Saccadic eye movements and localization of visual stimuli

Abstract

Visual localization phenomena were studied before, during, and after a saccade. Light flashes of .5 and 9 msec duration presented before and during the eye movement were mislocated in the saccade direction, the localization error being a time function. When the 9-msec duration stimulus and saccade did not overlap in time, a stripe was reported, when they did not, the stimulus was perceived as a point. If a long-duration stimulus moved perpendicularly to the saccade direction with the same "sigmoidal" velocity, a curvilinear trace was perceived, regardless of the linear trace of the image on the retina. A stimulus with stabilized retinal image was perceived as a stationary point during the saccade. A possible theory to deal with the data was suggested by modifying the algebra of outflow-inflow theories.When a visual stimulus is presented, one of the tasks presented to our visual system is to answer the question, "Where is it?" Our everyday experience shows this task to be performed relatively well. What is more, usually we localize surrounding objects properly, no matter where we look. In spite of the fact that a shift of gaze results in changes of the loci of the retinal image, under normal conditions object localization remains constant. This property of the visual system is known as "position constancy."Two of the explanations of position constancy are provided by the outflow and inflow theories, which are described briefly as follows. A center, or mechanism, which receives two "messages" is assumed to exist in the visual system. The first of these "messages" concerns the locus of the retinal image. The second provides information about the position of the eye. These two "messages" are somehow summated algebraically, and the resultant of this operation determines the perceived locus of the object. The difference between the two theories concerns the source of the information about eye position. According to the outflow theory (Holst, 1954;Holst & Mittelstaedt, 1950), this "message" comes from a hypothetical neural center from which the command to turn the eye originates, and it is thought that the "message" is a copy of the command for the eye movement. According to the alternative inflow theory (Sherrington, 1918), eye muscle proprioception provides this information.We will not deal with the outflow-inflow controversy in the present paper. The fact of importance for us is that both theories imply the same algebraic operations between information about the retinal locus of the object and about position of the eye. Thus, we shall consider them as one theory and call it "subtraction theory."Several authors (Bischof & Kramer, 1968;Matin, 1972;Matin & Matin, 1972; Matin, Matin, &Pearce, 1969;Matin, Matin, & Pola, 1970; Matin & Pearce, 1965;Monahan, 1972) have shown that a brief light stimulus presented during or just before voluntary saccadic eye movements is frequently mislocated by considerable amounts. The size of the error depends on the time at which the stimulus is presented relative to the saccade onset.M...

The Flash-Lag Phenomenon: Object Motion and Eye Movements

“…On the other hand, visible persistence of the flash is responsible for its later apparent displacement during the`visibility' phase, which is completely analogous to the movement of the afterimage during pursuit. A similar account may be given for other eye-movement-based flash mislocalization effects (Mach 1897;MacKay 1958MacKay , 1970Matin and Pearce 1965;Matin 1972;Mateeff 1978;O'Regan 1984;Honda 1989). …”

“…The disk was perceived as displaced in the direction of pursuit relative to the ring, and observers saw a vivid crescent-shaped`perceived void' (percept). Mislocalization of flashes caused by various types of eye movements has been investigated before (Mach 1897;MacKay 1958;Matin and Pearce 1965;MacKay 1970;Matin 1972;Ward 1976;Mateeff 1978;O'Regan 1984;Honda 1989). MacKay (1970) was the first to raise the possibility that saccadic mislocalization of test flashes was not due to saccadic eye movements per se.…”

The Geometry of Perisaccadic Visual Perception

“…However, in the laboratory it becomes possible to induce highly inaccurate spatial percepts that may provide insights into the brain mechanisms that underlie the perception of visual space. Specifically, previous work has shown that visual localization for probe stimuli presented briefly near the onset of saccades are characterized by a shift of the perceived position of the probe in the direction of the saccade (Matin and Pearce, 1965;Mateeff, 1978;Honda, 1989Honda, , 1991Schlag and Schlag-Rey, 1995;Lappe et al, 2000), and a compression of visual space, wherein subjects report that probe stimuli are closer to the saccade target than they really are (Honda, 1993;Morrone et al, 1997;Ross et al, 1997;Lappe et al, 2000;Kaiser and Lappe, 2004).…”

“…Consequently, the value of k 1 in this formulation is not meant to have any physiological significance, as it merely scales the relationship between two dimensionless quantities. Equation 5 does not account for an important feature of the data, namely the unidirectional shift in perceived LT position that accompanies perisaccadic compression (Matin and Pearce, 1965;Mateeff, 1978;Honda, 1989Honda, , 1991; Schlag and Schlag-Rey, 1995; Lappe et al, 2000) (see Introduction). As the shift phenomenon appears to depend far more on the temporal than the spatial structure of the stimulus (Schlag and Schlag-Rey, 1995;Pola, 2004), we have not attempted to incorporate it explicitly into our space-domain model.…”

Fusion of Visual and Auditory Stimuli during Saccades: A Bayesian Explanation for Perisaccadic Distortions

“…When asked to report the position of a visual stimulus flashed just before a saccade, subjects mislocated it, primarily in the direction of the saccade (Matin and Pearce, 1965;Mateeff, 1978;Honda, 1989). Typically, localization errors start up to 100 ms before saccadic onset and continue well after the saccade finishes, being maximal at saccadic onset.…”