The use of functional near infrared spectroscopy (fNIRS) has grown exponentially over the past decade, particularly among investigators interested in early brain development. The use of this ...neuroimaging technique has begun to shed light on the development of a variety of sensory, perceptual, linguistic, and social-cognitive functions. Rather than cast a wide net, in this paper we first discuss typical development, focusing on joint attention, face processing, language, and sensorimotor development. We then turn our attention to infants and children whose development has been compromised or who are at risk for atypical development. We conclude our review by critiquing some of the methodological issues that have plagued the extant literature as well as offer suggestions for future research.
•We critically review the literature on both typical and atypical development using fNIRS.•We offer recommendations for future research, particularly in atypical populations.•We focus on how fNIRS in typical development may help identify atypical trajectories.
Since the discovery of mirror neurons in premotor and parietal areas of the macaque monkey, the idea that action and perception may share the same neural code has been of central interest in social, ...developmental, and cognitive neurosciences. A fundamental question concerns how a putative human mirror neuron system may be tuned to the motor experiences of the individual. The current study tested the hypothesis that prior motor experience modulated the sensorimotor mu and beta rhythms. Specifically, we hypothesized that these sensorimotor rhythms would be more desynchronized after active motor experience compared to passive observation experience. To test our hypothesis, we collected EEG from adult participants during the observation of a relatively novel action: an experimenter used a claw-like tool to pick up a toy. Prior to EEG collection, we trained one group of adults to perform this action with the tool (performers). A second group comprised trained video coders, who only had experience observing the action (observers). Both the performers and the observers had no prior motor and visual experience with the action. A third group of novices was also tested. Performers exhibited the greatest mu rhythm desynchronization in the 8-13 Hz band, particularly in the right hemisphere compared to observers and novices. This study is the first to contrast active tool-use experience and observation experience in the mu rhythm and to show modulation with relatively shorter amounts of experience than prior mirror neuron expertise studies. These findings are discussed with respect to its broader implication as a neural signature for a mechanism of early social learning.
The desynchronization of alpha and beta oscillations (mu rhythm) in the central scalp EEG during action observation and action execution is thought to reflect neural mirroring processes. However, the ...extent to which mirror neurons (MNs) or other populations of neurons contribute to such EEG desynchronization is still unknown. Here, we provide the first evidence that, in the monkey, the neuronal activity recorded from the ventral premotor cortex (PMv) strongly contributes to the EEG changes occurring in the beta band over central scalp electrodes, during executed and observed actions. We simultaneously recorded scalp EEG and extracellular activity, Multi Unit Activity (MUA) and Local Field Potentials (LFP), from area F5 of two macaques executing and observing grasping actions. We found that MUA highly correlates with an increase in high gamma LFP power and, interestingly, such LFP power increase also correlates to EEG beta – and in part also to alpha – desynchronization. In terms of timing of signal changes, the increase in high gamma LFP power precedes the EEG desynchronization, during both action observation and execution, thus suggesting a causal role of PMv neuronal activity in the modulation of the alpha and beta mu-rhythm. Lastly, neuronal signals from deeper layers of PMv exert a greater contribution than superficial layers to the EEG beta rhythm modulation, especially during the motor task. Our findings have clear implications for EEG studies in that they demonstrate that the activity of different populations of neurons in PMv contribute to the generation of the mu-rhythm.
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.
Early psychosocial deprivation has profound effects on brain activity in the young child. Previous reports have shown increased power in slow frequencies of the electroencephalogram (EEG), primarily ...in the theta band, and decreased power in higher alpha and beta band frequencies in infants and children who have experienced institutional care.
We assessed the consequences of removing infants from institutions and placing them into a foster care intervention on brain electrical activity when children were 8 years of age. We found the intervention was successful for increasing high frequency EEG alpha power, with effects being most pronounced for children placed into foster care before 24 months of age.
The dependence on age of placement for the effects observed on high frequency EEG alpha power suggests a sensitive period after which brain activity in the face of severe psychosocial deprivation is less amenable to recovery.
