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IGERT Student Talks - Dr. Sunnia Chai & Rachel Sparks

Monday, April 13, 2009, 12:00pm - 07:00pm

Rutgers University

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Dr. Sunnia Chai, Rutgers University

Binocular rivalry between a sharp image and a low-pass filtered version of itself: Low-pass dominance increases with eccentricity

New corrective techniques ("monovision") for presbyopia correct one eye for near vision and the other for distance vision, creating two different focal distances. Our aim is to investigate relative dominance between a sharp (S) image in one eye and a blurred (B) version of S in the companion eye, mimicking monovision. Casual long observations (>8s) under steady fixation reveal that B's dominance increases as eccentricity increases.

We tested possible binocular rivalry as a function of eccentricity E using two paradigms: (1) We rendered the grey-level images S and B in red-black and green-black (counterbalancing color and spatial frequency content across trials). Observers reported the color of a circular patch at various eccentricities. This effectively indicated the relative dominance of S and B because of the correlation of color and spatial frequency content in the stimuli. (2) Using grey-level images for both eyes, observers detected a probe presented with equal probability to either S or B at various eccentricities. Their performance indicated the relative dominance of S and B, because probes are harder to detect on suppressed images and thresholds increase.

As a rule, S dominated B almost exclusively in the fovea (>80%). Paradigm (1): As E increased, the probability of reporting the color of B increased. Paradigm (2): As E increased, it became significantly more difficult to detect the probe on the S image, whereas detectability did not change significantly with E for the B image. The results in both paradigms are consistent with the following pattern of dominance: The dominance of S and B decreases and increases, respectively, with increasing E. We normally have the illusion of a sharp focused image throughout the visual field. S/B binocular stimulation is a rare case where we are made aware of the low-frequency dominance in the periphery.

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Rachel Sparks, Rutgers University

Tagged magnetic resonance imaging (tMRI) for cardiac motion tracking and classification

tMRI is a medical imaging technique that allows for feature
tracking within the heart muscle. These images thus allow for
anatomically accurate volumetric models of individual human hearts. My
talk will cover previous work done on constructing deformable models from
these images using feature extraction and tracking. Additionally, I will
discuss my plans to extend this work using shape analysis techniques to
classification of these images for medically relevant diagnosis.


IGERT Student Talks - Dr. Sunnia Chai & Rachel Sparks