The 10 Biggest Unknowns in Functional MRI

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The 10 Biggest Unknowns in Functional MRI

• Peter A. Bandettini, Ph.D
• bandettini_at_nih.gov
• Unit on Functional Imaging Methods
• Functional MRI Facility
• Laboratory of Brain and Cognition
• National Institute of Mental Health

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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Relationship between neuronal activity and BOLD.
Location
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Relationship between neuronal activity and BOLD.
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Sources of BOLD dynamic characteristics.
Pre-undershoot
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Sources of BOLD dynamic characteristics.
Post-undershoot
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Sources of BOLD dynamic characteristics.
Nonlinearity
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Sources of spatial and temporal variability.
Latency and Magnitude From Subject to Voxel.
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Sources of spatial and temporal variability.
Spatial Variation
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Whats really in the noise?
Spontaneous Fluctuation Correlation
0.3 Hz
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Whats really in the noise?
Correlation with External Measures
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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What is resting state?
Decreases during activation
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Are decreases related to resting correlations?
What is resting state?
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What is resting state?
Clinical applications?
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Other sources of functional contrast?
Blood Volume
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Other sources of functional contrast?
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Other sources of functional contrast?
Direct Neuronal Current Imaging
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Other sources of functional contrast?
In Vitro Results
Active condition black line Inactive condition
red line
A 0.15 Hz activity, on/off frequency B
activity C scanner noise (cooling-pump)
Petridou, et al (2003), HBM
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Other sources of functional contrast?
Temperature
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Ultimate temporal resolution?
In an ideal worldno hemodynamic variation over
space.
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Ultimate temporal resolution?
Voxel-wise hemodynamic variation
Magnitude
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Ultimate temporal resolution?
Task Timing Modulation
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Ultimate temporal resolution?
Neuronal Communication Timing
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Ultimate spatial resolution?
Resolving columns with single shot EPI is a goal..
using SENSE, 32 channels, 7T, and perhaps
partial k-space we might get to 0.5 mm3
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Ultimate clinical utility?
Needs Real time feedback Characterization of
confounding effects Robust yet incisive set of
probe tasks Baseline information?
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Best processing and display methods?
Processing
fMRI data, and noise is time and space varying in
predictable and unpredictable ways over several
temporal and spatial scales
Signal and noise models Model free, open ended,
methods?
Classification methods? Multivariate
methods? Connectivity (across time and space
scales?)
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Best processing and display methods?
Display
To convey -collapsed multidimensional
data -sense of data quality
Surface Glass brain ROI Time courses Example
slices Connectivity maps? Quality index?
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The 10 Biggest Unknowns in Functional MRI

• Relationship between neuronal activity and BOLD.
• Sources of BOLD dynamic characteristics.
• Sources of spatial and temporal variability.
• Whats really in the noise?
• Whats resting state?
• Other sources of functional contrast?
• Ultimate temporal resolution?
• Ultimate spatial resolution?
• Ultimate clinical utility?
• Best processing and display methods?

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Functional Imaging Methods Unit Functional MRI
Facility
Post Docs Hauke Heekeren David Knight Anthony
Boemio Niko Kriegeskorte
Staff Scientists Sean Marrett Jerzy
Bodurka Frank Ye Wen-Ming Luh Rasmus Birn
Computer Specialist Adam Thomas
Scanning Technologists Karen Bove-Bettis Paula
Rowser Alda Ottley Ellen Condon
Graduate Student Natalia Petridou
Program Assistant Kay Kuhns
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Relationship between neuronal activity and BOLD
contrast?
Magnitude
Location
Inhibition
Why?
Neg. BOLD
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Source of BOLD Characteristics?
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Sources of variability?
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Whats really in the noise?
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What is resting state?
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Comparison of phase and magnitude of the MR
signal in measuring neuronal activity for Petes
sake1,2 James M. Kilner, Klaas E. Stephan,
Oliver Josephs, Karl J. Friston Wellcome
Department of Imaging Neuroscience, 12 Queen
Square, London
Phase
BOLD
Mag
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Ultimate temporal resolution?
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Other sources of functional contrast?