Psychology
Electroencephalogram (EEGs) and Event-Related Potentials (ERPs)
Electroencephalogram (EEG) is a non-invasive technique that records electrical activity in the brain, providing information about brain function and activity. Event-Related Potentials (ERPs) are specific patterns in the EEG that are time-locked to sensory, cognitive, or motor events, allowing researchers to study cognitive processes such as attention, memory, and perception.
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10 Key excerpts on "Electroencephalogram (EEGs) and Event-Related Potentials (ERPs)"
eBook - ePub- Aaron Newman(Author)
- 2019(Publication Date)
- SAGE Publications Ltd(Publisher)
440) and concluded that these waves corresponded ‘to a summation of the brief responses of individual neurones’ (p. 471). Soon after, the first event-related potentials (ERPs – sometimes also called evoked potentials or EPs) were recorded by Pauline and Hallowell Davis (Davis, Davis, Loomis, Harvey, & Hobart, 1939; Davis, 1939). The distinction between EEG and ERP is an important one in the field, and quite simply EEG refers to continuous recordings of ongoing electrical brain activity, whereas ERPs are EEG signals time-locked to particular events, such as the presentation of a specific stimulus or a motor response. As we will see, both EEG and ERPs are used in cognitive neuroscience; however, ERPs are the more commonly used technique because they allow us to associate brain activity with specific, experimentally controlled events. As this is the first chapter describing a neuroimaging technique, a number of key concepts are introduced that are common to many, if not all, techniques of cognitive neuroscience and so we will spend some time explaining these concepts. Rest assured, the time invested understanding concepts of data acquisition and signal processing will serve you well in chapters to come. What Are We Measuring? Physiological Basis of the EEG Signal EEG is recorded from electrodes (typically numbering 3–256) placed on the scalp, which are connected to an amplifier that boosts the size of the signals before saving them digitally on a computer, as shown in Figure 3.1. EEG can also be recorded directly from the cortical surface via electrodes placed during neurosurgery, but in this chapter we focus on non-invasive recordings. The EEG electrodes measure electrical activity generated by the brain; however, we cannot measure the activity of individual neurons. This is because the brain contains millions of neurons, located relatively far away from the EEG recording electrodes. Rather, the EEG signal represents the summed activity of many neurons
- Linda J. Luecken, Linda C. Gallo(Authors)
- 2007(Publication Date)
- SAGE Publications, Inc(Publisher)
C H A P T E R 18 Electroencephalography and Event-Related Potentials D AREN C. J ACKSON C ORY A. B. J ACKSON B rain electrophysiology can be defined as the study of electrical potentials on the scalp and the inferences regarding brain function based on these scalp potentials. This approach to the study of brain function incorporates experimental, technical, and ana-lytical elements of traditional psychophysiol-ogy as well as modern neuroimaging. Through creative use of basic electroencephalographic (EEG) recordings and waveforms derived from event-related potential (ERP) techniques, researchers have made diverse contributions to the clinical, cognitive, and affective sciences. For example, baseline EEG metrics (i.e., “rest-ing” EEG measured in the absence of an experimental task) have an impressive history of providing insight into affective processes in both healthy and clinical populations (see Davidson, Jackson, & Kalin, 2000, for a review). Asymmetrical patterns of frontal lobe activation have been shown to predict responses to pleasant and unpleasant emo-tional stimuli, sensitivity to punishment and reward, ability to regulate negative emotion, and risk for affective disorders. Of particular interest to health psychologists, frontal asymmetry has also been associated with immune function and stress response (e.g., Rosenkranz et al., 2003). Furthermore, a unique advantage of EEG and ERP techniques is their exquisite temporal precision. This resolution allows us to go beyond the measurement of resting brain activation, to isolate and exam-ine specific sensory, cognitive, and motor pro-cesses with millisecond accuracy. It is important to note that electrophysio-logical measures are often used to interrogate very rapid changes in regional brain activity associated with psychological processes that are typically inaccessible or unavailable to conscious awareness—that is, processes of which research participants are unaware and thus unable to report.
