(p. ix) Preface
(p. ix) Preface
The primary goal of this handbook is to provide a comprehensive and thorough overview of research on ERP components for researchers in the mind and brain sciences. Our goal was to provide a single, comprehensive resource that researchers can use to learn about ERP components. We sought to provide breadth by covering a range of components and research domains and depth by devoting whole chapters to individual components and topics. We anticipate that most readers will initially peruse just a few chapters to learn about the components they regularly encounter, but that they will continue to come back to the volume as additional components become relevant throughout their evolving careers. The volume was designed to serve as a reference for ERP researchers of all levels of expertise, as well as researchers who use other techniques but wish to learn more about ERPs.
Origins of the Handbook
Over 100,000 studies using ERP components have been published, and the field continues to grow each year. Although these studies can be subdivided into a much smaller literature on each individual ERP component, finding and reviewing all of the relevant work on a single ERP component can be a daunting task. We see this every year at the ERP Boot Camp, an annual 10-day summer ERP workshop at UC Davis, where the participants often ask us where they can learn more about the X component (where X might be P300, N170, N400, P600, ERN, etc.). Our answer in the past was limited to something like, “Sorry, but there isn’t a recent and comprehensive review. Here’s a list of 40 journal articles you should read.” This is an unsatisfactory answer, both for us and for the participants, because a thorough knowledge of the major ERP components is essential in the design and interpretation of ERP experiments. Furthermore, top ERP researchers rarely limit their research to a single ERP component, but rather use a range of ERP components depending on which is best suited for answering the question of interest in a given study. The ability to choose the most appropriate ERP component for answering a question and designing an experiment that properly uses that component requires extensive knowledge of ERP components.
We therefore assembled a volume in which leading ERP researchers wrote comprehensive overviews of the major ERP components in a format that is accessible to researchers with limited knowledge about ERPs, yet still useful to researchers with extensive ERP experience. Personally, we have found the drafts of the chapters to be extremely useful in our own research and writing, and we hope that others find the finished chapters equally useful.
(p. x) Some readers may wonder whether an entire volume devoted solely to ERP components is warranted. In fact, an anonymous reviewer of our initial proposal for this volume raised this very issue. The review was thoughtful and detailed, but the gist can be summarized by the following excerpts:
The concept of a component is a reasonable foundation for much ERP research, but much difficulty comes up in practice. There can be great difficulty in some circumstances in knowing when the one component of interest has been produced, as well as in assuring that other overlapping components do not have an undue influence on the measure in question…
… it is often unwise to accept the assumption that each positive or negative deflection in the ERP waveform corresponds to a particular component. Deflections may be based on the summation of multiple components, which themselves are unknown, such that the amplitude and latency of the composite peak does not provide a valid characterization of any of the individual components.
Accordingly, many ERP investigations in cognitive neuroscience no longer exemplify the strict component-centered approach, wherein a chief experimental goal was to understand an ERP component per se, and its associated cognitive process. Instead, difference-centered approaches have become prevalent, whereby experimental variables are manipulated based on theory-driven goals concerning specific neurocognitive functions.
We agree fully with this reviewer. As discussed in Chapter 1 of this volume, ERP components can be difficult to define and challenging to isolate. It is often unclear which component has changed across conditions or across groups, and it can be difficult to be certain that the same underlying component is being observed in different studies. As a result, ERP studies that have had a large impact outside the community of ERP researchers have often used designs based on difference waves that do not depend on identifying specific ERP components (see the discussion of component-independent experimental designs in Chapter 1).
Why, then, should we devote a 22-chapter volume to ERP components? The answer is that sophisticated ERP researchers typically design their experiments to take advantage of their knowledge of the properties of specific components, even if the conclusions of that experiment do not depend on isolating a specific component. Knowing about ERP components can help researchers determine what questions can be addressed with ERPs, because a psychological or neural process can be studied only if variations in that process lead to a measurable change in the ERP. And knowing what factors influence the amplitude and latency of an ERP component can help in creating an optimal design that generates robust ERP effects. For example, before attempting to use ERPs to study grammatical abnormalities in children with autism, one must first determine whether any ERP components exist that are sensitive to grammatical variables. Once these components are known, experiments can be designed that examine grammatical variables that have a clear ERP signature using parameters that optimize the robustness of the ERP signal. Consequently, a volume focusing on ERP components, in which researchers can gain breadth of knowledge about the available components as well as depth of knowledge about the properties of individual components, is much needed.
(p. xi) Organization of the Handbook
A terrific lineup of ERP researchers (including the discoverers of several ERP components) contributed chapters to this handbook, and we were extremely pleased by the comprehensive and insightful nature of the chapters they wrote. Authors were asked to address specific questions relating to: (1) defining and identifying the components; (2) isolating the components; (3) describing the neural and psychological processes reflected by the components; (4) which brain systems contribute to the generation of the components; and (5) the major variables affecting the amplitude and latency of the components.
The handbook is organized into four main sections. The first section contains three chapters devoted to broader issues surrounding ERP components, including the definition and isolation of ERP components in general, the relationship between EEG oscillations and ERP components, and the formal mathematical approach embodied by Independent Component Analysis. This section is extremely important because, although the concept of an ERP component is broadly used, the concept is rarely defined or discussed in the contemporary ERP literature. Furthermore, knowledge about EEG oscillations and Independent Component Analysis is essential to researchers wishing to evaluate new and evolving work using these approaches. We hope these chapters will be helpful to beginning ERP researchers who are just learning about the concept of an ERP component and to more advanced researchers who are familiar with the general concept but would like to develop a more sophisticated perspective. Each chapter in this section will be most useful if read in its entirety.
The second section contains a set of chapters focused on individual components that are often examined in isolation, including the basic sensory ERP components, the N170 component, the mismatch negativity, the P300 component, the slow anticipatory components, the lateralized readiness potential, and the error-related negativity. The chapters in this section are useful to anyone interested in learning more about these specific components. Some readers may wish to read these chapters in their entirety, and others may take advantage of the subheadings to read specific portions of interest.
The third section is composed of chapters that review multiple components related to a specific psychological domain, including chapters on attention, visual perception, working memory, long-term memory, language, and emotion. These chapters should be useful as a reference for researchers who conduct ERP research within these domains and also for researchers who use other techniques but wish to be able to better understand and evaluate ERP research in their field. Moreover, researchers who wish to apply ERPs to the study of a new domain may find these chapters useful as a guideline to adapting ERPs for use in a field. For example, emotion may not seem amenable to ERP methods at first glance, and understanding the process of applying ERPs to study emotion may provide a useful model for adapting ERPs to other domains. It should also be noted that there is some overlap between the components covered in this section and the components covered in the section on individual ERP components. In this way, the present volume provides both an in-depth methodology-focused account of individual components (p. xii) and a contextualized description of the use of the components to answer broader questions about the mind and brain.
The final section focuses on how ERP components vary across different groups of individuals, including chapters focused on infant and child development, aging, schizophrenia, depression, neurological disorders, and nonhuman primates. These chapters review a range of components, which will include many of the components covered in the second section of the volume (readers should consult the individual component chapters for more detailed discussions of the components). These chapters will be especially useful to ERP researchers who focus on these groups of individuals, as well as researchers who use other techniques but wish to evaluate ERP research within their domain. In addition, researchers who wish to apply ERP research to study a population not addressed in the present section may find the chapters useful as a general guideline to the application of ERPs in the study of special populations.