Identifying sparse connectivity patterns in the brain using resting state fMRI
fMRI analysis of functional brain connectivity in three ...
Transcript of fMRI analysis of functional brain connectivity in three ...
fMRI analysis of functional brain connectivity in three language tasks in
schizophrenia
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1Department of Physics and Astronomy, University of British Columbia6224 Agricultural Road, Vancouver, British Columbia, Canada, V6T 1Z1
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Acknowledgements:
OUTLINE
1. Motivation2. Theory3. Experiment Details4. Resources5. Summary
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1.1 Overview of schizophrenia and current treatment options
POSITIVEHallucinations
Delusions
DISORGANIZEDDisorganized affect &
speech
NEGATIVEPoverty of Speech
Flat Affect
SYMPTOMS
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COGNITIVEImpaired memory,
attention & executive function
1.1 Overview of schizophrenia and current treatment options
● Treatment Options
○ Pharmaceuticals
■ Typical & Atypical
Antipsychotics
■ Side effects, moderate
efficacy & resistance
4https://www.psycom.net/clozaril-clozapine
1.1 Overview of schizophrenia and current treatment options
● Treatment Options
○ Cognitive Therapy
■ Cognitive Behavioural Therapy (CBT)
■ Metacognitive Training (MCT)
■ Moderate efficacy
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1.1 Overview of schizophrenia and current treatment options
Adjunct & Improved
Treatments
● Ex. Neuromodulation
Pharmaceuticals
● Side effects● Limited efficacy● Resistance
Cognitive Therapy
● Limited efficacy
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1.2 Neuromodulation
● Neurons & Brain Networks
○ Neurons = nervous system cells
○ Communicate by releasing
neurotransmitters upon electrical
impulses
7https://www.neuroscientificallychallenged.com/glossary/neuron/Neuron
1.2 Neuromodulation
● Neurons & Brain Networks
○ Found in networks
throughout brain
○ Brain network activity can
change
8https://www.studzine.com/brain-artificial-intelligence-neural-networks/
9Auditory Language Default
ModeInternal
AttentionResponse
1.2 Neuromodulation
● Neuromodulation
○ Modify neural oscillatory electrical signals to increase or
decrease the likelihood of neuron activation
○ Transcranial Alternating Current Stimulation
10http://www.medicalexpo.com/prod/electrical-geodesics/product-68326-544197.html
1.3 Contribution of fMRI
● Neuromodulation
○ Requires spatial and temporal resolution
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fMRI EEG3-5 mm cm1 SPATIAL
1-3 s ms2 TEMPORAL
BOLD signal
Neuron firing
patterns3 USEFUL TO
MEASURE
1.3 Contribution of fMRI
BOLD Signal = Blood Oxygenation Level Dependent Signal
12Glover, G. H. (2011). Overview of Functional Magnetic Resonance Imaging
1.3 Contribution of fMRI
● Neuromodulation
○ Requires spatial and temporal resolution
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fMRI EEG3-5 mm cm1 SPATIAL
1-3 s ms2 TEMPORAL
BOLD signal
Neuron firing
patterns3 USEFUL TO
MEASURE
THEORY
2. Theory1. Functional Magnetic Resonance Imaging (fMRI)2. BOLD Signal3. fMRI-Constrained Principal Component Analysis
(fMRI-CPCA)
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2.1 fMRI
● Nuclear Magnetic Resonance
○ Magnetic moment of protons from
H nuclei in water
○ Tip away from B0
○ Precession frequency: 𝟂 = 𝞬 B0
15https://my-ms.org/mri_physics.htm
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T2: Transverse component dephasing
T2*: Reversible dephasing due to field inhomogeneities
T1: Longitudinal component recovery
https://www.researchgate.net/figure/Schematic-of-T1-and-T2-relaxation-MRI-utilises-the-behaviour-of-protons-within-varying_fig2_227712215
2.1 fMRI
RF
B0
B0
2.1 fMRI
● Signal Localization
○ RF pulse selects slice
○ Frequency & Phase encoding
gradients localize within slice
17http://mriquestions.com/slice-selective-excitation.html
