Name: Insights into Visual Cortex Research Through Wide-View fMRI Mapping
Uploaded: 2023-12-08T12:40:00
Description: Watch this Scientific Journal Video about Insights into Visual Cortex Research Through Wide-View fMRI Mapping at JoVE.com

This work was supported by the National Institutes of Health [R01EY030996].

Research with human participants was performed in compliance with institutional guidelines at the University of Texas Health Science Center and Stony Brook University, with informed consent obtained from participants for these studies and use of their data.
1. Setup of MRI scanner and imaging protocols
<ol>
	<li>For fMRI, use a 3T MRI scanner with multi-channel receiver head coils. Different field strengths can also be used but may present difficulties with signal-to-noise r...

Advancing Visual Cortex Mapping for Enhanced Evaluation of Vision Disorders

<ol>
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K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+magnetic+resonance+imaging+of+human+brain+activity+during+primary+sensory+stimulation.">Dynamic magnetic resonance imaging of human brain activity during primary sensory stimulation.</a> Proceedings of the National Academy of Sciences. 89 (12), 5675-5679 (1992).</li><li>Ogawa, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intrinsic+signal+changes+accompanying+sensory+stimulation:+functional+brain+mapping+with+magnetic+resonance+imaging.">Intrinsic signal changes accompanying sensory stimulation: functional brain mapping with magnetic resonance imaging.</a> Proceedings of the National Academy of Sciences. 89 (13), 5951-5955 (1992).</li><li>Zhou, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinotopic+fMRI+reveals+visual+dysfunction+and+functional+reorganization+in+the+visual+cortex+of+mild+to+moderate+glaucoma+patients.">Retinotopic fMRI reveals visual dysfunction and functional reorganization in the visual cortex of mild to moderate glaucoma patients.</a> Journal of Glaucoma. 26 (5), 430-437 (2017).</li><li>Duncan, R. 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The above protocol for utilization of wide-view retinotopic fMRI is an innovative method to evaluate the effects of vision loss and eye diseases on the brain. Through wide-field retinotopic mapping of the visual cortex with the use of a wider-view screen, this approach allows for a more comprehensive understanding of the visual system's functional organization. This could lead to a better understanding of abnormalities in the brain's visual processing system, which occurs in neurodegeneration, such as in glaucoma<sup cla...

Functional magnetic resonance imaging (fMRI) is a valuable method to assess changes in regional neurovascular function within the visual cortex in response to stimuli, as changes in regional blood flow correlate to the activation of brain regions1,2. High-resolution retinotopic blood oxygenation level-dependent (BOLD) signal measurements represent changes in deoxyhemoglobin, which are driven by localized changes in blood flow and blood oxygenation within the brain1,2. BOLD activity patterns collected from fMRI data can be used to functionally map the peripheral and central visual cortex, as well as detect changes in the retinotopic map in response to visual impairment and neurodegeneration3.
Most previous fMRI studies made use of narrow-view (around &#177;12&#176; of the central visual field) non-retinotopic stimuli or simple retinotopic stimuli with narrow-view visual stimuli, which provided limited functional parcellation of the retinotopic representation in the visual cortex and limited assessment to only the central visual field, excluding the periphery3. Consequently, narrow-view fMRI data has reported inconsistent BOLD percent changes in glaucoma patients4,5,6. There is therefore a need for improved fMRI approaches to assessing the peripheral and central visual field, particularly in the evaluation of diseases such as glaucoma.
Glaucoma is the leading cause of irreversible blindness, affecting 10% of people by the age of 807. Glaucoma is caused by the progressive, irreversible neurodegeneration of retinal ganglion cells, which are responsible for transmitting visual stimuli to the brain through the optic nerve. In primary open-angle glaucoma (POAG), the most common form of glaucoma, increased intraocular pressure causes thinning of the retinal nerve fiber layer (RNFL), leading to the loss of peripheral vision followed by peripheral and central blindess8,9,10,11. Histological evidence from animal studies suggests that glaucoma additionally results in progressive neurodegeneration of the optic nerve, optic tract, lateral geniculate nucleus, optic radiation, and visual cortex12,13. MRI technology offers a minimally invasive method of assessing both blood oxygenation and neurodegeneration in the visual cortex. In patients with glaucoma, MRI has found evidence of gray-matter atrophy in the visual pathway13,14,15,16 and abnormal white matter in the optic chiasm, optic tract, and optic radiation1,17,18.
To further explore the effects on visual processing, fMRI can be used to detect brain function in response to visual cues. The protocol herein describes a novel method to obtain a low-cost, wide-view retinotopic map using high-resolution retinotopy fMRI with wide-field (&#62;100&#176;) stimuli, as described by Zhou et al3. Visual stimuli of expanding rings and rotating wedges were used to elicit retinotopic mapping of the eccentricity and polar angle for fMRI. BOLD fMRI percent changes were analyzed as a function of eccentricity to evaluate brain function, corresponding to both central and peripheral vision. The BOLD fMRI percent change may be used to visualize activation throughout the visual cortex. These fMRI measures provide a reliable new method to evaluate neurodegenerative changes and their functional effects on the visual cortex found in eye diseases involving visual field defects, such as glaucoma.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1/4&#34;-20 nylon machine screws, knurled head thumb screw</td>
			<td></td>
			<td></td>
			<td>to attach rod to PVC frame</td>
		</tr>
		<tr>
			<td>1-1/4 inch PVC pipe</td>
			<td></td>
			<td></td>
			<td>length of ~5-10 ft is needed</td>
		</tr>
		<tr>
			<td>3T MRI scanner</td>
			<td>Siemens</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>6-32 nylon machine screws, rounded head</td>
			<td></td>
			<td></td>
			<td>to attach mirror/screen to rod</td>
		</tr>
		<tr>
			<td>8-channel head array coil</td>
			<td>Siemens</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>90 degree PVC elbow, 1-1/4 inch fitting</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acrylic mirror</td>
			<td></td>
			<td></td>
			<td>Width and length of 25-30cm</td>
		</tr>
		<tr>
			<td>Acrylic rod</td>
			<td></td>
			<td></td>
			<td>1 inch width, ~ 2 ft long depening on size of scanner bore and head coil</td>
		</tr>
		<tr>
			<td>E-Prime</td>
			<td>Psychology Software Tools</td>
			<td></td>
			<td>to prepare and present visual stimuli paradigms</td>
		</tr>
		<tr>
			<td>Plywood sheet, 1/2 inch thick</td>
			<td></td>
			<td></td>
			<td>Size should be at least as large as the scanner bore. Cut as bore-sized frame for the projection screen</td>
		</tr>
		<tr>
			<td>Rear projection screen</td>
			<td></td>
			<td></td>
			<td>Size should be at least as large as the scanner bore</td>
		</tr>
	</tbody>
</table>