eBook - ePubPsychophysiology
Human Behavior & Physiological Response
- John L. Andreassi(Author)
- 2013(Publication Date)
- Psychology Press(Publisher)
5 Event-Related Brain Potentials and Behavior I: Measurement, Motor Activity, Hemispheric Asymmetries, and Sleep Another measure of brain activity, derived from EEG recordings, is the event-related brain potential (ERP). Unlike the EEG, which represents spontaneous brain activity, the ERP is generated as a response to specific stimuli, and is an average of a number of samples. These ERPs are time-locked to stimulus events and have proven valuable to the psychophysiologist interested in a record of brain responses to stimuli, even when no other noticeable response occurs. A great deal of research effort has been devoted to studying the relationship between ERPs and human psychological activities. Most of the work has been conducted over the past 35 years and is continuing at a high rate. What makes the ERP so appealing is the possibility of relating specific brain responses to discrete psychological states and events. The extensive research on ERPs indicates that it rivals heart activity as the most popular physiological variable studied by psychophysiologists. The ERP has been found to be dependent on both physical and psychological characteristics of stimuli, although in some instances, ERPs are independent of specific stimuli. For example, brain responses have been found to occur at the precise time that stimuli were expected but not actually presented (Sutton, Teuting, Zubin, & John, 1967). When ERPs occur independently of external stimuli, they are called endogenous, indicating that they are produced by internal events. Those ERPs produced as a reaction to specific external events are called exogenous potentials. Vaughan (1969) proposed the term event-related potentials to refer to a variety of brain responses that show stable time relationships to actual or anticipated stimuli
eBook - ePubPsychophysiology
Human Behavior and Physiological Response
- John L. Andreassi(Author)
- 2010(Publication Date)
- Psychology Press(Publisher)
6Event-Related Brain Potentials and Behavior I: Measurement, Motor Activity, Hemispheric Asymmetries, and SleepAnother measure of brain activity, derived from EEG recordings, is the event-related brain potential (ERP) . Unlike the EEG, which represents spontaneous brain activity, the ERP is generated as a response to specific stimuli, and is an average of a number of samples. These ERPs are time locked to stimulus events and have proven valuable to the psychophysiologist interested in a record of brain responses to stimuli, even when no other noticeable response occurs. A great deal of research effort has been devoted to studying the relationship between ERPs and human psychological activities. Most of the work has been conducted over the past 40 years and is continuing at a high rate. What makes the ERP so appealing is the possibility of relating specific brain responses to discrete psychological states and events and obtaining a more complete picture of the behavior being studied. The extensive research on ERPs indicates that it rivals heart activity as the most popular physiological variable studied by psychophysiologists and neuroscientists.The ERP has been found to be dependent on both physical and psychological characteristics of stimuli, although in some instances, ERPs are independent of specific stimuli. For example, brain responses have been found to occur at the precise time that stimuli were expected but not actually presented (Sutton, Teuting, Zubin, & John, 1967). When ERPs occur independently of external stimuli they are called endogenous, indicating that they are produced by internal events. Those ERPs produced as a reaction to specific external events are called exogenous potentials.Vaughan (1969) proposed the term event-related potentials to refer to a variety of brain responses that show stable time relationships to actual or anticipated stimuli. Those ERPs were classified by Vaughan as (a) sensory ERPs, (b) motor potentials, (c) long-latency potentials, and (d) steady potential shifts (SPS)
- Darin D. Dougherty, Scott L. Rauch, Jerrold F. Rosenbaum, Darin D. Dougherty, Scott L. Rauch, Jerrold F. Rosenbaum(Authors)
- 2008(Publication Date)
- American Psychiatric Association Publishing(Publisher)
Source. Reprinted from Kandel ER, Schwartz JH, Jessell TM (eds.): Principles of Neural Science, 3rd Edition. New York, McGraw-Hill, 1991, p. 779. Copyright 1991, The McGraw-Hill Companies. Used with permission. Electroencephalography, ERPs, and Magnetoencephalography 119 squared and calculated in a series of frequency bands (the power spectrum) for approximately 25 seconds. An- other important measure is coherence—a measure of the phase consistency of two signals (i.e., the extent to which EEG signals from different brain regions have fre- quency components that are time-locked to each other). Coherence varies between 0 and 1 and is analo- gous to a correlation coefficient of the signal between two brain areas. It is thought to reflect the degree of functional connectivity between brain regions, al- though its functional physiological significance re- mains unclear. Clinical Use in Psychiatric Practice When electroencephalography was first introduced by Hans Berger in 1929, the hope was that it would di- rectly aid the diagnosis of the major mental disor- ders—schizophrenia, depression, and anxiety. This hope has long since been abandoned. Nonetheless, the EEG remains a valuable part of psychiatric clinical practice. It is mainly helpful in the diagnosis of neuro- logical disorders—such as delirium, dementia, and ep- ilepsy—that must often be ruled out in the differential diagnosis of many “nonorganic” psychiatric disorders. Figure 6–2. Electroencephalogram (EEG) recorded in a human subject at rest from the scalp surface at various points over the left and right hemispheres. Three pairs of EEG electrodes are positioned so as to overlie the frontal, temporal, and occipital lobes. Beta activity—the EEG activity with the highest frequency and lowest amplitude—is recorded over the frontal lobes. Alpha activity—a signature of a brain in a relaxed and wakeful state—is recorded in the occipital and temporal lobes.
