Functional organization of human visual cortex in occipital polymicrogyria

Dumoulin, Serge O.; Jirsch, Jeffrey; Bernasconi, Andrea

doi:10.1002/hbm.20370

Cited by 24 publications

(14 citation statements)

References 57 publications

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“…Dysplastic tissue can involve visual structures, but the lesions are so heterogeneous in terms of extent and distribution that the corresponding visual impairment can be extremely variable. Also, functional visual tissue can develop within the dysplastic cortex, allowing significant levels of visual sparing 16 . These factors make the prediction of visual outcome from early neuroimaging very difficult.…”

Section: Visual Disorders In Children With Early Brain Lesionsmentioning

confidence: 99%

“…2). In a recent study, three individuals with bilateral parasagittal occipital polymicrogyria and normal vision were analysed with retinotopic mapping 16 . Normal cortical responses and organization of early visual areas were found, suggesting that dysplastic tissue can be actively involved in the processing of visual information, presumably because of plastic reorganization within the polymicrogyric cortex.…”

Section: Is Recovery Of Normal Conscious Vision Possible?mentioning

confidence: 99%

“… Possible mechanisms of functional reorganization underlying recovery of normal conscious vision in individuals with congenital brain damage. (a) Damage involves the primary visual cortex, but functional tissue is still present within the lesion; 16,51,52 (b) Primary visual function is reorganized in areas of the occipital lobe that are outside the usual boundaries of the primary visual cortex; 55 (c) The geniculo‐striate pathway curve around the lesion bypassing it, and reach the calcarine cortex 65,66 …”

Section: Is Recovery Of Normal Conscious Vision Possible?mentioning

confidence: 99%

“…Also, functional visual tissue can develop within the dysplastic cortex, allowing significant levels of visual sparing. 16 These factors make the prediction of visual outcome from early neuroimaging very difficult.…”

Section: Pathogenesis Of Damage and Vulnerability Of The Visual Systemmentioning

confidence: 99%

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Plasticity of the visual system after early brain damage

Guzzetta

D’Acunto

Rose

et al. 2010

Develop Med Child Neuro

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The aim of this review is to discuss the existing evidence supporting different processes of visual brain plasticity after early damage, as opposed to damage that occurs during adulthood. There is initial evidence that some of the neuroplastic mechanisms adopted by the brain after early damage to the visual system are unavailable at a later stage. These are, for example, the ability to differentiate functional tissue within a larger dysplastic cortex during its formation, or to develop new thalamo-cortical connections able to bypass the lesion and reach their cortical destination in the occipital cortex. The young brain also uses the same mechanisms available at later stages of development but in a more efficient way. For example, in people with visual field defects of central origin, the anatomical expansion of the extrastriatal visual network is greater after an early lesion than after a later one, which results in more efficient mechanisms of visual exploration of the blind field. A similar mechanism is likely to support some of the differences found in people with blindsight, the phenomenon of unconscious visual perception in the blind field. In particular, compared with people with late lesions, those with early brain damage appear to have stronger subjective awareness of stimuli hitting the blind visual field, reported as a conscious feeling that something is present in the visual field. Expanding our knowledge of these mechanisms could help the development of early therapeutic interventions aimed at supporting and enhancing visual reorganization at a time of greatest potential brain plasticity.Brain plasticity consists of the modifications to the central nervous system in response to environmental stimulation, which allow us to learn new skills, remember new information, and recover from brain injury. 1 Mechanisms of neuronal plasticity are more powerful during early development. For example, children are faster than adults in learning a new language or in achieving complex skills such as playing a musical instrument. 2 Similarly, children lacking proper environmental inputs early in life are more susceptible to an abnormal development of the functions related to those inputs (the principle of sensitive periods 3 ).The presence of more powerful mechanisms of neuronal plasticity during early development should imply that recovery from brain damage is more effective after early lesions than after lesions occurring later in life. This principle was first suggested by Paul Broca in 1865 4 and then more systematically explored by Margaret Kennard in the late 1930s. 5 Since then, most of the studies of different species have supported this general principle, although describing a more complex picture, which takes into consideration several other aspects beyond timing of the insult, including the location and extension of injury (e.g. focal versus diffuse), the clinical phenotype (e.g. presence of seizures), or the genetic susceptibility of the individual. 6 Today, there is general agreement that the way the bra...

