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– 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

• 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