Parallel attentional facilitation of features and objects in early visual cortex.

Nika Adamian,Søren K Andersen,Steven A Hillyard

doi:10.1111/psyp.13498

Nika Adamian, Søren K Andersen + Show 1 more

Open Access

https://doi.org/10.1111/psyp.13498

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Abstract

Selective attention can enhance the processing of attended features across the entire visual field. Attention also spreads within objects, enhancing all internal locations and task‐irrelevant features of selected objects. Here, we examine the extent to which attentional enhancement of a feature spreads across attended and unattended objects. Two fully overlapping counter‐rotating bicolored surfaces of light and dark random dots were presented on a gray background of intermediate luminance. This stimulus creates a percept of two separate semitransparent surfaces and allows the measurement of feature‐ and object‐based selections while controlling spatial attention. On each trial, human participants attended to a subset of dots defined by feature (luminance polarity) and object (surface) in order to detect brief episodes of radial motion while ignoring any events in the unattended groups of dots. Attentional selection was assessed by means of steady‐state visual evoked potentials (SSVEPs) and behavioral measures. SSVEP amplitudes recorded at medial occipital electrode sites were modulated both by surface‐based and luminance polarity‐based selection in a manner consistent with independent multiplicative enhancement of attentional effects in different dimensions in early visual cortex. This finding supports the view that feature‐based attention spreads across object boundaries, at least at an early stage of processing. However, SSVEPs elicited at more lateral electrode sites showed a hierarchical pattern of selection, potentially reflecting the binding of surface‐defining features with luminance features to enable surface‐based attention.

Highlights

The visual system has a limited processing capacity and is continuously bombarded with sensory stimulation
If feature‐ based attentional selection is not constrained by object boundaries, feature‐based enhancement of the attended dots should be extended to the dots of the attended luminance belonging to the unattended surface
This study set out to test the extent to which object‐based attention restricts the global spread of feature‐based enhancement

Summary

| INTRODUCTION

The visual system has a limited processing capacity and is continuously bombarded with sensory stimulation. The results typically show that translations in the attended surface are reported more accurately than translations in the unattended surface, suggesting that the cued perceptual surface is preferentially processed This form of surface‐based attention requires binding of continuously moving elements into a cohesive object and rules out the possibility of selection by space (surfaces are superimposed) or by a singular feature (direction of target motion is unpredictable). Festman and Braun (2010, 2012) found that the spread of surface‐based attention conforms to the global motion flow rather than following linear motion direction, suggesting that moving surfaces are treated like integrated objects and not as instances of local motion Overall, these studies support the view that surface‐based selection is a (perhaps primitive) form of object‐based selection, and surface boundaries might constrain the spread of purely feature‐based attention. If such constraints exist, the transfer of feature‐based attentional enhancement from one surface to the other should be impeded

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| RESULTS

Findings

| DISCUSSION