Population receptive field and connectivity properties of the early visual cortex in human albinism

Ahmadi, Khazar; Herbik, Anne; Wagner, Markus; Kanowski, Martin; Thieme, Hagen; Hoffmann, Michael B.

doi:10.1101/627265

Cited by 4 publications

(4 citation statements)

References 40 publications

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“…In patients with macular degeneration, Haak et al showed preserved corticocortical organization, when visually stimulated, between input-deprived portions of V1 > V2/V3 [24]. In early blind and anophthalmia cases, Bock et al found an intact corticocortical organization between V1 > V2/V3, even despite a complete absence of visual experience and retinal input [25]. Recently, Ahmadi et al [26] showed changes in corticocortical connections for V1 > V3 in albinotic participants.…”

Section: Discussionmentioning

confidence: 99%

Stimulus- and Neural-Referred Visual Receptive Field Properties following Hemispherectomy: A Case Study Revisited

Haak

Cornelissen

2019

Neural Plasticity

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Damage to the visual system can result in (a partial) loss of vision, in response to which the visual system may functionally reorganize. Yet the timing, extent, and conditions under which this occurs are not well understood. Hence, studies in individuals with diverse congenital and acquired conditions and using various methods are needed to better understand this. In the present study, we examined the visual system of a young girl who received a hemispherectomy at the age of three and who consequently suffered from hemianopia. We did so by evaluating the corticocortical and retinocortical projections in the visual system of her remaining hemisphere. For the examination of these aspects, we analyzed the characteristics of the connective fields (“neural-referred” receptive fields) based on both resting-state (RS) and retinotopy data. The evaluation of RS data, reflecting brain activity independent from visual stimulation, is of particular interest as it is not biased by the patient’s atypical visual percept. We found that, primarily when the patient was at rest, the connective fields between V1 and both early and late visual areas were larger than normal. These abnormally large connective fields could be a sign either of functional reorganization or of unmasked suppressive feedback signals that are normally masked by interhemispheric signals. Furthermore, we confirmed our previous finding of abnormal retinocortical or “stimulus-referred” projections in both early and late visual areas. More specifically, we found an enlarged foveal representation and smaller population receptive fields. These differences could also be a sign of functional reorganization or rather a reflection of the interruption visual information that travels, via the remainder of the visual pathway, from the retina to the visual cortex. To conclude, while we do find indications for relatively subtle changes in visual field map properties, we found no evidence of large-scale reorganization—even though the patient could have benefitted from this. Our work suggests that at a later developmental stage, large-scale reorganization of the visual system no longer occurs, while small-scale properties may still change to facilitate adaptive processing and viewing strategies.

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Section: Discussionmentioning

confidence: 99%

Stimulus- and Neural-Referred Visual Receptive Field Properties following Hemispherectomy: A Case Study Revisited

Haak

Cornelissen

2019

Neural Plasticity

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“…In this study we examined the BOLD contrast response characteristics of aberrant voxels in human albinism which respond to both the contra-and ipsilateral visual hemifields in the contralateral eye. Previous studies have shown that retinocortical miswiring in albinism results in partial cortical superposition of opposite hemifield representations in visual cortex such that single imaging voxels in these aberrant zones have two visual pRFs positioned roughly at mirror image locations across the vertical meridian (Ahmadi et al, 2019;Carvalho et al, 2020;Duwell et al, 2021;Hoffmann et al, 2003). However, while the opposite hemifield representation topographies are clearly superimposed at the macroscopic level and within individual voxels in albinism, it was still unclear whether the two conflicting hemifield inputs interact in any way.…”

Section: Discussionmentioning

confidence: 99%

“…The extent of these aberrant hemifield overlap zones varies across individual subjects with albinism depending on the severity of miswiring (Hoffmann et al, 2003). Individual fMRI voxels within the aberrant zones were demonstrated to have bilateral, dual pRFs positioned at roughly mirror image locations across the vertical meridian (Ahmadi, Herbik, Wagner, Kanowski, Thieme, & Hoffmann, 2019;Carvalho, Invernizzi, Ahmadi, Hoffmann, Renken, & Cornelissen, 2020;Duwell, Woertz, Mathis, Carroll, & DeYoe, 2021). However, the cellular and columnar organization of these aberrant cortical zones is still not known in human albinism, and it is unclear whether the opposing hemifield inputs interact in any way.…”

Section: Introductionmentioning

confidence: 99%

BOLD Contrast Response Characteristics of Aberrant Voxels with Bilateral Visual Population Receptive Fields in Human Albinism

