Electroencephalographic activity during perception of motion in childhood

Neurodevelopmental Effects of Perinatal TCDD Exposure Differ from Those of Other PCDD/Fs in Vietnamese Children Living near the Former US Air Base in Da Nang, Vietnam

This study reports that children exposed to 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), the major toxin in Agent Orange, from the breast milk of mothers residing near the former Da Nang US air base in Vietnam may have specific alterations in higher brain functions, resulting in social and communication deficits, including autism spectrum disorder (ASD). After the age of 8 years, girls with high TCDD showed increased attention deficit hyperactivity disorder (ADHD)-like behaviors and altered mirror neuron activity, which is often observed in children with ASD. However, no significant relationship between autistic traits and toxic equivalency values of polychlorinated dibenzodioxins and polychlorinated dibenzofurans (TEQ-PCDD/Fs) was found in these children. Notably, boys with high levels of TEQ-PCDD/Fs showed poor language and motor development in the first 3 years of life, although boys with high TCDD levels did not. However, at 8 years of age, boys with high TCDD showed reading learning difficulties, a neurodevelopmental disorder. These findings suggest that perinatal TCDD exposure impacts social-emotional cognitive functions, leading to sex-specific neurodevelopmental disorders-learning difficulty in boys and ADHD in girls. Future studies with a greater number of children exposed to high levels of TCDD are necessary to estimate the threshold values for neurodevelopmental effects.

Motor networks in children with autism spectrum disorder: a systematic review on EEG studies

Motor disturbance and altered motor networks are commonly reported in individuals with autism spectrum disorder (ASD). It has been suggested that electroencephalogram (EEG) can be used to provide exquisite temporal resolution for understanding motor control processes in ASD. However, the variability of study design and EEG approaches can impact our interpretation. Here, we conducted a systematic review on recent 11 EEG studies that involve motor observation and/or execution tasks and evaluated how these findings help us understand motor difficulties in ASD. Three behavior paradigms with different EEG analytic methods were demonstrated. The main findings were quite mixed: children with ASD did not always show disrupted neuronal activity during motor observation. Additionally, they might have intact ability for movement execution but have more difficulties in neuronal modulation during movement preparation. We would like to promote discussions on how methodological selections of behavioral tasks and data analytic approaches impact our interpretation of motor deficits in ASD. Future EEG research addressing the inconsistency across methodological approaches is necessary to help us understand neurophysiological mechanism of motor abnormalities in ASD.

Effects of perinatal dioxin exposure on mirror neuron activity in 9-year-old children living in a hot spot of dioxin contamination in Vietnam

BACKGROUND

For 8 years, we have followed up a birth cohort comprising 241 mother-and-infant pairs living around the Da Nang airbase, a hot spot of dioxin contamination in Vietnam, and have reported the impacts of perinatal dioxin exposure on the neurodevelopment of children at various ages. In the present study, 9 years after birth, we investigated the effects of perinatal dioxin exposure on mu and theta rhythms by analyzing EEG power during the execution and observation of hand movements, which indicate mirror neuron system activity.

METHODS

One hundred fifty-five 9-year-old children (86 boys and 69 girls) from the Da Nang birth cohort participated in the EEG examination with free viewing of hand movements. The dioxin levels in their mothers' breast milk, measured 1 month after birth, were used as perinatal dioxin exposure markers. A log transform of the ratio of EEG power during execution or observation of the hand movements relative to the power during observation of a bouncing ball for theta and mu rhythms was used to evaluate mirror neuron activity.

RESULTS

In both brain hemispheres, the log power ratio in the theta band was significantly higher (i.e., less reduction of power) during observation of hand movements in girls exposed to high levels of TCDD. In boys, however, dioxin congeners other than TCDD, including HxCDDs and several PCDF congeners, contributed to increased log power ratios in the theta band. Particularly for PCDF congeners, the log power ratios in the lowest group among 4 exposure groups were lowest and significantly increased (i.e., decreasing reduction of power) with increasing dose.

