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Characterization of the Blood Oxygen Level Dependent Functional Magnetic Resonance Imaging Response in Amblyopia

Algaze, Antonio
http://rave.ohiolink.edu/etdc/view?acc_num=osu1039109427

Abstract Details

2002, Doctor of Philosophy, Ohio State University, Biomedical Engineering.
Blood oxygen level dependent (BOLD) functional magnetic resonance imaging (FMRI) was implemented at 1.5 Tesla to characterize visual cortex activation patterns in human amblyopia. The dissertation consists of three main components. First, the voxel-wise repeatability of visual cortex FMRI results was assessed using a mixed-effects ANOVA group analysis. Two stimuli were presented monocularly and binocularly to ten subjects in two independent scanning sessions. Visual cortex activation maps were found to be repeatable regardless of the stimulus type or eye stimulated. The second study investigated interocular differences in the level and extent of activation in amblyopic and normal subjects. Five amblyopes and six normals were recruited. Stimuli included a homogeneous flickering field (8 Hz) and counterphasing (8 Hz) vertical sinusoidal gratings at 0.5, 1 and 2 cpd. Amblyopes exhibited a larger (P<0.05) interocular activation difference compared to normals. Dominant eye stimulation was found to elicit a stronger BOLD response and larger extent of activation in the visual cortex compared to the amblyopic eye. In summary, FMRI was found to be sensitive to amblyopia-related deficits in the human visual cortex and, hence, has potential for basic amblyopia research. The third study investigated the effects of levodopa (L-dopa) on the level and extent of visual cortex activation. Six amblyopes and nine normals were recruited. A baseline FMRI session was followed by a second session 90 minutes after L-dopa. Visual stimuli included counterphased (4 Hz) vertical sinusoidal gratings at 1 and 2 cpd. The FMRI response was characterized by the total volume and the average level of activation. An interocular absolute difference (IAD) was defined in terms of said measures for between-population analysis of monocular data. After L-dopa, visual acuity improved significantly (P=0.03) in the amblyopic eye. The FMRI response to L-dopa was population-specific, as indicated by a treatment-by-population interaction for the volume of activation IAD (P=0.018), as well as for the volume (P=0.026) and level (P=0.043) of activation elicited by binocular stimulation. Furthermore, a significant (P<0.05) decrease in the volume of activation was found exclusively for the amblyopic eye after L-dopa, in spite of improvement in visual acuity.
Cynthia Roberts (Advisor)
123 p.
Engineering, Biomedical
BOLD; FMRI; AMBLYOPIA; VISUAL CORTEX; REPEATABILITY; L-DOPA

Recommended Citations

Citations

  • Algaze, A. (2002). Characterization of the Blood Oxygen Level Dependent Functional Magnetic Resonance Imaging Response in Amblyopia [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039109427

    APA Style (7th edition)

  • Algaze, Antonio. Characterization of the Blood Oxygen Level Dependent Functional Magnetic Resonance Imaging Response in Amblyopia. 2002. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1039109427.

    MLA Style (8th edition)

  • Algaze, Antonio. "Characterization of the Blood Oxygen Level Dependent Functional Magnetic Resonance Imaging Response in Amblyopia." Doctoral dissertation, Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039109427

    Chicago Manual of Style (17th edition)

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© 2002, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.