Hyperscanning-the simultaneous recording of brain activity from multiple individuals-and the study of inter-brain synchronization is gaining popularity in social neuroscience. MEG/EEG hyperscanning studies often estimate inter-brain functional connectivity using phase-based metrics applied to oscillatory brain signals, assuming matching peak frequencies between the individuals studied. However, in reality peak frequencies typically differ between subjects and even between brain regions. Using simulated MEG/EEG signals, we systematically assessed how inter-individual frequency differences affect commonly used connectivity measures. Phase-based metrics were highly sensitive to frequency differences across individuals, whereas amplitude envelope correlation remained comparatively stable under these conditions. Our results underscore the need for connectivity metrics specifically tailored for inter-brain analyses. These findings are relevant to a range of disciplines that are increasingly integrating hyperscanning into their methodological toolkits.

Abstract This chapter is devoted to stimulation and monitoring devices needed to run MEG and EEG experiments. The MEG environment is very challenging for various sensory stimulators because any moving magnetic or magnetized materials near the subject will cause serious artifacts. The devices introduced in this chapter include auditory, visual, and tactile stimulators, stimulators to trigger acute pain, devices to produce passive movements to activate proprioceptors, and olfactory and gustatory stimulators. The operating principles of the stimulators are described in a concise manner. Some devices for monitoring a subject’s behavior are briefly mentioned. The chapter ends with a section on phantoms for MEG/EEG systems as aids to understand source analysis and artifact removal.

Abstract This chapter provides an overview of basic human brain organization and function and their assessment. The chapter starts by emphasizing the importance of timing in human brain function and behavior, and it briefly touches the methods for obtaining this information. The text continues with a description of the functional structure of the brain, including both cerebral cortex and cerebellum as well as the connections between cortical regions and between thalamus and cortex. The chapter ends with description of the major building blocks of electric signaling in neurons, including the movement of charged ions in and out of the cell, membrane potentials, action potentials, and postsynaptic potentials.

Humans all around the world are drawn to creating and consuming art due to its capability to evoke emotions, but the mechanisms underlying art-evoked emotions remain poorly characterized. Here we show how embodiement contributes to emotions evoked by a large database of visual art pieces. In four experiments, we mapped the subjective feeling space of art-evoked emotions (n = 244), quantified “bodily fingerprints” of these emotions (n = 615), and recorded the subjects’ interest annotations (n = 306) and eye movements (n = 21) while viewing the art. We show that art evokes a wide spectrum of emotional feelings, and that the bodily fingerprints triggered by art are central to these feelings, especially in artworks where human figures are the subjectively most salient Altogether these results support the model that bodily sensations are central to the aesthetic emotional experience.

Abstract This chapter examines neurophysiological responses related to various cognitive processes, expectation of stimuli and events, and stimulus probability. The responses include the contingent negative variation, the electric and magnetic mismatch responses, P300, the N400 family of responses typically occurring during processing of speech and language, and the error-related negativity that arises when subjects commit an error. The attributes of these responses, the variables that modulate them, and their likely neural generators are discussed. Although these responses have been known for many decades, here they are discussed within the same predictive coding framework as they seem to be related to complex and goal-directed human behavior that unfolds in uncertain and surprising environments.

This chapter briefly describes the various types of evoked and event-related responses that can be recorded in response to auditory stimulation, such as clicks and tones, and speech. Transient auditory-evoked responses are generally grouped into three major categories according to their latencies: (a) brainstem auditory evoked potentials occur within the first 10 ms, typically with 5–7 deflections, (b) middle-latency auditory-evoked potentials occur within 12 to 50 ms, and (c) long-latency auditory-evoked potentials range from about 50 to 250 ms with generators in the supratemporal auditory cortex. Steady-state auditory responses can be elicited by periodic stimuli, They can be used in frequency-tagging experiments, for example in following inputs from the left and right ear to the auditory cortices of both hemispheres.

Abstract This chapter takes a comprehensive look at physiological and nonphysiological artifacts commonly encountered in MEG and EEG studies. After description of the occurrence, morphology, and topographical distribution of the artifacts, suggestions are given for their removal. Physiological artifacts can be caused by eye movements and blinks; muscle contractions (in the face, head, and body); heart’s pulsation and electrical activity; respiration; and sweating. Examples of nonphysiological artifacts are provided and include power-line noise, response-box artifacts, and artifacts generated by poorly sited EEG electrodes, or malfunctioning MEG or EEG sensors. We also discuss artifacts produced by other equipment used in conjunction with EEG/MEG, such as magnetic resonance imaging (MRI) scanners and noninvasive brain stimulators. The chapter concludes with some thoughts about how to ensure that the measured signals arise from the brain.