CONCLUSION

Perinatal TCDD exposure may influence the mirror neuron system of the brain, which plays an important role for social-emotional behavior in children, particularly in girls living in a hot spot of dioxin contamination in Vietnam.

Developmental trajectory of interpersonal motor alignment: Positive social effects and link to social cognition

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Interpersonal motor alignment (IMA) has positive effects on healthy social life.

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IMA - mimicry, synchrony, automatic imitation - is studied throughout development.

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It relies on motor resonance brain mechanisms identified throughout development.

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It is modulated by contextual and personal factors.

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IMA is underinvestigated in adolescence, yet it may aid to enhance resilience.

Interpersonal motor alignment is a ubiquitous behavior in daily social life. It is a building block for higher social cognition, including empathy and mentalizing and promotes positive social effects. It can be observed as mimicry, synchrony and automatic imitation, to name a few. These phenomena rely on motor resonance processes, i.e., a direct link between the perception of an action and its execution. While a considerable literature debates its underlying mechanisms and measurement methods, the question of how motor alignment comes about and changes in ontogeny all the way until adulthood, is rarely discussed specifically. In this review we will focus on the link between interpersonal motor alignment, positive social effects and social cognition in infants, children, and adolescents, demonstrating that this link is present early on in development. Yet, in reviewing the existing literature pertaining to social psychology and developmental social cognitive neuroscience, we identify a knowledge gap regarding the healthy developmental changes in interpersonal motor alignment especially in adolescence.

Musical Role Asymmetries in Piano Duet Performance Influence Alpha-Band Neural Oscillation and Behavioral Synchronization

Recent work in interpersonal coordination has revealed that neural oscillations, occurring spontaneously in the human brain, are modulated during the sensory, motor, and cognitive processes involved in interpersonal interactions. In particular, alpha-band (8-12 Hz) activity, linked to attention in general, is related to coordination dynamics and empathy traits. Researchers have also identified an association between each individual's attentiveness to their co-actor and the relative similarity in the co-actors' roles, influencing their behavioral synchronization patterns. We employed music ensemble performance to evaluate patterns of behavioral and neural activity when roles between co-performers are systematically varied with complete counterbalancing. Specifically, we designed a piano duet task, with three types of co-actor dissimilarity, or asymmetry: (1) musical role (starting vs. joining), (2) musical task similarity (similar vs. dissimilar melodic parts), and (3) performer animacy (human-to-human vs. human-to-non-adaptive computer). We examined how the experience of these asymmetries in four initial musical phrases, alternatingly played by the co-performers, influenced the pianists' performance of a subsequent unison phrase. Electroencephalography was recorded simultaneously from both performers while playing keyboards. We evaluated note-onset timing and alpha modulation around the unison phrase. We also investigated whether each individual's self-reported empathy was related to behavioral and neural activity. Our findings revealed closer behavioral synchronization when pianists played with a human vs. computer partner, likely because the computer was non-adaptive. When performers played with a human partner, or a joining performer played with a computer partner, having a similar vs. dissimilar musical part did not have a significant effect on their alpha modulation immediately prior to unison. However, when starting performers played with a computer partner with a dissimilar vs. similar part there was significantly greater alpha synchronization. In other words, starting players attended less to the computer partner playing a similar accompaniment, operating in a solo-like mode. Moreover, this alpha difference based on melodic similarity was related to a difference in note-onset adaptivity, which was in turn correlated with performer trait empathy. Collectively our results extend previous findings by showing that musical ensemble performance gives rise to a socialized context whose lasting effects encompass attentiveness, perceptual-motor coordination, and empathy.

