October 01, 2009 — The Biomedical Engineering Society has selected Xiwu Cao, a PhD student
in Biomedical Engineering, to receive a Graduate Research Award for his
paper, entitled "Dependence of Retinal Ganglion Cell Responses on
Textures of Natural Scenes". This paper will be presented in the form of
a platform presentation at the 2009 Biomedical Engineering Society
Conference in Pittsburgh (October 7-9).

Cao conducted his research under the supervision of Professor Norberto
Grzywacz. The overarching goal of his project is to aid the development
of a retinal prosthesis by building a computational model of how retinal
ganglion cells (RGCs) respond to natural images. Cao's study showed
that, to design correct camera-electrode transformations to stimulate
RGCs, one should not overlook the contributions from visual textures of
light stimuli. To explain the response to textures, he proposed
abandoning the standard model of retinal processing, which
mathematically, consists of a linear filter followed by a point/static
nonlinearity (rectification and/or saturation). Instead, he demonstrated
that one can account for the data by assuming that the filter
implemented by the RGC integrates the outputs of multiple nonlinear
subunits, which originate in either its dendrites or its presynaptic
inputs. Earlier this year, Cao won the BME department's top graduate
prize, the 2009 Grodins Graduate Award.