Brain Imaging Technologies

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Watching the Living Human Brain
by Combining Noninvasive Brain Imaging
Technologies
Armin Fuchs Center for Complex Systems Brain
Sciences
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Resolutions of Imaging Technologies
10-3s
EEG MEG
1s
103s
1mm
1-5cm
5mm
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Magnetoencephalography MEG
Quantity measured components of the magnetic
field Order of magnitude 100fT Temporal
Resolution ms Spatial Resolution cm Cost
expensive Advantage Clean signals Disadvantage
Insensitive to radial currents
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MEG Technology
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Magnetic field on subjects head and in polar
projection
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Electroencephalography EEG
Quantity measured electric potential on the
scalp surface Order of magnitude 20uV Temporal
Resolution ms Spatial Resolution cm Cost
cheap Advantage easy to record Disadvantage
signals get smeared before they reach the scalp
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EEG Technology
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Magnetic Resonance Imaging MRI
Quantity measured water content of the brain
tissue Knowledge gained brain structure Temporal
Resolution min Spatial Resolution mm Cost
expensive Advantage 3D-volume resolution Disadvan
tage no functional or temporal information
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f/MRI Technology
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T1 weighted Images
T2 weighted Images
PD weighted Images
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Tissue Classification
T2 weighted
PD weighted
T1 weighted
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Inversion Recovery Images
Echo Planar Images
Diffusion Tensor Images
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Diffusion Tensor Imaging The wires of the brain
Functional Anisotropy
Main Directions of Diffusion
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Functional Magnetic Resonance Imaging fMRI
Quantity measured ratio between oxy- and
deoxyhemoglobin Knowledge gained activated
areas Temporal Resolution sec Spatial
Resolution mm Cost expensive Advantage
3D-volume resolution Disadvantage low temporal
resolution, no straight forward analysis
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How does a brain get red and yellow spots ?
Echo planar volumes taken in 3 sec !!
Task
Rest
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movement
both
sensory
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A little Movie
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Combining Technologies to get a better picture
about what is going on inside the brain with high
spatial and temporal resolution
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Datasets recorded using different Imaging
Technologies !!
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All data has to be in the same coordinate system
!!
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Using the gray-white matter boundary as an
anatomical constraint
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A coordinate system on the cortical surface and
sensitivity of EEG and MEG for different locations
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Parameterization of the cortical surface
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Linear Beamforming
Signal Power

Covariance matrix
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Activity along the gray-white matter boundary
from fMRI
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Comparing activity from fMRI and MEG
SAM
Anatomical constraints
fMRI
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Time-course of activity along the central sulcus
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How these experiments are done !!
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Resonance and Phase Resetting in the Human Brain
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Resonance or Constructive Interference
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Phase Resetting in EEG