ABSTRACT
Macular degeneration (MD) is retinal disease that causes severe visual impairment in nearly 7 million people in
the U.S. This disease causes the progressive deterioration of photoreceptors in the center of the retina, known
as the macula, and renders patients unable to see in the center of the visual field. As a consequence, patients
with MD must rely on peripheral vision, making even the simplest everyday tasks, such as reading or
recognizing faces, much more difficult. Reliance on peripheral vision is extremely problematic, as it possesses
substantially lower resolution compared to central vision. In fact, many patients never fully adapt to using
peripheral vision effectively. Interestingly, however, some patients become particularly skilled at using their
spared peripheral vision. Prior work suggests that this adaptation to using peripheral vision happens at a
processing stage beyond the retina, specifically in visual cortex. There is debate in the literature about
whether or not brain regions that formerly responded to central (lost) vision remap their function to respond to
peripheral (spared) vision. We address a different form of plasticity here: remodeling of the brain regions
which originally responded to peripheral (spared) vision so that they are more capable of taking on the
functions of central vision. Our hypothesis is that peripherally-representing visual cortex builds new
connections after experience, and this changes the structure and function of that region. Using neuroimaging
(Magnetic Resonance Imaging) in human participants, we have generated preliminary evidence that suggests
that some of these changes may exist in the form of alterations to brain structure (neurite density and cortical
thickness) and brain function (functional connectivity). For example, we have observed that the parts of visual
cortex that respond to peripheral vision have greater cortical thickness in MD patients compared to healthy
controls, suggesting a possible compensatory mechanism that may be associated with enhanced use of
peripheral vision. Additionally, we have observed that peripheral regions of early visual cortex in MD patients
are more strongly functionally connected to later visual areas that selectively respond to specific types of visual
stimuli, such as facial features and words/letters. We will test the hypothesis that better use of peripheral
vision in MD is associated with enhanced functional connectivity and enhanced structure (neurite
density and cortical thickness). More specifically, we predict that enhanced visual function in MD will be
related to stronger functional connectivity between peripheral areas of primary visual cortex and later visual
areas that respond preferentially to categories of stimuli (i.e.- faces, and words). Additionally, we predict that
greater neurite density and cortical thickness in primary visual cortex will be related to behavioral performance
on visual processing tasks. These findings will help provide insight towards improving therapeutic interventions
for MD, as well as uncover knowledge about the adult brain’s potential for adaptation to changes in experience.