Developmental changes in infants' processing of happy and angry facial expressions: a neurobehavioral study

Event-related brain potentials were measured in 7- and 12-month-old infants to examine the development of processing happy and angry facial expressions. In 7-month-olds a larger negativity to happy faces was observed at frontal, central, temporal and parietal sites (Experiment 1), whereas 12-month-olds showed a larger negativity to angry faces at occipital sites (Experiment 2). These data suggest that processing of these facial expressions undergoes development between 7 and 12 months: while 7-month-olds exhibit heightened sensitivity to happy faces, 12-month-olds resemble adults in their heightened sensitivity to angry faces. In Experiment 3 infants' visual preference was assessed behaviorally, revealing that the differences in ERPs observed at 7 and 12 months do not simply reflect differences in visual preference.     

Frontal brain electrical activity (EEG) and heart rate in response to affective infant-directed (ID) speech in 9-month-old infants

Many studies have shown that infants prefer infant-directed (ID) speech to adult-directed (AD) speech. ID speech functions to aid language learning, obtain and/or maintain an infant's attention, and create emotional communication between the infant and caregiver. We examined psychophysiological responses to ID speech that varied in affective content (i.e., love/comfort, surprise, fear) in a group of typically developing 9-month-old infants. Regional EEG and heart rate were collected continuously during stimulus presentation. We found the pattern of overall frontal EEG power was linearly related to affective intensity of the ID speech, such that EEG power was greatest in response to fear, than surprise than love/comfort; this linear pattern was specific to the frontal region. We also noted that heart rate decelerated to ID speech independent of affective content. As well, infants who were reported by their mothers as temperamentally distressed tended to exhibit greater relative right frontal EEG activity during baseline and in response to affective ID speech, consistent with previous work with visual stimuli and extending it to the auditory modality. Findings are discussed in terms of how increases in frontal EEG power in response to different affective intensity may reflect the cognitive aspects of emotional processing across sensory domains in infancy.     

Withdrawn and intrusive maternal interaction style and infant frontal EEG asymmetry shifts in infants of depressed and non-depressed mothers

The effects of maternal interaction style (intrusive/withdrawn) on the development of brain electrical activity were studied in infants of depressed and non-depressed mothers shortly after birth and again at 3-6 months of age. Infants of depressed mothers exhibited significantly greater relative right frontal EEG activation than infants of non-depressed mothers. Infants of depressed withdrawn mothers exhibited greater relative right frontal EEG activation than infants of depressed intrusive mothers. Furthermore, while infants of depressed mothers with intrusive interaction styles showed a shift towards greater relative left frontal EEG activation from birth to 3-6 months, infants of depressed mothers with withdrawn interaction styles showed a shift towards greater relative right frontal EEG activation.     

Generalization of deferred imitation during the first year of life

Infants first generalize across contexts and cues at 3 months of age in operant tasks but not until 12 months of age in imitation tasks. Three experiments using an imitation task examined whether infants younger than 12 months of age might generalize imitation if conditions were more like those in operant studies. Infants sat on a distinctive mat in a room in their home (the context) while an adult modeled actions on a hand puppet (the cue). When they were tested 24 h later, 6-month-olds generalized imitation when either the mat or the room (but not both) differed, whereas 9-month-olds generalized when both the mat and the room differed. In addition, 9-month-olds who imitated immediately also generalized to a novel test cue, whereas 6-month-olds did not. These results parallel results from operant studies and reveal that the similarity between the conditions of encoding and retrieval-not the type of task-determines whether infants generalize. The findings offer further evidence that memory development during infancy is a continuous function.     

Longitudinal study of perception of structured optic flow and random visual motion in infants using high‐density EEG

Electroencephalogram (EEG) was used in infants at 3–4 months and 11–12 months to longitudinally study brain electrical activity as the infants were exposed to structured forwards and reversed optic flow, and non‐structured random visual motion. Analyses of visual evoked potential (VEP) and temporal spectral evolution (TSE, time‐dependent amplitude changes) were performed on EEG data recorded with a 128‐channel sensor array. VEP results showed infants to significantly differentiate between the radial motion conditions, but only at 11–12 months where they showed shortest latency for forwards optic flow and longest latency for random visual motion. When the TSE results of the motion conditions were compared with those of a static non‐flow dot pattern, infants at 3–4 and 11–12 months both showed significant differences in induced activity. A decrease in amplitudes at 5–7 Hz was observed as desynchronized theta‐band activity at both 3–4 and 11–12 months, while an increase in amplitudes at 9–13 Hz was observed as synchronized alpha‐band activity only at 11–12 months. It was concluded that brain electrical activities related to visual motion perception change during the first year of life, and these changes can be observed both in the VEP and induced activities of EEG. With adequate neurobiological development and locomotor experience infants around 1 year of age rely, more so than when they were younger, on structured optic flow and show a more adult‐like specialization for motion where faster oscillating cell assemblies have fewer but more specialized neurons, resulting in improved visual motion perception.     

