1. Functional Brain mapping using ECoG (electrocorticography)
Keren Rosenberg
Seminar computational method March 08

2. Use of ECoG for identification of functional brain areas
ECoG stimulations: determine critical location by disrupting the function.
ECoG recordings: mapping endogenous cortical function, reflecting normal cortical function.

3. Functionally event results in:
ERD
(Event-related desynchronization)
ERS
(Event-related synchronization)
ERP
(Event-related potentials)
not phase-locked
phase-locked
Hand movement: decrease in Mu rhythm
(9-13 Hz)
Closing eyes and relaxation: increase in alpha (9-12 Hz)

4. Real-time functional brain mapping using electrocorticography (ECoG)
Kai J. Miller, Marcel denNijs, Pradeep Shenoy, John W. Miller, Rajesh P.N. Rao and Jeffrey G. Ojemann
NeuroImage (2007)

5. Aim
Improving the identification of functional correlates using ECoG recordings.

6. Different analysis techniques:
Miller, K. J. et al. J. Neurosci. 2007;27:
Copyright ©2007 Society for Neuroscience

7. Method Using HFB band-pass of 76-200 Hz which is called: “Ҳ index”
8 patients with peri rolandic electrodes
ECoG: 4 mm diameter, 1 cm inter-electrode spacing
Amplifier: Hz
Data was processed online using BCI2000

8. Task Repeated opening and closing hand for 3-s block and 3-s rest.
This was repeated 15 times stating with 10 seconds of rest.
Analysis was only of first 5 blocks.

9. Data analysis X index band-passed
80 ms windows Log power of data was calculated
Mean and SD of the log power were determined for the baseline period.
For activity period, the baseline was subtracted for each time window.
Generation of cortical activation map.

10. A reliable increase with function was over the entire 76–200 Hz interval
Spectogram from a single electrode for 15s hand movement vs. 10s baseline.
Decrease in mu rhythm in hand movement

11. localized activity for the first 15 s of movement
Offline hand motor area mapping. The bar plots indicate the sum of suprathreshold activity for each electrode.

12. Movement vs. baseline- 8 subjects
Chi Index
Freq 30 76
200
Averaged difference between movement and baseline in log power in the most responsive electrode
Mean, superimposed, activation across all 8 patients

13. Real time mapping
Supra-threshold activity immediately upon initiation of the handshake,
Activation of hand sensorimotor cortex throughout the handshake.
Movie

14. Discussion
Reliable maps of cortical function can be obtained using the power in the “χ-index .
The results can be assessed immediately, in real time.
This method can be applied to clinical and research mapping of human cortex.
However…
No comparison to other methods such as fMRI or ECoG stimulations.
Showed correspondence to Intra Operative Stimulations only in 3 subjects.
Not all of the subjects showed focal pattern of activation.

15. Case Study Keren Rosenberg Dr. Kipervasser Svetlana llana Podlipsky
Dr. Hadas Okon-Singer
Uri Gordon
Andrey Zhdanov
Dr. David Papo
Prof. Itzhak Fried
Dr. Talma Hendler
Dr. Kipervasser Svetlana
Dr. Fani Andelman
David Yosef

16. Case Study 21 years old male (T.B) with epilepsy No focal lesion
Pre-surgical multi-modal evaluation:
fMRI
ElectroCorticoGraphy (EcoG) stimulations
EcoG recordings

17. Paradigm– Finger tapping:
External
Internal
2 2 2
# # #
Simple
2 1 3
# $ %
Complex
Block design – 12 task blocks – 6 sequences X 3 sec=18 seconds 13 rest blocks

18. Correspondance between fMRI and Stripes4 8
t(106)
p<
Activation maps of patient T.B
All motor vs. rest
Group activation map

19. EcoG stimulus evoked event related potentials (ERPs)
Internal simple
External simple
stimulus onset
stimulus onset
Move to notes: Readiness potentials preceding voluntary movements in the SMA were higher for freely selected movements than for movements in a fixed direction. (Praamstra et al., 1995)

20. Summary
In the SMA, amplitude differences locked to cue depends on source of planning