Experimental Methods:Experimental Methods:Theory and Application ofTheory and Application ofFunctional Functional NeuroimagingNeuroimaging
Emiliano RicciardiLaboratory of Clinical Biochemistry and Molecular Biology,
University of Pisa, Italy
10th International Training Seminar in Child & Adolescent PsychiatryJune 23‐28, 2013 - Monastero Santa Croce, Bocca di Magra, Italy
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Pietrini et al. Am J Psychiatry 2003;160:1907-1908
Functional Imaging Evolution
Friston K., Science 2009
• Bioengineering• Statistics• Physics
• Psychology• Neurology• Pharmacology
• Marketing/Business• Moral and Ethics• Law
In vivo brain functional methodologies
• Qualitative and functional characterization
Functional Brain Imaging : Advantages
Functional Brain Imaging : Advantages
• Dissection of the different steps of information
processing
CentralExecutive
Phonologicalloop
EpisodicBuffer
VisuospatialSketchpad
LanguageLong-termMemory
SemanticMemory
Flui
dSy
stem
sCr
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llize
dSy
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• Versatile approach (e.g. variation of acquisition parameters, experimental modulation, pharmacological probing, etc.)
1 s delay 6 s delay
11 s delay 16 s delay
Functional Magnetic Resonance Imaging : Advantages
• Correlation with different diagnostic tools
Pietrini et al., Am J Psychiatry 1999
White et al., Field Strenght 2008
Peripheral parameters Peripheral parameters (HR, SCR, etc.),(HR, SCR, etc.),neuropsychological neuropsychological characterization, characterization, behavioral measuresbehavioral measures
Structural dataStructural data (e.g. (e.g. anatomy, fiber tracking, anatomy, fiber tracking, cortical thickness, etc.)cortical thickness, etc.)
Functional Brain Imaging : Advantages
• Acquisition of original information
Haxby et al., Science 2001
Functional Brain Imaging : Advantages
Why in vivo?1. in vitro and in vivo differences2. Anatomical ‘constraints’
Functional neuroimaging
Why in vivo?3. Functional segregation and integration
Functional neuroimaging
Why in vivo?4. Limitations
of animalmodels
Functional neuroimaging
The legacy of Angelo Mosso
Functional neuroimaging
Angelo Mosso (1881):Concerning the Circulation of the Blood in the Human BrainVerlag von Viet & Company: Leipzig, pages 66-67
Petzold e Murthy, Neuron 2011
The cerebrovascular unit:where the ‘signal’ comes from
↑ Neuronalsynapticactivity
↑ ActivityNa+/K+
pump
↑ ATPRequest
↑ Glucoseand
oxygenrequest
↑ Cerebralbloodflow
sypply
↑ Glucoseoxydative
metabolismand ATP
production
EEG, MEG, TMS
EEG, EEG, MEG, TMSMEG, TMS
H215O‐PET,
fMRI, ASLHH22
1515OO‐‐PET, PET, fMRIfMRI, ASL, ASL
18FDG‐PETsMRI
1818FDGFDG‐‐PETPETsMRIsMRI
The cerebrovascular unit:where the ‘signal’ comes from
Positron Emission Tomography
Positron-emitting nuclides (es. 18Fluoride, 15Oxygen)
Positron Emission Tomography
• Resting condition
• Visual stimulation
occhi chiusi 1 occhio 2 occhi scenacomplessa
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Positron Emission Tomography
18FDG -glucosio
18F-fluorodopa
18F-fluoroetilspiperone
HC
AD
Positron Emission Tomography
Towards a biochemistry of mind?
