The emergence of the EEG dominant rhythm across the first year of life.

The spectral composition of EEG provides important information on the function of the developing brain. For example, the frequency of the dominant rhythm, a salient features of EEG data, increases from infancy to adulthood. Changes of the dominant rhythm during infancy are yet to be fully characterized, in terms of their developmental trajectory and spectral characteristics. In this study, the development of dominant rhythm frequency was examined during a novel sustained attention task across 6-month-old (n = 39), 9-month-old (n = 30), and 12-month-old (n = 28) infants. During this task, computer-generated objects and faces floated down a computer screen for 10 s after a 5-second fixation cross. The peak frequency in the range between 5 and 9 Hz was calculated using center of gravity (CoG) and examined in response to faces and objects. Results indicated that peak frequency increased from 6 to 9 to 12 months of age in face and object conditions. We replicated the same result for the baseline. There was high reliability between the CoGs in the face, object, and baseline conditions across all channels. The developmental increase in CoG was more reliable than measures of mode frequency across different conditions. These findings suggest that CoG is a robust index of brain development across infancy.

Face race and sex impact visual fixation strategies for upright and inverted faces in 3- to 6-year-old children.

Everyday face experience tends to be biased, such that infants and young children interact more often with own-race and female faces leading to differential processing of faces within these groups relative to others. In the present study, visual fixation strategies were recorded using eye tracking to determine the extent to which face race and sex/gender impact a key index of face processing in 3- to 6-year-old children (n = 47). Children viewed male and female upright and inverted White and Asian faces while visual fixations were recorded. Face orientation was found to have robust effects on children's visual fixations, such that children exhibited shorter first fixation and average fixation durations and a greater number of fixations for inverted compared to upright face trials. First fixations to the eye region were also greater for upright compared to inverted faces. Fewer fixations and longer duration fixations were found for trials with male compared to female faces and for upright compared to inverted unfamiliar-race faces, but not familiar-race faces. These findings demonstrate evidence of differential fixation strategies toward different types of faces in 3- to 6-year-old children, illustrating the importance of experience in the development of visual attention to faces.

A label isn't just a label: Brief training leads to label-dependent visuo-cortical processing in adults.

The current study examines the extent to which hearing individual-level names (e.g., Jimmy) and category-level labels (e.g., Hitchel) paired with novel objects impacts neural responses across a brief (6 min) learning period. Event-related Potentials (ERPs) were recorded while adult participants (n = 44) viewed and heard exemplars of two different species of named novel objects. ERPs were examined for each labeling condition and compared across the first and second half of the learning trials (∼3 min/half). Mean amplitude decreased for the P1 and increased for the N170 from the first to the second half of trials. The decrease in P1 was right lateralized. In addition, the P1 amplitude recorded over right occipitotemporal regions was greater than left occipitotemporal areas, but only for objects paired with individual-level labels. Category-level labels did not show regional P1 differences. The N250 component was greatest over the right occipitotemporal region and was enhanced for objects labeled with individual-level relative to category-level names during the second half of trials. Overall, these findings highlight the unfolding of label-dependent visual processing across a short training period in adults. The results suggest that linguistic labels have an important, top-down impact, on visual processing and that label specificity shapes visuo-cortical responses within a 6-min learning period.

Differential neural responses to faces paired with labels versus faces paired with noise at 6- and at 9-months.

Labeling objects or faces in the first year of life shapes subsequent attention and perception. Three months of hearing individual-level, unique labels for previously unfamiliar faces promotes face differentiation and impacts neural processing during the first year of life. However, it is currently unclear whether verbal labeling influences visual processing of faces during label learning and whether these effects differ across the first year of life. The current study examined the impact of individual-level labels versus a non-speech noise on neural responses to monkey faces. Event-related potentials (ERPs) were recorded while infants viewed two species of monkey faces: one paired with labels and one paired with a non-speech noise. At 9 months, neural responses differentiated monkey faces paired with labels relative to those paired with noise during both the first and second halves of the experiment. Nine-month-olds exhibited a faster P1 latency, marginally greater N290 amplitude and reduced P400 amplitude to labeled faces relative to a non-speech noise. However, 6-month-olds' neural responses did not differentiate monkey faces paired with labels from those paired with a non-speech noise until the second half of trials and only showed this effect for P1 latency and N290 amplitude. The results of this study suggest that overall, infants differentiate faces labeled with individual-level labels from those paired with a non-speech noise, however, 6-month-olds require more exposure to the label-face pairings than 9-month-olds.

