19-04-2011, 03:49 PM
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1. INTRODUCTION
A brain-computer interface uses electrophysiological signals to control remote devices. Most current BCIs are not invasive. They consist of electrodes applied to the scalp of an individual or worn in an electrode cap. These electrodes pick up the brain’s electrical activity (at the microvolt level) and carry it into amplifiers. These amplifiers amplify the signal approximately ten thousand times and then pass the signal via an analog to digital converter to a computer for processing. The computer processes the EEG signal and uses it in order to accomplish tasks such as communication and environmental control. BCIs are slow in comparison with normal human actions, because of the complexity and noisiness of the signals used, as well as the time necessary to complete recognition and signal processing.
The phrase brain-computer interface (BCI) when taken literally means to interface an individual’s electrophysiological signals with a computer. A true BCI only uses signals from the brain and as such must treat eye and muscle movements as artifacts or noise. On the other hand, a system that uses eye, muscle, or other body potentials mixed with EEG signals, is a brain-body actuated system.
Figure 1.1: Scheme of an EEG-based Brain Computer Interface with on-line feedback.
The EEG is recorded from the head surface, signal processing techniques are used to extract features. These features are classified, the output is displayed on a computer screen. This feedback should help the subject to control its EEG patterns.
The BCI system uses oscillatory electroencephalogram (EEG) signals, recorded during specific mental activity, as input and provides a control option by its output. The obtained output signals are presently evaluated for different purposes, such as cursor control, selection of letters or words, or control of prosthesis. People who are paralyzed or have other severe movement disorders need alternative methods for communication and control. Currently available augmentative communication methods require some muscle control. Whether they use one muscle group to supply the function normally provided by another (e.g., use extraocular muscles to drive a speech synthesizer) .Thus, they may not be useful for those who are totally paralyzed (e.g. brainstem stroke) or have other severe motor disabilities. These individuals need an alternative communication channel that does not depend on muscle control. The current and the most important application of a BCI is the restoration of communication channel for patients with locked-in-syndrome.
2. What is BCI
A brain-computer interface (BCI), sometimes called a direct neural interface or a brain-machine interface, a research deals with a direct communication pathway between a either accept commands from the brain or send signals to it (for example, to human or animal brain and an external device. In one-way BCIs, computers restore vision) but not both. Throughout the world, such research is surprisingly extensive and expanding. BCIs are often aimed at assisting, augmenting or repairing human cognitive or sensory-motor functions. BCIs read electrical signals or other manifestations of brain activity and translate them into a digital form that computers can understand, process, and convert into actions of same kind, such as moving a cursor or turning on a TV.BCI can help people with inabilities to control computers, wheelchairs, televisions or other devices with brain activity.
BCI research is rapidly approaching a level of first-generation medical practice for use by individuals whose neural pathways are damaged, and use of BCI technologies is accelerating rapidly in nonmedical arenas of commerce as well, particularly in the gaming, automotive, and robotics industries. The technologies used for BCI purposes are cutting-edge, enabling, and synergistic in many interrelated arenas, including signal processing, neural tissue engineering, multiscale modeling, systems integration, and robotics.
Among the possible brain monitoring methods, the scalp recorded electroencephalogram (EEG) constitutes an adequate alternative because of its good time resolution, relative simplicity and noninvasiveness. The EEG signals are analyzed and mapped into actions inside the computer rendered environment. A BCI allows a person to communicate with or control the external world without using the brain's normal output pathways of peripheral nerves and muscles. Messages and commands are expressed not by muscle contractions, but rather by electrophysiological signals from the brain. BCls provide an alternative communication and control option for the severely disabled.
3. HISTORY
3.1 Discovering the basics
The history of Brain-Computer-Interfaces (BCI) starts with Hans Berger's discovery of the electrical activity of human brain and the development of electroencephalograpy (EEG).Berger studied medicine at the University of Jena and received his doctorate in 1897. He became a professor in 1906 and the director of the University's psychiatry and neurology clinic in 1919. In 1924 Berger was the first one who recorded an EEG from a human brain. By analyzing EEGs Berger was able to identify different waves or rhythms which are present in a brain, as the Alpha Wave (8 – 12 Hz), also known as Berger's Wave.
