Haphazard neural connections underlie the visual deficits of cats with strabismic or deprivation amblyopia. 2005

Guy Gingras, and Donald E Mitchell, and Robert F Hess
Psychology Department, Dalhousie University, Halifax Nova Scotia, B3H 4J1, Canada.

Identification of the neural basis of the visual deficits experienced by humans with amblyopia, particularly when associated with strabismus (strabismic amblyopia), has proved to be difficult in part because of the inability to observe directly the neural changes at various levels of the human visual pathway. Much of our knowledge has necessarily been obtained on the basis of sophisticated psychophysical studies as well as from electrophysiological explorations on the visual pathways in animal models of amblyopia. This study combines these two approaches to the problem by employing similar psychophysical probes of performance on animal models of two forms of amblyopia (deprivation and strabismic) to those employed earlier on human amblyopes (Hess & Field, 1994, Vis. Res., 34, 13397-13406). The tests explore two competing explanations for the visual deficits, namely an evenly distributed loss of neural connections (undersampling) with the amblyopic eye as opposed to disordered connections with this eye (neural disarray). Unexpectedly, the results in animal models of deprivation amblyopia were not in accord with expectations based upon an even distribution of lost connections with the amblyopic eye. However, the results were similar to those observed in a strabismic amblyopic animal and to strabismic amblyopic humans. We suggest that deprivation amblyopia may be accompanied by an uneven loss of connections that results in effective neural disarray. By contrast, amblyopia associated with strabismus might arise from neural disarray of a different origin such as an alteration of intrinsic cortical connections.

UI MeSH Term Description Entries
D009434 Neural Pathways Neural tracts connecting one part of the nervous system with another. Neural Interconnections,Interconnection, Neural,Interconnections, Neural,Neural Interconnection,Neural Pathway,Pathway, Neural,Pathways, Neural
D001766 Blindness The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of EYE DISEASES; OPTIC NERVE DISEASES; OPTIC CHIASM diseases; or BRAIN DISEASES affecting the VISUAL PATHWAYS or OCCIPITAL LOBE. Amaurosis,Bilateral Blindness,Blindness, Bilateral,Blindness, Legal,Blindness, Monocular,Blindness, Unilateral,Sudden Visual Loss,Unilateral Blindness,Blindness, Acquired,Blindness, Complete,Blindness, Hysterical,Blindness, Transient,Acquired Blindness,Amauroses,Bilateral Blindnesses,Complete Blindness,Hysterical Blindness,Legal Blindness,Monocular Blindness,Sudden Visual Losses,Transient Blindness,Visual Loss, Sudden
D002415 Cats The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801) Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D002450 Cell Communication Any of several ways in which living cells of an organism communicate with one another, whether by direct contact between cells or by means of chemical signals carried by neurotransmitter substances, hormones, and cyclic AMP. Cell Interaction,Cell-to-Cell Interaction,Cell Communications,Cell Interactions,Cell to Cell Interaction,Cell-to-Cell Interactions,Communication, Cell,Communications, Cell,Interaction, Cell,Interaction, Cell-to-Cell,Interactions, Cell,Interactions, Cell-to-Cell
D002454 Cell Differentiation Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs. Differentiation, Cell,Cell Differentiations,Differentiations, Cell
D004195 Disease Models, Animal Naturally-occurring or experimentally-induced animal diseases with pathological processes analogous to human diseases. Animal Disease Model,Animal Disease Models,Disease Model, Animal
D000550 Amblyopia A nonspecific term referring to impaired vision. Major subcategories include stimulus deprivation-induced amblyopia and toxic amblyopia. Stimulus deprivation-induced amblyopia is a developmental disorder of the visual cortex. A discrepancy between visual information received by the visual cortex from each eye results in abnormal cortical development. STRABISMUS and REFRACTIVE ERRORS may cause this condition. Toxic amblyopia is a disorder of the OPTIC NERVE which is associated with ALCOHOLISM, tobacco SMOKING, and other toxins and as an adverse effect of the use of some medications. Anisometropic Amblyopia,Lazy Eye,Amblyopia, Developmental,Amblyopia, Stimulus Deprivation-Induced,Amblyopia, Suppression,Stimulus Deprivation-Induced Amblyopia,Amblyopia, Anisometropic,Amblyopia, Stimulus Deprivation Induced,Amblyopias,Amblyopias, Anisometropic,Amblyopias, Developmental,Amblyopias, Stimulus Deprivation-Induced,Amblyopias, Suppression,Anisometropic Amblyopias,Deprivation-Induced Amblyopia, Stimulus,Deprivation-Induced Amblyopias, Stimulus,Developmental Amblyopia,Developmental Amblyopias,Eye, Lazy,Eyes, Lazy,Lazy Eyes,Stimulus Deprivation Induced Amblyopia,Stimulus Deprivation-Induced Amblyopias,Suppression Amblyopia,Suppression Amblyopias
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D000831 Animals, Newborn Refers to animals in the period of time just after birth. Animals, Neonatal,Animal, Neonatal,Animal, Newborn,Neonatal Animal,Neonatal Animals,Newborn Animal,Newborn Animals
D012683 Sensory Deprivation The absence or restriction of the usual external sensory stimuli to which the individual responds. Deprivation, Sensory,Deprivations, Sensory,Sensory Deprivations

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