The developmental time course and topographic distribution of individual-level monkey face discrimination in the infant brain.

The ability to discriminate between faces from unfamiliar face groups has previously been found to decrease across the first year of life. Here, individual-level discrimination of faces within a previously unfamiliar group was investigated by measuring neural responses to monkey faces. Six- and 9-month-old infants (n = 42) completed a Fast Periodic Visual Stimulation (FPVS) task while steady state visual evoked potentials (ssVEPs) were recorded. Using an oddball task design (e.g., infrequent changes in face identity) faces were presented at a 6Hz (1 face approximately every 167ms) stimulation rate and every 1.2Hz different individual monkey faces were presented. Significant SNRs at 1.2Hz in both 6- and 9-month-old infants suggest that neural responses, recorded over posterior scalp regions, remain sensitive to individual-level differences within an unfamiliar face group despite previous behavioral evidence of decreased discrimination. However, the topographic distribution of the 1.2Hz response varied by age, suggesting that 6- and 9-month-old infants are using different neural populations to discriminate unfamiliar faces at the individual level.

An eye tracking investigation of attentional biases towards affect in young children.

This study examines attentional biases in the presence of angry, happy and neutral faces using a modified eye tracking version of the dot probe task (DPT). Participants were 111 young children between 9 and 48 months. Children passively viewed an affective attention bias task that consisted of a face pairing (neutral paired with either neutral, angry or happy) for 500 ms that was followed by a 1,500-ms asterisk probe on 1 side of the screen. Congruent trials were trials in which the probe appeared on the same side of the screen as the emotional face and incongruent trials were trials in which the probe appeared on the opposite side of the emotional face. The latency to fixate on the probe, rather than the traditional task's button press latency, was measured for both types of trials and a bias score was calculated by subtracting the latency to the probe on congruent trials from that on incongruent trials. The results of the current study indicate positive internal reliability of this modified version of the DPT as well as the presence of a bias toward both angry and happy faces during the first 4 years of life. The successful use of the modified version of the DPT for use on the eye tracker presents a promising methodological tool for research on early attentional behavior and provides a tool for comprehensive longitudinal studies of identified risk factors for anxiety. (PsycINFO Database Record

Caregivers and strangers: The influence of familiarity on gaze following and learning.

This study examines how social cues facilitate learning by manipulating the familiarity of a social cue. Participants were forty-nine infants between 12-18 months. Infants were taught a novel label for a novel object under two pre-recorded gaze conditions-one in which the caregiver was seen gazing at a novel object while a verbal label was played, and one in which a stranger was seen gazing at a novel object while a verbal label was played. Learning was only evident in the caregiver condition and only in the infants most skilled at following their caregivers' gaze. The results of the current study suggest that both the familiarity of the cuer and the infant's own ability to follow the gaze of the cuer play important roles in the infant's learning in this task.

Children With Fragile X Syndrome Display Threat-Specific Biases Toward Emotion.

BACKGROUND: Fragile X syndrome (FXS) is the most common form of inherited intellectual disability. FXS is caused by a silencing of the FMR1 gene that results in a loss or absence of the gene's protein product, fragile X mental retardation protein. The phenotype of FXS is consistently associated with heightened anxiety, although no previous study has investigated attentional bias toward threat, a hallmark of anxiety disorders, in individuals with FXS. METHODS: The current study employed a passive-viewing eye-tracking version of the dot probe task to investigate attentional biases toward emotional faces in young children with FXS (n = 47) and without FXS (n = 94). RESULTS: We found that the FXS group showed a significantly greater bias toward threatening emotions than toward positive emotions. This threat specificity was not seen in either a mental age-matched group or a chronological age-matched group of typically developing children. Unlike the typically developing groups, the FXS group showed no bias toward positive emotion. CONCLUSIONS: The current study shows that children with FXS have a significant bias toward threatening information, an attentional profile that has been linked with anxiety. It also supports the use of eye-tracking methodology to index neural and attentional responses in young children with FXS.