Borg et al., Am J Psychiatry, 2003
Positron Emission Tomography:single patient evalutation
GROUP A GROUP B
RESULTS
SPATIALREALIGNMENT
ANDNORMALIZATION
(e.g. MNI, TalairachAtlas)
#1
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#5
…n
STATISTICALEVALUATION
(ANOVA, T-TEST, CORRELATION)
Positron Emission Tomography:Group comparison
((DrevetsDrevets e e collcoll., 2000)., 2000)
Positron Emission Tomography:Group comparison
TASK REST DIFFERENCE
STATISTICAL AVERAGE
SPATIAL NORMALIZATIONINDIVIDUAL DIFFERENCES
Positron Emission Tomography:Task condition comparison
Positron Emission Tomography:Task condition comparison
Calarge et al., Am J Psychiatry, 2003
Magnetic Resonance Imaging Structural
Functional
Diffusion Spectroscopy
And much more, such as perfusion, angiography, ASL,
CDI, SWI, etc. Modified from Brain Imaging Center website
Neural activity oxyhemoglobin fMRI signal
MRI fMRI
Single image
Several images(e.g, every 2-3 s for 5 minutes)
High resolution(1 mm)
Low Resolution(~3 mm)
fMRIRelies on Blood Oxygenation Level Dependent (BOLD)
…
MRI vs. fMRI
Scanner and tissue-related parameters influence image acquisition
T2WT2W
PDWPDW
T1WT1W
What does happen to oxygen use?
BOLD: Blood Oxygenation Level Dependent
BOLD Contrast Imaging
O2
BASELINEBASELINE
O
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ACTIVATIONACTIVATION
L. Pauling, C. D. Coryell, PNAS, 1936.K.R. Thulborn, J. C. Waterton, et al., Biochim. Biophys. Acta., 1982S. Ogawa, T. M. Lee, A. R. Kay, D. W. Tank, PNAS, 1990.
oxyHb
deoxyHb
Oxygenated and deoxygenated hemoglobin have different magnetic properties
BOLD Contrast Imaging
deoxyhemoglobin T2* MR signal
blood flow deoxyhemoglobin T2* MR signal
BOLD Contrast Imaging
Data analyses (Data analyses (postprocessingpostprocessing))
reconstructionreconstruction registrationregistration smoothingsmoothing
RationaleRationale: define your : define your hypothesishypothesis
Preprocessing and Preprocessing and experimental sessionexperimental session
Results interpretation, Results interpretation, correlation with behavioral correlation with behavioral and clinical findingsand clinical findings
Experimental paradigmExperimental paradigm
Subject selection and Subject selection and screeningscreening
Experimental brain Experimental brain imaging flow chartimaging flow chart
Measuring skin conductance and peripheral parameters (e.g. EKG, pO2)
Visual, tactile and aural stimulation with MR-compatible devices
Movement control
Functional MRI experimental setup
1. Block Design
2. Mixed Block Design
3. Slow Event-Related
4. Fast Event-Related
5. Self-Paced
6. Sparse intermixed
Different strategies to neural recruitment
STIMULI – ACTIVATIONNO STIMULI - BASELINE
BOLD Contrast Imaging
O2
BASELINEBASELINE
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ACTIVATIONACTIVATION
Overview of Analysis/1
MotionCorrection
Smoothing
SpatialNormalisation
General General Linear Linear ModelModel
fMRI time-series Design matrix
Anatomical Reference
•Conventional analysis of fMRI data focuses on finding macroscopic brain regions that are involved in specific mental activities•After reconstruction, the output of the scanning session consists of a series of 3D images of the brain
• Correction for head motion and physiological effects, spatial and/or temporal filtering (smoothing) are generallyapplied
• A variety of methods are usedto correlate the voxel time series with the task in order toproduce maps of task-dependent activation (e.g. common hypothesis-driven methodspredict the shape of the response to the stimulus, and calculate correlationcoefficients between each pixel time course and this reference waveform)
Cortical surface representation of specific neural patterns
2D3D surfingROI analyses
Correlation analysis though modeling the hemodynamicresponse
Significant correlationsare reported as
‘activated’ voxels
Overview of Analysis/2
Once you get you stimulus-specific response:
•Connectivity: structural, functional and effective
•Psychophysiological interaction: correlations with
behavioral/clinical/peripheral measures
•Multivariate and machine learning approaches
• Signal variability and complexity measures
Overview of Analysis/3
Different steps of a research line...
