10-06-2013, 12:35 PM
BRAIN-COMPUTER INTERFACE
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INTRODUCTION
Brain-Computer interface is a staple of science fiction writing. Init's earliest incarnations nomechanism was thought necessary, as the technology seemed so far fetched that no explanation was likely. As more became known about the brain however, the possibility has become more real and the science fiction more technically sophisticated. Recently, the cyberpunk movement has adopted the idea of "jacking in", sliding "biosoft" chips into slots implanted in the skull (Gibson, W. 1984).
Although such biosofts are still science fiction, there have been several recent steps toward interfacing the brain and computers. Chief among these are techniques for stimulating and recording from areas of the brain with permanently implanted electrodes and using conscious control of EEG to control computers.
Some preliminary work is being done on synapsing neurons on silicon transformers and on growing neurons into neural networks on top of computer chips.The most advanced work in designing a brain-computer interface has stemmed from the evolution of traditional electrodes. There are essentially two main problems, stimulating the brain (input) and recording from the brain (output).
Traditionally, both input and output were handled by electrodes pulled from metal wires and glass tubing.Using conventional electrodes, multi-unit recordings can be constructed from mutlibarrelled pipettes. In addition to being fragile and bulky, the electrodes in these arrays are often too far apart, as most fine neural processes are only .1 to 2 µm apart.Pickard describes a new type of electrode, which circumvents many of the problems listed above. These printed circuit micro-electrodes (PCMs) are manufactured in the same manner of computer chips. A design of a chip is photoreduced to produce an image on a photosensitive glass plate. This is used as a mask, which covers a UV sensitive glass or plastic film.
A PCM has three essential elements:
1) the tissue terminals,
2) a circuit board controlling or reading from the terminals
3) a Input/Output controller-interpreter, such as a computer.
The circuit board and computer are often located outside the skull, to minimize tissue invasion, allow for long-term implantation and permit the electrodes to be detached between trials.In addition to the ability to make multiple, closely spaced recordings, PCMs often outperform the traditional electrodes in a number of electronic measures .
Introduction to Bionics
Scientists have known for a long time that the human neurosystem uses electrical signals to transmit commands from the brain to the rest of the body. Now they are designing devices that speak directly to the nerves themselves. Bionics is that branch of science that helps to create a human machine interface by making use of computer technology.There was a time when Bionics was the stuff of science fiction. “We have the technology” was the theme of a popular TV series, creative writers produced fantastic stories of mechanized men, people imagined replacing body parts, improving the quality of life, revolutionizing medicine with far flung ideas like prosthetic arms, legs, mechanical eyes and ears. There’s no limit to what man has imagined. But often when people ponder these possibilities they look at them as just that, possibilities. Not everyone realizes that science fiction is quickly becoming scientific fact!
The Artificial Retina Component Chip (ARCC)
The Artificial Retina Component Chip is being developed by Dr Wentai Liu of North Carolina State University, the doctoral student Elliot McGucken of the University of North Carolina and Dr Mark Humayun of Johns Hopkins State University.
The ARCC has two main parts, a photovoltaic- powered circuit that provides photo sensing, processing, and neural stimuli and an electrode array which is at least 0.5 mm away from the retina that connects the chip to the nerve. The electrodes do not directly pass current to stimulate the nerve ganglia; instead they charge a plate that stimulates the ganglia later in turn, so as to minimize the possibility of the risk of damage to the retinal tissue.
The device works by "exciting" the remaining neurons of the retina. The silicon chip is two millimeters square, coated with photosensors and electrodes, and is 0.02 mm thick, so as to allow the light from the objects to pass through the chip to the artificial photosensors on the other side of the chip. Figure 7 shows the retinal chip along with the other component of the system
Artificial Silicon Retina (ASR)
ASR was designed and created by brothers Alan and Vincent Chow, the co-founders of Optobionics Corporation. The silicon ship is 2mm in diameter and 1/1000 inch thick with approximately 3500 microscopic photovoltaic cells named micro photodiodes each with its own stimulating electrode
Bionic Ear
For centuries, people believed that only a miracle could restore hearing to the deaf. It was not until forty years ago that scientists first attempted to restore normal hearing to the deaf by electrical stimulation of the auditory nerve. The first experiments were discouraging as the patients reported that speech was unintelligible. However, as researchers kept investigating different techniques for delivering electrical stimuli to the auditory nerve, the auditory sensations elicited by electrical stimulation gradually came closer to sounding more like normal speech.