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Section: Visual Disorders In Children With Early Brain Lesionsmentioning

confidence: 99%

Section: Is Recovery Of Normal Conscious Vision Possible?mentioning

confidence: 99%

Section: Is Recovery Of Normal Conscious Vision Possible?mentioning

confidence: 99%

Section: Pathogenesis Of Damage and Vulnerability Of The Visual Systemmentioning

confidence: 99%

See 2 more Smart Citations

Plasticity of the visual system after early brain damage

Guzzetta

D’Acunto

Rose

et al. 2010

Develop Med Child Neuro

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“…In children with malformations of cortical development, for example, a different mechanism was shown, consisting of the development of a functioning cortex within the dysplastic tissue. 7 Normal cortical organization of early visual areas on functional MRI was found in children with diffuse occipital polymicrogyria and normal vision, suggesting that dysplastic tissue can be actively involved in the processing of visual information, as a result of plastic reorganization within the abnormal cortex.…”

mentioning

confidence: 98%

Plasticity of the visual system after congenital brain damage: a few weeks can matter

Guzzetta¹

2010

Develop Med Child Neuro

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This article is a commentary on Jacobson et al., pp e184-e187 of this issue.In the late 1930s, Margaret Kennard was among the first to propose that recovery from brain damage is more effective following early lesions than after lesions occurring later in life. 1 She also recognized, however, that the sparing effect on functions such as locomotion and grasping observed in infant monkeys, was not shared by vision, which failed to be restored after early damage to the occipital cortex. 1 Does this mean, then, that the visual system is equally plastic at all stages of brain development? If we exclude the blindsight phenomenon, i.e. the (predominantly) unconscious visual perception in the blind field, there is still little evidence to show that an actual lesion of the geniculostriate pathway is compatible with sparing of vision. In a large series of children with congenital hemiplegia almost 10 years ago, we found that some children, despite showing clear damage to the optic radiations or the occipital cortex on magnetic resonance imaging (MRI), had perfectly normal visual fields. 2 Our findings suggested a higher level of plasticity in the young visual brain, but the underlying mechanisms and the factors that could justify the variability between participants were a mystery to us.In their study, Jacobson et al. 3 start putting some of the pieces of the puzzle in place. In their series of children with congenital hemiplegia, they found that damage to the central visual pathway was compatible with normal vision, but only when the lesion had occurred early in the third trimester of gestation or earlier, thus showing that not only the timing of the insult is important, but even a few weeks can matter. What happens, then, in such a short time to change so dramatically brain response to damage?Around the early part of the third trimester of gestation, white matter can be particularly vulnerable to insult, exposing the developing optic radiations to injury. However, plasticity of thalamocortical fibres is remarkable at this time. The afferents from the subplate zone are still migrating into the cortical plate, and there is a significant amount of growth-promoting molecules and axonal guidance cues. 4 This particular environment gives the brain additional opportunities for plastic reorganization. Somatosensory function, for example, was shown to be particularly resilient to brain damage occurring early in the third trimester. 5 A recent study combining magneto-encephalography and diffusion tractography, provided convincing evidence that in these infants, somatosensory projections might still develop after the lesion has occurred, and bypass it to reach their cortical destination in the postcentral gyrus. 6 This mechanism is also likely to be active for other thalamocortical pathways, including optic radiations, but it is certainly not the only one. In children with malformations of cortical development, for example, a different mechanism was shown, consisting of the development of a functioning cortex within the dysplastic ...

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Functional MRI of the Visual System

Dumoulin

2015

fMRI: From Nuclear Spins to Brain Functions

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Functional organization of human visual cortex in occipital polymicrogyria

Cited by 24 publications

References 57 publications

Plasticity of the visual system after early brain damage

Plasticity of the visual system after early brain damage

Plasticity of the visual system after congenital brain damage: a few weeks can matter

Functional MRI of the Visual System

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