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Introduction to Infant EEG and Event-Related Potentials

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Introduction to Infant EEG and Event-Related Potentials Introduction to infant EEG and event-related potentials Michelle de Haan Institute of Child Health, University College London, UK It is many decades since investigators first employed the electroencephalo- gram (EEG) to study the function of infants’ central nervous systems (for reviews see Bell, 1998; Schmidt & Fox, 1998). While initially investigators focused on how changes in the ongoing EEG related to the behavioural states of sleep and wakefulness (Lindsely, 1939; Smith, 1938), in subsequent years they also began to study event-related activity including evoked (e.g., Galambos & Despland, 1980; Sokol & Dobson, 1976) and endogenous responses (e.g., Courchesne, Ganz, & Norcia, 1981; Vaughan, 1975). In recent years, with the growing interest in understanding the neural bases of human perception, cognition, and emotion, there has been increased interest in use of EEG and event-related potentials (ERPs) to study these processes as they develop in human infants. This is because EEG and ERPs are among the only ways to study brain activity in healthy infants (see Meek, 2002, for discussion of another method that can be used with healthy infants, optical imaging). Other brain-imaging methods commonly used with adults and older children pose significant risks or would require sedation in young infants, making them unsuitable unless required for clinical purposes. That there is now a sufficient body of literature in the field of infant EEG and ERPs to warrant an entire volume on this topic is testament to how quickly the field has grown in the last few years. This is in spite of the fact that these data can be quite challenging to collect from young infants. Cooper- ation with placement of the electrodes and leaving them in place for the duration of the experiment, minimising movement during the experiment to prevent artefacts, and ensuring that the baby participates in the experiment as needed (e.g., by attending to visual stimuli) can all represent challenges (see DeBoer et al., Chapter 1, for discussion of practical aspects of recording infant EEG and ERPs). Once these challenges are overcome, others present themselves in analysis and interpretation of the data, as in many instances the relationship between components observed in infant ERPs and those known in adults is not obvious. The chapters in this volume demonstrate that these challenges can be overcome and reliable EEG and ERP data can be recorded from infants in a variety of paradigms and ages. Chapter 1 (DeBoer et al.) provides an 2 De Haan overview of methods for recording and analysing EEG and ERP, with an emphasis on the special issues related to using these techniques with infants. Chapters 2–4 focus on visual potentials, from visual evoked responses (McCulloch, Chapter 2) to face-sensitive components (de Haan et al., Chapter 3) and components related to visual attention and memory (de Haan, Chapter 4). In Chapter 2, McCulloch outlines techniques for recording visual evoked potentials (VEPs) and describes the picture they provide of the development of the visual system in infancy, in both typical and atypical development. In Chapter 3, de Haan, Johnson, and Halit describe ERP components related to infants’ processing of faces, how these relate to com- ponents in the adult ERP, and how developmental changes in these com- ponents inform theories of the development of face processing. In Chapter 4, de Haan focuses on ERP components related to infant recognition memory and attention, describing the development of the negative central (Nc) component and various slow waves. Chapters 5–7 focus on auditory potentials, including those related to audi- tory recognition (deRegnier, Chapter 5), the mismatch negativity (Cheour, Chapter 6), and those related to speech and language (Molfese et al., Chapter 7). In Chapter 5, de Regnier outlines the brain circuits involved in auditory recognition memory and presents data demonstrating differences in ERP response to the mother’s vs a stranger’s voice in neonates. When the same auditory recognition paradigm is used with infants at risk for later memory impairment, there is evidence of atypical auditory ERP memory responses very early in life. In Chapter 6, Cheour describes what is perhaps one of the most well-studied ERP components, mismatch negativity (MMN). She discusses issues in identifying the infant MMN, and its differences from and similarities to the adult component, as well as its usefulness in detecting cognitive impairment early in life. In Chapter 7, Molfese, Molfese, and Pratt discuss the use of infant ERPs to predict later language and reading devel- opment. They present impressive findings indicating that ERPs to speech and non-speech