Brain-computer interface (BCI) realizes a direct communication
between the human brain and the external environment
by translating human intentions into control signals
[1]. A BCI allows an individual with severe motor
disabilities or aphasia to have effective control over devices
such as computers, wheelchairs, assistive appliances
and neural prostheses. A BCI system detects the specific
patterns in a brain activity and translates these patterns
into meaningful control commands. Recently, electroencephalogram
(EEG)-based BCI is attracting much attention
due to their noninvasiveness and high communication
speed. Current EEG-based BCIs fall into four main categories
such as imagery of event related synchronization
(ERS) / desynchronization (ERD), event related potentials
(ERP), visual evoked potentials (VEP) and slow cortical
potentials (SCP) [1].