Neural Network. Eung Je Woo Department of Biomedical Engineering Impedance Imaging Research Center (IIRC) Kyung Hee University Korea

Transcription

1 Neural Network Eung Je Woo Department of Biomedical Engineering Impedance Imaging Research Center (IIRC) Kyung Hee University Korea

2 Neuron and Nervous System 2

3 Neuron (Excitable Cell) and Muscle 3 Malmivuo and Plonsey, 1995

4 Neuron and Nerve Conduction Nerve Action Potential Muscle Neuronal Current 4 Malmivuo and Plonsey, 1995

5 Fundamental Quantity Length (dimension or size) in meter (m) Time (sequence or duration or interval) in second (s) Mass in kilogram (kg) Charge in coulomb (C) Temperature in kelvin (K) Amount of substance in mole (mol) Luminous intensity in candela (cd) 5

6 Charged Particle and Charge Density Free electron and hole are mobile Unbounded ion and molecule are mobile Bounded atom and molecule are immobile but may vibrate Polar molecule has no net charge but dipole moment and may rotate Mass Charge Size Position m, Q, r, d 6

7 Electric Field Space with nothing Space with a single charged particle Space with two charged particles Space with multiple charged particles Space with a charge density distribution z r Q r y Q 0 x 7

8 Potential or Voltage Space with electric field E(r) Put a point charge at r1 from the infinity (a reference point) Move the point charge from r1 to r2 E(r) r 2 Q r r 1 Q r 8

9 Membrane Potential 9

10 Membrane Potential 10

11 Membrane Potential 11

12 Membrane Potential 12

13 Membrane Potential 13

14 Action Potential during Neural Activity R (ohms) AP [mv] CAP [mv] Action Potential (AP) 8 6 Compound AP Impedance D s [%] s Crab Nerve V1 V Time [ms] Time [ms] Current Source Action Potential 14

15 Neuronal Source Current t 1 t 2 t 3 Purves et al., Grimnes and Martinsen, 2008

16 Brain 10 7 Neurons/cm Synapses/Neuron Neurons 10-6 m 10-5 m 10-4 m 10-3 m 10-2 m 10-1 m Blue Brain Project 16

17 Voltage Imaging using MEA (Microelectrode Array) Gandolfo et al., Journal of Neural Engineering,

18 Voltage Imaging using MEA (Microelectrode Array) Abdoun et al., Frontiers in Neuroinformatics,

19 Voltage Imaging using MEA (Microelectrode Array) Viventi et al., Nature Neuroscience,

20 Voltage Imaging using Voltage-sensitive Dye Dye Loading Imaging Grienberger and Konnerth, Neuron,

21 Voltage Imaging using Voltage-sensitive Dye Grienberger and Konnerth, Neuron,

22 Voltage Imaging using Voltage-sensitive Dye Peterka et al., Neuron,

23 Functional Connectomics From Anatomy to Connectivity Graph (Brain s Wiring Diagram) Cell, Tissue, Animal Human Bock et al., Nature, Park and Friston, Science, 2013

24 Functional MRI Sagittal Midbrain Coronal Thalamus P S L 7 Cuneus 6 R A I 5 ` Medulla Superior frontal gyrus Axial Lingual gyrus Occipital lobe Middle frontal gyrus Inferior frontal gyrus Insula Thalamus Superior temporal gyrus 3 Lingual gyrus Occipital lobe From Hyung Joong Kim 24

25 Diffusion Tensor MRI T2-weighted Image FA Color-coded FA Tractographic Images 25

26 Nervous System 26 Malmivuo and Plonsey, 1995

27 Intra-cardiac Nerve Conduction 27 Malmivuo and Plonsey, 1995

28 Equivalent Dipole Current Source Atrial Depolarization (80 ms) Septal Depolarization (220 ms) Apical Depolarization (230 ms) Left Ventricular Depolarization (240 ms) Left Ventricular Depolarization (250 ms) Depolarized Ventricles (350 ms) Ventricular Repolarization (450 ms) Repolarized Ventricles (600 ms) 28 Malmivuo and Plonsey, 1995

29 Body as an Active Volume Conductor u s r, - + Conductivity Voltage Volume Source Density (Flow Source Density) s r, t Φ r, t = J nc r, t = I F r, t in V s r, t Φ r, t n = 0 on V Total Current Density Neuronal Current Density (Volume Dipole Moment Density) J r, t = J nc r, t s r, t Φ r, t 29 Return Current Density Malmivuo and Plonsey, 1995

30 Volume Conduction and Biosignal + u 1 - White lines are current stream lines. Black lines are equipotential lines. + u u t 1 t 2 t 3 u u 3 u 2 u 1 t 1 t 2 t 3 30 t

31 Bio-electric Signal (ECG) s r, t u r, t = f r, t = J nc r, t in Ω s r, t u r, t n = 0 on Ω Amplifier ECG Medical Instrumentation: Application and Design, 3 rd ed., by J. G. Webster 31

32 Bio-electric Signal (ECG) 32 Grimnes and Martinsen, 2008

33 Bio-electric Signal (EEG) s r, t u r, t = f r, t = J nc r, t in Ω s r, t u r, t n = 0 on Ω EEG f r, t Amplifier 33

34 Bio-electric Signal (EEG) 34 Malmivuo and Plonsey, 1995

35 Bio-electric Signal (EEG) 35 Malmivuo and Plonsey, 1995

36 Bio-magnetic Signal (MEG) (Superconducting Quantum Interference Device) SQUID MEG f r, t s r, t u r, t = f r, t = J nc r, t in Ω s r, t u r, t n = 0 on Ω J r, t = J nc r, t s r, t u r, t B r, t = μ 0 4π Ω J r, t r r r r 3 dr 36

37 EOD