A model for the Chaotic Oscillations of Congenital Nystagmus
Autor(a) principal: | |
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Data de Publicação: | 2004 |
Outros Autores: | |
Tipo de documento: | Artigo de conferência |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10174/6901 |
Resumo: | Congenital nystagmus (CN) is an incurable pathological spontaneous oscillation of the eyes with an onset in the first few months of life. The pathophysiology of CN is mysterious. There is no consistent neurological abnormality, but the majority of patients have a wide range of unrelated congenital visual abnormalities affecting either the cornea, lens, retina or optic nerve. In this theoretical study, we show that these eye oscillations could develop as an adaptive response to maximize visual contrast with poor foveal function in the infant visuomotor system, at a time of peak neural plasticity. We argue that in a visual system with abnormally poor high spatial frequency sensitivity, image contrast is not only maintained by keeping the image on the fovea (or its remnant) but also by some degree of image motion. Using the calculus of variations, we show that the optimal trade-off between these conflicting goals is to generate oscillatory eye movements with increasing velocity waveforms, as seen in real CN. When we include a stochastic component to the start of each epoch (quick-phase inaccuracy) various observed waveforms (including pseudo-cycloid) emerge as optimal strategies. Using the delay embedding technique, we find a low fractional dimension as reported in real data. We further show that, if a velocity command-based pre-motor circuitry (neural integrator) is harnessed to generate these waveforms, the emergence of a null region is inevitable. We conclude that CN could emerge paradoxically as an ‘optimal’ adaptive response in the infant visual system during an early critical period. This can explain why CN does not emerge later in life and why CN is so refractory to treatment. It also implies that any therapeutic intervention would need to be very early in life. |
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A model for the Chaotic Oscillations of Congenital NystagmusVisionEye movement disordersCongenital nystagmus (CN) is an incurable pathological spontaneous oscillation of the eyes with an onset in the first few months of life. The pathophysiology of CN is mysterious. There is no consistent neurological abnormality, but the majority of patients have a wide range of unrelated congenital visual abnormalities affecting either the cornea, lens, retina or optic nerve. In this theoretical study, we show that these eye oscillations could develop as an adaptive response to maximize visual contrast with poor foveal function in the infant visuomotor system, at a time of peak neural plasticity. We argue that in a visual system with abnormally poor high spatial frequency sensitivity, image contrast is not only maintained by keeping the image on the fovea (or its remnant) but also by some degree of image motion. Using the calculus of variations, we show that the optimal trade-off between these conflicting goals is to generate oscillatory eye movements with increasing velocity waveforms, as seen in real CN. When we include a stochastic component to the start of each epoch (quick-phase inaccuracy) various observed waveforms (including pseudo-cycloid) emerge as optimal strategies. Using the delay embedding technique, we find a low fractional dimension as reported in real data. We further show that, if a velocity command-based pre-motor circuitry (neural integrator) is harnessed to generate these waveforms, the emergence of a null region is inevitable. We conclude that CN could emerge paradoxically as an ‘optimal’ adaptive response in the infant visual system during an early critical period. This can explain why CN does not emerge later in life and why CN is so refractory to treatment. It also implies that any therapeutic intervention would need to be very early in life.Centro de Geofísica de Évora2012-12-21T10:35:13Z2012-12-212004-01-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/conferenceObjecthttp://hdl.handle.net/10174/6901http://hdl.handle.net/10174/6901engHarris, C.M. & Berry, D.L. A Distal Model of Congenital Nystagmus as Nonlinear Adaptive Oscillations. 12th International Workshop on Nonlinear Dynamics of Electronic Systems 9-13 May 2004, Evora, Portugal.http://www.gbv.de/dms/tib-ub-hannover/494622601.pdfnaonaosimnddberry@uevora.pt360Harris, Christopher M.Berry, David L.info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2024-01-03T18:46:36Zoai:dspace.uevora.pt:10174/6901Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-20T01:01:32.878590Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
A model for the Chaotic Oscillations of Congenital Nystagmus |
title |
A model for the Chaotic Oscillations of Congenital Nystagmus |
spellingShingle |
A model for the Chaotic Oscillations of Congenital Nystagmus Harris, Christopher M. Vision Eye movement disorders |
title_short |
A model for the Chaotic Oscillations of Congenital Nystagmus |
title_full |
A model for the Chaotic Oscillations of Congenital Nystagmus |
title_fullStr |
A model for the Chaotic Oscillations of Congenital Nystagmus |
title_full_unstemmed |
A model for the Chaotic Oscillations of Congenital Nystagmus |
title_sort |
A model for the Chaotic Oscillations of Congenital Nystagmus |
author |
Harris, Christopher M. |
author_facet |
Harris, Christopher M. Berry, David L. |
author_role |
author |
author2 |
Berry, David L. |
author2_role |
author |
dc.contributor.author.fl_str_mv |
Harris, Christopher M. Berry, David L. |
dc.subject.por.fl_str_mv |
Vision Eye movement disorders |
topic |
Vision Eye movement disorders |
description |
Congenital nystagmus (CN) is an incurable pathological spontaneous oscillation of the eyes with an onset in the first few months of life. The pathophysiology of CN is mysterious. There is no consistent neurological abnormality, but the majority of patients have a wide range of unrelated congenital visual abnormalities affecting either the cornea, lens, retina or optic nerve. In this theoretical study, we show that these eye oscillations could develop as an adaptive response to maximize visual contrast with poor foveal function in the infant visuomotor system, at a time of peak neural plasticity. We argue that in a visual system with abnormally poor high spatial frequency sensitivity, image contrast is not only maintained by keeping the image on the fovea (or its remnant) but also by some degree of image motion. Using the calculus of variations, we show that the optimal trade-off between these conflicting goals is to generate oscillatory eye movements with increasing velocity waveforms, as seen in real CN. When we include a stochastic component to the start of each epoch (quick-phase inaccuracy) various observed waveforms (including pseudo-cycloid) emerge as optimal strategies. Using the delay embedding technique, we find a low fractional dimension as reported in real data. We further show that, if a velocity command-based pre-motor circuitry (neural integrator) is harnessed to generate these waveforms, the emergence of a null region is inevitable. We conclude that CN could emerge paradoxically as an ‘optimal’ adaptive response in the infant visual system during an early critical period. This can explain why CN does not emerge later in life and why CN is so refractory to treatment. It also implies that any therapeutic intervention would need to be very early in life. |
publishDate |
2004 |
dc.date.none.fl_str_mv |
2004-01-01T00:00:00Z 2012-12-21T10:35:13Z 2012-12-21 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
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info:eu-repo/semantics/conferenceObject |
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conferenceObject |
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publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10174/6901 http://hdl.handle.net/10174/6901 |
url |
http://hdl.handle.net/10174/6901 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Harris, C.M. & Berry, D.L. A Distal Model of Congenital Nystagmus as Nonlinear Adaptive Oscillations. 12th International Workshop on Nonlinear Dynamics of Electronic Systems 9-13 May 2004, Evora, Portugal. http://www.gbv.de/dms/tib-ub-hannover/494622601.pdf nao nao sim nd dberry@uevora.pt 360 |
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info:eu-repo/semantics/openAccess |
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openAccess |
dc.publisher.none.fl_str_mv |
Centro de Geofísica de Évora |
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Centro de Geofísica de Évora |
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reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
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RCAAP |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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