Expectation Suppression in Early Visual Cortex Depends on Task Set.

Elexa St John-Saaltink,Christian Utzerath,Hakwan C Lau,Peter Kok,Floris P De Lange,Suliann Ben Hamed

doi:10.1371/journal.pone.0131172

Elexa St John-Saaltink, Christian Utzerath + Show 4 more

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https://doi.org/10.1371/journal.pone.0131172

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Abstract

Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response. However, it is unclear whether this expectation suppression is an automatic phenomenon or is instead dependent on the type of task a subject is engaged in. To investigate this, human subjects were presented with visual grating stimuli in the periphery that were either predictable or non-predictable while they performed three tasks that differently engaged cognitive resources. In two of the tasks, the predictable stimulus was task-irrelevant and spatial attention was engaged at fixation, with a high load on either perceptual or working memory resources. In the third task, the predictable stimulus was task-relevant, and therefore spatially attended. We observed that expectation suppression is dependent on the cognitive resources engaged by a subjects’ current task. When the grating was task-irrelevant, expectation suppression for predictable items was visible in retinotopically specific areas of early visual cortex (V1-V3) during the perceptual task, but it was abolished when working memory was loaded. When the grating was task-relevant and spatially attended, there was no significant effect of expectation in early visual cortex. These results suggest that expectation suppression is not an automatic phenomenon, but dependent on attentional state and type of available cognitive resources.

Highlights

Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response [1, 2]
While valid expectations about task-relevant stimulus features often lead to behavioural improvements, post-hoc t-tests on behavioural data from the grating task confirmed that there was no behavioural benefit of predictability on accuracy (t32 = -1.03, p = 0.31) or RT (t32 = -0.20, p = 0.84)
To probe whether the effect of expectation depended on the task participants engaged in, we investigated the BOLD response in voxels in primary visual cortex that responded to the grating stimuli

Summary

Introduction

Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response [1, 2] This effect has been found in visual [1, 3, 4] and auditory [5, 6] cortices, and in both electrophysiological [1, 5] and haemodynamic [3, 4, 7] measurements. In contrast to this notion other authors found no effect of expectation on sensory activity when stimuli were unattended [9], suggesting that expected background stimuli are not automatically suppressed

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