1. Electroencephalography Electrical potential is usually measured at many sites on the head surface

2. Electroencephalography Electrical potential is usually measured at many sites on the head surface More is sometimes better

3. Electroencephalography EEG changes with various states and in response to stimuli

4. The Event-Related Potential (ERP) Embedded in the EEG signal is the small electrical response due to specific events such as stimulus or task onsets, motor actions, etc.

5. The Event-Related Potential (ERP) Embedded in the EEG signal is the small electrical response due to specific events such as stimulus or task onsets, motor actions, etc. Averaging all such events together isolates this event-related potential

6. The Event-Related Potential (ERP) We have an ERP waveform for every electrode

7. The Event-Related Potential (ERP) We have an ERP waveform for every electrode Sometimes that isn’t very useful

8. The Event-Related Potential (ERP) We have an ERP waveform for every electrode Sometimes that isn’t very useful Sometimes we want to know the overall pattern of potentials across the head surface –isopotential map

9. The Event-Related Potential (ERP) We have an ERP waveform for every electrode Sometimes that isn’t very useful Sometimes we want to know the overall pattern of potentials across the head surface –isopotential map Sometimes that isn’t very useful - we want to know the generator source in 3D

10. Brain Electrical Source Analysis Given this pattern on the scalp, can you guess where the current generator was?

11. Brain Electrical Source Analysis Given this pattern on the scalp, can you guess where the current generator was?

12. Brain Electrical Source Analysis Source Analysis models neural activity as one or more equivalent current dipoles inside a head- shaped volume with some set of electrical characteristics

13. Brain Electrical Source Analysis Initiate the model

14. Brain Electrical Source Analysis Initiate the model Project “Forward Solution”

15. Brain Electrical Source Analysis Initiate the model Project “Forward Solution” Compare to actual data

16. Brain Electrical Source Analysis Adjust the model Project “Forward Solution” Compare to actual data

17. Brain Electrical Source Analysis This is most likely location of dipole Project “Forward Solution” Compare to actual data