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Event-related potentials


The Event-Related Potential (ERP)

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 provides 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.  

Basic features of an ERP system

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 density - Research 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 analytical software provided by other companies. 

Additional information

ActiveTwo

ActiveTwo is a powerful high-resolution biosignal acquisition system that incorporates some revolutionary concepts.  Active electrode technology is just one of the significant innovations in the ActiveTwo system.  By placing active electronics within millimeters of the actual electrode contact, ActiveTwo virtually eliminates the need to prepare the skin before applying electrodes.  This can cut measurement preparation time by an estimated 15 -30 minutes for most laboratories!

f-EEG

f-EEGTM,by Kappametrics, incorporates revolutionary technology for capturing EEG data concurrently with fMRI.  f-EEG, employs patent pending noise cancellation techniques to eliminate the large radio frequency, electrostatic and magnetic noise produced by the fMRI scanner and enables the real-time collection of physiologic EEG data during fMRI scans. 

Mind-Fi

Mind-Fi is a wireless 63 channel active EEG head-cap that enables participants to project their thoughts in real-time anywhere in a coverage area of 20x20 feet (6x6 meters).

Active electronics on the cap eliminate the need for scalp abrasion resulting in cap setup time of only about 5 minutes. The cap weighs only a few ounces, so it’s comfortable to wear and it will stay put as subjects move through the environment.

To wash, just remove the tiny transmitter and place it on the charger.

g.USBamp

g.USBamp - g.tec's latest 24 bit biosignal acquisition device - is the perfect tool for recording multimodal biosignal data with highest quality. This allows to investigate brain-, heart-, muscle-activity, eye movement, respiration, galvanic skin response and other body signals.  g.USBamp is USB 2.0 enabled and comes with 16 simultaneous sampled biosignal channels.