BRAIN-GATE SYSTEM

ABSTRACT: The mind-to-movement system that allows a quadriplegic man to control a computer using only his thoughts is a scientific milestone. It was reached, in large part, through the brain gate system. The device was designed to help those who have lost control of their limbs, or other bodily functions, such as patients with amyotrophic lateral sclerosis (ALS) or spinal cord injury. This system has become a boon to the paralyzed. It will be possible for a patient with spinal cord PRINCIPLE OF OPERATION: The principle of operation behind the Brain Gate System is that with intact brain function, brain signals are generated even though they are not sent to the arms, hands and legs. The computer chip, which is implanted into the brain, monitors brain activity in the patient and converts the intention of the user into computer commands. The signals are interpreted and translated into cursor movements, offering the user an alternate Brain Gate pathway to control a computer with thought, just as individuals who have the ability to move their hands use a mouse. The Brain Gate System is based on Cyber kinetics platform technology to sense, transmit, analyze and apply the language of neurons .The Brain Gate Neural Interface Device is a proprietary brain-computer interface that consists of an internal neural signal sensor and external processors that convert neural signals into an output signal under the users own control

injury to produce brain signals that relay the intention of moving the paralyzed limbs, as signals to an implanted sensor, which is then output as electronic impulses. These impulses enable the user to operate mechanical devices with the help of a computer cursor. The system is also the first to allow a human to control his surrounding environment using his mind. FUNCTIONING:

SENSOR.The 'Brain Gate' contains tiny spikes known as electrodes that can sense electromagnetic signature of neurons that will extend down about one millimeter into the brain after being implanted beneath the skull. The activity is translated into electrically charged signals and are then sent and decoded using a program, which can move a robotic arm, a computer cursor, or even a wheelchair NEUROPROSTHETIC DEVICE: A neuroprosthetic device known as Brain gate, converts brain activity into computer commands. A sensor is implanted on the brain, and electrodes are hooked up to wires that travel to a pedestal on the scalp. From there, a fiber

optic cable carries the brain activity data to a nearby computer.

Lets see how potential difference is created. But before that lets know the constitution of cells. PLASMA MEMBRANE Inside the cells plasma membrane is present. The outer part of which is dipped in extra cellular fluid and inner part is dipped in intra cellular fluid. There are actually three stages of plasma membrane 1. Polarisation (resting state) 2. Depolarisation 3. Repolarisation POLARISATION: In a resting state Na+ ions predominate in extra cellular fluid and K+ ions predominate in intra cellular fluid. As a whole there is a +ve charge in outer part of the membrane and -ve charge in inner part of the membrane.

MOTOR CORTEX Every part of the body has a particular region of the primary motor cortex that controls its movement. The area 6 of the motor cortex decides which set of muscle is to be contracted. The area 4 activates those muscles through motor neurons by calling various other part of brain. They observed that depending on what part of the cortex they stimulated, a different part of body contracted.

HOW INFORMATION IS TRANSMITTED THROUGH NERVE FIBRE Everything that the brain does from adding a row of numbers to directing the arm to swat a fly creates a potential difference in the brain. The information is transmitted from the cell to the motor cortex by means of action potential only.

DEPOLARISTION: When an external stimulus is given to the nerve fibre a disturbance is created. The plasma membrane becomes permeable to Na+ ions. Suddenly huge number of Na+ ions diffuses inside the nerve fibre and the K+ ions move outwards but in fewer amounts than the Na+ ions. Hence depolarization occurs i.e., reversal of charge in outer and inner part of membrane

DEPOLARISATION TO REPOLARISATION: When the action potential cannot generate sufficient voltage to stimulate the next area of the membrane depolarization stops and depolarization starts. Because of the increase in Na+ ion concentration in the inner part of the membrane ,the membrane becomes less permeable to the Na+ ions whereas the permeability of the membrane to k+ ions increases. This is called repolarization. i.e., the original state of the polarization is reached. This way of depolarization is called ACTION POTENTIAL". The main cause of communication through nerve fiber

the thought produced in the motor cortex. PREPROCESSING: The raw EEG signal requires some preprocessing before the feature extraction. This preprocessing includes removing unnecessary frequency bands, averaging the current brain activity level, transforming the measured scalp potentials to cortex potentials and denoising. DETECTION: Detection means to try to find out these mental tasks from the EEG signal. It can be done in time-domain, e.g. by comparing amplitudes of the EEG and in frequency-domain. This involves usually digital signal processing for sampling and band pass filtering the signal, then calculating these time -or frequency domain features and then classifying them. CONTROL: The final part consists of applying the will of the user to the used application. The user chooses an action by controlling his brain activity, which is then detected and classified to corresponding action. Feedback is provided to user by audio-visual means e.g. when typing with virtual keyboard, letter appears to the message box etc.

What the brain gate does then? Now this potential difference (Action potential ) is captured by our electrodes and is transmitted via fiber optic to the digitizer. The digitizer converts the signal into some 0s&1s and that is fed into the computer Thus we have successfully given a path to the propagation of brain commands from the brain to the computer via brain gate. Now when external device is connected to the computer they work according to CONCLUSION: Matthew Nagle, a 25-year-old Massachusetts man with a severe spinal cord injury, has been paralyzed from the neck down since 2001.After taking part in a clinical trial of this system; he has opened e-mail, switched TV channels, turned on lights. He even moved a robotic hand from his wheelchair. This marks the first time that neural movement signals have been recorded and decoded in a human with spinal cord injury.

Future implications are mind blowing. We can have a robot completely controlled by thoughts which can do any work and any work obviously very efficiently. There wont be any masterminds paralyzed like Astrophysics STEPHEN HAWKINS. It can be a boon not only to the paralyzed but also to the entire humanity. REFERNCES: Brain gate turning thoughts into actions: www.cyberkineticsinc.com Brain machine brain machine interface takes place: www.gizmag.com/go/3503/ Brain gate Wikipedia the free encyclopedia:www.wikipedia.co m