2.1 fMRI
● Echo Planar Imaging
18http://mriquestions.com/echo-planar-imaging.html
2.2 BOLD Signal
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Oxyhemoglobin = Diamagnetic
↓ magnetic susceptibility
↑ T2*
↑ Intensity
Deoxyhemoglobin = Paramagnetic
↑ magnetic susceptibility
↓ T2*
↓ Intensity
2.3 fMRI-CPCA
● fMRI-CPCA
○ Determine functional brain networks
○ Estimate post-stimulus BOLD signal changes
○ Test effects of experimental manipulations
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2.3 fMRI-CPCA
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ZInputData
GCConstrainedVariance
EResidualVariance
UComponent
Scores
DSingularValues
V’RightSingular
Vectors
GDesignMatrix
PPredictorWeights
Principal Component Analysis
Plot against time
Component Loadings:
VD/√(m-1)
Multivariate Least-squares Linear Regression
Regression
2.3 fMRI-CPCA
● Z Activation Matrix
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Raw Preprocessed
2.3 fMRI-CPCA
● G Design Matrix
○ Encodes task timing
○ Scans X Conditions at post-stimulus time
○ Finite Impulse Response model
○ Expected signal: 1
○ Otherwise: 0
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GDesignMatrix
2.3 fMRI-CPCA
● Z matrix regressed onto G matrix with multivariate least-squares linear regression
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2.3 fMRI-CPCA
● Principal Component Analysis extracts components from GC
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VOXELS
SCAN
S
GCVariance
constrainedbyFIRmodel
ULeftSingularVectors
DSingularValues
V’RightSingular
Vectors
Component Scores
2.3 fMRI-CPCA
● Columns represent component loadings, or anatomical correlates of each brain network
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DSingularValues
VRightSingular
Vectors
√(m-1)
Component Loadings
2.3 fMRI-CPCA
● Predictor weights indicate importance of each column in G for a given component
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UComponent
Scores
GDesignMatrix
PPredictorWeights
2.3 fMRI-CPCA
● Predictor weights plotted against time give the hemodynamicresponse (HDR) for the component
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PPredictorWeights
2.3 fMRI-CPCA
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ZInputData
GCConstrainedVariance
EResidualVariance
UComponent
Scores
DSingularValues
V’RightSingular
Vectors
GDesignMatrix
PPredictorWeights
Principal Component Analysis
Plot against time
Component Loadings:
VD/√(m-1)
Multivariate Least-squares Linear Regression
Regression
Experiment Details
3. Experiment Details1. Language Tasks2. Functional Brain Networks3. Procedure
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3.1 Language Tasks
Metrical Stress
(MS)
31Headache
3 sec
2 sec
+
Breakfast
+3 sec
2 sec
3.1 Language Tasks
Thought Generating
Task
(TGT) 32Instructions
ITI: Visual Distractor
ITI: Visual Distractor
5 sec
15 sec
6 sec
5 sec
2 sec
Camera
“something you…”
Table
“something you…”
3.1 Language Tasks
Semantic Association
(SA)33
3.3 Procedure
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1
fMRI Scan Preprocessing
SPM8
Networks & HDR
fMRI-CPCA
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Statistical Analysis
SPSS Repeated measures ANOVAs
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Network Classification
Templates HDR
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4. Resources
● Access to MS, TGT and SA datasets
● SPM 8 Software
● fMRI-CPCA Software
● SPSS Software
● Computer time
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5. Summary
● fMRI may be used to examine BOLD signal
● Determine functional networks from three language tasks in both healthycontrols and schizophrenia patients with fMRI-CPCA
● Increase understanding of spatial localization of brain networks and influencepotential neuromodulation methods for schizophrenia patients
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