Doll play provides opportunities for children to practice social skills by creating imaginary worlds, taking others’ perspectives, and talking about others’ internal states. Previous research using ...functional near‐infrared spectroscopy (fNIRS) found a region over the posterior superior temporal sulcus (pSTS) was more active during solo doll play than solo tablet play, implying that doll play might present opportunities for rehearsing theory of mind and empathy skills, even when playing alone. In this research, we addressed this more directly by investigating 4–8‐year‐old children's (N = 33) use of internal state language (ISL; i.e., references to emotions, desires, and cognitions) when playing with dolls and on tablets, both by themselves and with a social partner, and their associated brain activity in the pSTS using fNIRS. We found that children used more ISL about others when playing with dolls than when playing on tablets, particularly when they were playing alone. This mirrored the patterns seen in pSTS activity in previous research. When individual variability in ISL about others was considered, more ISL about others was linked to stronger pSTS activation. Thus, variability in pSTS activity during play is not about the perceptual or physical differences between toys (e.g., dolls are more human‐like) but about what children think about when they engage in different kinds of play. This is the first research to investigate brain activity during spontaneously occurring ISL and indicates that children have a tendency to take and discuss others’ perspectives during doll play, with implications for social processing in the brain. A video of this article can be viewed at https://youtu.be/58HgxbuhBzU.
► The mu rhythm is optimal to investigate the mirror neuron system in infancy. ► Studies in monkeys demonstrate that the MN system is functional very early after birth. ► Mu rhythm changes during ...ontogeny reflect events related to the sensorimotor system. ► Very likely the MN system is the underlying neural system that supports newborn imitation.
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.
At birth, human infants and newborns of other primate species demonstrate the capacity to attend and to respond to facial stimuli provided by a caregiver. Newborn infants are also capable of ...exhibiting a range of facial expressions. Identification of the neural underpinnings of these capacities represents a formidable challenge in understanding social development. One possible neuronal substrate is the mirror-neuron system assumed to activate shared motor cortical representations for both observation and production of actions. We tested this hypothesis by recording scalp EEG from 1- to 7-day-old newborn rhesus macaques who were observing and producing facial gestures. We found that 5–6 Hz EEG activity was suppressed both when the infants produced facial gestures and while they were observing facial gestures of a human experimenter, but not when they were observing nonbiological stimuli. These findings demonstrate the presence of neural reactivity for biological, communicatively relevant stimuli, which may be a likely signature of neuronal mirroring. The basic elements of the mirror-neuron system appear to operate from the very first days of life and contribute to the encoding of socially relevant stimuli.
It has long been hypothesized that pretend play is beneficial to social and cognitive development. However, there is little evidence regarding the neural regions that are active while children engage ...in pretend play. We examined activation of prefrontal and posterior superior temporal sulcus (pSTS) regions using near-infrared spectroscopy while 42 four- to eight-year-old children freely played with dolls or tablet games with a social partner or by themselves. Social play activated right prefrontal regions more than solo play. Children engaged the pSTS during solo doll play but not during solo tablet play, suggesting they were rehearsing social cognitive skills more with dolls. These findings suggest social play utilizes multiple neural regions and highlight how doll play can achieve similar patterns of activation, even when children play by themselves. Doll play may provide a unique opportunity for children to practice social interactions important for developing social emotional skills, such as empathy.
People tend to automatically imitate others’ facial expressions of emotion. That reaction, termed “facial mimicry” has been linked to sensorimotor simulation—a process in which the observer’s brain ...recreates and mirrors the emotional experience of the other person, potentially enabling empathy and deep, motivated processing of social signals. However, the neural mechanisms that underlie sensorimotor simulation remain unclear. This study tests how interfering with facial mimicry by asking participants to hold a pen in their mouth influences the activity of the human mirror neuron system, indexed by the desynchronization of the EEG mu rhythm. This response arises from sensorimotor brain areas during observed and executed movements and has been linked with empathy. We recorded EEG during passive viewing of dynamic facial expressions of anger, fear, and happiness, as well as nonbiological moving objects. We examine mu desynchronization under conditions of free versus altered facial mimicry and show that desynchronization is present when adult participants can freely move but not when their facial movements are inhibited. Our findings highlight the importance of motor activity and facial expression in emotion communication. They also have important implications for behaviors that involve occupying or hiding the lower part of the face.
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