Papers available: disparity tuning and motion-stereo integration

[Ning Qian]

The following two papers on disparity tuning of binocular cells and
on motion-stereo integration are available from our WWW homepage at:

http://brahms.cpmc.columbia.edu

-----------------------------------------------------------------------
        Binocular receptive field models, disparity tuning, 
                  and characteristic disparity

                    Yudong Zhu and Ning Qian
                      Columbia University

                (To appear in Neural Computation)

Disparity tuning of visual cells in the brain depends on the structure
of their binocular receptive fields (RFs).  Freeman and coworkers have
found that binocular RFs of a typical simple cell can be
quantitatively described by two Gabor functions with the same Gaussian
envelope but different phase parameters in the sinusoidal modulations
\cite{Freeman90}.  This phase-parameter based RF description, however,
has recently been questioned by \citeasnoun{Wagner93} based on their
identification of a so-called characteristic disparity (CD) in some
cells' disparity tuning curves.  They concluded that their data favor
the traditional binocular RF model which assumes an overall positional
shift between a cell's left and right RFs.  Here we set to resolve
this issue by studying the dependence of cells' disparity tuning on
their underlying RF structures through mathematical analyses and
computer simulations.  We model the disparity tuning curves in Wagner
and Frost's experiments and demonstrate that the mere existence of
approximate CDs in real cells cannot be used to distinguish the
phase-parameter based RF description from the traditional
position-shift based RF description.  Specifically, we found that
model simple cells with either type of RF description do not have a
CD.  Model complex cells with the position-shift based RF description
have a precise CD, and those with the phase-parameter based RF
description have an approximate CD.  We also suggest methods for
correctly distinguishing the two types of RF descriptions.  A hybrid
of the two RF models may be required to fit the behavior of some real
cells and we show how to determine the relative contributions of the
two RF models.

This paper is also available from NEUROPROSE:

FTP-host: archive.cis.ohio-state.edu
FTP-filename: /pub/neuroprose/qian.cd.ps.Z

......................................................................

A Physiological Model for Motion-stereo Integration and a Unified 
          Explanation of the Pulfrich-like Phenomena

              Ning Qian and Richard A. Andersen
               Columbia University and Caltech

               (To appear in Vision Research)

Many psychophysical and physiological experiments indicate that visual
motion analysis and stereoscopic depth perception are processed
together in the brain.  However, little computational effort has been
devoted to combining these two visual modalities into a common
framework based on physiological mechanisms.  We present such an
integrated model in this paper.  We have previously developed a
physiologically realistic model for binocular disparity computation
\cite{Qian94e}.  Here we demonstrate that under some general and
physiological assumptions, our stereo vision model can be combined
naturally with motion energy models to achieve motion-stereo
integration.  The integrated model may be used to explain a wide range
of experimental observations regarding motion-stereo interaction.  As
an example, we show that the model can provide a unified account of
the classical Pulfrich effect \cite{Morgan75} and the generalized
Pulfrich phenomena to dynamic noise patterns \cite{Tyler74,Falk80} and
stroboscopic stimuli \cite{Burr79}.

-----------------------------------------------------------------------