VISUAL STABILITY ACROSS SACCADIC EYE MOVEMENTS: BBS Call for Comm.

[Stevan Harnad]

Below is the abstract of a forthcoming target article by BRUCE
BRIDGEMAN et al on VISUAL STABILITY ACROSS SACCADIC EYE MOVEMENTS that
has been accepted for publication in Behavioral and Brain Sciences
(BBS), an international, interdisciplinary journal providing Open Peer
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    A THEORY OF VISUAL STABILITY ACROSS SACCADIC EYE MOVEMENTS

                Bruce Bridgeman
                Program in Experimental Psychology
                University of California
                Santa Cruz, CA 95064

                A.H.C. van der Heijden
                Department of Psychology
                Leiden University
                Wassenaarsweg 52
                2333 AK Leiden, The Netherlands

                Boris M Velichkovsky
                Department for Psychology and Knowledge Engineering
		Moscow State University
                Moscow 103009, Russia

KEYWORDS: space constancy, proprioception, efference copy, space
perception, saccade, eye movement, modularity, visual stability.

ABSTRACT: We identify two aspects of the problem of how there is
perceptual stability despite an observer's eye movements. The first,
visual direction constancy, is the (egocentric) stability of apparent
positions of objects in the visual world relative to the perceiver. The
second, visual position constancy, is the (exocentric) stability of
positions of objects relative to each other. We analyze the constancy
of visual direction despite saccadic eye movements.

Three information sources have been proposed to enable the visual
system to achieve stability: the structure of the visual field,
proprioceptive inflow, and a copy of neural efference or outflow to the
extraocular muscles. None of these sources by itself provides adequate
information to achieve visual direction constancy; present evidence
indicates that all three are used.

Our final question concerns the information processing operations that
result in a stable world. The three traditional solutions involve
elimination, translation, and evaluation. All are rejected. From a
review of the physiological and psychological evidence we conclude that
no subtraction, compensation or evaluation need take place. The problem
for which these solutions were developed turns out to be a false one.
We propose a "calibration" solution: correct spatiotopic positions are
calculated anew for each fixation. Inflow, outflow, and retinal
sources are used in this calculation: saccadic suppression of
displacement bridges the errors between these sources and the actual
extent of movement.

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