Berger analyzed the interrelation of alternations in his EEG wave diagrams with brain diseases. EEGs permitted completely new possibilities for the research of human brain activities. However, it took until 1970 before the first development steps were taken to use brain activities for simple communication systems. The Advanced Research Project Agency (ARPA) of the government of the United State of America became interested in this field of research. They had the vision of increasing the performance of mental high load tasks by enhancing human abilities with artificial computer power. However these ambitious goals were never fulfilled but the first steps into the right direction were taken.
3.1.1 Monkey follows…
As almost all experiments which include a certain risk for human lives, the first experiments were conducted with animals more precisely on primates. The first wireless intracortial brain-computer interface was built by Philip Kennedy and his colleagues by implanting neurotrophic cone electrodes into monkey brains.
Miguel Nicolelis, a Brazilian physicist and scientist became the most popular proponent of using multiarea recordings from neural ensembles as input for BCI applications. In the 90s Nicolelis team did inital studies on rats, followed by the development of a BCI system that was able to decode monkeys' brain activities. This data was used to translate the monkeys' movement to rudimentary robot action. By the year 2000, Nicolelis' group implanted electrode arrays into multiple brain areas of owl monkeys. They built a BCI system that was capable of reproducing a monkey's movement, while reaching for food or using a joystick in real time. However, the system has to be considered as an open-loop BCI, as the monkeys got no feedback from their actions by the BCI. They proceeded with their research and conducted experiments in rhesus monkeys. The monkeys were trained to reach and grasp for objects on a screen by manipulating a joystick. Using velocity and grasping action prediction their BCI system was able to control a robot. The robot was hidden from the monkey but the monkey was provided with feedback of the robot's performance by the visual display.
3.1.2 Humans follows
However, not only monkeys were objects to BCI research but also humans participated in
experiments with both invasive (which means direct contact to the neurons by whatever means) and non-invasive approaches. There have been many experiments using various techniques for “reading the brain” such as the EEG, MEG, fMRI or similar methods.
One of the first persons who benefit from all the years of BCI research is Matt Nagle. In 2004 an electrode array was implanted into his brain to restore functionalities he had lost due to paralysis.
The system required some training but finally he was able to control the TV, check emails and do basically everything that can be achieved by using a mouse.
Today many researchers at a lot of universities and laboratories are continuing BCI research. However, the present-days achievments are very impressive but there is still a lot of research and studying to be done until the whole potential of Brain-Computer-Interfaces can be tapped.
1. INTRODUCTION
A brain-computer interface uses electrophysiological signals to control remote devices. Most current BCIs are not invasive. They consist of electrodes applied to the scalp of an individual or worn in an electrode cap. These electrodes pick up the brain’s electrical activity (at the microvolt level) and carry it into amplifiers. These amplifiers amplify the signal approximately ten thousand times and then pass the signal via an analog to digital converter to a computer for processing. The computer processes the EEG signal and uses it in order to accomplish tasks such as communication and environmental control. BCIs are slow in comparison with normal human actions, because of the complexity and noisiness of the signals used, as well as the time necessary to complete recognition and signal processing.
The phrase brain-computer interface (BCI) when taken literally means to interface an individual’s electrophysiological signals with a computer. A true BCI only uses signals from the brain and as such must treat eye and muscle movements as artifacts or noise. On the other hand, a system that uses eye, muscle, or other body potentials mixed with EEG signals, is a brain-body actuated system.
Figure 1.1: Scheme of an EEG-based Brain Computer Interface with on-line feedback.
The EEG is recorded from the head surface, signal processing techniques are used to extract features. These features are classified, the output is displayed on a computer screen. This feedback should help the subject to control its EEG patterns.
The BCI system uses oscillatory electroencephalogram (EEG) signals, recorded during specific mental activity, as input and provides a control option by its output. The obtained output signals are presently evaluated for different purposes, such as cursor control, selection of letters or words, or control of prosthesis. People who are paralyzed or have other severe movement disorders need alternative methods for communication and control. Currently available augmentative communication methods require some muscle control. Whether they use one muscle group to supply the function normally provided by another (e.g., use extraocular muscles to drive a speech synthesizer) .Thus, they may not be useful for those who are totally paralyzed (e.g. brainstem stroke) or have other severe motor disabilities. These individuals need an alternative communication channel that does not depend on muscle control. The current and the most important application of a BCI is the restoration of communication channel for patients with locked-in-syndrome.