Mu-oscillation changes related to the development of anticipatory postural control in children and adolescents

Anticipatory postural adjustments (APAs) cancel the destabilizing effects of movement on posture. Across development, the maturation of APAs is characterized by an accurate adjustment of the timing parameters of electromyographic (EMG) response. The study aimed at investigating the maturation of cortical oscillations involved in the improvement of APAs efficiency. Thirty-six healthy participants (8–16 yr) performed the bimanual load-lifting task in which subjects are instructed to lift a load, placed on the left forearm, with the right hand. EMG data were acquired over the biceps brachii on the postural arm to the determine EMG response onset. Electroencephalographic signals were analyzed in the time-frequency domain by convolution with complex Gaussian Morlet wavelets. Electrophysiological signature of APAs in children and adolescents consisted of a mu-rhythm desynchronization over the sensorimotor cortex contralateral to the postural arm. Across development, the mu-rhythm desynchronization was characterized by a progressive shift forward of the onset of the desynchronization, lower amplitude, and velocity. These changes occurred along with an alteration of the timing of the EMG response, as shown by an earlier onset of the flexor inhibition with increasing age. The maturational changes in the Mu-oscillations might sustain the development of APAs. A possible role of the Mu-oscillation in the generation of postural command is discussed.

NEW & NOTEWORTHY Across development, our study showed a progressive shift forward of the parameters of the mu-rhythm desynchronization. These changes occurred along with an alteration of the timing parameters of the electromyographic response, as shown by an earlier onset of the flexor inhibition with increasing age. The progressive development of APAs during childhood and adolescence might therefore be sustained by maturational electrophysiological changes that include mu-rhythm oscillation modifications in the postural sensorimotor cortex.

Action-skilled observation: Issues for the study of sport expertise and the brain

With a growing body of research devoted to uncovering regions of the brain implicated in action observation following various action-related experiences, including sport, we ask what we know from this research, and what we still need to know, as it pertains to sport and the brain. To do this, we review and integrate knowledge garnered from developmental work, short-term motor learning studies, and most significantly sport athletes across varying skill levels. We consider various neurophysiological methods, including TMS, fMRI, and EEG, which have been used to help uncover brain regions involved in action-skilled observation. We are particularly interested in how these processes are related to action prediction and the detection of deceptive actions among athlete groups. This research is considered within broad theoretical frameworks related to action-simulation and prediction, although our main focus is on the brain regions that have been implicated in skilled action observation and the implications of this research for knowledge and further study of sport expertise.

Frontal Functional Connectivity of Electrocorticographic Delta and Theta Rhythms during Action Execution Versus Action Observation in Humans

We have previously shown that in seven drug-resistant epilepsy patients, both reaching-grasping of objects and the mere observation of those actions did desynchronize subdural electrocorticographic (ECoG) alpha (8-13 Hz) and beta (14-30) rhythms as a sign of cortical activation in primary somatosensory-motor, lateral premotor and ventral prefrontal areas (Babiloni et al., 2016a). Furthermore, that desynchronization was greater during action execution than during its observation. In the present exploratory study, we reanalyzed those ECoG data to evaluate the proof-of-concept that lagged linear connectivity (LLC) between primary somatosensory-motor, lateral premotor and ventral prefrontal areas would be enhanced during the action execution compared to the mere observation due to a greater flow of visual and somatomotor information. Results showed that the delta-theta (<8 Hz) LLC between lateral premotor and ventral prefrontal areas was higher during action execution than during action observation. Furthermore, the phase of these delta-theta rhythms entrained the local event-related connectivity of alpha and beta rhythms. It was speculated the existence of a multi-oscillatory functional network between high-order frontal motor areas which should be more involved during the actual reaching-grasping of objects compared to its mere observation. Future studies in a larger population should cross-validate these preliminary results.

