up to a hundred electrodes each, placed on the cerebral cortex.
• Synchron has developed a minimally invasive BCI that is not implanted directly into the brain but instead sits in the blood vessels in the head. The implantation is done using a tiny metal stent, through which the BCI is introduced into the head.

Current and future applications of BCI technologies

To date, BCIs’ most critical application is supporting people with significant physical disabilities. BCIs are already being used to assist individuals with disabilities or specific conditions like locked-in syndrome (LiS) in their mobility, communication and independence. Medically used BCIs, for example, enable patients to move a robotic arm, communicate using a spelling machine or control devices through thought. However, medical BCI applications are still in the prototype phase. In the entertainment and wellness sector, some products are already ready for the market. For example, non-invasive BCI headsets, which reduce stress using biofeedback systems, are already available.

Various other scenarios are conceivable in the future. Brain-computer interfaces may drive the development of neuroprosthetics, allowing users to experience sensation or connect with robots to complete complex tasks. Bidirectional BCIs could make it possible to communicate brain-to-brain, upload thoughts to cloud servers and connect directly to the internet. Whether BCI technologies will establish themselves in the long term depends not only on technological progress but also on societal acceptance.

What are the opportunities and risks associated with brain-computer interfaces?

Brain-computer interfaces have the potential to lead to disruptive changes in various societal areas, not only in medicine but also when used for optimization in areas like work, school and daily life as well as in fields such as virtual reality. Theoretically, BCIs could activate skills and capacities previously unimaginable—like learning a language by directly downloading it to your brain. However, several technological challenges remain to be addressed before this is possible.

Despite these advantages, brain-computer interfaces also pose significant risks. Reading brain activity enables the analysis of highly sensitive personal data. Critics warn that BCIs could be misused to influence individuals’ thoughts and behavior. Additionally, BCIs are still technically immature and error-prone, which can result in undesirable consequences. To ensure user safety, ethical, legal and social implications must be carefully considered.