Targeting adolescent mothers with depressive symptoms for early intervention

Infants of mothers with depressive symptoms show developmental delays if symptoms persist over the first 6 months of the infant's life, thus highlighting the importance of identifying those mothers for early intervention. In Study 1, mothers with depressive symptoms (n = 160) and mothers without depressive symptoms (n = 100) and their infants were monitored to identify variables from the first 3 months that predict which mothers would still be symptomatic at 6 months. A "dysregulation" profile was noted for the infants of depressed mothers, including lower Brazelton scores, more indeterminate sleep, and elevated norepinephrine, epinephrine, and dopamine levels at the neonatal period, and greater right frontal EEG activation, lower vagal tone, and negative interactions at the 3- and 6-month periods. A group of maternal variables from the neonatal and 3-month assessments accounted for 51% of the variance in the mothers' continuing depressive symptoms. These variables included greater right frontal EEG activation, lower vagal tone, and less positive interactions at 3 months, and elevated norepinephrine, serotonin, and cortisol levels at the neonatal stage. In Study 2, a similar sample of mothers with depressive symptoms (n = 160) and without depressive symptoms (n = 100) was recruited and followed to 3 months. Those symptomatic mothers who had values above (or below) the median (depending on the negative direction) on the predictor variables identified in Study 1 (taken from the first 3 months) were then randomly assigned to an intervention or a control group at 3 months. These groups were then compared with each other, as well as with the group without depressive symptoms, at 6 and 12 months. The intervention, conducted from 3 to 6 months, consisted of free day care for the infants and a rehab program (social, educational, and vocational) plus several mood induction interventions for the mothers, including relaxation therapy, music mood induction, massage therapy, and mother-infant interaction coaching. Although the mothers who received the intervention continued to have more depressive symptoms than did the nondepressed mothers, their interactions significantly improved and their biochemical values and vagal tone normalized. Their infants also showed more positive interations, better growth, fewer pediatric complications, and normalized biochemical values, and by 12 months their mental and motor scores were better than those of the infants in the control group.     

Frontal brain electrical activity (EEG) distinguishes valence and intensity of musical emotions

Using recent regional brain activation/emotion models as a theoretical framework, we examined whether the pattern of regional EEG activity distinguished emotions induced by musical excerpts which were known to vary in affective valence (i.e., positive vs. negative) and intensity (i.e., intense vs. calm) in a group of undergraduates. We found that the pattern of asymmetrical frontal EEG activity distinguished valence of the musical excerpts. Subjects exhibited greater relative left frontal EEG activity to joy and happy musical excerpts and greater relative right frontal EEG activity to fear and sad musical excerpts. We also found that, although the pattern of frontal EEG asymmetry did not distinguish the intensity of the emotions, the pattern of overall frontal EEG activity did, with the amount of frontal activity decreasing from fear to joy to happy to sad excerpts. These data appear to be the first to distinguish valence and intensity of musical emotions on frontal electrocortical measures.     

Postnatal maternal symptoms of depression and child emotion dysregulation: The mediation role of infant EEG alpha asymmetry

In a community-based sample of 104 infants and their mothers, we hypothesized a pathway from postnatal maternal symptoms of depression to child emotion dysregulation, and tested at 6 months of age the mediation role of alpha asymmetry at frontal and parietal sites. We recorded infant resting-state EEG at 6 months of age. Child emotion dysregulation was measured at 24 months by the Child Behavior Checklist Dysregulation Profile derived from the CBCL 1½-5. Maternal depression symptoms were scored 6 months after the delivery by the Anxious/Depressed scale of the Adult Self-Report. We used structural equation modeling to test the mediation model from maternal depression symptoms to child emotion dysregulation mediated by frontal and parietal alpha asymmetry. The mediation model provided an excellent fit to the data [χ2(3) = 3.088, p = .378; RMSEA = .017, CFI = .1.00; SRMR = 0.040] and explained 23.3% of the variance in child emotion dysregulation. The indirect path via parietal alpha asymmetry was significant (β = .065; SE = .033; 95% CI = .001–.139; p = .048), i.e. greater levels of maternal depression symptoms predicted left parietal alpha asymmetry, which predicted higher levels of child emotion dysregulation. The direct effect, i.e. the pathway linking maternal depression symptoms and child emotion dysregulation above and beyond the indirect effects, was also significant. We found evidence for a partial mediation role of left parietal alpha asymmetry in a longitudinal pathway from postnatal maternal symptoms of depression to child emotion dysregulation, providing support for left parietal asymmetry as an index of biological vulnerability to emotion dysregulation in the first years of life.     

