Introduction (1) Nervous System & EEG. Introduction (2)

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1 Introduction () Nervous System & EEG Achmad Rizal BioSPIN Chapter 7, Biointrumentation, Webster Nervous system is defined as all cell, tissues, and organ that regulate the body s response to internal & external stimuli Nervous system is comprised of neuron cell, the conducting elemen of nervous system responsible for transfering information across the body Neuron cell & muscle cell excitable cell ARL-EL4703-Instrumentasi Biomedis Introduction () Resting potential potential between inside and outside of membrane cell electric impulse is generated by differential ion permeability of membrane In the cell, potassium (K + )channel allow diffusion of K+ion out of the cell while sodium Na+ ion diffuse into cell This Na+-K+ pump, which requires ATP to operate, pump two K+ ion into the interior for every three Na+ion pump out K+ and Na+ are continously diffusing across the membrane from where just pumped, but at slower rate Since there are more K+ ion inside the cell than outside, a potenstial exist The magnitude of the equilibrium membrane resting potenstial Vm ( RT / nf)ln[ K Vm 0.065log 0 [ K + ] e + ] e /[ K /[ K + ] i + ] i ARL-EL4703-Instrumentasi Biomedis 3 ARL-EL4703-Instrumentasi Biomedis 4 Stimulus Electronic Action potential stimulator Indifferent electrode 0 V m Micropipet electroderesting potential 70 mv Time 0 0 ms Figure 7. The action potential of the nerve axon in response to electric stimulus. The depolarization process first occurs at the stimulation site. The action potential then travels downstream to the recording site where a penetrating micropipet is used to pick up the intracellular potential with respect to an indifferent reference potential. ARL-EL4703-Instrumentasi Biomedis 5 Na Outside cell Plasma membrane Inside cell Resting phase There is no Na + diffusion into the cell and K + out of the cell ARL-EL4703-Instrumentasi Biomedis 6 K +

2 Na + Na Repolarizing phase K + Depolarizing phase K + K + permeability increases, K + flows out Na gate close, resting potensial regerated The Na + permeability increases, Na + enters the cell interior, ARL-EL4703-Instrumentasi Biomedis 7 ARL-EL4703-Instrumentasi Biomedis 8 Na Undershoot phase K + Membrane potential (mv) t K + flow out to reach resting potential ARL-EL4703-Instrumentasi Biomedis 9 ARL-EL4703-Instrumentasi Biomedis 0 Conduction along a nerve Result of depolarization of small patch of membrane Conduction along a nerve fiber (more generally axons and dendrites) Saltatory conduction along myelinated fibers in nerves, spinal cord Neuron Schematic ARL-EL4703-Instrumentasi Biomedis Organization of Peripheral Nervous System Reflex arc Sense organ (e.g. receptors) Sensory nerve (transfers information from receptor to CNS) CNS (i.e. information processing station) Motor nerve (transfers information from CNS to effector organ) Effector Organ (i.e. muscles) Simplest example Knee reflex ARL-EL4703-Instrumentasi Biomedis

3 Reflex Arc ARL-EL4703-Instrumentasi Biomedis 3 Organization of Peripheral Nervous System Junctional Transmission Communication links between Neurons and neuron conntections: called synapses Neurons and effector organs, called end-plate region Electrochemical transmission via neurotransmitters: (Inhibitory and Excitatory; chemical, gaseous) Acetylcholine GABA Glutamate Dopamine Nitric oxide Postsynaptic channel opening and membrane depolarization Transmission of action potential Presynaptic release of ARL-EL4703-Instrumentasi Biomedis 4 neurotransmitter Electroneurogram (ENG) Measures nerve field potentials Use of needle electrodes Stimulate the peripheral and measure the conduction velocity Used in assessing neuromuscular disorders: peripheral nerve injury, muscular dystrophy Electroencepalogram (EEG) EEG provides information about the health and function of the brain by detecting electric impulse EEG can help diagnose condition such as epilepsy, brain tumor, cerebral palsy, brain injury, stroke, liver, kidney disease, or brain death EEG typically 00μV and frequency response Hz Typically recorded with the subject awake and resting ARL-EL4703-Instrumentasi Biomedis 5 ARL-EL4703-Instrumentasi Biomedis 6 5. Theory / 4 Electroencephalography is a method which is used to detect brain activity. Electroencephalogram is a mean to measure EEG signal Electroencephalogram consists of electrode signal embedded on head skin and signal processing block EEG signal characteristics at very low magnitude (5µV - 00µV). Frequency Hz to 30 Hz. Very low electric current < ma EEG first time has found by Berger on (99) 5. Theory / 4 Typical Frequency and Amplitudo on Brain Waves Frequency (Hz) Signal Condition Amplitud o (µv) -4 Delta Just sleep and get up Theta Emotion and frustation 0 Rilex and eyes is 8-3 Alpha 0-00 closed Respon to Think and 3-30 Beta 5-0 stimulate, sleepy Signal Image ARL-EL4703-Instrumentasi Biomedis 7 ARL-EL4703-Instrumentasi Biomedis 8 3

