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Netta Levin

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5 papers

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YNIMG Journal 2025 Journal Article

Cortical visual field representation and data integration following optic neuritis

Ruth Abulafia
Pieter B. de Best
Ayelet McKyton
Adi Vaknin-Dembinsky
Panayiota Petrou
Atira S. Bick
Netta Levin

Optic neuritis (ON) is an inflammatory, demyelinating optic neuropathy commonly associated with multiple sclerosis. Its clinical presentation typically includes monocular vision loss, with most visual functions recovering within several weeks. In addition to spontaneous remyelination, brain adaptation has been suggested to play a role in the recovery process. To further investigate this hypothesis, we examined cortical visual field representation and data integration during the first year following a first-ever ON episode. Eight ON participants and ten controls underwent fMRI scans under three viewing conditions: two monocular conditions (affected/fellow eye for ON; dominant/non-dominant eye for controls) and one binocular condition (both eyes open). For each condition, population receptive field (pRF) and connective field (CF) modeling were applied to assess spatial properties and sampling extent across the early visual cortical hierarchy (V1-V3). Consistent with previous studies, controls demonstrated an increase in average pRF and CF sizes along the visual hierarchy, with no significant differences between viewing conditions. In contrast, the ON group exhibited unique patterns. In the fellow eye condition, the typical pRF size increase along the visual hierarchy was absent, primarily due to reduced pRF sizes in V3. Additionally, in the affected eye, CF sizes were significantly larger than in the fellow eye. These modulations may reflect enhanced resolution for the unaffected eye and an increased extent of data processing when visual input is impaired (originating from the affected nerve). Therefore, we suggest that these cortical changes may be part of a spatial adaptation mechanism.

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YNICL Journal 2022 Journal Article

Structural changes to primary visual cortex in the congenital absence of cone input in achromatopsia

Barbara Molz
Anne Herbik
Heidi A. Baseler
Pieter B. de Best
Richard W. Vernon
Noa Raz
Andre D. Gouws
Khazar Ahmadi

Autosomal recessive Achromatopsia (ACHM) is a rare inherited disorder associated with dysfunctional cone photoreceptors resulting in a congenital absence of cone input to visual cortex. This might lead to distinct changes in cortical architecture with a negative impact on the success of gene augmentation therapies. To investigate the status of the visual cortex in these patients, we performed a multi-centre study focusing on the cortical structure of regions that normally receive predominantly cone input. Using high-resolution T1-weighted MRI scans and surface-based morphometry, we compared cortical thickness, surface area and grey matter volume in foveal, parafoveal and paracentral representations of primary visual cortex in 15 individuals with ACHM and 42 normally sighted, healthy controls (HC). In ACHM, surface area was reduced in all tested representations, while thickening of the cortex was found highly localized to the most central representation. These results were comparable to more widespread changes in brain structure reported in congenitally blind individuals, suggesting similar developmental processes, i.e., irrespective of the underlying cause and extent of vision loss. The cortical differences we report here could limit the success of treatment of ACHM in adulthood. Interventions earlier in life when cortical structure is not different from normal would likely offer better visual outcomes for those with ACHM.

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YNIMG Journal 2020 Journal Article

Conduction delays in the visual pathways of progressive multiple sclerosis patients covary with brain structure

Shai Berman
Yael Backner
Ronnie Krupnik
Friedemann Paul
Panayiota Petrou
Dimitrios Karussis
Netta Levin
Aviv A. Mezer