Mirror neuron activation as a function of explicit learning: changes in mu-event-related power after learning novel responses to ideomotor compatible, partially compatible, and non-compatible stimuli

Questions regarding the malleability of the mirror neuron system (MNS) continue to be debated. MNS activation has been reported when people observe another person performing biological goal-directed behaviors, such as grasping a cup. These findings support the importance of mapping goal-directed biological behavior onto one's motor repertoire as a means of understanding the actions of others. Still, other evidence supports the Associative Sequence Learning (ASL) model which predicts that the MNS responds to a variety of stimuli after sensorimotor learning, not simply biological behavior. MNS activity develops as a consequence of developing stimulus-response associations between a stimulus and its motor outcome. Findings from the ideomotor literature indicate that stimuli that are more ideomotor compatible with a response are accompanied by an increase in response activation compared to less compatible stimuli; however, non-compatible stimuli robustly activate a constituent response after sensorimotor learning. Here, we measured changes in the mu-rhythm, an EEG marker thought to index MNS activity, predicting that stimuli that differ along dimensions of ideomotor compatibility should show changes in mirror neuron activation as participants learn the respective stimulus-response associations. We observed robust mu-suppression for ideomotor-compatible hand actions and partially compatible dot animations prior to learning; however, compatible stimuli showed greater mu-suppression than partially or non-compatible stimuli after explicit learning. Additionally, non-compatible abstract stimuli exceeded baseline only after participants explicitly learned the motor responses associated with the stimuli. We conclude that the empirical differences between the biological and ASL accounts of the MNS can be explained by Ideomotor Theory.

Assessing human mirror activity with EEG mu rhythm: A meta-analysis

A fundamental issue in cognitive neuroscience is how the brain encodes others' actions and intentions. In recent years, a potential advance in our knowledge on this issue is the discovery of mirror neurons in the motor cortex of the nonhuman primate. These neurons fire to both execution and observation of specific types of actions. Researchers use this evidence to fuel investigations of a human mirror system, suggesting a common neural code for perceptual and motor processes. Among the methods used for inferring mirror system activity in humans are changes in a particular frequency band in the electroencephalogram (EEG) called the mu rhythm. Mu frequency appears to decrease in amplitude (reflecting cortical activity) during both action execution and action observation. The current meta-analysis reviewed 85 studies (1,707 participants) of mu that infer human mirror system activity. Results demonstrated significant effect sizes for mu during execution (Cohen's d = 0.46, N = 701) as well as observation of action (Cohen's d = 0.31, N = 1,508), confirming a mirroring property in the EEG. A number of moderators were examined to determine the specificity of these effects. We frame these meta-analytic findings within the current discussion about the development and functions of a human mirror system, and conclude that changes in EEG mu activity provide a valid means for the study of human neural mirroring. Suggestions for improving the experimental and methodological approaches in using mu to study the human mirror system are offered.

Revisiting mu suppression in autism spectrum disorder

Two aspects of the EEG literature lead us to revisit mu suppression in Autism Spectrum Disorder (ASD). First and despite the fact that the mu rhythm can be functionally segregated in two discrete sub-bands, 8-10 Hz and 10-12/13 Hz, mu-suppression in ASD has been analyzed as a homogeneous phenomenon covering the 8-13 Hz frequency. Second and although alpha-like activity is usually found across the entire scalp, ASD studies of action observation have focused on the central electrodes (C3/C4). The present study was aimed at testing on the whole brain the hypothesis of a functional dissociation of mu and alpha responses to the observation of human actions in ASD according to bandwidths. Electroencephalographic (EEG) mu and alpha responses to execution and observation of hand gestures were recorded on the whole scalp in high functioning subjects with ASD and typical subjects. When two bandwidths of the alpha-mu 8-13 Hz were distinguished, a different mu response to observation appeared for subjects with ASD in the upper sub-band over the sensorimotor cortex, whilst the lower sub-band responded similarly in the two groups. Source reconstructions demonstrated that this effect was related to a joint mu-suppression deficit over the occipito-parietal regions and an increase over the frontal regions. These findings suggest peculiarities in top-down response modulation in ASD and question the claim of a global dysfunction of the MNS in autism. This research also advocates for the use of finer grained analyses at both spatial and spectral levels for future directions in neurophysiological accounts of autism.

