Abstract
BackgroundWhen studying attentional orienting processes, brain activity elicited by symbolic cue is usually compared to a neutral condition in which no information is provided about the upcoming target location. It is generally assumed that when a neutral cue is provided, participants do not shift their attention. The present study sought to validate this assumption. We further investigated whether anticipated task demands had an impact on brain activity related to processing symbolic cues.Methodology/Principal FindingsTwo experiments were conducted, during which event-related potentials were elicited by symbolic cues that instructed participants to shift their attention to a particular location on a computer screen. In Experiment 1, attention shift-inducing cues were compared to non-informative cues, while in both conditions participants were required to detect target stimuli that were subsequently presented at peripheral locations. In Experiment 2, a non-ambiguous “stay-central” cue that explicitly required participants not to shift their attention was used instead. In the latter case, target stimuli that followed a stay-central cue were also presented at a central location. Both experiments revealed enlarged early latency contralateral ERP components to shift-inducing cues compared to those elicited by either non-informative (exp. 1) or stay-central cues (exp. 2). In addition, cueing effects were modulated by the anticipated difficulty of the upcoming target, particularly so in Experiment 2. A positive difference, predominantly over the posterior contralateral scalp areas, could be observed for stay-central cues, especially for those predicting that the upcoming target would be easy. This effect was not present for non-informative cues.Conclusions/SignificanceWe interpret our result in terms of a more rapid engagement of attention occurring in the presence of a more predictive instruction (i.e. stay-central easy target). Our results indicate that the human brain is capable of very rapidly identifying the difference between different types of instructions.
Highlights
The human mind is capable of selecting and holding sensory information that is task-relevant and discarding what is not relevant
2.1 Experiment 1 The goal of this experiment was to investigate the time-course of the processes involved in attentional orienting, as revealed by comparing eventrelated brain potentials (ERPs) activity elicited by attention shift-inducing cues against a non-informative, ‘‘neutral’’ baseline condition
We investigated the effects of task demands on the attentional orienting processes by manipulating the stimulus onset asynchronies (SOAs) between the cue and the subsequent imperative stimulus, as well by precueing the difficulty of the imperative stimulus
Summary
The human mind is capable of selecting and holding sensory information that is task-relevant and discarding what is not relevant. Of the components that were originally reported in the literature, the early-directing attention negativity (EDAN) [12] was observed as a negatively shifted waveform over the posterior areas contralateral to the location indicated by the cue, at a latency of about 200–300 ms after cue onset. While this component was originally thought to reflect attentional control operations, presumably representing a change in neural sensitivity of the perceptual brain areas, more recent evidence suggested that the EDAN may reflect attentional processing of the cue itself [13]. We further investigated whether anticipated task demands had an impact on brain activity related to processing symbolic cues
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