sounds in neonates and young infants can predict a sizeable amount of the variance in language and reading skills at school age. Chapters 8–10 focus on other aspects of the EEG, with Chapter 8 (Marshall & Fox) examining ERP and EEG emotion-related responses, Chapter 9 (Stroganova & Orekhova) focusing on EEG and infants’ states, particularly different states of wakefulness, and Chapter 10 (Csibra & Johnson) reporting on event-related oscillations in perceptual-cognitive tasks. In Chapter 8, Marshall and Fox report on individual differences in both EEG and ERP responses and how they relate to individual differences in emotion and tem- perament. Their findings suggest that temperamental differences among infants may be an important factor to consider in interpreting results from ERP group studies. In Chapter 9, Stroganova and Orekhova discuss devel- opment of the EEG in relation to infant states, raising important questions regarding variations in the EEG during wakefulness and definition of infant EEG rhythms (e.g., alpha) in relation to those observed in adults. In Introduction 3 Chapter 10, Csibra and Johnson described a relatively recent approach to analysing infant brain activity, event-related oscillations, and describe how these have been used to study the neural correlates of perceptual binding and memory for hidden objects in infancy. Several questions and themes run throughout these chapters, including the usefulness of infant EEG/ERP in early detection of impairments in percep- tion and cognition, and how best to define infant brain activity with respect to adult brain activity, and these and other themes are discussed further in Chapter 11 (de Haan). A glossary of terms is also provided at the end of the book, with the hope that it will make the chapters more accessible to those less familiar with the field and its terminology. The main purpose of creating this volume was to provide a reference useful to both those active in the field and those new to it. For those already involved in infant EEG and ERP research, the chapters in this book will provide a very useful reference drawing together numerous studies, and may also help to broaden their outlook, as often researchers tend to focus on a particular type of ERP and may not be fully aware of work that is related but carried out in another domain. For those new to the field, it is hoped that the introduction provided by Chapter 1 and the glossary will form the back- ground for informed reading of the remaining chapters devoted to more specific topics. Ideally, the exciting findings reported here will recruit new researchers into the field and help to take the field forward in the decades to come. REFERENCES Bell, M. A. (1998). The ontogeny of the EEG during infancy and childhood: Implications for cognitive development. In B. Barreau (Ed.), Neuroimaging in child neuropsychiatric disorders (pp. 97–111) Berlin: Springer. Courchesne, E., Ganz, L., & Norcia, A. M. (1981). Event-related brain potentials to human faces in infants. Child Development, 52, 804–811. Galambos, R., & Despland, P. A. (1980). The auditory brainstem response (ABR) evaluates risk factors for hearing loss in the newborn. Pediatric Research, 14, 159–163. Lindsely, D. B. (1939) A longitudinal study of the occipital alpha rhythm in normal children: Frequency and amplitude standards. Journal of Genetic Psychology, 55, 197–213. Meek, J. (2002). Basic principles of optical imaging and application to the study of infant development. Developmental Science, 5, 371–380. Schmidt, L. A., & Fox, N. A. (1998). Electrophysiological indices I: Quantitative elec- troencephalography. In C. E. Coffey & R. A. Brumback (Eds.), Textbook of pediatric neuropsychiatry (pp. 315–329). Washington, DC: American Psychiatric Press. Smith, J. R. (1938). The electroencephalogram during normal infancy and childhood: I Rhythmic activities present in the neonate and their subsequent development. Journal of Genetic Psychology, 53, 431–453. 4 De Haan Sokol, S., & Dobson, V. (1976). Pattern reversal visually evoked potentials in infants. Investigative Ophthalmology, 15, 58–62. Vaughan, H. G. Jr. (1975). Electrophysiologic analysis of regional cortical maturation. Biological Psychiatry, 10, 513–526. 1 Methods for acquiring and analyzing infant event-related potentials Tracy DeBoer University of Minnesota, USA Lisa S. Scott University of Colorado at Boulder, USA Charles A. Nelson University of Minnesota, USA A primary goal of developmental cognitive neuroscience is to elucidate the relation between brain development and cognitive development (see Nelson & Luciana, 2001). The study of this relation in children older than 5–6 years lends itself to many of the same tools used in the adult, such as functional magnetic resonance imaging (fMRI). However, in children younger than this, limitations in motor and linguistic abilities,
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