EEG mu rhythm in typical and atypical development

Electroencephalography (EEG) is an effective, efficient, and noninvasive method of assessing and recording brain activity. Given the excellent temporal resolution, EEG can be used to examine the neural response related to specific behaviors, states, or external stimuli. An example of this utility is the assessment of the mirror neuron system (MNS) in humans through the examination of the EEG mu rhythm. The EEG mu rhythm, oscillatory activity in the 8-12 Hz frequency range recorded from centrally located electrodes, is suppressed when an individual executes, or simply observes, goal directed actions. As such, it has been proposed to reflect activity of the MNS. It has been theorized that dysfunction in the mirror neuron system (MNS) plays a contributing role in the social deficits of autism spectrum disorder (ASD). The MNS can then be noninvasively examined in clinical populations by using EEG mu rhythm attenuation as an index for its activity. The described protocol provides an avenue to examine social cognitive functions theoretically linked to the MNS in individuals with typical and atypical development, such as ASD. 

Skin color has no impact on motor resonance: evidence from mu rhythm suppression and imitation

It has been suggested that physical similarity with an observed model facilitates action-perception and understanding. Indeed, a number of studies have shown that observing actors of one's own race facilitate motor, sensory and pain resonance, possibly mediated by the human mirror-neuron system (hMNS). However, most of these studies have used stimuli that included emotional or cultural components, hence obscuring the precise contribution of physical similarity to resonance phenomena per se. The goal of the present study was to assess the effect of physical similarity (skin color) on motor resonance using stimuli that have no emotional and cultural components. We used both behavioral (imitation) and electrophysiological measures (mu-rhythm) to assess the effects of skin color on the hMNS during the observation of simple finger movements. Our results show that, in line with previous results, observation of biological movements resulted in faster reaction times and greater mu-rhythm suppression compared to non-biological movements. However, physical similarity did not affect imitation speed or mu-rhythm desynchronization. These results suggest that physical similarity with an observed action in terms of skin color does not modulate hMNS activity, and that the enhanced resonance effects reported in the previous studies are likely attributable to cultural and emotional aspects.

The mirror mechanism and mu rhythm in social development

Since the discovery of mirror neurons (MNs) in the monkey there has been a renewed interest in motor theories of cognitive and social development in humans by providing a potential neural mechanism underlying an action observation/execution matching system. It has been proposed that this system plays a fundamental role in the development of complex social and cognitive behaviors such as imitation and action recognition. In this review we discuss what is known about MNs from the work using single-cell recordings in the adult monkey, the evidence for the putative MN system in humans, and the extent to which research using electroencephalography (EEG) methods has contributed to our understanding of the development of these motor systems and their role in the social behaviors postulated by the MN hypothesis. We conclude with directions for future research that will improve our understanding of the putative human MN system and the functional role of MNs in social development.

Developmental changes in mu suppression to observed and executed actions in autism spectrum disorders

There has been debate over whether disruptions in the mirror neuron system (MNS) play a key role in the core social deficits observed in autism spectrum disorders (ASD). EEG mu suppression during the observation of biological actions is believed to reflect MNS functioning, but understanding of the developmental progression of the MNS and EEG mu rhythm in both typical and atypical development is lacking. To provide a more thorough and direct exploration of the development of mu suppression in individuals with ASD, a sample of 66 individuals with ASD and 51 typically developing individuals of 6-17 years old were pooled from four previously published studies employing similar EEG methodology. We found a significant correlation between age and mu suppression in response to the observation of actions, both for individuals with ASD and typical individuals. This relationship was not seen during the execution of actions. Additionally, the strength of the correlation during the observation of actions did not significantly differ between groups. The results provide evidence against the argument that mirror neuron dysfunction improves with age in individuals with ASD and suggest, instead, that a diagnosis-independent developmental change may be at the root of the correlation of age and mu suppression.

