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

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 http://en.wikipedia.org/wiki/Human_brain https://eprints.usq.edu.au/19846/ 2/Bashar_2011_whole.pdf

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

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

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

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

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

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 Brain Skull Scalp Source EEG Channels

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

14. Dipole Source Model

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

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

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

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

19. Potential at any Single Scalp Electrode Due to All Dipoles r is the position vector of the scalp electrode r dip - i is the position vector of the ith dipole d i 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. Nested Head Tissues Hallez et al., J. NeuroEng. Rehab., 2007, open access. http://www.jneuroengrehab.com/content/4/1/46 BRAIN SKULL SCALP

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

27. Home Work: Loading EEG Data Files in Computer RAM and Familiarization EEGLAB (needs MATLAB) available at http://sccn.ucsd.edu/eeglab/ http://sccn.ucsd.edu/eeglab/ Sample EEG Data: http://sccn.ucsd.edu/eeglab/data/headit.html 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 YOU This presentation is available at http://www.isibang.ac.in/~kaushikhttp://www.isibang.ac.in/~kaushik