Electroencephalographic or EEG signals collectedŁ on the human scalp
are sustained fluctuations of electrical potential that reflect corresponding
variations in the upper layers of the brain cortex below tbe scalp surface.
The signal structure is that of a stochastic time series with almost
stationary epochs of various lengths separated by sharper transitions
or disruptions. Amplitudes are small (up to a few tenths of microvolts)
and spectral decomposition reveals that very little power remains
at frequencies above 30 Hz. Most of it is contained
at very low frequencies (< 1 Hz) and within the narrow bands of specific rhythms
(and particularly of the 8-13 Hz alpha rhythm) that appear
and disappear somewhat randomly in time. Signals collected on two or more
electrodes exhibit changing leveis of correlation, due either to physical proximity
(that is, sharing of immediate influences from the cortical surface) or to
actual coordination between different cortical sites,
thus reflecting shared neuron activity within the brain itself.
Spectral content and correlation have been related to various emotional and behavioral states.
Imbedded in this sustained "spontaneous" or "ongoing" electrical activity, short (0.5-2 sec) and distinctive waveforms can be found that are evoked, for instance, when a brief sensory message (stimulus) such as a brief illumination of the visual field or a tap on the forearm is received by the subject. These 'evoked responses" are small (a few microvolts) and somewhat buried in the ongoing activity. The characteristics ot the stimulus determine the evoked potential waveform together with the stimulus "environment," such as tbe Ievel of attention of the subject, the "expectation set," and the meaning of the stimulus in the context of the experiment.
Can these observable electrical brain signals be put to work as carriers of information in man-computer communication or for the purpose of controlling such external apparatus as prosthetic devices or spaceships? Even on the sole basis of the present states of the art of computer science and neurophysiology, one may suggest that such a feat is potentially around the corner.
The Brain Computer Interface project, described later in this chapter, was meant to be a first attempt to evaluate the feasibility and practicality of utilizing the brain signals in a man-computer dialogue while at the same time developing a novel tool for the study of the neurophysiological phenomena that govern the production and the control of observable neuroelectric events.
The long-range implications of systems of that type can only be speculated upon at present. To provide a direct link between the inductive mental processes used in solving problems and the symbol-manipulating, deductive capabililies of lhe computer, is, in a sense, the ultimate goal in man-machine communication. It would indeed elevate the computer to a genuine prosthetic extension of the brain. To achieve that goal with adequate generality is a formidable task that will require considerable advances in neurophysiology (to identify appropriate correlates of mental states and decisions in external signals), in signal analysis techniques (to sort and identify the relevant information carriers from the garbled and diffuse mixture that reaches the scalp), and in computer science (to develop appropriate software within the constraints introduced by the nature of brain messages). While such major advances are still in the future, some progress in that direction is attainable with the present state of the art, which can open the door to a broad range of applications related to brain function and malfunction. By identifying those brain states that would optimize perception or learning, we can considerably increase the efficiency of computer-assisted learning programs. Studies of perception, investigations of dyslexia and epilepsy, studies of the effect of hallucinogenic drugs, and the development of early diagnosis of brain tumors that affect perception, are possible clinical applications, as would be the extension of such systems to the control of prosthetic devices. CYBERSPACE BIONICS
Jacques J. Vidal University of California, Los Angeles, USA email@example.com
INTRODUCTION It can be safely predicted that, not very far into the next century, computer technology will have lifted a strange new world from the void and dragged a significant portion of humanity into it. They could be called citizens of Cyberspace, a world with a topological rather than geographical structure, and one that cuts across all space and time boundaries. At this time, most earthlings still perceive computers as just the last of a series of industrial events that have shaped modern life as have the introduction of railroads, automobiles or airplanes. Certainly, the telegraph and the telephone brought up a revolution in communications. Radio and Television brought distant ears and eyes inside our homes that increassed our awareness of other places and other cultures. Yet, and regardless of how much our individual lifstyle dependens on these, they have not cut into the deep individual and social layers of human life. By all indications this revolution is different, The elusive nature and function of computers in human society is changing from its actuarial and librarian origins into something new and still in search of a shape. Cyberspace citizens are likely to live in two world simultaneously, crossing the mirror a few times every days for gainful work, cultural nutrition, learning, social intercourse, entertainment and even sex.
The forces at work have two major technological aspects. The first is the wrapping of the world into an increasingly dense computer net. The second is the narrowing of the gap that still exists between the human body boundaries to the natural world, limbs, special senses and tactile skin with the input channels and display modes of computers. The most visible manifestation of the first is the Internet , a continually expanding and evolving computer network that nearly double in size every year and now spans the whole world and use all available transmission media, from ordinary phone lines to satellites or fiber optics links. The Internet make interactive information distribution, information gathering, commercial transactions and personal communication instantly available across the world for the benefit of governments, academies, commercial companies and individuals.
At this writing, some fifty millions of users can communicate with each others and access information and services at over ten millions hosts across the world. The second aspect involve a collection of human-computer interfacing technologies that progressively will converge and coalesce to mediate the contacts between individual humans and the rest of the cybersphere. On the Internet the World Wide Web embodies this phenomenon. Documents on the web are not limited to text but are multimedia, i.e., contains images and sound as well. Text itself can also be richly formatted.
Creating an effective bridge between the human brain processes responsible for perception and inductive problem solving and the general symbol-manipulating capabilities of the computer is the goal that drives human-machine communication. The technologies used on the web which refine graphic interfaces with multimedia can make the human-computer interaction much more natural and eventually less treatening for ordinary users. Indeed, new tools are regularly appearing on the web bringing into the unified realm of internet continually improved images and sounds and even allows communication to take place in real-time, emulating and perhaps soon displacing telephones, videophones and teleconferencing.
Recent and less familiar developments in interface design and artefacts engage the human body more intimately into the human- machine dialogue. Virtual Reality, while still an emerging technology has already become a household word. Natural behaviors such as speech, gestures and facial expressions can provide direct computer input, and the computer outputs can take extremely realistic and even hypnotic qualities by surrounding users with compelling visual imagery, lifelike multidirectional sound and even tactile special effects.
Finally, specific biological signals with definite, is often complex and often ambiguous relation to brain states have been used in special situations. To extract cognitive information directly from the brain, to become part of the messages flowing from human user to machine would elevate the computer to the status of a true brain prosthetic, rather than an alien piece of supporting hardware. This paper briefly reviews past efforts in this progression from primitive to advanced human-computer interfaces and examines the promises of recent brain probing research.
Cyberspace Bionics will appear in