Trends in Cognitive Sciences
Volume 4, Issue 11, 1 November 2000, Pages 432-440
Journal home page for Trends in Cognitive Sciences

Review
Event-related potential studies of attention

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Abstract

Over the past 30 years, recordings of event-related potentials (ERPs) from normal individuals have played an increasingly important role in our understanding of the mechanisms of attention. This article reviews some of the recent ERP studies of attention, focusing on studies that isolate the operation of attention in specific cognitive subsystems such as perception, working memory, and response selection. Several conclusions are drawn. First, under some conditions attention modulates the initial feedforward volley of neural activity in intermediate visual processing areas. Second, these early effects can be observed for both the voluntary allocation of attention and for the automatic capture of attention following a peripheral visual transient. Third, these effects are present not only when attention is directed to a location in 2-dimensional space, but also when attention is directed to one of two spatially overlapping surfaces. Fourth, attention does not modulate sensory activity unless sensory systems are overloaded; when sensory systems are not taxed, attention may instead operate to influence memory or response processes. That is, attention operates to mitigate information overload in whichever cognitive subsystems are overloaded by a particular combination of stimuli and task.

Section snippets

Evidence for early selection

Perhaps the most fundamental question about attention is whether attention modulates information processing at a sensory stage or at a later stage. There are obvious cases in which attention operates after a stimulus has been perceived; for example, we may see a stimulus and simply choose not to make an overt response to it. It is much more difficult to determine whether attention can sometimes suppress the sensory processing of a stimulus. In fact, it is not clear that traditional behavioral

Neural substrates of early selection

As described in Box 3, it is extremely difficult to localize the neural generator sources of an ERP component. However, significant progress has recently been made in identifying the neural origins of the ERP attention effects, particularly the P1 modulation. First, it has been possible to demonstrate that an earlier ERP component called the C1 wave is generated in striate cortex (area V1; see Box 3)15., 16. but is not influenced by attention17., 18., 19.. This finding indicates that attention

Early selection in other paradigms

The ERP studies described so far have primarily used variants of the experimental paradigm shown in Fig. 1, but this is not a paradigm that has been widely used in traditional cognitive studies of attention. However, similar results have been observed with more common tasks such as spatial cuing3., 8., 30. and visual search31., 32..

In spatial cuing studies, a cue stimulus directs the subject to attend to a particular location on each trial, and a target is then presented either at the attended

Late selection in dual-task paradigms

Selection occurs at early stages of processing under some conditions, but there are many conditions under which both attended and unattended stimuli are fully identified and attention operates at a post-perceptual stage. Lavie47., 48. has proposed that selection operates at an early stage only under conditions of high perceptual load. This makes sense: why should attention suppress the perception of an unattended stimulus unless the perceptual system is overloaded? Luck and Hillyard11 have

Isolating different cognitive subsystems

Recent ERP studies have supported this conceptualization of attention by showing that attention operates in different cognitive subsystems for different tasks. In particular, the early-selection studies described in the preceding sections have been complemented by ERP studies of two paradigms in which attention would be expected to operate at later stages, namely the attentional blink paradigm and the psychological refractory period paradigm. These paradigms are very different from those used

ERP support for a multiple subsystems view

This theoretical analysis of the attentional blink and psychological refractory period paradigms has been supported by recent ERP experiments (see Box 4 for a discussion of the methods necessary for isolating ERPs under conditions of rapid stimulation). In the attentional blink paradigm, a variety of ERP components have been compared to determine the first stage at which processing is suppressed during the attentional blink51., 52.. As illustrated in Fig. 2c, no change in amplitude or latency

Conclusions

Together with the experiments on early selection described at the beginning of this article, these experiments illustrate how ERPs have been used to show that attention can operate in different cognitive subsystems under different conditions. Most existing ERP studies have explored coarsely defined cognitive subsystems (e.g. early versus late), but the excellent temporal resolution of the ERP technique should make finer distinctions possible, especially when appropriate experimental designs are

Acknowledgements

Preparation of this article was supported by grant SBR 98-09126 from the National Science Foundation, by grant MH56877 from the National Institute of Mental Health, and by grant RG0136 from the Human Frontier Science Program.

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