Organization of the visual cortex in human albinism

MB Hoffmann, DJ Tolhurst, AT Moore… - Journal of …, 2003 - Soc Neuroscience
Journal of Neuroscience, 2003Soc Neuroscience
In albinism there is an abnormal projection of part of the temporal retina to the visual cortex
contralateral to the eye. This projection, together with the normally routed fibers from nasal
retina, provides a cortical hemisphere with visual input from more than the normal hemifield
of visual space. In many mammalian models of albinism, a possible sensory mismatch in the
visual cortex is avoided either by reorganization of the thalamocortical connections to give
the abnormal input an exclusive cortical representation, or by the abnormal input being …
In albinism there is an abnormal projection of part of the temporal retina to the visual cortex contralateral to the eye. This projection, together with the normally routed fibers from nasal retina, provides a cortical hemisphere with visual input from more than the normal hemifield of visual space. In many mammalian models of albinism, a possible sensory mismatch in the visual cortex is avoided either by reorganization of the thalamocortical connections to give the abnormal input an exclusive cortical representation, or by the abnormal input being substantially suppressed. In this study we examine, with fMRI, how the human visual cortex topographically maps its input in albinism. We find that the input from temporal retina is not substantially suppressed and forms a retinotopic mapping that is superimposed on the mapping of the nasal retina in striate and extrastriate areas. The abnormal routing of temporal fibers is not total, with the line of decussation shifting to between 6 and 14° into temporal retina. Our results indicate that the abnormal input to visual cortex in human albinism does not undergo topographic reorganization between the thalamus and cortex. Furthermore, the abnormal input is not significantly suppressed in either striate or extrastriate areas. The topographic mapping that we report in human does not conform, therefore, to the commonly observed patterns in other mammals but takes the form of the “true albino” pattern that has been reported rarely in cat and in the only other individual primate studied.
Soc Neuroscience
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