Adverse rearing environments and neural development in children: the development of frontal electroencephalogram asymmetry

BACKGROUND

Children raised in institutional settings experience marked deprivation in social and environmental stimulation. This deprivation may disrupt brain development in ways that increase risk for psychopathology. Differential hemispheric activation of the frontal cortex is an established biological substrate of affective style that is associated with internalizing psychopathology. Previous research has never characterized the development of frontal electroencephalogram asymmetry in children or evaluated whether adverse rearing environments alter developmental trajectories.

METHODS

A sample of 136 children (mean age = 23 months) residing in institutions in Bucharest, Romania, and a sample of community control subjects (n = 72) participated. Half of institutionalized children were randomized to a foster care intervention. Electroencephalogram data were acquired at study entry and at ages 30, 42, and 96 months. A structured diagnostic interview of psychiatric disorders was completed at 54 months.

RESULTS

Children exhibited increases in right relative to left hemisphere frontal activation between the second and fourth years of life, followed by an increase in left relative to right hemisphere activation. Children reared in institutions experienced a prolonged period of increased right hemisphere activation and a blunted rebound in left frontal activation. Foster care placement was associated with improved developmental trajectories but only among children placed before 24 months. The development trajectory of frontal electroencephalogram asymmetry in early childhood predicted internalizing symptoms at 54 months.

CONCLUSIONS

Exposure to adverse rearing environments can alter brain development, culminating in heightened risk for psychopathology. Interventions delivered early in life have the greatest potential to mitigate the long-term effects of these environments.

Delayed maturation in brain electrical activity partially explains the association between early environmental deprivation and symptoms of attention-deficit/hyperactivity disorder

BACKGROUND

Children raised in institutional settings are exposed to social and environmental circumstances that may deprive them of expected environmental inputs during sensitive periods of brain development that are necessary to foster healthy development. This deprivation is thought to underlie the abnormalities in neurodevelopment that have been found in previously institutionalized children. It is unknown whether deviations in neurodevelopment explain the high rates of developmental problems evident in previously institutionalized children, including psychiatric disorders.

METHODS

We present data from a sample of children raised in institutions in Bucharest, Romania (n = 117) and an age- and sex-matched sample of community control subjects (n = 49). Electroencephalogram data were acquired following entry into the study at age 6 to 30 months, and a structured diagnostic interview of psychiatric disorders was completed at age 54 months.

RESULTS

Children reared in institutions evidenced greater symptoms of attention-deficit/hyperactivity disorder, anxiety, depression, and disruptive behavior disorders than community controls. Electroencephalogram revealed significant reductions in alpha relative power and increases in theta relative power among children reared in institutions in frontal, temporal, and occipital regions, suggesting a delay in cortical maturation. This pattern of brain activity predicted symptoms of hyperactivity and impulsivity at age 54 months, and significantly mediated the association between institutionalization and attention-deficit/hyperactivity disorder symptoms. Electroencephalogram power was unrelated to depression, anxiety, or disruptive behaviors.

CONCLUSIONS

These findings document a potential neurodevelopmental mechanism underlying the association between institutionalization and psychiatric morbidity. Deprivation in social and environmental conditions may perturb early patterns of neurodevelopment and manifest as psychiatric problems later in life.

Atypical activation of the mirror neuron system during perception of hand motion in autism

Disorders in the autism spectrum are characterized by deficits in social and communication skills such as imitation, pragmatic language, theory of mind, and empathy. The discovery of the "mirror neuron system" (MNS) in macaque monkeys may provide a basis from which to explain some of the behavioral dysfunctions seen in individuals with autism spectrum disorders (ASD).We studied seven right-handed high-functioning male autistic and eight normal subjects (TD group) using functional magnetic resonance imaging during observation and execution of hand movements compared to a control condition (rest). The between group comparison of the contrast [observation versus rest] provided evidence of a bilateral greater activation of inferior frontal gyrus during observation of human motion than during rest for the ASD group than for the TD group. This hyperactivation of the pars opercularis (belonging to the MNS) during observation of human motion in autistic subjects provides strong support for the hypothesis of atypical activity of the MNS that may be at the core of the social deficits in autism.

