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Functional brain mapping using magnetic resonance imaging. Signal changes accompanying visual stimulation.
1Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis.
Investigative Radiology
|December 1, 1992
Summary
Functional brain imaging using magnetic resonance (MR) detected signal changes in the visual cortex during stimulation. These findings map brain activity and suggest increased blood flow and oxygenation with neural activation.
Area of Science:
- Neuroimaging
- Functional Magnetic Resonance Imaging (fMRI)
Background:
- Magnetic resonance (MR) signal changes in the brain can indicate neural activity.
- Previous studies have explored MR signal alterations during visual stimulation.
Purpose of the Study:
- To investigate transient increases in water proton MR signals in the human primary visual cortex during visual stimulation.
- To generate high-spatial-resolution human functional brain maps using these signal changes.
Main Methods:
- Utilized gradient echo imaging at 4-Tesla field strength.
- Acquired images every approximately 5 seconds to monitor time dependence.
- Analyzed signal intensity changes in relation to echo times.
Main Results:
- Detected easily detectable (5%-20%) transient increases in MR signal intensity in the visual cortex during stimulation.
- Signal increases were primarily in gray matter, enabling functional brain mapping.
- Observed time-dependent signal changes and a reduction in the activated area over time.
- Fractional signal change amplitude decreased with shorter echo times, suggesting T2 or T2* dependence.
Conclusions:
- The observed signal changes are consistent with increased regional cerebral blood flow (rCBF) during neural activation.
- Increased venous blood oxygenation likely accompanies the elevated rCBF.
- High-spatial and temporal resolution functional brain maps can be produced using these MR signal changes.