functional magnetic resonance imaging (fmri) of the visual cortex with wide-view retinotopic stimulation

High-resolution retinotopic blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) with a wide-view presentation can be used to functionally map the peripheral and central visual cortex. This method for measuring functional changes of the visual brain allows for functional mapping of the occipital lobe, stimulating &gt;100&#176; (&plusmn;50&#176;) or more of the visual field, compared to standard fMRI visual presentation setups which usually cover &lt;30&#176; of the visual field. A simple wide-view stimulation system for BOLD fMRI can be set up using common MR-compatible projectors by placing a large mirror or screen close to the subject's face and using only the posterior half of a standard head coil to provide a wide-viewing angle without obstructing their vision. The wide-view retinotopic fMRI map can then be imaged using various retinotopic stimulation paradigms, and the data can be analyzed to determine the functional activity of visual cortical regions corresponding to central and peripheral vision. This method provides a practical, easy-to-implement visual presentation system that can be used to evaluate changes in the peripheral and central visual cortex due to eye diseases such as glaucoma and the vision loss that may accompany them.

Functional Magnetic Resonance Imaging (fMRI) of the Visual Cortex with Wide-View Retinotopic Stimulation

Nine participants diagnosed with POAG (four males, 36-74 years old) and nine age-matched healthy volunteers (six males, 53-65) were evaluated using the aforementioned wide-view fMRI protocol, as previously described by Zhou et al3. POAG was confirmed clinically in patients with an open angle by assessment of the presentation of visual field defects consistent with glaucoma, optic disc cupping, and/or an intraocular pressure (IOP) greater than 21 mmHg3. A wide-view visual pr...

Watch this Scientific Journal Video about Insights into Visual Cortex Research Through Wide-View fMRI Mapping at JoVE.com

Insights into Visual Cortex Research Through Wide-View fMRI Mapping 

We have developed techniques for mapping the visual cortex function utilizing more of the visual field than is commonly used. This approach has the potential to enhance the evaluation of vision disorders and eye diseases.

High-resolution retinotopic blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) with a wide-view presentation can be ...

This research focuses on providing a practical, cost-effective visual presentation system to evaluate changes in the visual cortex due to ophthalmic diseases. We provide a method to create a wide viewing angle, retina atopic map, using FMRI to assess the functional activity of the visual cortex. A current experimental challenge is that standard systems for presenting visual stimuli for FMRI only cover small area of the visual fields, and with the view partially obstructed by the head coil.This protocol provides method for wide view and unobstructed stimuli that balances cost, efficacy, and precision. Our protocol provides an affordable, moderately wide view of up to a hundred degrees of the visual field. Compared to other techniques, it avoids distortions, additional costs for projector lenses or fiber optic bundles, and other complexities, such as the need for contact lenses.Our findings can be used to expand the understanding of the visual cortex, enabling the mapping of peripheral and central regions via an affordable, wide view FMRI system. This could enhance the management of visual impairments in eye diseases such as glaucoma, which involves dysfunction of the visual system in the brain.