Changes in brain morphology in albinism reflect reduced visual acuity

Bridge, Holly; Hagen, Elisabeth von dem; Davies, George J.; Chambers, C. M.; Gouws, André; Hoffmann, Michael B.; Morland, Antony B.

doi:10.1016/j.cortex.2012.08.010

Cited by 44 publications

(60 citation statements)

References 36 publications

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“…Our results agreed with the findings of smaller optic nerve, tract and chiasm in PWA reported by previous studies (Schmitz et al, ; Von dem Hagen et al, ; Bridge et al, ). Our results indicate that DTI tractography may be able to demonstrate group level chiasmal misrouting in albinism.…”

Section: Discussionsupporting

confidence: 94%

“…The post orbital visual pathway was studied using high‐resolution T1‐weighted MRI imaging to measure cisternal optic nerves, chiasm, optic tracts and V1 cortical thickness. Our aim was to confirm previous reports regarding altered morphology of these structures in PWA (Schmitz et al, ; Bridge et al, ; Mcketton et al, ).…”

Section: Introductionsupporting

confidence: 71%

“…Using a similar technique to Bridge et al, we have found that PWA do indeed have increased cortical thickness at the occipital pole. Bridge et al found reduced gyrification in PWA, which might explain why the earlier voxel based morphometry study may have reported reduced cortical volume in albinism (Von dem Hagen et al, ; Bridge et al, ). We previously reported corroboratory evidence using functional MRI that an increased interhemispheric functional connectivity of the visual processing areas is present in albinism, which may be an adaptation to the upstream structural changes in the visual pathway (Welton et al, ).…”

Section: Discussionmentioning

confidence: 95%

“…Using voxel based morphometry, Von dem Hagen et al found that PWA have a reduction in grey matter volume in the occipital cortex (Von dem Hagen et al, ). A more recent study by Bridge et al used surface based analysis to conclude that visual cortex thickness is increased in PWA (Bridge et al, ). Bridge et al suggested that the difference in results between the two previous studies were due to the two different analysis techniques being employed.…”

Section: Discussionmentioning

confidence: 99%

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Aberrant visual pathway development in albinism: From retina to cortex

Ather

Proudlock

Welton

et al. 2018

Human Brain Mapping

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Albinism refers to a group of genetic abnormalities in melanogenesis that are associated neuronal misrouting through the optic chiasm. We perform quantitative assessment of visual pathway structure and function in 23 persons with albinism (PWA) and 20 matched controls using optical coherence tomography (OCT), volumetric magnetic resonance imaging (MRI), diffusion tensor imaging and visual evoked potentials (VEP). PWA had a higher streamline decussation index (percentage of total tractography streamlines decussating at the chiasm) compared with controls (Z = −2.24, p = .025), and streamline decussation index correlated weakly with inter‐hemispheric asymmetry measured using VEP (r = .484, p = .042). For PWA, a significant correlation was found between foveal development index and total number of streamlines (r = .662, p < .001). Significant positive correlations were found between peri‐papillary retinal nerve fibre layer thickness and optic nerve (r = .642, p < .001) and tract (r = .663, p < .001) width. Occipital pole cortical thickness was 6.88% higher (Z = −4.10, p < .001) in PWA and was related to anterior visual pathway structures including foveal retinal pigment epithelium complex thickness (r = −.579, p = .005), optic disc (r = .478, p = .021) and rim areas (r = .597, p = .003). We were unable to demonstrate a significant relationship between OCT‐derived foveal or optic nerve measures and MRI‐derived chiasm size or streamline decussation index. Our novel tractographic demonstration of altered chiasmatic decussation in PWA corresponds to VEP measured cortical asymmetry and is consistent with chiasmatic misrouting in albinism. We also demonstrate a significant relationship between retinal pigment epithelium and visual cortex thickness indicating that retinal pigmentation defects in albinism lead to downstream structural reorganisation of the visual cortex.

