Electroencephalogram (EEG) Hsiao-Lung Chan Dept Electrical Engineering Chang Gung University chanhl@mail.cgu.edu.tw
Cerebral function examination Electroencephalography (EEG) Near infrared ray spectroscopy (NIRS) Magnetoencephalography (MEG) Magnetic resonance image (MRI)
EEG recording M. Bear et al, Neuroscience: exploring the brain, Lippincott Williams & Wilkins, 2001. EEG 3
Neurons & interconnections EEG 4
Axon ( 軸突 ) to synapse ( 突觸 ) via neurotransmitter EEG 5
Origin of biopotentials Na + Cl - Extracellular domain Phospholipid bilayer Intracellular domain K + EEG 6
Action potential Na + + + + + + + + + + Outside cell Plasma membrane Inside cell Na + + + + + + + + + + 1 Resting phase K + 3 Repolarizing phase K + Na + Na + + + + + + + + + + + + + + + + + + + 2 Depolarizing phase K + 4 Undershoot phase K + Membrane potential (mv) +50 0 50 100 1 2 3 4 t EEG 7
Action potential EEG 8
Simplified synapse in biologocal neuron EEG 9
Active channel: sodium-potassium pump Remove 3 Na + for every 2 k + outside K+ Na+ inside K+ Na+ M. Bear et al, Neuroscience: exploring the brain, Lippincott Williams & Wilkins, 2001. EEG 10
Brain Cerebrum ( 大腦 ) Receives and processes conscious sensation Generates thought, and controls conscious activity Hypothalamus ( 丘腦下部 ) controls most vegetative and endocrine functions, including body temperature Medulla ( 延腦 ) Vital centers that regulates heart rate, respiratory rate, blood pressure, blood vessel, etc. Cerebellum ( 小腦 ) Controls motor activities and muscle contractions EEG 11
Cerebral functional areas EEG 12
Cerebrum Gray matter refer to cerebral cortex ~ 25 mm thick but contains ~ 100 billion neurons Pyramidal neuron EEG 13
EEG rhythms (8 ~ 13 Hz) Alpha Beta Alpha (>13 ~ 30 Hz) (4 ~ <8 Hz) (<4 Hz) EEG 14
EEG changes in sleep EEG 15
Sleep stages EEG 16
Sleep spindle EEG 17
K-complex, fusion of vertical wave and sleep spindle EEG 18
Sleep stages 3 nonrapid eye movement (REM) (N1, N2, N3) Wakefulness (W) with alpha rhythm and frontal beta rhythm N1 (drowsiness) with irregular slow waves at 37 Hz N2 (light sleep) vertex sharp wave slow wave occipital sharp transients sleep spindle
Sleep stages (cont.) N2 (light sleep) N3 (deep sleep) R (REM sleep) sleep spindle rapid eye movement K complex slow wave slow wave occipital sharp transients
Bispectral index monitor (BIS) A high bispectrum value indicates a phase coupling among the triplet of frequencies, f 1, f 2, and (f 1 +f 2 ) The BIS was shown to reduce the incidence of anesthesia awareness (Myles et al., 2004) BIS ranges from 0 to 100, a BIS value below 60 has been shown to prevent anesthesia awareness (Baura, 2008) EEG 21
Sleep monitoring using wearable brain wave device Z.Q. score Not only helps you with quantifying your sleep, but also tells others you re awake. EEG 22
Lempel-Ziv complexity EEG 23
EEG waveform recorded from one patient under sevoflurane in different states LZ complexity awake state intermediate state asleep state EEG 24
Original 10-20 system of electrode placement EEG 25
EEG electrode placement EEG 26
Referential montage: reference is based on the average of the A1 and A2 channels (ears) EEG 27
Epileptic seizures A seizure results from abnormal discharges of cortical neurons Partial-onset seizures Generalized-onset seizures EEG 28
EEG spikes or abnormal waveform in epilepsy John G. Webster, Medical Instrumentation, application and design, 3rd Ed., Houghton Mifflin, 2000. EEG 29
Vaga nerve stimulation for preventing seizure EEG 30
Brain-computer interface EEG 31
Control robotic arms using braincomputer interface Belle, a monkey in Brain Machine Interface study Articles from Scientific American, Nature, http://www.youtube.com/watch?v=7kctohnrvum&feature=related http://www.youtube.com/watch?v=qrt8qcx3bco EEG 32
Tetraplegia (Quadiplegia) Cervical (neck) injuries usually result in four limb paralysis. Injuries above the C4 level may require a ventilator or electrical implant for the person to breathe.
Cortical neuroprothesis EEG 34
From primates to humans Miguel Nicolelis et al, Duke University Scientific American 2002, Nature Review Neuroscience 2003. BrainGate Collaboration Brown University, Nature 2012 EEG 35
The BrainGate neural interface system (Brown University) An implanted microelectrode array EEG 36
Raster plot Action potentials recorded from motor cortex Each bar indicates neuronal firing at a given moment Time EEG 37
Control computer cursor by thinking (The BrainGate in 2006) EEG 38
Reach for and grasp objects using robotic arms controlled by brain activity A 58-year-old woman, paralyzed by a stroke for almost 15 years uses her thoughts to control a robotic arm, grasp a bottle of coffee, serve herself a drink, and return the bottle to the table. BrainGate Collaboration Brown University, Nature 2012 EEG 39
A vision of future A neurochip would amplify arrays of microwires implanted in motor cortex, convert the thoughts into a train of radio-frequency signals, and send them to a backpack computer. The computer would convert the signals into motor commands for stimulating muscle nerves to move arm controlling a wheelchair or a robotic arm Control Robots with the Mind Scientific American 2002 EEG 40
Reference Leif Sörnmo, Pablo Laguna, Bioelectrical Signal Processing in Cardiac and Neurological Applications, Academic Press, 2005, John Enderle, Susan Blanchard, Joseph Bronzino, Introduction to Biomedical Engineering, Academic Press, 2000. John G. Webster, Bioinstrumentation, John Wiley & Sons, 2003. John G. Webster, Medical Instrumentation, application and design, 3 rd Ed., Houghton Mifflin, 2000. F.M. Ham, I. Kostanic, Principle of Neurocomputing for Science & Engineering, McGraw Hill, 2001. G. D. Baura, Medical device technologies, Elsevier Inc., 2012. EEG 41