eBook - PDF- Hans O. Luders(Author)
- 2008(Publication Date)
- CRC Press(Publisher)
ERPs are based on the observation that the brain activities change in response to a stimulus given from the outside world. Voltage changes, or potentials, which occur time-locked to the stimulus, constitute the ERPs. In early studies, the term ‘evoked-potential’ or EP was employed because the potentials were believed to reflect brain activity strictly ‘evoked’ by the presentation of the stimulus, or activity associated with basic sensory processes. The more neutral term ‘event-related’ was later introduced because it was real- ized that the potentials reflected more than just evoked activ- ity. ERPs, therefore, can be described as voltage fluctuations that are associated in time with some physical or mental occurrence. These potentials can be recorded from the human scalp and extracted from the ongoing background EEG by means of filtering and signal averaging. The time-locked nature of ERP recording along with their millisecond resolu- tion make ERPs very useful for determining the temporal sequence/location of cortical events. 4–6 The consensus among neurologists and electrophysiolo- gists is that the ERP reflects activity generated within the brain. However, the relationship between what is occurring within the brain and what is observed at the scalp is not trans- parent. ERPs recorded from the scalp are the reflection of net electrical fields associated with the activity of large popula- tions of neurons. The electrical fields can be measured at the scalp only when the associated neuronal population have a certain common geometric configuration (which is perpendi- cular to the cortical surface) and are activated synchronously. Biophysical and neurophysiologic considerations strongly suggest that scalp-recorded ERP waveforms are principally a reflection of post-synaptic (dendritic) potentials, but not of axonal action potentials. 7–10 It is certain, however, that much neuronal activity is never apparent at the scalp.
eBook - ePub- Michael D. Rugg(Author)
- 2013(Publication Date)
- Psychology Press(Publisher)
The chapter starts with a few references to some basics of electrical (event-related potentials (ERP s)) and magnetic (event-related fields (ERF)) recording. This is followed by a short tutorial on the physiology and physics of electrical and magnetic activity, a discussion of the types of inference that can and cannot be drawn from such measurements, and a cursory overview of the most widely used terms in cognitive electrophysiology. We conclude with a few specific examples of cognitive ERP and ERF research. 7.1 Event-related activity: Electrical (ERPS) and magnetic (ERFS) An ERP/ERF experiment requires a willing participant, electrodes for recording the brain wave activity or a magnetometer, some means of presenting stimuli, amplifiers and a digitizer that turns the analogue data into a digital form for storage, further representation and analyses. Technical details about electrodes, electrode placement, amplifiers, magnetic recordings, digitization and analyses can be found in a number of articles and books (Cooper et al. 1974, Regan 1989, Hamalainen et al. 1993, Rugg & Coles 1995). There are many ways to look at electrical and magnetic activity in both the temporal and spatial domains. The emphasis of this chapter is on scalp activity, specifically that which is time-locked or synchronized to some external stimulus or event. Typically, the earliest or so-called “exogenous” components of the ERP are used in a clinical setting to assess the integrity of the peripheral or central nervous system, although they are clearly essential for understanding cognitive effects as well (for more in-depth discussion see Desmedt 1988, Starr & Don 1988, Regan 1989). Since the evoked response to a single stimulus at the scalp is quite small (5–10μV), it must be extracted from the background activity via averaging
- P.A. Allen, T.R. Bashore(Authors)
- 1995(Publication Date)
- North Holland(Publisher)
ERPs reflect changes in electrophysiological activity generated in the brain when an individual receives some form of sensory stimulation or initiates a pre- designated movement. The ERP is manifest as a series of voltage-time fluctuations that are most apparent in time-locked averages of EEG activity derived from repeated occurrences of the critical event. Each deflection in the series, identified separately as components of the ERP, represents synchronous changes in the electrical activity of large populations of neurons. The latency and amplitude of these components may be sensitive to variations in the physical characteristics of the eliciting stimulus, in the nature of the intended movement, or in the processing demands of a task. These signals are recorded using electrodes that are affixed to the scalp at a number of different sites. The locations of these sites have been standardized so that brain electrical ACKNOWLEDGEMENTS: This chapter was written while the second author was a Visiting Professor at the University of Amsterdam, supported by the Experimental Psychology Graduate School (EPOS) in the Netherlands, by a visitor's grant from NWO (The Dutch Organization for Pure Research), and by a stipend from the Research Corporation at the University of Northern Colorado. In addition, preparation of this chapter was supported in part by grants to the second author from the National Institute on Aging (AG04581, AG12263), and by a research grant from NWO to M.W. van der Molen that provides postdoctoral support for the first author. Using event-related brain potentials 295 activity recorded in different clinics or laboratories throughout the world can be compared (Jasper, 1958). This system, known as the 10-20 or International Electrode Placement System, has established the sites shown in Figure 1 as standard. In most ERP studies, recording electrodes are placed along what are called the midline scalp sites, Fz, Cz, and Pz.
