A brief introduction to the use of event-related potentials in studies of perception and attention

Abstract

Because of the precise temporal resolution of electrophysiological recordings, the event-related potential (ERP) technique has proven particularly valuable for testing theories of perception and attention. Here, I provide a brief tutorial on the ERP technique for consumers of such research and those considering the use of human electrophysiology in their own work. My discussion begins with the basics regarding what brain activity ERPs measure and why they are well suited to reveal critical aspects of perceptual processing, attentional selection, and cognition, which are unobservable with behavioral methods alone. I then review a number of important methodological issues and often-forgotten facts that should be considered when evaluating or planning ERP experiments.

Figure 1

Idealized event-related potential (ERP) waveforms elicited during a visual search task. The left panel shows a bilateral stimulus array to which the waveforms are time locked and a model of the human head with the placement of a subset of electrodes from the 10/20 system. The bottom-right panel illustrates how ERPs are extracted from the raw electroencephalogram (EEG). The middle-right panel shows the classic sequence of ERP components elicited during a visual task with left visual field targets at occipital-temporal electrode sites. The top-right panel shows the sequence of ERP components observed during the performance of the task requiring a response with a finger on the left hand that could either be correct or incorrect. Note that the P3 and ERN components are not typically lateralized but instead have fairly broad scalp distributions with central maxima.

Figure 2

Idealized event-related potential (ERP) waveform evoked by a brief auditory stimulus. Waveforms shown would be expected from a central electrode site (i.e., Cz).

Figure 3

Example of a waveform in which the prestimulus noise is equal in amplitdue to the potential effects of interest. These are actual data recorded from electrode O1 and averaged across two subjects with approximately 150 artifact-free trials elicited by each type of stimulus to illustrate the need for sufficient power and clean baselines.

Figure 4

Hypothetical waveforms illustrating the difficulty of measuring the latency of an ERP component from the moment of peak voltage. A) Demonstration of how high-frequency noise can bias the measurement of latency based on the peak. B) Illustration of how measuring peak latency of waveforms in two conditions can lead to qualitatively different patterns than the less biased method of measuring factional-area latency. Gray region shows the measurement window.

Figure 5

Number of event-related potential papers by year of publication. Data derived from PsychInfo searches for the terms event-related potential, ERP, or evoked potential in any search field.