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

Advancing Visual Cortex Mapping for Enhanced Evaluation of Vision Disorders

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.

Author Spotlight: Insights into Visual Cortex Research Through Wide-View fMRI Mapping 

Funksjonell magnetisk resonanstomografi (fMRI) av den visuelle cortex med bredsyns retinotopisk 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-deltakerforberedelse og visuell cortexskanning

Begynn med å instruere deltakeren til å feste på det sentrale korset under bildebehandlingsskanningene. Demonstrer kort visuell stimulering for å gjøre deltakeren kjent med prosedyren. Plasser deltakeren komfortabelt på skannerbordet og immobiliser deltakerens hode i den bakre halvdelen av hodespolegruppen med skumpolstring for å redusere bevegelsesartefakter.Gi øreplugger for å beskytte hørselen. Bruk skannerens posisjoneringssystem til å flytte bordet inn i skannerboringen. Plasser vidvinkelspeilet 10 centimeter fra deltakerens øyne.Juster speilet for å opprettholde en jevn visningsvinkel. Start fMRI-skanning med en lokaliseringsskanning, som omfatter tre ortogonale plan og justerer skanneren for frekvens- og shimmingkalibrering. Fortsett med en MP-RAGE anatomisk skanning for forbedret EPI-stykkeposisjonering.Ved starten av fMRI-protokollen, instruer deltakeren om å feste seg på det hvite korset på toppen av en grå bakgrunn ved stimuliens senter i 10 sekunder. Lag visuelle stimuli ved hjelp av et kompatibelt program ved å vise en serie roterende kiler i 30 sekunder. Kilene skal strekke seg til kanten av skjermen eller speilet med et åtte-hertz kontrast-reverserende svart og hvitt sjakkbrettmønster.Presenter det hvite korset i ytterligere 10 sekunder. Gjenta kryssfiksering og stimuleringsvisning med det andre 30-sekunders visuelle stimuleringsparadigmet, bestående av ekspanderende og sammentrekkende ringer. Oppretthold et kontrastreverserende svart-hvitt-sjakkbrettmønster på åtte hertz med 100 % kontrast under eksperimentet.Når avbildningen er fullført, skyver du bordet ut av skannerboringen, slik at deltakeren forblir stille. Deretter fjerner du skjermen og fjerner speilet før du plasserer den fremre delen av hodespolen. Plasser bordet tilbake i midten av skanneren.Skaff deg en rask lokaliseringsskanning for å ta hensyn til enhver bevegelse, etterfulgt av en MP-RAGE-skanning ved hjelp av hele hodespolen. Polarkartene viste ingen åpenbare forskjeller mellom de primære åpenvinklede DrDeramus-deltakerne og friske deltakere. Eksentrisitetskartene viste at den sentrale regionen av parafovea som ble aktivert av de mindre ringstimuliene, virket større hos den primære åpenvinklede DrDeramus-pasienten.BOLD prosentvise endringer ved forskjellige eksentrisiteter ble redusert hos primære åpenvinklet glaukompasienter, spesielt ved mer perifere eksentrisiteter. De dristige endringene ble signifikant redusert mellom de to gruppene, mer ved større eksentrisiteter. BOLD-prosentendringene i gjennomsnitt for sentral visjon var bare litt og ikke signifikant redusert hos primære åpenvinklede DrDeramus-pasienter, mens endringene ble signifikant redusert 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 ...