Temporal Uncertainty Separates Flashes from Their Background during Saccades

Abstract

It is known that spatial localization of flashed objects fails around the time of rapid eye movements (saccades). This mislocalization is often interpreted in terms of a combination of shifts and deformations of the brain's representation of space to account for the eye movement. Such temporary remapping of positions in space should affect all elements in a scene, leaving ordinal relationships between positions intact. We performed an experiment in which we presented flashes on a background with red and green regions to human subjects. We found that flashes that were presented on the green part of the background around the time of a saccade were readily reported to have been presented on the red part of the background and vice versa. This is inconsistent with the notion of a temporary shift and deformation of perceived space. To explain our results, we present a model that illustrates how temporal uncertainty could give rise to the observed spatial mislocalization. The model combines uncertainty about the time of the flash with a bias to localize targets where one is looking. It reproduced the pattern of mislocalization very accurately, showing that perisaccadic mislocalization can best be explained in terms of temporal uncertainty about the moment of the flash.

Spatiotemporal integration for tactile localization during arm movements: a probabilistic approach

“…These models are able to explain compression effects but not the localization biases independently of flash location. Indeed, a recent model that can explain both compression and biases is a temporal uncertainty model (Maij et al 2011a;Maij et al, unpublished observations), which also provides the basis of the present tactile localization model.…”

“…Note that the perisaccadic localization model by Maij et al (2011a; unpublished observations) also includes a foveal bias, to represent the brain's assumption that if flashes are perceived then they must have occurred close to the fovea (Brenner et al 2006(Brenner et al , 2008. Maij et al (2011a;unpublished observations) modeled this foveal bias as an a priori distribution centered on the direction of gaze at the moment of the flash, resulting in the flash being attracted to the fovea, i.e., a compression toward eye position (e.g., Lappe et al 2000;Ross et al 1997).…”

“…Maij et al (2011a;unpublished observations) modeled this foveal bias as an a priori distribution centered on the direction of gaze at the moment of the flash, resulting in the flash being attracted to the fovea, i.e., a compression toward eye position (e.g., Lappe et al 2000;Ross et al 1997). In the tactile localization model we assume the prior distribution to be flat.…”

“…We developed a tactile localization model, following an approach similar to that proposed for perisaccadic mislocalization of briefly presented visual stimuli (Maij et al 2011a;Maij et al, unpublished observations). Figure 2A shows a graphical description of the model, which assumes statistically optimal processing of the sensory signals involved, including the tactile receptors and arm position signals.…”

“…That is, human participants make systematic errors when localizing objects flashed around the time of saccades (Honda 1989;Lappe et al 2000;Maij et al 2009;Mateeff 1978;Matin and Pearce 1965;Ross et al 1997;Schlag and Schlag-Rey 1995). While previous models suggest that these localization errors arise from the temporal low-pass filtering properties of retinal (Pola 2004(Pola , 2007 or extraretinal (Dassonville et al 1992) processing, a more recent account suggests that temporal uncertainty in combining information about the object's retinal location and information about eye position is responsible for the mislocalization effect (Maij et al 2011a;Maij et al, unpublished observations). Would this account of temporal uncertainty generalize to errors in dynamic tactile localization?…”