In developed countries, multiple sclerosis (MS) is the leading cause of non-traumatic neurological disability in young adults. MS is a chronic demyelinating disease of the central nervous system, in which myelin is attacked, changing white matter structure and leaving lesions. The demyelination has a direct effect on white matter conductivity. This effect can be examined in the visual system, where damage is highly prevalent in MS, leading to substantial delays in conduction, commonly measured with visual evoked potentials (VEPs). The structural damage to the visual system in MS is often estimated with MRI measurements in the white matter. Recent developments in quantitative MRI (qMRI) provide improved sensitivity to myelin content and new structural methods allow better modeling of the axonal structure, leading researchers to link white matter microstructure to conduction properties of action potentials along fiber tracts. This study attempts to explain the variance in conduction latencies down the visual pathway using structural measurements of both the retina and the optic radiation (OR). Forty-eight progressive MS patients, participants in a longitudinal stem-cell therapy clinical trial, were included in this study, three and six months post final treatment. Twenty-seven patients had no history of optic neuritis, and were the main focus of this study. All participants underwent conventional MRI scans, as well as diffusion MRI and qMRI sequences to account for white matter microstructure. Optical coherence tomography scans were also obtained, and peripapillary retinal nerve fiber layer (pRNFL) thickness and macular volume measurements were extracted. Finally, latencies of recorded VEPs were estimated. Our results show that in non-optic neuritis progressive MS patients there is a relationship between the VEP latency and both retinal damage and OR lesion load. In addition, we find that qMRI values, sampled along the OR, are also correlated with VEP latency. Finally, we show that combining these parameters using PCA we can explain more than 40% of the inter-subject variance in VEP latency. In conclusion, this study contributes to understanding the relationship between the structural properties and conduction in the visual system in disease. We focus on the visual system, where the conduction latencies can be estimated, but the conclusions could be generalized to other brain systems where the white matter structure can be measured. It also highlights the importance of having multiple parameters when assessing the clinical stages of MS patients, which could have major implications for future studies of other white matter diseases.

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YNICL Journal 2018 Journal Article

Comparison of probabilistic tractography and tract-based spatial statistics for assessing optic radiation damage in patients with autoimmune inflammatory disorders of the central nervous system

Joseph Kuchling
Yael Backner
Frederike C. Oertel
Noa Raz
Judith Bellmann-Strobl
Klemens Ruprecht
Friedemann Paul
Netta Levin

Background: Diffusion Tensor Imaging (DTI) can evaluate microstructural tissue damage in the optic radiation (OR) of patients with clinically isolated syndrome (CIS), early relapsing-remitting multiple sclerosis and neuromyelitis optica spectrum disorders (NMOSD). Different post-processing techniques, e.g. tract-based spatial statistics (TBSS) and probabilistic tractography, exist to quantify this damage. Objective: To evaluate the capacity of TBSS-based atlas region-of-interest (ROI) combination with 1) posterior thalamic radiation ROIs from the Johns Hopkins University atlas (JHU-TBSS), 2) Juelich Probabilistic ROIs (JUEL-TBSS) and tractography methods using 3) ConTrack (CON-PROB) and 4) constrained spherical deconvolution tractography (CSD-PROB) to detect OR damage in patients with a) NMOSD with prior ON (NMOSD-ON), b) CIS and early RRMS patients with ON (CIS/RRMS-ON) and c) CIS and early RRMS patients without prior ON (CIS/RRMS-NON) against healthy controls (HCs). Methods: Twenty-three NMOSD-ON, 18 CIS/RRMS-ON, 21 CIS/RRMS-NON, and 26 HCs underwent 3 T MRI. DTI data analysis was carried out using JUEL-TBSS, JHU-TBSS, CON-PROB and CSD-PROB. Optical coherence tomography (OCT) and visual acuity testing was performed in the majority of patients and HCs. Results: = 0.094). No significant differences between CIS/RRMS-ON and HC were detected by any of the methods. Conclusions: All DTI post-processing techniques facilitated the detection of OR damage in patient groups with severe microstructural OR degradation. The comparison of distinct disease groups by use of different methods may lead to different - either false-positive or false-negative - results. Since different DTI post-processing approaches seem to provide complementary information on OR damage, application of distinct methods may depend on the relevant research question.

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YNIMG Journal 2006 Journal Article

Normal and abnormal fMRI activation patterns in the visual cortex after recovery from optic neuritis

Netta Levin
Tanya Orlov
Shlomo Dotan
Ehud Zohary

Recovery to normal or near normal visual acuity after an optic neuritis episode is common, despite frequent persistence of conduction abnormalities, evident in prolonged visual evoked potential (VEP) latencies. Improvement of visual function is commonly attributed to peripheral nerve recovery. However, central reorganization processes may also be involved. To assess this, we compared the patterns of fMRI activation, elicited by stimulation of the affected and the normal eye, along the visual cortical hierarchy. Activation was assessed in 8 subjects, which recovered clinically from an episode of optic neuritis but still had prolonged VEP latencies. In all patients, reduced fMRI activation was seen in V1 during stimulation of the affected eye, compared to the normal eye. The fMRI signal difference decreased in magnitude with progression along the visual hierarchy, and in some regions within the lateral occipital complex even showed the opposite preference (for the affected eye). These results may indicate a built-in robustness of the object-related areas to disruption of the visual input. Alternatively, it could reflect an adaptive functional reorganization of the cortical response to an abnormal input.

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