Event-Related Potentials

The event-related potential, known as the ERP, is an average EEG response to an external event, and it is distinguished from an evoked potential by the fact that part of the ERP comes from the brain activity associated with cognitive activity involved in processing a stimulus or preparing an action.  The ERP is derived by averaging EEG activity preceding and/or following external events of interest (a stimulus or an action by the subject).  ERP is widely used in research, and although many potential clinical applications for ERP techniques have been proposed, none of these techniques are widely used in medical applications.  ERP represents a low-cost, non-invasive tool with high temporal precision for measuring functional brain activity.  As a result of this unique combination of strengths, the ERP technique has opened up a wide variety of basic research possiblities and it has breathed new life into the field of EEG.  

Below you can click the links to take you to specific products that support event-related potential applications.

Basic features of an ERP system:

Digital EEG - An EEG system to be used for ERP needs to be compterized and digital.  There was a time when EEG systems were designed to write raw waveforms directly to paper, but any relatively new EEG system these days will be digital. 

Trigger - The basic requirement for an EEG system to be used in ERP research is a trigger.  A trigger is a mechanism by which the EEG system can be synchronized with a stimulus or action or by which EEG data can be marked to allow off-line analysis with respect to the event of interest,  Modern ERP systems use TTL trigger inputs for stimuli presented on a separate computer or by another device, but some modern systems can also be programmed to do both data acquisition and stimulus delivery on the same PC/processor in an interleaved fashion, thus eliminating the need for triggering.

High spatial sampling densityResearch has shown that increasing spatial sampling density at the scalp can be useful in distinguishing multiple generators of the scalp potentials measured in an ERP experiment.  Thus, many modern ERP systems are designed with the capability to record from more channels than traditional EEG systems have offered.  Typical research ERP systems have 64 or more channels.  That is not to say that interesting and useful research cannot be done with fewer channels, but the trend is toward higher numbers of channels.

Fast electrode application - Modern ERP systems also are designed to allow large numbers of electrodes to be applied rapidly without sacrificing signal quality.

Analytical software / open file format - Systems designed for ERP research also generally include analytical software, but some manufacturers opt for an open file format that is supported by open-source analytical software or software provided by other companies.

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