Gentili et al., Brain Res Bull, 2008
Different steps of a research line...
Gentili et al., Brain Res Bull, 2008
Different steps of a research line...
Gentili et al., Brain Res Bull, 2008
Different steps of a research line...
Gentili et al., Brain Res Bull, 2009
Different steps of a research line...
Gentili et al., Brain Res Bull, 2009
Different steps of a research line...
Dan
ti et
al.,
Fron
t Sys
Neu
rosc
i, 20
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Different steps of a research line...
Dan
ti et
al.,
Fron
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Neu
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i, 20
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What fMRI Can Do(routine fMRI)
Help in understanding healthy brain organization-map networks involved with specific behavior, stimulus, or performance-characterize changes over time (seconds to years)-determine correlates of behavior (response accuracy, etc…)
Current Clinical Applications-presurgical mapping
Current Clinical Research-assessment of recovery and plasticity-clinical population characterization with probe task or resting state
Courtesy of Peter Bandettini
What fMRI Can’t Do(what are the problems with fMRI?)
•Too low SNR for routine clinical use (takes too long)
•Requires patient cooperation (too sensitive to motion)
•Too low spatial resolution (each voxel has several million neurons)
•Too low temporal resolution (hemodynamics are variable and sluggish)
•Too indirectly related to neuronal activity
•Too many physiologic variables influence signal
•Requires a task (BOLD cannot look at baseline maps)
•Too confined space and high acoustic noise.
Courtesy of Peter Bandettini
Looking to the future…
Technology
Applications
Metodology
Interpretation
BOLD Contrast Imaging…
StimulusNeuralActivity
BloodVolume
OxygenMetabol.
BloodFlow
[Hb] change
BOLDRESPONSE
InterpretationInterpretation
Stimulusprocessing,
sensory deficits,
compliance to the task and to
MR environment
Disease-related aspects that could affect BOLD signal
Neuronal loss, brain
atrophy, etc.
Angiopathy
Drug modulation,
aging-related disorders,
etc.
Sereno et al.@3T, 1995
Yacoub et al.@7T, 2008
HighHigh--field MRIfield MRITechnologyTechnologyRetinotopyRetinotopy
The The ‘‘boostboost’’ of novel of novel analytical approachesanalytical approaches
AnalyticalAnalytical
Decoding techniques
Action Non-action
Stimuli presentation
Non-action Action…
fMRI
Action Non-action Non-action Action…
Patterns of brain activity
Training set
Action Non-action Non-action…
Test set
Classifierf(v)
Accuracy of classification
Hierarchical clustering
Action Non-action Non-action Action…
Similarityof
representation
Actions Non-actions
Classification principle
Discriminationmaps
“[…] the DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure. […] Indeed, symptom-based diagnosis […] has been largely replaced in the past half century as we have understood that symptoms alone rarely indicate the best choice of treatment.”, Tom Insel, NIHM Director
Memory disorders (e.g. Alzheimer)
Mood disorders (e.g. depression)
Language disorders
Poldrack et al., 2012, Plos Comp Biol
Research Domain Criteria to assess CNS disorders?
Pol
drac
ket
al.,
2012
, Plo
sC
omp
Bio
l
languagedisorders
mood/anxiety disorders and
drug abuse
psychotic and externalizing
disorders
autism and memory
disorders
The restless brainThe restless brainApplicationsApplications
From imaging to From imaging to imagenesimagenesApplicationsApplications
What fMRI May Do
Complementary use for clinical diagnoses-utilization of clinical research results for diagnoses-prediction of pathology
Clinical treatment and assessment of therapy-better understanding mechanism of pathology for focused therapy--understanding of drug effectunderstanding of drug effect-assessment of therapy progress, biofeedback-epileptic foci mapping-neurovascular physiology assessment
Non clinical uses-lie detection-prediction of behavior tendencies -brain/computer interface
cellular
nanomolecular
brain areas
social
body
In vivo brain functional methodologies In vivo brain functional methodologies
Pietrini et al. Am J Psychiatry 2003;160:1907-1908