2. What is BCI
A brain-computer interface (BCI), sometimes called a direct neural interface or a brain-machine interface, a research deals with a direct communication pathway between a either accept commands from the brain or send signals to it (for example, to human or animal brain and an external device. In one-way BCIs, computers restore vision) but not both. Throughout the world, such research is surprisingly extensive and expanding. BCIs are often aimed at assisting, augmenting or repairing human cognitive or sensory-motor functions. BCIs read electrical signals or other manifestations of brain activity and translate them into a digital form that computers can understand, process, and convert into actions of same kind, such as moving a cursor or turning on a TV.BCI can help people with inabilities to control computers, wheelchairs, televisions or other devices with brain activity.
BCI research is rapidly approaching a level of first-generation medical practice for use by individuals whose neural pathways are damaged, and use of BCI technologies is accelerating rapidly in nonmedical arenas of commerce as well, particularly in the gaming, automotive, and robotics industries. The technologies used for BCI purposes are cutting-edge, enabling, and synergistic in many interrelated arenas, including signal processing, neural tissue engineering, multiscale modeling, systems integration, and robotics.
Among the possible brain monitoring methods, the scalp recorded electroencephalogram (EEG) constitutes an adequate alternative because of its good time resolution, relative simplicity and noninvasiveness. The EEG signals are analyzed and mapped into actions inside the computer rendered environment. A BCI allows a person to communicate with or control the external world without using the brain's normal output pathways of peripheral nerves and muscles. Messages and commands are expressed not by muscle contractions, but rather by electrophysiological signals from the brain. BCls provide an alternative communication and control option for the severely disabled.
3. HISTORY
3.1 Discovering the basics
The history of Brain-Computer-Interfaces (BCI) starts with Hans Berger's discovery of the electrical activity of human brain and the development of electroencephalograpy (EEG).Berger studied medicine at the University of Jena and received his doctorate in 1897. He became a professor in 1906 and the director of the University's psychiatry and neurology clinic in 1919. In 1924 Berger was the first one who recorded an EEG from a human brain. By analyzing EEGs Berger was able to identify different waves or rhythms which are present in a brain, as the Alpha Wave (8 – 12 Hz), also known as Berger's Wave.
Berger analyzed the interrelation of alternations in his EEG wave diagrams with brain diseases. EEGs permitted completely new possibilities for the research of human brain activities. However, it took until 1970 before the first development steps were taken to use brain activities for simple communication systems. The Advanced Research Project Agency (ARPA) of the government of the United State of America became interested in this field of research. They had the vision of increasing the performance of mental high load tasks by enhancing human abilities with artificial computer power. However these ambitious goals were never fulfilled but the first steps into the right direction were taken.
3.1.1 Monkey follows…
As almost all experiments which include a certain risk for human lives, the first experiments were conducted with animals more precisely on primates. The first wireless intracortial brain-computer interface was built by Philip Kennedy and his colleagues by implanting neurotrophic cone electrodes into monkey brains.
Miguel Nicolelis, a Brazilian physicist and scientist became the most popular proponent of using multiarea recordings from neural ensembles as input for BCI applications. In the 90s Nicolelis team did inital studies on rats, followed by the development of a BCI system that was able to decode monkeys' brain activities. This data was used to translate the monkeys' movement to rudimentary robot action. By the year 2000, Nicolelis' group implanted electrode arrays into multiple brain areas of owl monkeys. They built a BCI system that was capable of reproducing a monkey's movement, while reaching for food or using a joystick in real time. However, the system has to be considered as an open-loop BCI, as the monkeys got no feedback from their actions by the BCI. They proceeded with their research and conducted experiments in rhesus monkeys. The monkeys were trained to reach and grasp for objects on a screen by manipulating a joystick. Using velocity and grasping action prediction their BCI system was able to control a robot. The robot was hidden from the monkey but the monkey was provided with feedback of the robot's performance by the visual display.
3.1.2 Humans follows
However, not only monkeys were objects to BCI research but also humans participated in
experiments with both invasive (which means direct contact to the neurons by whatever means) and non-invasive approaches. There have been many experiments using various techniques for “reading the brain” such as the EEG, MEG, fMRI or similar methods.
One of the first persons who benefit from all the years of BCI research is Matt Nagle. In 2004 an electrode array was implanted into his brain to restore functionalities he had lost due to paralysis.
The system required some training but finally he was able to control the TV, check emails and do basically everything that can be achieved by using a mouse.
Today many researchers at a lot of universities and laboratories are continuing BCI research. However, the present-days achievments are very impressive but there is still a lot of research and studying to be done until the whole potential of Brain-Computer-Interfaces can be tapped.
