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Functional Brain Signal Processing: EEG & fMRI Lesson 1

M.Tech. (CS), Semester III, Course B50. Functional Brain Signal Processing: EEG & fMRI Lesson 1. Kaushik Majumdar Indian Statistical Institute Bangalore Center kmajumdar@isibang.ac.in. Brain Signal Type. Functional (EEG, MEG, PET, fMRI) Structural (CT, MRI). Motivation to Study EEG.

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Functional Brain Signal Processing: EEG & fMRI Lesson 1

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  1. M.Tech. (CS), Semester III, Course B50 Functional Brain Signal Processing: EEG & fMRILesson 1 Kaushik Majumdar Indian Statistical Institute Bangalore Center kmajumdar@isibang.ac.in

  2. Brain Signal Type • Functional (EEG, MEG, PET, fMRI) • Structural (CT, MRI)

  3. Motivation to Study EEG • Monitoring state of consciousness. • Brain Computer Interface. • Understanding cognitive processes. • Monitoring pathological brain conditions.

  4. Human Brain or Neocortex https://eprints.usq.edu.au/19846/2/Bashar_2011_whole.pdf http://en.wikipedia.org/wiki/Human_brain

  5. Functional Organization: Brodmann’s Areas http://spot.colorado.edu/~dubin/talks/brodmann/brodmann.html http://en.wikipedia.org/wiki/Human_brain

  6. Electroencephalogram (EEG) Acquisition: 10 – 20 System http://www.ese.wustl.edu/~nehorai/research/eegmeg/EMEG-Overview.html http://en.wikipedia.org/wiki/10-20_system_%28EEG%29

  7. Majumdar, IEEE Trans. Biomed. Eng., vol. 56(4), p. 1228 – 1235, 2009. Channels by Number

  8. Multi-Channel EEG Signals http://maxim.ece.illinois.edu/teaching/fall08/

  9. Mountcastle, Brain, 120:701-722, 1997. Six Layer Cortex

  10. Cortical Basis of Scalp EEG Baillet et al., IEEE Sig. Proc. Mag., Nov 2001, p. 16.

  11. Head Tissue Layers

  12. Forward Problem : Schematic Head Model EEG Channels Source Scalp Skull Brain

  13. Dipole Source Model (parametric model) Distributed Source Model (nonparametric model) Source Models

  14. Dipole Source Model

  15. Majumdar, IEEE Trans. Biomed. Eng., vol. 56(4), p. 1228 – 1235, 2009. Distributed Source Model

  16. Kybic et al., Phys. Med. Biol., vo. 51, p. 1333 – 1346, 2006 Forward Calculation • Poisson’s equation in the head

  17. Hallez et al., J. NeuroEng. Rehab., 2007, open access. http://www.jneuroengrehab.com/content/4/1/46 Published Conductivity Values

  18. Hallez et al., J. NeuroEng. Rehab., 2007, open access. http://www.jneuroengrehab.com/content/4/1/46 6 Parameter Dipole Geometry

  19. Potential at any Single Scalp Electrode Due to All Dipoles r is the position vector of the scalp electrode rdip - i is the position vector of the ith dipole di is the dipole moment of the ith dipole

  20. Potential at All Scalp Electrodes

  21. For N Electrodes, p Dipoles, T Discrete Time Points

  22. Generalization V = GD + n G is gain matrix, n is additive noise.

  23. EEG Gain Matrix Calculation For detail of potential calculations see Geselowitz, Biophysical J., 7, 1967, 1-11.

  24. Gain Matrix : Elaboration

  25. Hallez et al., J. NeuroEng. Rehab., 2007, open access. http://www.jneuroengrehab.com/content/4/1/46 Nested Head Tissues SKULL BRAIN SCALP

  26. Hallez et al., J. NeuroEng. Rehab., 2007, open access. http://www.jneuroengrehab.com/content/4/1/46 Finite Elements Method

  27. Home Work: Loading EEG Data Files in Computer RAM and Familiarization • EEGLAB (needs MATLAB) available at http://sccn.ucsd.edu/eeglab/ • Sample EEG Data: http://sccn.ucsd.edu/eeglab/data/headit.html

  28. Must Reading • Baillet, Mosher & Leahy, “Electromagnetic brain mapping,” IEEE Sig. Proc. Mag., p. 14 – 30, Nov 2001. • Hallez et al., “Review on solving the forward problem in EEG source analysis,” J. Neuroeng. Rehab., open access, available at http://www.jneuroengrehab.com/content/4/1/46

  29. THANK YOUThis presentation is available at http://www.isibang.ac.in/~kaushik

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