About ERPs

Event-related potentials (ERPs) are a series of positive and negative voltage deflections in the ongoing EEG that are time-locked to sensory, motor, or cognitive events. These electrical potentials represent the summation of electrical activity of large numbers of neuronal elements acting in synchrony during information processing.

	P300: The P300 is a positive ERP component peaking at approximately 300 ms after stimulus onset. The P300 is typically elicited by novel and low probability (rare) stimuli, but is also sensitive to other parameters such as task relevance. The P300 is one of the most commonly used ERP components in the study of the effects of drugs of abuse on cognitive processing.
	CNV: The CNV (contingent negative variation) is a negative deflection that is typically elicited in a Go/No-go paradigm between a warning stimulus (S1) and an imperative stimulus (S2). The CNV can be sub-divided into an early and late component. The early component is also referred to as the "O" or "Orienting" wave, while the late component is commonly referred to as the "E" or "Expectancy" wave. The "E" wave is thought to reflect anticipation of a response to S2.

Purpose

This study examined the effect of graded monetary reward on the CNV and P300 components in normal healthy adults.

Method

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. 

Results

A CNV was observed between the warning and target stimuli. The mean amplitude of the late portion of the CNV was significantly larger after Go stimuli than No-Go stimuli, but was unaffected by monetary reward. In contrast, the peak amplitudes of the P300 component to the warning and target stimuli were significantly larger in the high money condition than in the low money or no money conditions. This effect corresponded with subjective ratings of interest and excitement about the task.

The role of the P300 in processing different monetary rewards is consistent with its role in emotional valuation of stimuli and is intriguing vis-à-vis the P300's decrease after cocaine administration. This role cannot be attributed to motor performance (reaction time or error rate).        

Presented at the Cognitive Neuroscience Society, 2003 (New York, NY)