SPM 2002 Experimental Design

1
SPM 2002Experimental Design
Daniel Glaser Institute of Cognitive
Neuroscience, UCL Slides from Rik Henson,
Christian Buchel, Karl Friston, Chris Frith,
Cathy Price,Ray Dolan The Wellcome Department of
Cognitive Neurology, UCL London UK
http//www.fil.ion.ucl.ac.uk/spm
2
Data transformations
Statistical parametric map (SPM)
Image time-series
Design matrix
Kernel
Realignment
Smoothing
General linear model
Gaussian field theory
Statistical inference
Normalisation
p lt0.05
Template
Parameter estimates
3
Stimuli
SPMT

isoluminant stimuli (even)

V5
isochromatic stimuli (odd)
speed
4
A taxonomy of design

• Categorical designs
• Subtraction - Pure insertion and cognitive
  subtraction
• - Differential event-related fMRI
• Conjunction - Testing multiple hypotheses
• Parametric designs
• Linear - Cognitive components and dimensions
• Nonlinear - Polynomial expansions and
  neurometric functions
• - Nonlinear event-related fMRI
• Factorial designs
• Categorical - Additive factors and pure
  insertion
• - Psychopharmacological designs
• - Adaptation, modulation and dual-task
  inference
• Parametric - Linear and nonlinear interactions
• - Psychophysiological Interactions

5
A categorical analysis
Experimental design Word generation G Word
repetition R R G R G R G R G R G R G
G - R Intrinsic word generation
6
Differential event-related fMRI
BOLD EPI fMRI at 2T, TR 3.2sec. Words presented
every 16 secs (i) studied words or (ii) new words
Parahippocampal responses to words
SPMF testing for evoked responses
studied words
SPMF testing for differences
new words
Peri-stimulus time secs
7
Cognitive Conjunctions
Components Object Recognition R Phonological
Retrieval P Visual Processing V Tasks Object
naming R,P,V,RxP Colour naming P,V Object
viewing R,V Colour viewing V The Conjunction
R,V - V R,V,P, RxP - V,P R, RxP
R R
Object recognition responses (R)
viewing naming
8
A parametric analysis
The nonlinear effect of time assessed with the
SPMT
9
Nonlinear parametric responses
Inverted U response to increasing word
presentation rate in the DLPFC
SPMF
42 wpm
Regression and design matrix
10
Neurometric functions Extrastriate responses to
stimuli of increasing duration Stimulus-specific
or contextual effects?
SPMF
Adaptation of neuronal responses
timems
Attentional modulation
0 exposure duration ms 800
11
Hemodynamic responses to words in the left
peri-auditory region

• BOLD EPI T2 at 2 Tesla TR 1.7s
• 34s epochs of aurally presented words at 0, 10,
  15, 30, 60 and 90 words per minute
• 1200 volume time-series

Event-related
State-related responses
60 wpm
30 wpm
32 secs
Peri-stimulus time
SPMF
12
Context-sensitive responses
time
stimulus n
stimulus n-1
stimulus n1
interaction between stimuli
response n
13
Volterra series - a general nonlinear
input-output model
response y(t)
input u(t)
nonlinear saturation
Simulated input
kernel estimates
14
Nonlinear hemodynamic responses
kernel coefficients - h
SPMF p lt 0.001
SPMF testing H0 kernel coefficients h 0
15
Nonlinear hemodynamic responses - implications
Hemodynamic response interference in terms of the
effect of a prior stimulus
nonlinear saturation
16
Rate-dependent responses Processing one stimulus
in the context of others
ERPs - single words
Integrated response
42 wpm
1400ms
42 wpm
600ms
1400ms
?
84 wpm
700ms
Rate wpm
nonlinear interactions
17
Peri-auditory responses in PET and fMRI
Linear rCBF responses
right
rCBF
left
right
Nonlinear BOLD responses
BOLD
Word presentation rate
Word presentation rate
18
A factorial analysis
Time x condition interactions (i.e.
adaptation) assessed with the SPMT
19
Interactions and context-sensitive effects
A 2 x 2 layout
Context 1 (no naming)
1
2
Context 2 (naming)
4
3
without A with A (e.g.. recognition)
interaction effect (A x Context)
A
A
task 1 2
3 4
Context 1
Context 2
20
Interaction effects in the left inferotemporal
region
A PET study of object naming
Components Visual processing V Object
recognition R Phonological retrieval P Interacti
on RxP Conjunction (name object - shape)
(view object - shape) (R RxP) R
R Interaction (name object - shape) -
(view object - shape) (R RxP) - R
RxP

Object-specific activations
adjusted rCBF
Context no naming naming
21
Psychopharmacological studies

• PET, 6 subjects, 6 conditions
• 3 x 2 factorial design, Buspirone x Memory

left parahippocampal responses
sub- supra-
pre-
acute-
pre acute post
post-
22

Dissociating the direct and modulatory effects of
context
A direct effect of context C
Context-sensitive effect S x N
response
response
time
time
S
C
response
response
frequency
frequency
23
Responses in the right posterior
superior temporal region
to increasing rates (15 - 90 wpm) of word
production
84
rCBF ml/dl/min
77
whilst repeating words and producing new ones
24
Interactions between set and event-related
responses Attentional modulation of V5 responses
attention to motion
attention to colour
25
Non-linear parametric interactions
Increasing word presentation rate in a subject
and patient with a CVA
SPMF
Differential responses in the left hippocampus
26
Psychophysiological interactions
Context
X
source
target
Set
stimuli
Context-sensitive connectivity
Modulation of stimulus-specific responses
source
source
target
target
27
Psychophysiological interactions in the right
inferotemporal region Modulation of
face-selective responses by PPC
SPMZ
Face stimuli
Faces
PPC
adjusted rCBF
IT
Objects
medial parietal activity
28
Psychophysiological interactions Attentional
modulation of V2 - V5 contribution
SPMT
V5 activity
Attention
time
attention
V2
V5 activity
V5
no attention
V2 activity