Segmented spin-echo echo-planar imaging improves whole-brain BOLD functional MRI in awake pigeon brains

Area of Science:

• Neuroscience
• Biomedical Engineering
• Animal Cognition Research

Background:

• High-field functional magnetic resonance imaging (fMRI) in avian brains is crucial for understanding cognitive behaviors.
• Air cavities in bird skulls cause magnetic field inhomogeneities, limiting fMRI data acquisition.
• Existing methods like rapid acquisition with relaxation enhancement (RARE) fMRI have limited blood oxygen level-dependent (BOLD) sensitivity and temporal resolution.

Purpose of the Study:

• To implement and evaluate a two-segmented spin-echo echo-planar imaging (SE-EPI) sequence for whole-brain fMRI in awake pigeons.
• To compare the performance of the novel SE-EPI sequence against the single-shot RARE sequence for avian fMRI.
• To assess the suitability of SE-EPI for investigating neural networks, such as the auditory network.

Main Methods:

• Development and application of a two-segmented SE-EPI MRI sequence.
• Acquisition of whole-brain fMRI data in awake pigeons.
• Comparative analysis of SE-EPI and single-shot RARE sequences regarding BOLD sensitivity, signal-to-noise ratio (SNR), temporal resolution, and activation pattern symmetry.

Main Results:

• The two-segmented SE-EPI sequence achieved whole-brain coverage in awake pigeons.
• SE-EPI demonstrated over twice the BOLD sensitivity compared to RARE within a shorter acquisition time (3s vs 4s).
• SE-EPI produced more symmetric and larger activation patterns with similar image and temporal SNR, and reduced energy deposition.

Conclusions:

• Two-segmented SE-EPI is a viable and advantageous alternative to RARE for avian fMRI.
• This method enhances BOLD sensitivity and temporal resolution, crucial for studying neural networks in birds.
• The improved sequence facilitates more comprehensive whole-brain analyses of cognitive functions in avian models.