- Phakkharawat Sittiprapaporn(Author)
- 2017(Publication Date)
- IntechOpen(Publisher)
Chapter 1 Event-Related Potentials for the Study of Cognition Manuel Vazquez-Marrufo Additional information is available at the end of the chapter http://dx.doi.org/10.5772/intechopen.69308 Abstract Despite the vast literature on event-related potentials (ERPs), many clinical professionals are still unaware of the huge variety of possible applications they offer. The aim of this chapter is not to show the classical use of ERPs, focused on analyzing the first steps of information processing (sensory pathways). On the contrary, this chapter will be focused on the use of these ERPs in the assessment of cognitive function. In particular, this chap -ter is mainly focused on the use of ERPs to better understand the neural bases of cogni -tive impairment from the electrical activity of the brain. Describing all the possible ERP components and their cognitive meaning is a huge endeavor, and this chapter will only be focused on three of them: contingent negative variation (CNV), mismatch negativity (MMN), and P300. To improve the reader’s knowledge about these ERPs in cognition, a specific description will be given about the stimulation required to obtain the specific component, the topography, and latency shown. Moreover, a description of the neuro -physiological bases of the component, its relationship with psychological processes and neural sources will be also included. Pathological alterations suffered by the component will also be briefly described. Keywords: cognition, ERPs, latency, neural sources, pathology, topography 1. Introduction Since the 1960s, a prolific literature has been produced on the field of event-related potentials (ERPs), related to the study of cognitive activity in the brain. In the beginning, these studies were more directed to the study of sensory and motor pathways. However, from studies such as in Refs. [ 1–3], ERPs were related to cognitive processes such as relevance of the stimulus, uncertainty, or mismatch with a previous stimulus.
- Leif Sörnmo, Pablo Laguna(Authors)
- 2005(Publication Date)
- Academic Press(Publisher)
So far, no single biological or mathematical model has been put forward which fully explains the diversity of EEG pat- terns, and, accordingly, EEG interpretation largely remains a phenomeno- logical clinical discipline [ 21. 25 26 Chapter 2. The Electroencephalogram--A Brief Background Visual scrutiny was for many years the sole approach to EEG interpreta- tion but has today been supplemented by the capabilities offered by modern, powerful computers. The interpretation is significantly facilitated, although not even close to being fully automated, by an array of digital signal process- ing methods designed for a variety of purposes, e.g., improvement of SNR, quantification of various signal characteristics, and extraction of new infor- mation not readily available by visual inspection [3-5]. Signal processing methods can be divided into two general categories: methods developed for the analysis of spontaneous brain activity (the background EEG ''1) and brain potentials which are evoked by various sensory and cognitive stimuli (evoked potentials, EPs). While the former category of methods certainly has helped to gain a better understanding of the EEG, the analysis of EPs is critically dependent on the availability of signal processing techniques. In recent years, the study of brain function has been revolutionized by the introduction of various imaging modalities: positron emission tomography (PET), single photon emission computed tomography (SPECT), and mag- netic resonance imaging (MRI), which can produce two- or three-dimensional images with good spatial resolution. These modalities extend the informa- tion inferred from an electrophysiological investigation by providing detailed information on, e.g., anatomy and blood flow in different regions of the brain. As a result, the EEG has today lost part of its dominance in clinical routine; however, it remains a very powerful tool in the diagnosis of many diseases such as epilepsy, sleep disorders, and dementia.
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