Electroencephalogram and heart rate measures of working memory at 5 and 10 months of age

We recorded electroencephalogram (EEG; 6-9 Hz) and heart rate (HR) from infants at 5 and 10 months of age during baseline and performance on the looking A-not-B task of infant working memory (WM). Longitudinal baseline-to-task comparisons revealed WM-related increases in EEG power (all electrodes) and EEG coherence (medial frontal-occipital electrode pairs) at both ages. WM-related decreases in HR were only present at 5 months, and WM-related increases in EEG coherence became more localized by 10 months. Regression analyses revealed that baseline-to-task changes in psychophysiology accounted for variability in WM performance at 10 but not 5 months. HR and EEG power (medial frontal and lateral frontal electrodes) were unique predictors of variability in 10-month WM performance. These findings are discussed in relation to frontal lobe development and represent the first comprehensive longitudinal analysis of age-related changes in the behavioral and psychophysiological correlates of WM.     

Instrumental and vocal music effects on EEG and EKG in neonates of depressed and non-depressed mothers

Neonates (M age = 16 days) born to depressed and non-depressed mothers were randomly assigned to hear an audiotaped lullaby of instrumental music with vocals or without vocals. Neonatal EEG and EKG were recorded for 2 min (baseline) of silence and for 2 min of one or the other music presentation. Neonates of non-depressed mothers showed greater relative right frontal EEG asymmetry to both types of music, suggesting a withdrawal response. Neonates of depressed mothers on the other hand showed greater relative left frontal EEG asymmetry to the instrumental without vocal segment, suggesting an approach response, and greater relative right frontal EEG asymmetry to the instrumental with vocal segment, suggesting a withdrawal response. Heart rate decelerations occurred following the music onset for both groups of infants, however, compared to infants of non-depressed mothers, infants of depressed mothers showed a delayed heart rate deceleration, suggesting slower processing and/or delayed attention. These findings suggest that neonates of depressed and non-depressed mothers show different EKG and EEG responses to instrumental music with versus without vocals.     

Development of infant sustained attention and its relation to EEG oscillations: an EEG and cortical source analysis study

The current study examined the relation between infant sustained attention and infant EEG oscillations. Fifty‐nine infants were tested at 6 (N = 15), 8 (N = 17), 10 (N = 14), and 12 (N = 13) months. Three attention phases, stimulus orienting, sustained attention, and attention termination, were defined based on infants' heart rate changes. Frequency analysis using simultaneously recorded EEG focused on infant theta (2–6 Hz), alpha (6–9 Hz), and beta (9–14 Hz) rhythms. Cortical source analysis of EEG oscillations was conducted with realistic infant MRI models. Theta synchronization was found over fontal pole, temporal, and parietal electrodes during infant sustained attention for 10 and 12 months. Alpha desynchronization was found over frontal, central and parietal electrodes during sustained attention. This alpha effect started to emerge at 10 months and became well established by 12 months. No difference was found for the beta rhythm between different attention phases. The theta synchronization effect was localized to the orbital frontal, temporal pole, and ventral temporal areas. The alpha desynchronization effect was localized to the brain regions composing the default mode network including the posterior cingulate cortex and precuneus, medial prefrontal cortex, and inferior parietal gyrus. The alpha desynchronization effect was also localized to the pre‐ and post‐central gyri. The present study demonstrates a connection between infant sustained attention and EEG oscillatory activities.     

Behavioral reactivity and approach-withdrawal bias in infancy

Seven hundred seventy-nine infants were screened at 4 months of age for motor and emotional reactivity. At age 9 months, infants who showed extreme patterns of motor and negative (n = 75) or motor and positive (n = 73) reactivity and an unselected control group (n = 86) were administered the Laboratory Temperament Assessment Battery, and baseline electroencephalogram data were collected. Negatively reactive infants showed significantly more avoidance than positively reactive infants and displayed a pattern of right frontal electroencephalogram asymmetry. Positively reactive infants exhibited significantly more approach behavior than controls and exhibited a pattern of left frontal asymmetry. Results support the notion that approach-withdrawal bias underlies reactivity in infancy.     