In complex regional pain syndrome (CRPS), the representation area of the affected limb in the primary sensorimotor cortex (SM1) reacts abnormally during sensory stimulation and motor actions. We recorded 3T functional magnetic resonance imaging resting‐state data from 17 upper‐limb CRPS type 1 patients and 19 healthy control subjects to identify alterations of patients' SM1 function during spontaneous pain and to find out how the spatial distribution of these alterations were related to peripheral symptoms. Seed‐based correlations and independent component analyses indicated that patients' upper‐limb SM1 representation areas display (i) reduced interhemispheric connectivity, associated with the combined effect of intensity and spatial extent of limb pain, (ii) increased connectivity with the right anterior insula that positively correlated with the duration of CRPS, (iii) increased connectivity with periaqueductal gray matter, and (iv) disengagement from the other parts of the SM1 network. These findings, now reported for the first time in CRPS, parallel the alterations found in patients suffering from other chronic pain conditions or from limb denervation; they also agree with findings in healthy persons who are exposed to experimental pain or have used their limbs asymmetrically. Our results suggest that CRPS is associated with a sustained and somatotopically specific alteration of SM1 function, that has correspondence to the spatial distribution of the peripheral manifestations and to the duration of the syndrome.

Abstract This chapter examines the advantages, disadvantages, and pitfalls of multimodal assessment of brain function. Studies combining MEG/EEG with fMRI in similar setups have resulted in seemingly conflicting findings regarding the time courses of hemodynamic and neurophysiological responses. Two simple models are presented for explaining these conflicting observations in terms of the hemodynamic delay and white-matter transmission times. It is proposed that fMRI signals are dominated by activation transmitted via dense and thin neuronal fibers, whereas MEG/EEG signals likely reflect the most synchronously active neural populations connected by thick, fast-conducting fibers. The chapter closes with some exciting new EEG literature describing noninvasive brain stimulation with TMS, tDCS, tACS, and focused ultrasound, and it also introduces the developing hybrid MEG–MRI. Finally, it is posited that using multiple methods in systems and cognitive/social neuroscience is the new normal in the 21st century.

Abstract This chapter focuses on how to acquire data and, once that is completed, how to perform basic preprocessing and ultimately put the data into a standard format that can be understood and shared with other scientists. The behavior of analog filters is described, and the interactions between filtering and data acquisition parameters, such as data sampling rate, and associated pitfalls in data acquisition are examined in detail. The use of simulated EEG and MEG signals for testing preprocessing routines are discussed. The issue of standardization of data formats is addressed and details of the BIDS (Brain Imaging Data Standard) standards for MEG and EEG data are explained.

This chapter discusses olfactory and visceral responses as well as the MEG/EEG signature of multisensory interaction. Olfactory stimuli can be embedded in a continuous humified airflow where the stimuli are presented at intervals of tens of seconds to avoid short-term habituation. Visceral stimulation typically requires purpose-built stimulating electrodes for direct access to the viscera. Studies of multisensory interaction are necessary because our everyday experiences involve inputs from multiple senses, the temporal coincidence of which allows the brain to construct representations of unique objects or events. Detection and correct interpretation of the nonlinear multisensory interactions call for careful considerations of both the sites of interaction and the changes in the amplitudes of evoked responses and spontaneous activity.

Abstract This chapter is devoted to task-related neurophysiology of the human visual system. Starting with a brief historical introduction of how task-related responses were first averaged, the discussion continues with some early controversies in the field. The types of transient and steady-state visual responses that can be recorded from the human retina and cerebral cortex are then briefly outlined, followed by introducing the most important experimental stimulus parameters that affect the evoked responses: visual acuity, distance and visual angle of the stimulus, full-field or partial-field (foveal, extrafoveal) visual stimulation, luminance and contrast, and spatial and temporal frequencies. Presentation of visually evoked electric and magnetic signals and their neural sources starts from the retinogram and continues to transient and steady-state visual responses, frequency tagging, multifocal stimulation, and differential responses from the ventral and dorsal streams. The chapter closes with a brief look at decoding stimulus categories.

Abstract This chapter covers the wide range of neurophysiological responses associated with the processing of social information. The discussion begins by presenting ecologically valid perspectives that incorporate setups for both one-person and two-person neuroscience. In contrast to early experiments in social neuroscience that applied static stimuli and considered the subject as an observer, the newer approaches consider the subject as an active, engaged participant whose brain does not stay the same during the whole experiment. The examples include neurophysiological responses to viewing static and dynamic faces, face parts and bodies, and other persons’ emotional expressions, all the way to action observation and mirroring. The chapter ends by discussing hyperscanning methods for MEG and EEG and by reviewing some existing studies and possible pitfalls. Finally, work devoted to the neurophysiology of human verbal communication is briefly examined.

