George A. Geri

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It is estimated by means of electron microscopy that the optic nerve of the turtle Pseudemys scripta elegans contains 394,900 fibers of which approximately 80% are myelinated. The total fiber count agrees well with counts obtained from electron microscopic studies on other turtle species. There are, however, differences among these species in the percentage(More)
In order to test a model of peripheral vision, various contrast sensitivity functions (CSF's) and fundamental eccentricity constants (FEC's) [see J. Opt. Soc. Am. A 8, 1762 (1991)] were applied to real-world, wide-field (6.4 degrees-32 degrees eccentricity) images. The FEC is used to model the change in contrast sensitivity as a function of retinal(More)
BACKGROUND Night-vision goggles (NVGs) provide only a restricted field of view and have other characteristics that may affect the head and eye movements used in visual search. METHODS We measured head scan patterns, the magnitude and duration of gaze saccades, and fixation duration as subjects searched computer generated imagery either with or without(More)
In two experiments, we manipulated the properties of 3-D objects and terrain texture in order to investigate their effects on active heading control during simulated flight. Simulated crosswinds were used to introduce a rotational component into the retinal flow field that presumably provided the visual cues used for heading control An active control task(More)
Similarity ratings were obtained to determine the minimum number of Gabor components that would produce a comparison texture that appeared preattentively similar to a 64-component standard texture. All textures were chosen to be both specifiable by a relatively small number of localized spectral components and sufficiently complex to approximate natural(More)
Intraocular scatter of monochromatic light was assessed in three subjects (ages 21, 38, and 43) using the equivalent veil technique. For an annular stimulus of 3 deg inner and 8 deg outer diameter, the scattered illuminance at the center averaged 1.2% of the surround and was independent of wavelength from 420 to 650 nm. These results are inconsistent with(More)
Saccaadic response preferences and latencies were measured using dual targets presented at 5, 10 and 15 deg along the horizontal meridian in either one or both visual hemifields. In the unihemifield condition, subjects exhibited a strong preference (about 95%) in favor of the target presented closer to the original fixation point. Further, the presence of(More)