Duwell,

Woertz,

Mathis

et al. 2024

Preprint

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Albinism is an inherited disorder characterized by disrupted melanin production in the eye, and often in the skin and hair. This retinal hypopigmentation is accompanied by pathological decussation of many temporal retinal afferents at the optic chiasm during development, ultimately resulting in partially superimposed representations of opposite visual hemifields in each cortical hemisphere. Within these aberrant regions of hemifield overlap, individual voxels have been shown to have bilateral, dual population receptive fields (pRFs) responding to roughly mirror-image locations across the vertical meridian. Nonetheless, how these two conflicting inputs combine to determine a voxel’s response to image contrast is still unknown. To address this, we stimulated the right and left hemifields with separately controlled sinusoidal gratings, each having a variety of contrasts (0, 8, 20, 45, 100%), and extracted voxel-wise BOLD response amplitudes to each contrast combination in visual areas V1-V3. We then compared voxels’ responses to each hemifield stimulated individually with conditions when both hemifields were stimulated simultaneously. We hypothesized that simultaneous stimulation of the two pRF components will result in either a suppressive or facilitative interaction. However, we found that BOLD responses to simultaneous stimulation appeared to reflect simple summation of the neural activity from the individual hemifield conditions. This suggests that the superimposed opposite hemifield representations do not interact. Thus, dual pRFs in albinism likely reflect two co-localized, but functionally independent populations of neurons each of which respond to a single hemifield. This finding is commensurate with psychophysical studies which have shown no clear perceptual interaction between opposite visual hemifields in human albinism.

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“…The estimation of pRF properties, the delineation of the visual areas, and the visualization on the smoothed mesh surface were performed using Vistasoft, as described in (Ahmadi, Fracasso, et al 2019;Ahmadi, Herbik, et al 2019) . Polar angle and eccentricity maps were extracted and the misrouting extent was measured by calculating the mean eccentricity value [in degrees of visual angle] for the abnormal representation in a ROI drawn at the fundus of the calcarine sulcus that coincided with the representation of the horizontal meridian.…”

Section: Fmri Data Analysismentioning

confidence: 99%

Quantifying nerve decussation abnormalities in the optic chiasm

Puzniak

Ahmadi

Kaufmann

et al. 2019

Preprint

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Objective: The human optic chiasm comprises partially crossing optic nerve fibres. Here we used diffusion MRI (dMRI) for the in-vivo identification of the abnormally high proportion of crossing fibres found in the optic chiasm of people with albinism. Methods:In 9 individuals with albinism and 8 controls high-resolution 3T dMRI data was acquired and analyzed with a set of methods for signal modeling [Diffusion Tensor (DT) and Constrained Spherical Deconvolution (CSD)], tractography, and streamline filtering (LiFE, COMMIT, and SIFT2).The number of crossing and non-crossing streamlines and their weights after filtering entered ROC-analyses to compare the discriminative power of the methods based on the area under the curve (AUC). The dMRI results were cross-validated with fMRI estimates of misrouting in a subset of 6 albinotic individuals.1 Results: We detected significant group differences in chiasmal crossing for both unfiltered DT (p=0.014) and CSD tractograms (p=0.0009) also reflected by AUC measures (for DT and CSD: 0.61 and 0.75, respectively), underlining the discriminative power of the approach. Estimates of crossing strengths obtained with dMRI and fMRI were significantly correlated for CSD (R 2 =0.83, p=0.012).The results show that streamline filtering methods in combination with probabilistic tracking, both optimized for the data at hand, can improve the detection of crossing in the human optic chiasm. Conclusions:Especially CSD-based tractography provides an efficient approach to detect structural abnormalities in the optic chiasm. The most realistic results were obtained with filtering methods with parameters optimized for the data at hand.Significance: Our findings demonstrate a novel anatomy-driven approach for the individualized diagnostics of optic chiasm abnormalities. Highlights• Diffusion MRI is capable of detecting structural abnormalities of the optic chiasm.• Quantification of crossing strength in optic chiasm is of promise for albinism diagnostics.• Optic chiasm is a powerful test model for neuroimaging methods resolving crossing fibers.

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Population receptive field and connectivity properties of the early visual cortex in human albinism

Cited by 4 publications

References 40 publications

Stimulus- and Neural-Referred Visual Receptive Field Properties following Hemispherectomy: A Case Study Revisited

Stimulus- and Neural-Referred Visual Receptive Field Properties following Hemispherectomy: A Case Study Revisited

BOLD Contrast Response Characteristics of Aberrant Voxels with Bilateral Visual Population Receptive Fields in Human Albinism

Quantifying nerve decussation abnormalities in the optic chiasm

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