Dynamic Causal Modelling for ERP/ERFs Practical session Marta Garrido and Stefan Kiebel Thanks to...
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Transcript of Dynamic Causal Modelling for ERP/ERFs Practical session Marta Garrido and Stefan Kiebel Thanks to...
Dynamic Causal Modelling for ERP/ERFs
Practical session
Marta Garrido and Stefan KiebelThanks to James Kilner and Karl Friston
• Hands on : application to the Mismatch Negativity (MMN)
• Demo
• Results
Outline
DCM for Evoked Responses
differences in the evoked responses
changes in effective connectivity
4,,1
functional connectivity vs. effective connectivity
causal architecture of interactions
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.
estimated by perturbing the system and
measuring the response
pseudo-random auditory sequence
80% standard tones – 500 Hz
20% deviant tones – 550 Hz
time
standards deviants
Oddball paradigm
Data acquisition and processing
raw data
preprocessing
data reduction to
principal spatial
modes
(explaining most
of the variance)
• convert to matlab file
• filter
• epoch
• down sample
• artifact correction
• average
ERPs / ERFs
128 EEG scalp electrodes
mode 2
mode 1
mode 3
time (ms)
-100 -50 0 50 100 150 200 250 300 350 400-4
-3
-2
-1
0
1
2
3
4
ms
V
standardsdeviants
HEOG VEOG
a
b
c
MMN
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.
DCM specification
A1 A1
STG
input
STG
IFG
a plausible model…
modulation of effective connectivity
Forward - F
Backward - B
Both - FB
Opitz et al., 2002
Doeller et al., 2003
rIFG
rSTG
rA1lA1
lSTG
lIFG
What are the mechanisms underlying the generation of the MMN?
1 2
3 4
5
visualiseoutput
estimate the model
Matlab spm eeg
number of svd components
sources or nodes in your graph
driving inputspecify extrinsic
connections
modulatory effect
DCM.AF DCM.AB DCM.AL
DCM.B
DCM.C
Intrinsic connectionsfrom
to
choose datachoose time
window
choose polhemus file
comparemodels
Demo
Results
Forward
Backward
Intrinsic
modulation of effective connectivity
A1 A1
input
IFG
A1 A1
input
STG STG
A1 A1
input
STG STG
A1 A1
input
IFG
STG STG
A1 A1
input
A1 A1
input
STG STG
A1 A1
input
IFGIFG
STG STG
IFG
A1 A1
input
IFG
STG STG
S2
S2i S4i
S4 S5
S5i
S6
S6i
-2.9
-2.85
-2.8
-2.75
-2.7
-2.65
-2.55
x 104
S2
S2i
S4 S4iS5
S5i S6
S6i
F -
neg
ativ
e fr
ee e
nerg
ymodel space
-2.6
results Bayesian Model Comparison
Thank you