1. Dynamic Causal Modelling for ERP/ERFs
Practical session
Marta Garrido and Stefan Kiebel
Thanks to James Kilner and Karl Friston

2. Hands on : application to the Mismatch Negativity (MMN)
Outline
Hands on : application to the Mismatch Negativity (MMN)
Demo
Results

3. estimated by perturbing the system and measuring the response
DCM for Evoked Responses
functional connectivity vs. effective connectivity
causal architecture of interactions
estimated by perturbing the system and measuring the response
The aim of DCM is to estimate and make inferences about the coupling among brain areas, and how that coupling is influences by changes in the experimental contex.
differences in the evoked responses
changes in effective connectivity

4. Data acquisition and processing
mode 1
Data acquisition and processing
Oddball paradigm
standards
deviants
mode 2
pseudo-random auditory sequence
80% standard tones – 500 Hz
20% deviant tones – 550 Hz
time
preprocessing
mode 3
raw data
convert to matlab file
filter
epoch
down sample
artifact correction
average
data reduction to principal spatial modes
(explaining most of the variance)
128 EEG
scalp electrodes
ERPs / ERFs
time (ms)

5. The Mismatch Negativity (MMN) is the ERP component elicited by deviations within a structured auditory sequence peaking at about 100 – 200 ms after change onset. b 4
standards
deviants 3
MMN
HEOG
VEOG 2 a 1 V m -1 -2 -3 -4
-100
-50 50
100
150
200
250
300
350
400 ms c

6. What are the mechanisms underlying the generation of the MMN?
DCM specification
a plausible model…
Forward - F
Backward - B
Both - FB 5
IFG 3 4
STG
STG
Opitz et al., 2002
lIFG
rIFG
lA1
rA1
lSTG
rSTG 1 2 A1 A1
input
Doeller et al., 2003
modulation of effective connectivity

7. Intrinsic connections
Matlab
spm eeg
choose time
window
choose data
number of svd
components
choose
polhemus file
sources or nodes
in your graph
DCM.AF
DCM.AB
DCM.AL to
specify extrinsic
connections
driving input
DCM.C
modulatory effect
Intrinsic connections
from
DCM.B
estimate the model
compare
models
visualise
output

8. Demo

9. ERPs (channels)
ERPs (sources)

10. Coupling (A)
Coupling (B)

11. Coupling (C)
Input
Spatial overview

12. Dipoles
Response

13. Model Comparison

14. Results

15. DCM specification – testing different models
STG
Forward
Backward
Lateral
input - F B
Forward and FB
IFG
modulation of effective connectivity

16. results Bayesian Model Comparison log-evidence group level subjects
Forward (F)
Backward (B)
Forward and Backward (FB)

17. modulation of effective connectivityS2 S4 S5 S6 A1
input
IFG
STG A1
input
IFG
STG A1
input
STG A1
input
Forward
Backward
Intrinsic
S2i
S4i
S5i
IFG A1
input
STG
S6i
IFG A1
input
STG A1
input
STG
modulation of effective connectivity A1
input

18. F - negative free energy
results
Bayesian Model Comparison 4
model space
x 10
-2.55
S5i S6
-2.6 S4
S4i
-2.65 S5
S6i
-2.7
F - negative free energy
-2.75
-2.8
S2i
-2.85
-2.9 S2

19. Thank you