The development of gaze following and its relation to language

We examined the ontogeny of gaze following by testing infants at 9, 10 and 11 months of age. Infants (N = 96) watched as an adult turned her head toward a target with either open or closed eyes. The 10- and 11-month-olds followed adult turns significantly more often in the open-eyes than the closed-eyes condition, but the 9-month-olds did not respond differentially. Although 9-month-olds may view others as 'body orienters', older infants begin to register whether others are 'visually connected' to the external world and, hence, understand adult looking in a new way. Results also showed a strong positive correlation between gaze-following behavior at 10-11 months and subsequent language scores at 18 months. Implications for social cognition are discussed in light of the developmental shift in gaze following between 9 and 11 months of age.     

Modeling development of frontal electroencephalogram (EEG) asymmetry: Sex differences and links with temperament

Asymmetric patterns of frontal brain electrical activity reflect approach and avoidance tendencies, with stability of relative right activation associated with withdrawal emotions/motivation and left hemisphere activation linked with approach and positive affect. However, considerable shifts in approach/avoidance‐related lateralization have been reported for children not targeted because of extreme temperament. In this study, dynamic effects of frontal electroencephalogram (EEG) power within and across hemispheres were examined throughout early childhood. Specifically, EEG indicators at 5, 10, 24, 36, 48, and 72 months‐of‐age (n = 410) were analyzed via a hybrid of difference score and panel design models, with baseline measures and subsequent time‐to‐time differences modeled as potentially influencing all subsequent amounts of time‐to‐time change (i.e., predictively saturated). Infant sex was considered as a moderator of dynamic developmental effects, with temperament attributes measured at 5 months examined as predictors of EEG hemisphere development. Overall, change in left and right frontal EEG power predicted declining subsequent change in the same hemisphere, with effects on the opposing neurobehavioral system enhancing later growth. Infant sex moderated the pattern of within and across‐hemisphere effects, wherein for girls more prominent left hemisphere influences on the right hemisphere EEG changes were noted and right hemisphere effects were more salient for boys. Largely similar patterns of temperament prediction were observed for the left and the right EEG power changes, with limited sex differences in links between temperament and growth parameters. Results were interpreted in the context of comparable analyses using parietal power values, which provided evidence for unique frontal effects.     

Development of sensitivity to information for impending collision

Infants were tested in three experiments to study the development of sensitivity to information for impending collision and to investigate the hypothesis that postural changes of very young infants in response to an approaching object are of a tracking rather than of a defensive nature. Experiment 1 involved the presentation of three types of shadow projection displays, specifying (1) collision, (2) noncollision, and (3) a nonexpanding rising contour, to infants from 1 to 9 months of age. Avoidance of collision appears to be absent in 1- to 2-month-olds, begins to develop in 4- to 6-month-olds, and is present in 8- to 9-month-old infants. In Experiment 2, 1- to 2-month-old infants were presented with optical expansion patterns which specified collision and noncollision. The top contour of these displays stayed at eye level. No significant difference was observed between reaction to the collision and the noncollision displays, suggesting that the young infants were tracking the displays and not attempting to avoid collision. Experiment 3 was designed to determine whether an approaching real object might elicit an avoidance response in infants not sensitive to an optical display specifying collision. No evidence of avoidance behavior was observed in the 1- to 2-month-olds; however, avoidance, as indexed by blinking, does appear to be present at 4 months of age.     

Longitudinal stability of temperamental exuberance and social-emotional outcomes in early childhood

The goals of the current study were to investigate the stability of temperamental exuberance across infancy and toddlerhood and to examine the associations between exuberance and social-emotional outcomes in early childhood. The sample consisted of 291 4-month-olds followed at 9, 24, and 36 months and again at 5 years of age. Behavioral measures of exuberance were collected at 9, 24, and 36 months. At 36 months, frontal electroencephalogram (EEG) asymmetry was assessed. At 5 years, maternal reports of temperament and behavior problems were collected, as were observational measures of social behavior during an interaction with an unfamiliar peer in the laboratory. Latent profile analysis revealed a high, stable exuberance profile that was associated with greater ratings of 5-year externalizing behavior and surgency, as well as observed disruptive behavior and social competence with unfamiliar peers. These associations were particularly true for children who displayed left frontal EEG asymmetry. Multiple factors supported an approach bias for exuberant temperament but did not differentiate between adaptive and maladaptive social-emotional outcomes at 5 years of age.     

