BRAIN COMPUTER INTERFACE –A NEW DIMENSION FOR COMMUNICATION AND CONTROL
Human Computer Interface(HCI) has been a growing field of research and development in recent years. Most of the effort has been dedicated to the design of user friendly and economic systems by means of innovative interfaces such as voice, vision and other input-output devices in virtual reality. Direct Brain Computer Interface (BCI) adds new dimension to HCI. Interesting research in this direction has already been initiated, motivated by the hope of creating new communication channels for persons with severe motor disabilities. In our paper we approach the problem of BCI from the view point if interactions in a multimedia rich environment for the general consumer market. However this is by no means incompatible with applications for motor impaired subjects. Here the main focus will be on one specific modality namely Electroencephalography (EEG) based BCI. Here EEG is used to pick up the electric signals produced in the brain according to the subject’s mentality. It is then compared with the standard signals obtained during the earlier training sessions in the signal preprocessing stage and if matched, produces the control signals accordingly. For reasons of efficiency,the BCI system has been designed around five operational modes going from simple to more sophisticated.
The main motivation today is to develop replacement communication and control means for severely disabled people, especially those who have lost all voluntary muscle control. What is communication?
Communication is referred to as a process to express and share experiences between humans. Such an experience can be either real or imaginary. As an extension of this we may be eager to know about the next revolution in the field of communication. Probably the two most significant will be those in media technologies on one hand and the interface between human and machines on the other hand. In our paper we will throw lights over the second trend.
A NEW COMMUNICATION MODALITY-BRAIN ACTIVITY:
Recent progress in technology allows us to probe and monitor physiological process inside our body for which no natural interfaces exist. In particular we can measure our blood pressure, heart rate variability, muscular activity and brain electrical activity in efficient and non invasive ways. It is natural to assume that such activity is used as information in new communication channels. In our paper we focus on brain electrical activity and review methods and procedures aiming at detecting and interpreting such signals for the purpose of command and control in a multimedia environment. A variety of noninvasive methods are available to monitor brain functions. This include EEG, magnetoencephelography (MEG), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI).
However PET, MEG and fMRI are expensive and complicated. Hence EEG is adapted for BCI. This is because EEG is easily recorded and processed with inexpensive equipments and offers practical possibility of a noninvasive communication.
An EEG is basically used for recording a very weak in the order of 5-100µV electrical potentials generated by the brain on the scalp. The EEG is normally recorded as a potential difference between a signal electrode placed on the scalp and a reference electrode. It is recommended to use a conductive paste to decrease the contact impedance and electrode migration .Due to signal levels, high gain, high quality amplifiers are placed between the electrodes and the acquisition devices.
It is a common practice to consider specific frequency bands thought to be associated with brain rythms viz the delta[δ(.5-4Hz)], theta[θ(4-7Hz)],alpha[α(8-13Hz)],beta[β(13-30Hz)].Alpha waves are of...