Changes in mu rhythm during action observation and execution in adults with Down syndrome: implications for action representation

The human mirror neuron system is thought to be the underlying basis of perception-action coupling involved in imitation and action understanding. In order to examine this issue we examined the recruitment of the mirror neuron system, as reflected in mu rhythm suppression in a population of adults with Down syndrome (DS) with known strengths in imitation but with impairments in perceptual-motor coupling. Ten healthy adults and 10 age-matched adults with (DS) participated in the study. Subjects were asked to make self-paced movements (execution), and view movements made by the experimenter (observation). The action consisted of reaching with the dominant hand to grasp and lift a cup. Cortical responses were recorded with a whole head magnetoencephalography (MEG) system. Both groups demonstrated significant attenuation of the mu rhythm in bilateral sensorimotor areas when executing the action. Typical adults also demonstrated significant mu suppression in bilateral sensorimotor areas during observation of the action. In contrast, when observing the movement, adults with DS showed a significantly reduced overall attenuation of mu activity with a distinct laterality in the pattern of mu suppression. These results suggest that there is a dysfunction in the execution/observation matching system in adults with DS and has implications for the functional role of the human mirror neuron system.

The mirror neuron system: grasping others? actions from birth?

In the adult human brain, the presence of a system matching the observation and the execution of actions is well established. This mechanism is thought to rely primarily on the contribution of so-called 'mirror neurons', cells that are active when a specific gesture is executed as well as when it is seen or heard. Despite the wealth of evidence detailing the existence of a mirror neuron system (MNS) in the adult brain, little is known about its normal development. Yet, a better understanding of the MNS in infants would be of considerable theoretical and clinical interest, as dysfunctions within the MNS have been demonstrated in neurodevelopmental disorders such as autism spectrum disorder. Arguments in favor of an innate, or very early, mechanism underlying action understanding mainly come from studies of neonatal imitation, the existence of which has been questioned by some. Here, we review evidence suggesting the presence of an MNS in the human child, as well as work that suggests, although indirectly, the existence of a mechanism matching the perception and the execution of actions in the human newborn.

EEG mu rhythm and imitation impairments in individuals with autism spectrum disorder

Imitation ability has consistently been shown to be impaired in individuals with autism. A dysfunctional execution/observation matching system has been proposed to account for this impairment. The EEG mu rhythm is believed to reflect an underlying execution/observation matching system. This study investigated evidence of differential mu rhythm attenuation during the observation, execution, and imitation of movements and examined its relation to behaviorally assessed imitation abilities. Fourteen high-functioning adults with autism spectrum disorder (ASD) and 15 IQ- and age-matched typical adults participated. On the behavioral imitation task, adults with ASD demonstrated significantly poorer performance compared to typical adults in all domains of imitation ability. On the EEG task, both groups demonstrated significant attenuation of the mu rhythm when executing an action. However, when observing movement, the individuals with ASD showed significantly reduced attenuation of the mu wave. Behaviorally assessed imitation skills were correlated with degree of mu wave attenuation during observation of movement. These findings suggest that there is execution/observation matching system dysfunction in individuals with autism and that this matching system is related to degree of impairment in imitation abilities.

A primer on motion visual evoked potentials

Motion visual evoked potentials (motion VEPs) have been used since the late 1960s to investigate the properties of human visual motion processing, and continue to be a popular tool with a possible future in clinical diagnosis. This review first provides a synopsis of the characteristics of motion VEPs and then summarizes important methodological aspects. A subsequent overview illustrates how motion VEPs have been applied to study basic functions of human motion processing and shows perspectives for their use as a diagnostic tool.

