Redwood Neuroscience
Title: Cortical disarray, undersampling and oversampling in
strabismic amblyopia: A
case study.
Abstract:
Amblyopia, a major cause of vision loss, is a developmental
disorder of visual perception commonly associated with strabismus
(squint). Although defined by a reduction
in visual acuity, severe distortions of perceived visual location are common in
strabismic amblyopia. These distortions can help us understand the
cortical coding of visual location and its development in normal vision, as
well as amblyopia.
The history of retinotopic mapping in the
visual cortex highlights the potential impact of amblyopia. Theories of amblyopia
include topological disarray of receptors in primary visual cortex, undersampling from the amblyopic eye compared with normal
eyes, and the presence of anomalous retinal correspondence or multiple cortical
representations of the strabismic fovea. We examined the distortions in a strabismic amblyope, using a popout localization task, in which normal observers made
errors dependent on the visual context of the stimulus. The localization errors of the strabismic amblyope were
abnormal. We found that none of the available theories could fully explain this
one patient's localization performance.
Instead, the observed behavior suggests multiple adaptations of the
underlying cortical topology are possible simultaneously in different parts of
the visual field.