Electroencephalogram (EEG) “Extracellular currents” Summed activity of post-synaptic currents generated by compensatory currents in the extracellular space Summation of the synchronous activity of thousands of neurons that have similar spatial orientation, radial to the scalp Currents that are tangential to the scalp are not picked up by the EEG Activity from deep sources is more difficult to detect than currents near the skull

History Duboi-Reymond (1848): reported the presence of electrical signals Caton (1875): measured “feeble” currents on the rabbit scalp Berger (1929) measured electrical signals in human Alpha and Beta waves, eye closed and open, mental task Sleep and Awake Illness and EEG Drug and EEG: Phenobarbital, morphine, cocaine Telepathic transmission 1930-50s: EEG used in psychiatric and neurological sciences relying on visual inspection of EEG patterns 1960s-70s: witness emergence of Quantitative EEG and confirmation of hemispheric specialization, e.g., left brain verbal and right brain spatial. 1980s+: observation of biofeedback

Waveform

Wave differentiation Alpha (8-12 Hz): posterior head regions, in adult in awake but relaxed. attenuate with eye opening or mental exertion Beta (12-30 Hz): active, busy or anxious thinking and active concentration Gamma (26-100 Hz): certain cognitive or motor function, most often artifactual Delta (<3 Hz): in adults in slow wave sleep / in babies Theta (4-7 Hz): in young children / in drowsiness or arousal in older children and adults / in meditation

The original figure of 10-20 system (Jasper, 1958)

The international 10-20 system A = Ear lobe, C = central, Pg = nasopharyngeal, P = parietal, F = frontal, Fp = frontal polar, O = occipital.

American Electroencephalographic Society (Sharbrough, 1991)

Lobes of the Brain Frontal Lobes: Personality, emotions, problem solving. Parietal lobes: Cognition, spatial relationships and mathematical abilities, nonverbal memory. Occipital lobes: Vision, color, shape and movement. Temporal lobes: Speech and auditory processing, language comprehension, long-term memory.

Can EEG work for BCI? Electrical activity generated by complex system of billions of neurons Brain is a “gelatinous mass” suspended in a conducting fluid Difficult to “register” electrode location Artifacts from motion, eyeblinks, swallows, heartbeat, sweating… Food, age, time of day, fatigue, motivation of subject Many EEG studies have reported reproducible changes in brain dynamics that are task dependent! Patients may “correct” their waveforms to achieve a normal state Kamiya (1962): demonstrated the controllability of alpha waves Communication in morse code by turning alpha waves on and off Stress management and sleep therapy Move a pac-man by stimulating alpha and beta waves Note that artifacts are a serious problem for real-time biofeedback applications

Matrix?

Real story 1: Monkey think, Robot Do www.nicolelislab.net. Learning to control a brain-machine interface for reaching and grasping by primates. Nicolelis et al., PLoS Biology 2003

Real story 2: ‘Ratbot’ Rat navigation guided by remote control Chapin et al., Nature, 2002

Motivation for BCI/BMI Research In USA, more than 200,000 patients live with the motor sequelae (consequences) of serious injury. There are two ways to help them restore some motor function: Repair the damaged nerve axons Build neuroprosthetic device

Brain Computer Interface (BCI)

http://ida.first.fhg.de/projects/bci/bbci_official/

EEG-based BCI non-invasive promising for some therapies time-consuming not suitable for precise control Mussa-Ivaldi & Miller, 2003

Control home appliances by mind Tsinghua Group Gao et al Appliance control Make phone call

Type words by mind Tübingen Group Birbaumer et al Type words by mind Tübingen Group Birbaumer et al., 2000, Hinterberger et al., 2004

Help impaired hand to grasp by mind Graz Group Pfurtscheller et al

Play video games by mind ECoG based BCI Video Pfurtscheller et al., 2003 Leuthardt et al.,2004

Neuron Spike based BMI high speed real time control precise control of movement invasive high risk for clinical application Nicolelis, 2001

Monkey control robot arm by mind Duke Group Nicolelis et al www.nicolelislab.net.

Real time control of 2D/3D movement Donoghue et al, 2002, Schwartz et al.,2002 2D movement control 3D movement control

Take home message Origin of EEG Pros and Cons of EEG in making BCI