Dynamic Causal Modelling for ERP/ERFs

Practical session

Stefan Kiebel and Rosalyn Moran

DCM for Evoked Responses

differences in the evoked responses

changes in effective connectivity

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 context.

estimated by perturbing the system and

measuring the response

A1 A1

STG

input

STG

modulation of effective connectivity

1 2

3 4

pseudo-random auditory sequence

80% standard tones – 500 Hz

20% deviant tones – 550 Hz

time

standards deviants

Oddball paradigm

Data acquisition and processing

raw datapreprocessing

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.

A1 A1

STG

input

STG

plausible models…

modulation of effective connectivity

Forward - FBackward - BBoth - FB

Opitz et al., 2002

Doeller et al., 2003

rSTG

rA1lA1

lSTG

Motivation for MMN model

1 2

3 4

visualiseoutput

estimate the model

Matlab spm eeg

number of spatial components

sources or nodes in your graph

driving inputspecify extrinsic connections

modulations

DCM.AF DCM.AB DCM.AL

DCM.B

DCM.C

Intrinsic connections

from

to

choose datachoose time

window

A1 A1

STG STG

ForwardBackward

Lateral

STG

input

A1 A1

STG STG

ForwardBackward

Lateral

input

A1 A1

STG

ForwardBackward

Lateral

input

Forward - F Backward - BForward and

Backward - FB

STG

DCM specification – testing different models

modulation of effective connectivity

Bayesian Model Comparison

results

Forward (F)

Backward (B)

Forward and Backward (FB)

subjects

log

-evi

denc

e

group level

fmyp ln

)(lnlnln jiij mypmypB

subN

jijiNsub mypmyyyp

121 )(ln|,...,,ln