Motor Imagery (MI)
Motor imagery is mental imagination of movement in body location such as hand, foot, and others.
In general, MI task induces EEG process of event-related desynchronization (ERD) in the alpha (8-12Hz) and beta (16-30Hz) frequency band (known as sensorimotor rhythm) at sensorimotor area.
Human’s sensory and motor cortex are spatially separated in body location. Reasons of this characteristic, spatial algorithm using for classification of each classes in BCI. Also,
subject’s optimal frequency which is generated ERD patterns in SMR different from each subjects, temporal-frequency optimization algorithms for obtaining MI features.
Steady State Visually Evoked Potentials (SSVEP)
Steady State Visually Evoked Potentials (SSVEP) are signals that are natural responses to visual stimulation at specific frequencies.
When the retina is excited by a visual stimulus ranging from 3.5 Hz to 75 Hz, the brain generates electrical activity at the same (or multiples of) frequency of the visual stimulus.
SSVEP’s are useful in research because of the excellent signal-to-noise ratio and relative immunity to artifacts.
The P300 (P3) wave is an event related potential (ERP) component elicited in the process of decision making. It is considered to be an endogenous potential, as its occurrence links not to
the physical attributes of a stimulus, but to a person’s reaction to it. More specifically, the P300 is thought to reflect processes involved in stimulus evaluation or categorization. It is
usually elicited using the oddball paradigm, in which low-probability target items are mixed with high-probability non-target (or “standard”) items.
When recorded by electroencephalography (EEG), it surfaces as a positive deflection in voltage with a latency (delay between stimulus and response) of roughly 250 to 500 ms.
The signal is typically measured most strongly by the electrodes covering the parietal lobe. The presence, magnitude, topography and timing of this signal are often used as metrics of
cognitive function in decision making processes. While the neural substrates of this ERP component still remain hazy, the reproducibility and ubiquity of this signal makes it a common
choice for psychological tests in both the clinic and laboratory.