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 analyse brain activity to convert it into control commands for computers. The meas­ure­ment of elec­tric­al brain activity is done using elec­trodes. Sub­sequently, spe­cial­ised al­gorithms process the captured signals to recognise 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 recognise and analyse 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 op­tim­isa­tion 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 behaviour. 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.