Discrete and continuous mechanisms of temporal selection in rapid visual streams

Sébastien Marti,Stanislas Dehaene

doi:10.1038/s41467-017-02079-x

Abstract

Humans can reliably detect a target picture even when tens of images are flashed every second. Here we use magnetoencephalography to dissect the neural mechanisms underlying the dynamics of temporal selection during a rapid serial visual presentation task. Multivariate decoding algorithms allow us to track the overlapping brain responses induced by each image in a rapid visual stream. The results show that temporal selection involves a sequence of gradual followed by all-or-none stages: (i) all images first undergo the same parallel processing pipeline; (ii) starting around 150 ms, responses to multiple images surrounding the target are continuously amplified in ventral visual areas; (iii) only the images that are subsequently reported elicit late all-or-none activations in visual and parietal areas around 350 ms. Thus, multiple images can cohabit in the brain and undergo efficient parallel processing, but temporal selection also isolates a single one for amplification and report.

Highlights

Humans can reliably detect a target picture even when tens of images are flashed every second
A subset of the available information is selected in space and time[1,2,3,4], and gated to awareness. Such parallel followed by serial processing is exemplified in rapid serial visual presentation (RSVP), an experimental paradigm in which series of stimuli are briefly flashed on a screen
We explored the dynamics of the selection mechanisms

Summary

Introduction

Humans can reliably detect a target picture even when tens of images are flashed every second. A subset of the available information is selected in space and time[1,2,3,4], and gated to awareness Such parallel followed by serial processing is exemplified in rapid serial visual presentation (RSVP), an experimental paradigm in which series of stimuli are briefly flashed on a screen (typically ~ 10 per second). The alternative hypothesis is that attention selects a single item at a given time, but operates serially over multiple items, enhancing the target stimulus and the surrounding distractors one after the other (“discrete selection”, Fig. 1a) Separating those two possibilities is fundamental to understand the overall parallel/serial architecture of vision and visual awareness

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