a neural model of smooth pursuit control and motion perception by MST

[Stephen Grossberg]

The following article is available at
http://www.cns.bu.edu/Profiles/Grossberg  in HTML, PDF, and Gzipped
postscript:

Pack, C., Grossberg, S. and Mingolla, E. (2000).  A neural model of smooth
pursuit control and motion perception by cortical area MST. Journal of
Cognitive Neuroscience, in press. Preliminary version available as
Technical Report CAS/CNS-TR-99-023, Boston: Boston University.

ABSTRACT:
Smooth pursuit eye movements are eye rotations that are used to maintain
fixation on a moving target.  Such rotations complicate the interpretation
of the retinal image, because they nullify the retinal
motion of the target, while generating retinal motion of stationary objects
in the background.  This poses a problem for the oculomotor system, which
must track the stabilized target image, while suppressing the optokinetic
reflex, which would move the eye in the direction of the retinal background
motion, which is opposite to the direction in which the target is moving.
Similarly, the perceptual system must estimate the actual direction and
speed of moving objects in spite of the confounding effects of the eye
rotation.  This paper proposes a neural model to account for the ability of
primates to accomplish these tasks.  The model simulates the
neurophysiological properties of cell types found in the superior  temporal
sulcus of the macaque monkey, specifically the medial superior temporal
(MST) region.  These cells process signals related to target motion,
background motion, and receive an efference copy of eye velocity during
pursuit movements.  The model focuses on the interactions between cells in
the ventral and dorsal subdivisions of MST, which are hypothesized to
process target velocity and background motion, respectively.  The model
explains how these signals can be combined to explain behavioral data about
pursuit maintenance and perceptual data from human studies, including the
Aubert-Fleischl phenomenon and the Filehne Illusion, thereby clarifying the
functional significance of  neurophysiological data about these MST cell
properties.  It is suggested that the connectivity used in the model may
represent a general strategy used by the brain in analyzing the visual
world.

Keywords: smooth pursuit, eye movements, visual cortex, MST, motion,
optokinetic nystagmus, target tracking, perception