Chapter 1.6 - Event-Related Potentials

Abstract

Event related potentials (ERPs) are scalp recorded voltage fluctuations that are time-locked to an event. The ERPs reflect stages of information processing in the sensory-related hierarchical neuronal networks, in the networks of cognitive control as well as in the memory and affective systems of the brain. The ERP amplitude is usually smaller than the amplitude of background EEG so that the reliable ERP is obtained by averaging EEG fragments in multiple trials. Each ERP represents a sum of potentials generated in widely distributed cortical sources. The functionally different sources of ERPs are called components and are associated with distinct hypothetical psychological operations. One way of separating the components is to obtain a difference between the two ERPs performed at conditions which differ in only one respect: presence or absence of a hypothetical operation. Recently methods of blind source separation have been applied in ERP research. They are 1) the single trial independent component analysis (ICA), 2) the group ICA on collection of ERPs in multiple tasks, 3) the group ICA on collection of ERPs in a single task, 4) the method of joint-diagonalization of covariance matrixes on collection of ERPs in a single task. The large amplitude ERPs are quite reliable measures of brain functioning with good to excellent test-retest reliability. Although ERP are quite stable in time they vary substantially from subject to subject reflecting inter-individual fundamental differences in information processing.