Sources of Electrical Brain Activity Most Relevant to Performance of Brain-Computer Interface Based on Motor Imagery

A brain-computer interface (BCI) provides a direct functional interaction between the human brain and the external device. Many kinds of signals (from electromagnetic to metabolic [23, 38, 42]) could be used in BCI. However the most widespread BCI systems are based on EEG recordings. BCI consists of a brain signal acquisition system, data processing software for feature extraction and pattern classification, and a system to transfer commands to an external device and, thus, providing feedback to an operator. The most prevalent BCI systems are based on the discrimination of EEG patterns related to execution of different mental tasks [14, 21, 24]. This approach is justified by the presence of correlation between brain signal features and tasks performed, revealed by basic research [24, 28, 30, 45]. By agreement with the BCI operator each mental task is associated with one of the commands to the external device. Then to produce the commands, the operator switches voluntary between corresponding mental tasks. If BCI is dedicated to control device movements then psychologically convenient mental tasks are motor imaginations. For example, when a patient controls by BCI the movement of a wheelchair its movement to the left can be associated with the imagination of the left arm movement and movement to the right with right arm movement. Another advantage of these mental tasks is that their performance is accompanied by the easily recognizable EEG patterns. Moreover, motor imagination is considered now as an efficient rehabilitation procedure to restore movement after paralysis [4]. Thus, namely the analysis of BCI performance based on motor imagination is the object of the present chapter.