Introduction to fMRI
–
Data acquisition
Tibor Auer
Department of Psychology
Research Fellow in MRI
RHUL Department of Psychology
Scanning the brain
RHUL Department of Psychology
House, M.D. Los Angeles, CA: Fox Broadcasting
Scanning the brain
RHUL Department of Psychology
House, M.D. Los Angeles, CA: Fox Broadcasting
How?
1. Static magnetic field
(2.9 Tesla)
2. Hydrogen nuclei
RHUL Department of Psychology
NMR
How?
1. Static magnetic field
(2.9 Tesla)
2. Hydrogen nuclei
3. Excitation via high frequency
electromagnetic pulse
(123 MHz)
RHUL Department of Psychology
NMR
How?
1. Static magnetic field
(2.9 Tesla)
2. Hydrogen nuclei
3. Excitation via high frequency
electromagnetic pulse
(123 MHz)
4. Resonance and Relaxation
RHUL Department of Psychology
NMR
How?
•
NMR  MRI
Nuclear Magnetic Resonance
1. Static magnetic field (2.9 Tesla)
2. Hydrogen Nuclei
3. Excitation via high frequency electromagnetic pulse (123 MHz)
4. Resonance and Relaxation
•
Magnetic Resonance Imaging
1. Special sequence for the spatial resolution of the NMR signal (NMR+)
2. Image reconstruction
RHUL Department of Psychology
Structural/Anatomical MRI
RHUL Department of Psychology
Functional MRI
•
Theory
Functional MRI: probing brain processes
• Location
• Connection
Perception
Action
Higher-level
• Reaction to stimulus/task
• Reaction to intervention
• Relationship with individual characteristics
Vision
Motion
Cognition
Hearing
Speech
Affection
• ...1
Tactile
sensation
RHUL Department of Psychology
Functional MRI
•
Functional MRI: probing vision
RHUL Department of Psychology
Implication
Functional MRI
•
Theory
BOLD (Blood Oxygenation Level Dependent) MRI response signal
• Stimulus : cycles of visual stimulus and rest
time
• Visual cortex: ↑ oxygen consumption  ↑ ↑ blood supply (oxygen supply)
• Energy useage by spiking:
• Postsynaptic activity and action potentials  neurotransmitter signalling
RHUL Department of Psychology
Functional MRI
BOLD (Blood Oxygenation Level Dependent) MRI response signal
• Stimulus : cycles of visual stimulus and rest
time
• Visual cortex: ↑ oxygen consumption  ↑ ↑ blood supply (oxygen supply)
• Oxyhaemoglobin > Deoxyhaemoglobin
diamagnetic
paramagnetic
• ↑ T2*-weighted MRI signal
• Statistics
RHUL Department of Psychology
signal
•
Theory
time
Functional MRI
•
Analysis
Analysis
• Stimulus : cycles of visual stimulus and rest
• ↑ T2*-weighted MRI signal
=
• Statistics
RHUL Department of Psychology
signal
+
time
Functional MRI
•
Functional MRI: probing vision
RHUL Department of Psychology
Implication
Questions?
House, M.D. Los Angeles, CA: Fox Broadcasting