EEG evidence for the presence of an action observation-execution matching system in children

In the adult human brain, passive observation of actions performed by others activates some of the same cortical areas that are involved in the execution of actions, thereby contributing to action recognition. This mechanism appears to occur through activation of a population of action-coding cells known as mirror neurons (MN). In the adult motor cortex, performing actions and observing human movement reduces the magnitude of the mu (8-13 Hz) rhythm, possibly reflecting MN system activity. Despite the wealth of information available regarding the adult MN system, little is known about its existence in children. Here, we used EEG to probe mu rhythm modulation in 15 children during observation and execution of hand actions. Our data show that mu rhythm attenuation occurs in children under 11 years old during observation of hand movements. Similarly to what has been reported in adults, observation of goal/object-orientated movement produces greater modulation of the mu rhythm than intransitive movement. These data confirm the existence of an observation-execution matching system in the immature human brain and may be of clinical value in the understanding of neurodevelopmental disorders associated with a faulty MN system, such as autism spectrum disorder.

A motor resonance mechanism in children? Evidence from subdural electrodes in a 36-month-old child

The presence of a neural mechanism matching execution and observation of actions in the adult human brain is well established. In children, however, description of a resonance motor mechanism is still preliminary. In the present study, we recorded electroencephalographic signals from a subdural 64-contact grid electrode in a 36-month-old child with epilepsy. Spectral analysis was performed on sequences where the child drew with her right hand, watched an experimenter drawing with his right hand or was at rest. Contact sites corresponding to sensorimotor areas were discovered where absolute power was decreased during both observation and execution of hand/arm actions. These data suggest the presence of a mirror neuron system early in the developing brain.

Impairment of a cortical event-related desynchronisation during a bimanual load-lifting task in children with autistic disorder

In autism, the abilities of communication are affected, associated with abnormalities of cognitive, sensorial and motor development. In a previous study based on a load-lifting task, we showed impairment of anticipation in children with autism as evidenced by kinematics and eletromyographic recordings [Neurosci. Lett. 348 (2003) 17]. In the present study, we assessed the cortical counterparts of the use of anticipatory postural adjustments in a group of control children and in a group of children with autism. The tasks required maintaining a stable forearm position despite imposed or voluntary lifting of an object placed either on the controlateral forearm or on a support. We investigated the differences between the two groups of children on the Event-Related Desynchronisation (ERD) which precedes movement onset in adults [Electroencephalogr. Clin. Neurophysiol. 46 (1979) 138]. Electroencephalogram (EEG) power evolution of a 6-8-Hz frequency band was averaged before and after imposed or voluntary movement onset. EEG reactivity of control and autistic children did not differ during the imposed unloading condition, but significant differences appeared in the voluntary unloading situations. Before lifting the object, control children showed an ERD above the left motor areas. An ERD also occurred above the right motor areas when the object was placed on their forearm. This indicates that the ERD can also translate the use of anticipatory postural adjustments. By contrast, children with autism did not show an ERD in the two voluntary situations. This suggests a central deficit of anticipation in both postural and motor control in children with autism.

Visual perception in children: human, animal and virtual movement activates different cortical areas

This study was designed to relate visual perception of motion (HUMAN, ANIMAL and VIRTUAL) to cortical activity (qEEG parameters). Thirty-four healthy right-handed children (29 months-94 months, mean age 5 years) viewed a video film showing a still image (a lake) and animated images with human, animal and virtual movement. EEGs were recorded while the children watched the video film. The power values of each frequency band theta 1: 3.5-5.5 Hz, theta 2: 5.5-7.5 Hz, alpha 1: 7.5-10.5 Hz, alpha 2: 10.5-13 Hz, beta 1: 13-18 Hz, beta 2: 18-25 Hz and beta 3: 25-35 Hz were analyzed in a four-way repeated-measures ANOVA (age x hemisphere x electrode x type of activation). Three main results were obtained: (1) younger children (< 5 years) showed higher power spectral values than older children; (2) there was specificity for real human movement in the left hemisphere; and (3) activations in the left- and right-hemispheres were different according to the movement visualized. These results indicate that in healthy children, human, animal and virtual movement activates different cortical areas.