The Fastest Saccadic Responses Escape Visual Masking

Sébastien M. Crouzet,Morten Overgaard,Niko A. Busch,Elkan Akyürek

doi:10.1371/journal.pone.0087418

Abstract

Object-substitution masking (OSM) occurs when a briefly presented target in a search array is surrounded by small dots that remain visible after the target disappears. The reduction of target visibility occurring after OSM has been suggested to result from a specific interference with reentrant visual processing while the initial feedforward processing is thought to be left intact. We tested a prediction derived from this hypothesis: the fastest responses, being triggered before the beginning of reentrant processing, should escape the OSM interference. In a saccadic choice reaction time task, which gives access to very early stages of visual processing, target visibility was reduced either by OSM, conventional backward masking, or low stimulus contrast. A general reduction of performance was observed in all three conditions. However, the fastest saccades did not show any sign of interference under either OSM or backward masking, as they did under the low-contrast condition. This finding supports the hypothesis that masking interferes mostly with reentrant processing at later stages, while leaving early feedforward processing largely intact.

Highlights

The interplay between feedforward and feedback processing is crucial for visual perception [1,2,3,4]
Accuracy Overall accuracy was identical in the Object-substitution masking (OSM), backward masking, and low-contrast conditions, but significantly lower compared to the common-offset condition (Fig. 2A, post-hoc tests corrected for multiple comparisons using a Tukey HSD criterion following a single-factor ANOVA with four conditions; F(3,12) = 9.43; Figure 2
Minimum saccadic reaction time (SRT) averaged across observers were in the range of previous reports using a similar protocol with natural scenes (Fig. 2C, from 125 ms in the backward masking to 152.5 ms in the low-contrast condition, see for example [19])

Summary

Introduction

The interplay between feedforward and feedback processing is crucial for visual perception [1,2,3,4] In psychophysics, this interplay has often been studied using visual masking [5,6], and object-substitution masking (OSM, referred to as commononset or four-dot masking). OSM occurs when a briefly presented target in a search array is surrounded by small dots that remain visible after the target disappears [2]. It is difficult for standard models of backward masking to account for the effect of such a trailing mask [2,7] (but see [8]). In contrast to other forms of masking such as backward masking [9], OSM has been proposed to selectively disrupt reentrant processing while leaving the initial feedforward sweep intact [10]

Objectives

Methods

Results

Conclusion