The effects of exposure to dynamic expressions of affect on 5-month-olds’ memory

The purpose of this study was to examine the behavioral effects of adults’ communicated affect on 5-month-olds’ visual recognition memory. Five-month-olds were exposed to a dynamic and bimodal happy, angry, or neutral affective (face–voice) expression while familiarized to a novel geometric image. After familiarization to the geometric image and exposure to the affective expression, 5-month-olds received either a 5-min or 1-day retention interval. Following the 5-min retention interval, infants exposed to the happy affective expressions showed a reliable preference for a novel geometric image compared to the recently familiarized image. Infants exposed to the neutral or angry affective expression failed to show a reliable preference following a 5-min delay. Following the 1-day retention interval, however, infants exposed to the neutral expression showed a reliable preference for the novel geometric image. These results are the first to demonstrate that 5-month-olds’ visual recognition memory is affected by the presentation of affective information at the time of encoding.     

Neurophysiology of sustained attention in early infancy: Investigating longitudinal relations with recognition memory outcomes

The ability to sustain attention is a critical cognitive domain that emerges in infancy and is predictive of a multitude of cognitive processes. Here, we used a heart rate (HR) defined measure of sustained attention to assess corresponding changes in frontal electroencephalography (EEG) power at 3 months of age. Second, we examined how the neural underpinnings of HR-defined sustained attention were associated with sustained attention engagement. Third, we evaluated if neural or behavioral sustained attention measures at 3-months predicted subsequent recognition memory scores at 9 months of age. Seventy-five infants were included at 3 months of age and provided usable attention and EEG data and 25 infants returned to the lab at 9 months and provided usable recognition memory data. The current study focuses on oscillatory power in the theta (4–6 Hz) frequency band during phases of HR-defined sustained attention and inattention phases. Results revealed that theta power was significantly higher during phases of sustained attention. Second, higher theta power during sustained attention was positively associated with proportion of time in sustained attention. Third, longitudinal analyses indicated a significant positive association between theta power during sustained attention on 9-month visual paired comparison scores such that higher theta power predicted higher visual paired comparison scores at 9-months. These results highlight the interrelation of the attention and arousal systems which have longitudinal implications for subsequent recognition memory processes.     

Massage and music therapies attenuate frontal EEG asymmetry in depressed adolescents

EEG asymmetry, specifically greater relative right frontal activation, is associated with negative affect. Depressed adults show stable patterns of this asymmetry. The present study assessed the effects of massage therapy and music therapy on frontal EEG asymmetry in depressed adolescents. Thirty adolescents with greater relative right frontal EEG activation and symptoms of depression were given either massage therapy (n = 14) or music therapy (n = 16). EEG was recorded for three-minute periods before, during, and after therapy. Frontal EEG asymmetry was significantly attenuated during and after the massage and music sessions.     

Do infants recognize the Arcimboldo images as faces? Behavioral and near-infrared spectroscopic study

Arcimboldo images induce the perception of faces when shown upright despite the fact that only nonfacial objects such as vegetables and fruits are painted. In the current study, we examined whether infants recognize a face in the Arcimboldo images by using the preferential looking technique and near-infrared spectroscopy (NIRS). In the first experiment, we measured looking preference between upright and inverted Arcimboldo images among 5- and 6-month-olds and 7- and 8-month-olds. We hypothesized that if infants perceive the Arcimboldo images as faces, they would prefer the upright images to the inverted ones. We found that only 7- and 8-month-olds significantly preferred upright images, suggesting that they could perceive the Arcimboldo images as faces. In the second experiment, we measured hemodynamic responses using NIRS. Based on the behavioral data, we hypothesized that 7- and 8-month-olds would show different neural activity for upright and inverted Arcimboldo images, as do adults. Therefore, we measured hemodynamic responses in 7- and 8-month-olds while they were looking at upright and inverted Arcimboldo images. Their responses were then compared with the baseline activation during the presentation of individual vegetables. We found that the concentration of oxyhemoglobin increased in the left temporal area during the presentation of the upright images compared with the baseline during the presentation of vegetables. The results of the two experiments suggest that (a) the ability to recognize the upright Arcimboldo images as faces develops at around 7 or 8 months of age and (b) processing of the upright Arcimboldo images is related to the left temporal area of the brain.