4 Condition and Activity 5. Theory 3 / 4 Delta Hz In sleeping condition, can easily dreaming, increase body immune, hipnosys EEG Signal collected by embedding transducer on head section, see these figures below. Teta 4-8 Hz Relax, positive thinking, creative, focus, meditation, easy dreaming, hypnagogic Alpha 8 - Hz Study hard, full relax, positive thinking Beta Low - 5 Hz Normal focus, maximum ability Beta Medium 5-8 Hz Strong mentality, strong focus, IQ Beta High 8-30 Hz Attractively, depressed. Normal focus, full consciousness Bipolar Electrode Model International Electrode Placement System ARL-EL4703-Instrumentasi Biomedis 9 ARL-EL4703-Instrumentasi Biomedis 0 5. Theory 4 / 4 Electrode set up in internationally way and experiment 6. Hardware Design / 6 Acquisition System and EEG Signal Monitoring Diagram Block ARL-EL4703-Instrumentasi Biomedis ARL-EL4703-Instrumentasi Biomedis 6. Hardware Design / 6 Out Put AD 60 Bipotensial Amplifier dan Differential Amplifier with Gain 0 times R G 49,4 kω 49,4 kω G 4,9 kω 49,4kΩ 49,4kΩ 0 4,9kΩ 6.68kΩ ARL-EL4703-Instrumentasi Biomedis 3 ARL-EL4703-Instrumentasi Biomedis 4 4

5 6. Hardware Design 3 / 6 Out Put HPF High Pass Filter nd orde with,4 times Cut Off 0.48 Hz gain R f 5k.45S G + +,45kali H( S) Ri k S + 4,7777S + 9,8736 f co 0,48Hz π 3,3kΩ 00 μ F ARL-EL4703-Instrumentasi Biomedis 5 ARL-EL4703-Instrumentasi Biomedis 6 6. Hardware Design 4 / 6 Out Put LPF Low Pass Filter nd order with,4 times Cut Off 8.3 gain R f 5k,45 G + +,45kali H( S) Ri k 0,000038S + 0,00888S + f 8. Hz co π R C π kω 470nF ARL-EL4703-Instrumentasi Biomedis 7 ARL-EL4703-Instrumentasi Biomedis 8 6. Hardware Design 5 / 6 Out Put Amplifier Each of Gain, 3, and 4 has 0 times gain and 5 th gain has gain G V R f R R f 0kΩ AV 0 times Ri kω AVtotal A 3 V o Vi ( ) ( ) times ARL-EL4703-Instrumentasi Biomedis 9 ARL-EL4703-Instrumentasi Biomedis 30 5

6 6. Hardware Design 6/ 6 6. Software Design / 4 ADC0804 Input Voltage Conformer Circuit V out V ( V R ) + ( V R ) i out i R + R ( V + 5) ref Conformer Circuit of Com. Serial and ADC SMOD f OSC TH baudrate TH E8 ( H) ARL-EL4703-Instrumentasi Biomedis 3 Software to convert parallel data format to serial data format; implemented on microcontroller AT89C05 using Assembly programming language. Software to monitor EEG signal, divide signal (alpha, betha,delta, tetha) implemented on PC using Borland Delphi 7. ARL-EL4703-Instrumentasi Biomedis 3 6. Software Design / 4 Software in microcontroller First, initializing microcontroller for baudrate setting and serial data format that used. Analog EEG signals read by ADC0804 by control of pin 3.3, 3.4 dan 3.5. Then the data are received in port microcontroller Paralel data are converted to serial data format and transferred to PC. ARL-EL4703-Instrumentasi Biomedis Analyzing System /3 Software Analyze for Monitoring EEG signal ARL-EL4703-Instrumentasi Biomedis Analyzing System 3/3 Sofware Analyze for Saving EEG signal Troubleshooting for EEG Delta Betha Tetha Alpa Abnormalities in EEG waveform maybe due to artifact categorized as follow Artifacts due to electrode problems may result : improper positioning poor contact poor electrode in the cap holding them dried-out gel oozing of tissue in needle electrode frayed connection Sweating ARL-EL4703-Instrumentasi Biomedis 35 ARL-EL4703-Instrumentasi Biomedis 36 6

7 Troubleshooting for EEG Artifacts due to physiological interference may may result from: the heart ECG Tongue and facial movement Eye movement Skeletal movement High scalp impedance breathing Troubleshooting for EEG Artifacts due to electrical interference (EI) may result from: 50 Hz sinusoid common mode interference (powerline) radio frequency interference due to use of an electrical surgical unit defibrillation presence of pacemaker and neural stimulator ARL-EL4703-Instrumentasi Biomedis 37 ARL-EL4703-Instrumentasi Biomedis 38 EEG Application EEG Application Controlling ARL-EL4703-Instrumentasi Biomedis 39 Evoked Potentials Electric response signal of the brain to a specific stimulus, usually in low amplitude (<5μV) EEG background signal (50 to 00μV) Usually signal averaging used to minimize background EEG & artifact Studies of evoked potential are useful in evaluating the functional integrity of sensory pathway Clinically abnormality can be detected by an increase in latency Detected by an electrode placed on the scalp ARL-EL4703-Instrumentasi Biomedis 40 EEG Application EEG Application Visual Evoked Potential during VEP testing, th subject stares at a central spot on reversing check board pattern m away The procedure is usually done twice to ensure reproducibility, and the two eyes are tested separately VEP evaluates the visual nervous system from eyes to the brain, help to diagnose certain visual or brain disorder ARL-EL4703-Instrumentasi Biomedis 4 Brainstem Auditory Evoked Potential / Brain Evoked Response Auditory during BAEP, rarefaction or condensation clicks at about 0 Hz stimulate one ear of the subject, and white noise masks the contralateral ear BAEP examination evaluates the nerves pathway from the ear to the brain It may help uncover the cause of hearing and balance problem as well as other nervous system disorders ARL-EL4703-Instrumentasi Biomedis 4 7

8 EEG Application Somatosensory Evoked Potential during SSEP testing, peripheral nerves are stimulated with a small electric current through bipolar electrodes on arms or legs skin. SSEP asseses the neurological pathway from the nerves in the arms/legs through the spinal cord to the brain Can be used to monitor coma patients, monitor patient during surgical procedures, test hearing ini infant and other whose hearing cannot be tested in the standard way ARL-EL4703-Instrumentasi Biomedis 43 8