Abstract The chapter gives a general overview of the basic physics and physiology of MEG and EEG signals. The relationship between electric charges and electric currents is described, as well as some basic laws that relate current to voltage, resistance, and conductivity. Next, the relationship between currents and magnetic fields is examined, followed by introduction of superconductivity and its relevance to MEG. This leads into a discussion of source currents in the brain and how they can be identified by solving the so-called inverse problem. It is shown that the shape and conductivity of the volume conductor—comprising different tissues of the head—affect MEG and EEG differently, as relating to the detectability of currents in the brain. General points about volume conduction and cancellation of activity are also stressed. The chapter ends by touching on the spatial and temporal resolution and precision of MEG and EEG.

Abstract This chapter highlights neurophysiological recordings from the human motor system from skeletal muscles to the cerebral cortex, as well as interactions between these two systems. A brief history of the field introduces the movement-related readiness potentials and fields for upper- and lower-limb acts. Studies of the coherence between muscular and brain activity are especially illuminating and technically robust, as exemplified by cortex–muscle coherence, corticokinematic coherence, and corticovocal coherence. The discussion extends beyond simple motor acts, such as button presses and repetitive finger movements, examining more complex motor actions and the role of predictive coding and proprioceptive feedback in motor control. The reader is also reminded about the importance of motor equivalence and inhibition in selecting the best motor pattern in each situation.

Abstract This chapter moves into neurodynamics, describing different types of canonical brain rhythms observed in the ongoing MEG/EEG. Three rhythms with similar frequency content in the 10-Hz range—the posterior vision-related alpha, the centrally distributed sensorimotor mu, and temporal-lobe originated hearing-related tau—can be separated from each other on the basis of topographic distributions and reactivity to different stimuli and tasks. Beta, theta, gamma, and delta-band activity, as well as ultra-slow oscillations, are described as well. The chapter continues with examples of coupling between various brain rhythms, and with a description of characteristic changes of MEG/EEG rhythms during different stages of sleep. Finally, effects of anesthetics and other drugs and substances of MEG/EEG are examined.

Abstract MEG–EEG Primer is the first ever volume to introduce and discuss MEG and EEG in a balanced manner side by side, starting from the methods’ physical and physiological bases and then advancing to data acquisition, analysis, visualization, and interpretation. The authors pay special attention to careful experimentation, guiding readers to differentiate brain signals from various artifacts and to ensure that the collected data are reliable. The book weighs the strengths and weaknesses of MEG and EEG relative to one another and to other methods used in systems, cognitive, and social neuroscience. The authors discuss the role of MEG and EEG in studying perception, action, cognition, and emotion, as well as examine the assessment of brain function in various clinical disorders. New developments in MEG and EEG hardware and software are also featured. The book aims to bring members of multidisciplinary research teams onto equal footing so that they can contribute to different aspects of MEG and EEG results and to be able to participate in future developments in the field. The book ends with a wider look at the role of time-sensitive MEG/EEG recordings in the current attempts to understand how the human brain works.

Abstract This brief chapter begins by describing the relatively different historical trajectories of the development of EEG and MEG methods, starting for EEG already in 1875 and for MEG in the 1960s. The main prominent brain rhythms (e.g., alpha and mu), well visible in both MEG and EEG, are briefly introduced. The principle of evoked MEG and EEG responses is described, explaining how they are triggered by incoming sensory stimuli or other events. The chapter ends by summarizing the various advantages and disadvantages of MEG and EEG methods, which are essential for understanding the side-by-side comparisons of electric and magnetic recordings presented in later chapters of the book.

Abstract This chapter discusses the strengths, pitfalls, and practicalities of MEG and EEG data analysis methods and visualization strategies. Data-set segmentation, signal-to-noise considerations, signal levels, and power are examined as these may drive the chosen data analysis strategy. After basic analyses of averaged and unaveraged data, brain microstates, event-related desynchronization/synchronization, temporal spectral evolution, and time-frequency analyses, phase synchronization, and cross-frequency coupling are discussed. Measures of the introduced association and functional/effective connectivity, as studied in the time or frequency domains, include correlation, coherence, phase-locking factor, phase-locking value, phase-lag index and their variants, mutual information, transfer entropy, cross-correlation, Granger causality, dynamic causal modeling, and graph-theoretical analysis. The MEG/EEG source modeling section covers forward and inverse problems, head models, single- and multidipole models, distributed models, and beamformers. After discussion of spatial resolution, source extent, and effects of synchrony complete the topics, the chapter ends with statistical considerations regarding signal detectability in individual and group-level data.

Abstract This chapter commences with the rich history of clinical EEG and charts the growing clinical MEG literature. The need for clinical neurophysiological tests with both high specificity and sensitivity is stressed. MEG and EEG have already provided useful clinical input on epileptic foci and mapping of sensory, language, cognitive, and memory function prior to surgery for seizure foci or brain tumors. A simple method is provided for localizing the central sulcus based on anatomical and functional criteria. Studies of hemispheric dominance for speech and language are discussed. A few applications are noted where EEG in particular, with its ease of use at the bedside, could play a greater role in patient assessment (e.g., in stroke, coma, and other critical illness). The chapter ends with speculation about why clinical applications for MEG have taken a long time to become established.