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Section: Discussionsupporting

confidence: 94%

Section: Introductionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Aberrant visual pathway development in albinism: From retina to cortex

Ather

Proudlock

Welton

et al. 2018

Human Brain Mapping

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“…Main elements of the relevant processing reside in the ventral visual cortex. Notably, the convolution of the ventral visual cortex is altered in albinism compared to controls [Bridge et al, ]. A potential cause of this altered cortical morphology might be the adaptation of the respective cortico‐cortical connectivity in response to the abnormal representations of lower tier cortical input stages.…”

Section: Introductionmentioning

confidence: 99%

Impact of chiasma opticum malformations on the organization of the human ventral visual cortex

Kaule

Wolynski

Gottlob

et al. 2014

Human Brain Mapping

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Congenital malformations of the optic chiasm, such as enhanced and reduced crossing of the optic nerve fibers, are evident in albinism and achiasma, respectively. In early visual cortex the resulting additional visual input from the ipsilateral visual hemifield is superimposed onto the normal retinotopic representation of the contralateral visual field, which is likely due to conservative geniculo-striate projections. Counterintuitively, this organization in early visual cortex does not have profound consequences on visual function. Here we ask, whether higher stages of visual processing provide a correction to the abnormal representation allowing for largely normal perception. To this end we assessed the organization patterns of early and ventral visual cortex in five albinotic, one achiasmic, and five control participants. In albinism and achiasma the mirror-symmetrical superposition of the ipsilateral and contalateral visual fields was evident not only in early visual cortex, but also in the higher areas of the ventral processing stream. Specifically, in the visual areas VO1/2 and PHC1/2 no differences in the extent, the degree of superposition, and the magnitude of the responses were evident in comparison to the early visual areas. Consequently, the highly atypical organization of the primary visual cortex was propagated downstream to highly specialized processing stages in an undiminished and unchanged manner. This indicates largely unaltered cortico-cortical connections in both types of misrouting, i.e., enhanced and reduced crossing of the optic nerves. It is concluded that main aspects of visual function are preserved despite sizable representation abnormalities in the ventral visual processing stream.

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Abnormal lateral geniculate nucleus and optic chiasm in human albinism

McKetton

Kelly

Schneider

2014

J of Comparative Neurology

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Our objective was to measure how the misrouting of retinal ganglion cell (RGC) fibers affects the organization of the optic chiasm and lateral geniculate nuclei (LGN) in human albinism. We compared the chiasmal structures and the LGN in both pigmented controls and patients with albinism by using high-resolution structural magnetic resonance imaging (MRI). We studied 12 patients with oculocutaneous albinism and 12 age-matched pigmented controls. Using a 3T MRI scanner, we acquired a T1 -weighted three-dimensional magnetization-prepared rapid gradient-echo (MPRAGE) image of the whole brain, oriented so that the optic nerves, chiasm, and tracts were in the same plane. We acquired multiple proton density-weighted images centered on the thalamus and midbrain, and averaged them to increase the signal, enabling precise manual tracing of the anatomical boundaries of the LGN. Albinism patients exhibited significantly smaller diameters of the optic nerves, chiasm and tracts, and optic chiasm and LGN volume compared with controls (P < 0.001 for all). The reductions in chiasmal diameters in the albinism compared with the control group can be attributed to the abnormal crossing of optic fibers and the reduction of RGCs in the central retina. The volume of the LGN devoted to the center of the visual field may be reduced in albinism due to fewer RGCs representing the area where the fovea would normally lie. Our data may be clinically useful in addressing how genetic deficits compromise proper structural and functional development in the brain.

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Changes in brain morphology in albinism reflect reduced visual acuity

Cited by 44 publications

References 36 publications

Aberrant visual pathway development in albinism: From retina to cortex

Aberrant visual pathway development in albinism: From retina to cortex

Impact of chiasma opticum malformations on the organization of the human ventral visual cortex

Abnormal lateral geniculate nucleus and optic chiasm in human albinism

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