Human discrimination of visual direction of motion with and without smooth pursuit eye movements

Anton E. Krukowski*, Kathleen A. Pirog, Brent R. Beutter, Kevin R. Brooks, Leland S. Stone

*Corresponding author for this work

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

It has long been known that ocular pursuit of a moving target has a major influence on its perceived speed (Aubert, 1886; Fleischl, 1882). However, little is known about the effect of smooth pursuit on the perception of target direction. Here we compare the precision of human visual-direction judgments under two oculomotor conditions (pursuit vs. fixation). We also examine the impact of stimulus duration (200 ms vs. ∼800 ms) and absolute direction (cardinal vs. oblique). Our main finding is that direction discrimination thresholds in the fixation and pursuit conditions are indistinguishable. Furthermore, the two oculomotor conditions showed oblique effects of similar magnitudes. These data suggest that the neural direction signals supporting perception are the same with or without pursuit, despite remarkably different retinal stimulation. During fixation, the stimulus information is restricted to large, purely peripheral retinal motion, while during steady-state pursuit, the stimulus information consists of small, unreliable foveal retinal motion and a large efference-copy signal. A parsimonious explanation of our findings is that the signal limiting the precision of direction judgments is a neural estimate of target motion in head-centered (or world-centered) coordinates (i.e., a combined retinal and eye motion signal) as found in the medial superior temporal area (MST), and not simply an estimate of retinal motion as found in the middle temporal area (MT).

Original languageEnglish
Pages (from-to)831-840
Number of pages10
JournalJournal of Vision
Volume3
Issue number11
DOIs
Publication statusPublished - 17 Dec 2003
Externally publishedYes

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