ERPs- Event-Related Potentials

Event-related potentials (ERPs) are components of the scalp-recorded electroencephalogram (EEG).  This non-invasive technology records the brain's extremely small electrical signals which continuously travel to the scalp.   

	A set of small gelled electrodes held onto the scalp allow analysis systems to collect and analyze these brainwaves.  We use a stretch cap to painlessly collect signals from up to 64 sites on the scalp at a time.
	From the mix of ongoing EEG brainwave potentials collected at the scalp, coordinated brain responses to visual, auditory, or somatosensory trigger events can be analyzed using signal averaging techniques.

Event-related potentials (e.g. the N1, P2, N2 and P3 peaks in the figure above) are the averaged responses time-locked to the experimental trigger event.  These ERP components reflect the brain activation that is consistently coordinated in response to the triggering events in experimental tasks.  

The very high resolution of the timing and intensity of ERP responses can reveal minute changes in sensory and cognitive brain responses.  These analyses provide an exciting complement to the excellent spatial resolution of brain activities provided by functional magnetic resonance imaging (fMRI).

For example, we examined the effect of reward salience on ERP components and behavior using a response inhibition paradigm in 16 healthy participants.  ERPs were recorded from 64 channels while subjects performed a warned reaction time Go/No-Go task where the warning stimulus (S1) signaled whether a response was required to the subsequent imperative stimulus (S2). Monetary reward conditions (high, low, none) were varied across blocks of trials. 

This study examined the effect of graded monetary reward on the CNV and P300 components in normal healthy adults.  The paradigm duplicates that used in our fMRI studies of drug addiction.  We are continuing to develop paradigms for assessing cognitive function that can be used in both fMRI and ERP analyses, with the near-term goal of acquiring ERPs during fMRI recordings.