Name: FMRI Participant Preparation and Visual Cortex Scanning
Uploaded: 2023-12-08T12:40:00
Description: Watch this Scientific Journal Video about FMRI Participant Preparation and Visual Cortex Scanning at JoVE.com

fmri participant preparation and visual cortex scanning

Fremme af visuel cortex-kortlægning for forbedret evaluering af synsforstyrrelser

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.

Forfatter Spotlight: Indsigt i visuel cortex-forskning gennem fMRI-kortlægning med bred visning 

Funktionel magnetisk resonansbilleddannelse (fMRI) af den visuelle cortex med bred visning af retinopisk stimulering

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.

Watch this Scientific Journal Video about FMRI Participant Preparation and Visual Cortex Scanning at JoVE.com

FMRI Participant Preparation and Visual Cortex Scanning  

fMRI-deltagerforberedelse og visuel Cortex-scanning

Begynd med at instruere deltageren om at fiksere på det centrale kryds under billedscanningerne. Demonstrer kort den visuelle stimulering for at gøre deltageren bekendt med proceduren. Placer deltageren komfortabelt på scannerbordet, og immobiliser deltagerens hoved i den bageste halvdel af hovedspolearrayet med skumpolstring for at reducere bevægelsesartefakter.Giv ørepropper for at beskytte deres hørelse. Brug scannerens positioneringssystem til at flytte bordet ind i scannerboringen. Placer vidvinkelspejlet 10 centimeter fra deltagerens øjne.Juster spejlet for at opretholde en ensartet synsvinkel. Start fMRI-scanning med en lokaliseringsscanning, der inkorporerer tre ortogonale planer og justerer scanneren for frekvens og shimming-kalibrering. Fortsæt med en MP-RAGE anatomisk scanning for forbedret EPI skivepositionering.I starten af fMRI-protokollen skal du instruere deltageren om at fiksere på det hvide kors oven på en grå baggrund i stimuliens centrum i 10 sekunder. Opret visuelle stimuli ved hjælp af et kompatibelt program ved at vise en række roterende kiler i 30 sekunder. Kilerne skal strække sig til kanten af skærmen eller spejlet med et kontrastvendt sort / hvidt skakbrætmønster på otte hertz.Præsenter det hvide kryds i yderligere 10 sekunder. Gentag krydsfikserings- og stimuleringsvisning med det andet 30-sekunders visuelle stimuleringsparadigme, der består af ekspanderende og sammentrækkende ringe. Oprethold et kontrastvendt sort-hvidt skakbrætmønster på otte hertz med 100 % kontrast under eksperimentet.Når billeddannelsen er afsluttet, skal du skubbe bordet ud af scannerboringen, og sørg for, at deltageren forbliver stille. Fjern derefter skærmen, og fjern derefter spejlet, før du placerer den forreste del af hovedspolen. Placer bordet tilbage i midten af scanneren.Få en hurtig lokaliseringsscanning for at tage højde for enhver bevægelse, efterfulgt af en MP-RAGE-scanning ved hjælp af den fulde hovedspole. De polære kort afslørede ingen åbenlyse forskelle mellem de primære åbenvinklede glaukom deltagere og raske deltagere. Excentricitetskortene viste, at den centrale region af parafoveaen, der blev aktiveret af de mindre ringstimuli, syntes større hos den primære åbenvinklede glaukompatient.BOLD-procentændringer ved forskellige excentriciteter blev reduceret hos primære åbenvinklede glaukompatienter, især ved mere perifere excentriciteter. BOLD-ændringerne blev signifikant reduceret mellem de to grupper, mere ved større excentriciteter. De BOLD-procentvise ændringer, der var gennemsnitlige for centralt syn, var kun lidt og ikke signifikant reduceret hos primære åbenvinklede glaukompatienter, mens ændringerne blev signifikant reduceret for perifert syn.

Research

JoVE Journal

Neuroscience

fMRI Participant Preparation and Visual Cortex Scanning

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 ...