Brain Computer Interface
The Dream
• Controlling the physical world with our thoughts
has always been the stuff of science fiction and
dreams.
• In today’s world, small demonstrations of such
feats abound.
– Commercial BCIs
– Commercial headsets for gaming
• NeuroSky
• Emotiv EPOC
Sensing the Brain
• EEG
– measures the electrical signals produced by nerve cells in
your brain
• fMRI
– Detects blood flow in the brain to identify areas of activity; a
blood-oxygen-level-dependent (BOLD) signal.
• NIRS
– Detects near IR light absorption to identify areas of activity,
another BOLD signal.
• Others
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CAT scan
PET
phMRI
TMS
Early Efforts
Brain Imaging
Animal brains
• Brain stem - controls the
reflexes and automatic
functions.
• Cerebellum - coordinates
limb movements.
• Hypothalamus and
pituitary gland - controls
body temperature and
behavioral responses such
as feeding, drinking, sexual
response, aggression and
pleasure.
• Cerebrum - integrates
information from all of the
sense organs, initiates motor
functions, controls emotions
and holds memory and
thought processes.
Cerebral Cortex
Parietal Lobe - involved in
the reception and processing
of sensory information from
the body.
Frontal Lobe - involved with
decision-making, problem
solving, and planning.
Occipital Lobe - involved
with vision.
Temporal Lobe - involved
with memory, emotion,
hearing, and language.
Somatosensory & Motor Cortex
Somatosensory
Motor
Your Electric Brain
• Brains are filled with neurons.
• Each neuron receives electrical
inputs from about 1000 other
neurons.
• Impulses are added together
leading to generation of an
electrical discharge called an
action potential.
• electric signals (i.e., action
potentials) zip from neuron to
neuron as fast as 250 mph
• Neurons communicate at
structures called synapses.
• Information moves around the
brain via electrical activity but
communication between
neurons is chemical.
EEG
• An EEG records electrical
signals from the brain
– Measures postsynaptic
potentials of neurons, via
electrodes on the scalp
• An EEG detects the
summed ionic currents of
thousands of pyramidal
neurons beneath each
electrode.
• The signals relayed to the EEG are typically
amplified 10,000 times and filtered.
Brain Wave Types
• EEGs record brain waves which are
oscillating electrical voltages in the brain
measuring a few millivolts.
• There are six widely recognized brain waves:
– Delta: 1-4 Hz.
– Theta: 4-7 Hz.
– Alpha: 8-12 Hz.
– Mu rhythm is alpha-range activity that is
seen over the sensorimotor cortex.
– Beta:12-30 Hz.
– Gamma: 30–100 Hz.
BCI Inputs
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Slow cortical activation
Mu and Beta rhythms
performance of different cognitive tasks
imagination of movement of different parts of the
body
• Steady-state evoked potential – the response of
the brain to a constant stimulus, in which the brain
activity has the same frequency as the stimulating
frequency
• visually evoked P300 potential – “oddball”
response
Training
Electrode Placement