Active BCI: A BCI system that requires users to actively modulate their brain signals to interact with an external device.
AEPs: Auditory-evoked potentials. The brain's electric response to sound.
ALS: Amyotrophic lateral sclerosis. Neurodegenerative disease.
AR: Augmented reality. Technology that overlays digital content over the real world.
BCI: Brain-computer interface. Technology that connects thoughts and feelings to computers.
BMI: Brain-machine interface. An alternative term for BCI, most commonly used when referring to implanted systems.
Closed-loop BCI: A real-time BCI system in which the brain and external devices bidirectionally interact with each other.
CNS: Central nervous system.
DBS: Deep brain stimulation.
ECG: Electrocardiogram or EKG.
ECoG: Electrocorticogram.
EEG: Electroencephalogram.
EEG Artifact: Refers to any signal in EEG that is not originated from the brain. Common EEG artifacts include ECG, EOG, EMG, movement, 50/60Hz power line noise.
EEG Frequency Bands: Frequency ranges of characteristic, oscillatory EEG activity, typically associated with specific spatial distributions and states of brain functioning. The five most commonly used frequency bands are delta (0.5-4), theta (4-8), alpha (8-12), beta (12-30), and gamma (>30).
EMG: Electromyogram.
EOG: Electrooculogram.
ERD/ERS: Event-related desynchronization / synchronization. A relative power decrease / increase of EEG in a specific frequency band during physical motor execution and mental motor imagery.
ERP: Event-related potential.
FES: Functional electrical stimulation.
(f)MRI: (functional) Magnetic resonance imaging.
fNIRS: Functional near infrared spectroscopy.
Hybrid BCI: A BCI that utilizes both brain and non-brain signals (e.g. eyes, heart, physiological or behavioral activity).
Invasive system: A system which requires cutting or entering a body part (skin and/or skull) using medical instruments. Intracortical recordings and ECoG are invasive approaches.
LFP: Local field potential.
MEG: Magnetoencephalogram.
micro-Volt: A unit of electric potential and EEG signal. EEG measures the electric potential difference between two locations in an electric field. EEG typically presents in micro-Volt (1 millionth of Volt) to reflect the small changes from brain activity.
Motor Imagery (MI): A mental process by which an individual rehearses or simulates a given action.
Neural Assembly: Or neural population or neuronal ensemble, refers to a population of neurons involved in a particular neural functioning.
Neurofeedback: A method based on reinforcement learning, where real-time feedback provided to users is supposed to reward and reinforce desired brain activity or inhibit unfavorable activity patterns.
Neuromodulation: A method to modulate neural activity through targeted delivery of a stimulus, such as electrical, electromagnetic, auditory, or chemical stimulation to specific neurological sites in the body.
Neuroprosthesis: A device that can enhance the input or output of a neural system. It can be used to enhance motor, sensory, cognitive, visual, auditory, and communicative deficits that arise from acquired brain injuries.
Neurostimulation: Usually refers to the electromagnetic approaches to neuromodulation, including DBS, TMS, tACS, tDCS.
Non-stationary Process: A process in which its statistical properties (such as mean, variance) change over time.
Passive BCI: A BCI that derives its output from naturally occurring brain activity to act as a complementary input providing information about ongoing user mental states (e.g., workload, emotional state, or attention levels)
Reactive BCI: A BCI that utilizes brain responses elicited by different stimuli (e.g., visual, auditory).
Real-time: Refers to a property of a BCI system in which the feedback from the system can be computed and delivered in a specified time constraint.
REM Sleep: Rapid eye movement sleep, characterized by random rapid movement of the eyes, accompanied by low muscle tone and vivid dreams.
Sampling rate: The number of samples taken per second (in Hertz).
Sensor: A device that senses the brain activity (via electrical field, magnetic field, or lights, etc) and produces an output signal for BCI applications.
Slow wave sleep: Often referred to as deep sleep or SWS, one of the sleep stages during non-rapid eye movement sleep, characterized by slow waves of EEG with a frequency range of 0.5–4 Hz.
SSVEP: Steady-state visual-evoked potential, a type of VEPs, an EEG response evoked by visual stimuli presented at a specific frequency.
tACS: Transcranial alternating current stimulation.
tDCS: Transcranial direct-current stimulation.
Time-locked: Refers to a property of a BCI system in which the feedback from the system is delivered at a specific phase of oscillations of brain activity.
TMS: Transcranial magnetic stimulation.
VEPs: Visual-evoked potentials.
VNS: Vagus nerve stimulation.
VR: Virtual Reality.