Optimal transfer of form and color information through the primate retina [electronic resource].

Hsu, Andrew Chen-Chou.
103 p.
Biomedical engineering
Local subjects:
Penn dissertations -- Neuroscience.
Neuroscience -- Penn dissertations.
System Details:
Mode of access: World Wide Web.
Processing and encoding of visual information begins at the first stage of the primate retina. Here, anatomical structures such as photoreceptor morphology, electrical coupling of cones, cone packing arrangement and density, and cone input to ganglion cells begin to shape luminance and hue information for transfer to further stages. We explored the significance of axon dimensions in the propagation of a graded voltage signal using a compartmental model of a primate rod and cone. Except for the longest foveal cones, axon dimensions do not limit efficient transfer of voltage. The metabolic constraint of transporting synaptic vesicles limits the axon morphology. Next, we evaluated the contribution of electrical coupling at the cone terminal by extending the ideal observer analysis of the visual system into the level of cone terminals. Coupling improves contrast sensitivity by about 50% at low spatial frequencies, which constitute more of the information content in natural scenes. At high frequencies, coupling reduces sensitivity and lowers spatial acuity. Cone coupling also has an additional cost for trichromacy. We evaluated this cost by constructing a model of the cone array and calculating how the action spectrum of each cone type is affected. A short-wavelength sensitive cones can not be coupled much without severely altering its action spectrum. Middle and long wavelength sensitive cones can be coupled with minimal impact on their spectra. Furthermore, it appears that the random arrangement of middle and long wavelengths sensitive cones minimizes the spectral blurring. Finally, to investigate which ganglion cell array might best serve as the anatomical site for the L-M opponent site, we extended the retinal model to the ganglion cell array and investigated the hue encoding capability of midget ganglion cells and putative L/M type II cells using an ideal observer. Performance of the ideal observer at the type II array on a threshold detection task designed to isolate human opponent mechanisms best matches human performance.
Thesis (Ph.D. in Neuroscience) -- University of Pennsylvania, 1998.
Source: Dissertation Abstracts International, Volume: 59-04, Section: B, page: 1521.
Advisers: Peter Sterling.
Local notes:
School code: 0175.
Sterling, Peter, advisor
University of Pennsylvania.
Contained In:
Dissertation Abstracts International 59-04B.
Access Restriction:
Restricted for use by site license.
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