|
|
|
 |
A. Ravishankar Rao
IBM T.J. Watson Research Center Yorktown Heights, NY
Friday, Feb. 4, 11:00am
LC 102, Brooklyn Campus, Polytechnic University
In this talk we address the problem of understanding the
cortical processing of color information. Unravelling the cortical
representation of color is a difficult task, as the neural pathways for
color processing have not been fully mapped, and there are few
computational modelling efforts devoted to color. Hence, we first
present a conjecture for an ideal target color map based on principles
of color opponency, and constraints such as retinotopy and the two
dimensional nature of the map.
We develop a computational model for the cortical processing of color
information that seeks to produce this target color map in a
self-organized manner. The input model consists of a luminance channel
and opponent color channels, comprising red-green and blue-yellow
signals. We use an optional stage consisting of applying an antagonistic
center-surround filter to these channels. The input is projected to a
restricted portion of the cortical network in a topographic way.
The units in the cortical map receive the color opponent input, and
compete amongst each other to represent the input. This competition is
carried out through the determination of a local winner. By simulating
a self-organizing map for color according to this scheme, we are largely
able to achieve the desired target color map. According to recent
neurophysiological findings, there is evidence for the representation of
color mixtures in the cortex, which is consistent with our model.
Furthermore, an orderly traversal of stimulus hues in the CIE
chromaticity map correspond to an orderly spatial traversal in the
primate cortical area V2. Our experimental results are also consistent
with this biological observation.
(Joint work with Guillermo Cecchi, Charles Peck and James Kozloski, also
at IBM Research)
For more information please contact Nasir Memon (memon at poly.edu).