Congenital Achiasma and See-Saw Nystagmus in VACTERL Syndrome

Prakash, Saurabh; Dumoulin, Serge O.; Fischbein, Nancy J.; Wandell, Brian A.; Liao, Yaping Joyce

doi:10.1097/wno.0b013e3181c28fc0

Cited by 25 publications

(24 citation statements)

References 19 publications

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“…Still visual function is relatively unaffected, with the exception of nystagmus and the absence of stereopsis. In line with previously reported achiasmic subjects (Apkarian et al, 1994; Apkarian et al, 1995; Prakash et al, 2010; Victor et al, 2000), the subjects made effective use of their vision in daily life, including sport activities and reading. They performed normal on various clinical tasks, including largely normal visual field sensitivities and no visual field defects associated with the abnormal representation of the nasal retina.…”

Section: Discussionsupporting

confidence: 83%

“…This poses a substantial challenge to the organization of visual field maps and prompts potential sensory conflicts. Despite these sizable aberrant projections, achiasmic humans have relatively normal visual function (Apkarian et al, 1994; Apkarian et al, 1995; Prakash et al, 2010; Victor et al, 2000). Therefore achiasma offers a unique opportunity to study the principles governing cortical map development in humans.…”

mentioning

confidence: 99%

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Plasticity and Stability of the Visual System in Human Achiasma

Hoffmann

Kaule

Levin

et al. 2012

Neuron

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Summary The absence of the optic chiasm is an extraordinary and extreme abnormality in the nervous system. The abnormality produces highly atypical functional responses in the cortex, including overlapping hemifield representations and bilateral population receptive fields in both striate and extrastriate visual cortex. Even in the presence of these large functional abnormalities, the effect on visual perception and daily life is not easily detected. Here we demonstrate that in two achiasmic humans the gross topography of the geniculo-striate and occipital callosal connections remains largely unaltered. We conclude that visual function is preserved by reorganization of intra-cortical connections instead of large-scale reorganizations of the visual cortex. Thus developmental mechanisms of local wiring within cortical maps compensate for the improper gross wiring to preserve function in human achiasma.

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Section: Discussionsupporting

confidence: 83%

mentioning

confidence: 99%

Plasticity and Stability of the Visual System in Human Achiasma

Hoffmann

Kaule

Levin

et al. 2012

Neuron

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“…An interesting and open question is whether the presence of a regular spatial structure, such as a map, is essential for proper visual function (Horton & Adams, 2005). Neurological case studies report that achiasmic subjects (Prakash, Dumoulin, Fischbein, Wandell & Liao, 2010, Victor, Apkarian, Hirsch, Conte, Packard, Relkin, Kim & Shapley, 2000) and albino subjects (Hoffmann et al, 2003) can have spatial vision but unconventional V1 field maps. In a dramatic example, Muckli et al (2009) recently observed the case of a young girl who developed with only one hemisphere (see also Werth (2006)).…”

Section: Cortical Visual Field Mapsmentioning

confidence: 99%

Imaging retinotopic maps in the human brain

2011

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A quarter-century ago visual neuroscientists had little information about the number and organization of retinotopic maps in human visual cortex. The advent of functional magnetic resonance imaging (MRI), a non-invasive, spatially-resolved technique for measuring brain activity, provided a wealth of data about human retinotopic maps. Just as there are differences amongst nonhuman primate maps, the human maps have their own unique properties. Many human maps can be measured reliably in individual subjects during experimental sessions lasting less than an hour. The efficiency of the measurements and the relatively large amplitude of functional MRI signals in visual cortex make it possible to develop quantitative models of functional responses within specific maps in individual subjects. During this last quarter century, there has also been significant progress in measuring properties of the human brain at a range of length and time scales, including white matter pathways, macroscopic properties of gray and white matter, and cellular and molecular tissue properties. We hope the next twenty-five years will see a great deal of work that aims to integrate these data by modeling the network of visual signals. We don’t know what such theories will look like, but the characterization of human retinotopic maps from the last twenty-five years is likely to be an important part of future ideas about visual computations.

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“…These pRF methods have successfully been used by a small group of labs to (1) investigate the normal organization of human visual cortex (e.g., [12,29,30]), (2) measure developmental plasticity in achiasmatic and sight recovery patients [31,32], and (3) examine cortical reorganization in aged-related macular degeneration [33]. Because pRF Modeling has proven so successful, it is likely that it will eventually replace TWR as the standard method for measuring VFMs.…”

Section: An Innovative Approach To Measure the Organization Of Human mentioning

confidence: 99%