Blood oxygenation level-dependent (BOLD) functional MRI of visual stimulation in the rat retina at 11.7 T

• Published in: NMR in biomedicine 2011-02, Vol.24 (2), p.188-193
• Main Authors: La Garza, Bryan H. De, Muir, Eric R., Li, Guang, Shih, Yen-Yu I., Duong, Timothy Q.
• Format: Article
• Language: English
• Subjects: Acetylcholine receptors; Animals; Atropine; blood flow; choroid; dark and light adaptation; Data processing; Evoked Potentials, Visual - drug effects; Eye; Functional magnetic resonance imaging; Hemodynamics; high magnetic field; high-resolution fMRI; Image processing; laminar specificity; Light effects; Magnetic Resonance Imaging - methods; Male; Muscles; N.M.R; Ophthalmic Solutions - pharmacology; Oxygen - blood; phenylephrine; Photic Stimulation; Probes; Rats; Rats, Sprague-Dawley; Reflexes; Retina; Retina - drug effects; Retina - physiology; spatial discrimination; Visual stimuli
• ISSN: 0952-3480; 1099-1492; 1099-1492
• DOI: 10.1002/nbm.1571

Although optically based imaging techniques provide valuable functional and physiological information of the retina, they are mostly limited to the probing of the retinal surface and require an unobstructed light path. MRI, in contrast, could offer physiological and functional data without depth limitation. Blood oxygenation level‐dependent functional MRI (BOLD fMRI) of the thin rat retina is, however, challenging because of the need for high spatial resolution, and the potential presence of eye movement and susceptibility artifacts. This study reports a novel application of high‐resolution (111 × 111 × 1000 µm3) BOLD fMRI of visual stimulation in the anesthetized rat retina at 11.7 T. A high‐field MRI scanner was utilized to improve the signal‐to‐noise ratio, spatial resolution and BOLD sensitivity. Visual stimuli (8 Hz diffuse achromatic light) robustly increased BOLD responses in the retina [5.0 ± 0.8% from activated pixels and 3.1 ± 1.1% from the whole‐retina region of interest (mean ± SD), n = 12 trials on six rats, p  0.05). BOLD fMRI of visual stimulation has the potential to provide clinically relevant data to probe hemodynamic neurovascular coupling and dysfunction of the retina with depth resolution. Copyright © 2010 John Wiley & Sons, Ltd. This study demonstrates high‐resolution BOLD fMRI of visual stimulation on the rat retina with 111×111×1000µm at 11.7T. BOLD fMRI of the retina provides depth‐resolved, clinically relevant information and could be used to study normal retinal function as well as dysfunction in diseased states.