Long-term recognition memory for faces assessed by visual paired comparison in 3- and 6-month-old infants

Episodic memory development: Bridging animal and human research

Human episodic memory is not functionally evident until about 2 years of age and continues to develop into the school years. Behavioral studies have elucidated this developmental timeline and its constituent processes. In tandem, lesion and neurophysiological studies in non-human primates and rodents have identified key neural substrates and circuit mechanisms that may underlie episodic memory development. Despite this progress, collaborative efforts between psychologists and neuroscientists remain limited, hindering progress. Here, we seek to bridge human and non-human episodic memory development research by offering a comparative review of studies using humans, non-human primates, and rodents. We highlight critical theoretical and methodological issues that limit cross-fertilization and propose a common research framework, adaptable to different species, that may facilitate cross-species research endeavors.

Eye-tracking paradigms for the assessment of mild cognitive impairment: a systematic review

Mild cognitive impairment (MCI), representing the 'transitional zone' between normal cognition and dementia, has become a novel topic in clinical research. Although early detection is crucial, it remains logistically challenging at the same time. While traditional pen-and-paper tests require in-depth training to ensure standardized administration and accurate interpretation of findings, significant technological advancements are leading to the development of procedures for the early detection of Alzheimer's disease (AD) and facilitating the diagnostic process. Some of the diagnostic protocols, however, show significant limitations that hamper their widespread adoption. Concerns about the social and economic implications of the increasing incidence of AD underline the need for reliable, non-invasive, cost-effective, and timely cognitive scoring methodologies. For instance, modern clinical studies report significant oculomotor impairments among patients with MCI, who perform poorly in visual paired-comparison tasks by ascribing less attentional resources to novel stimuli. To accelerate the Global Action Plan on the Public Health Response to Dementia 2017-2025, this work provides an overview of research on saccadic and exploratory eye-movement deficits among older adults with MCI. The review protocol was drafted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Electronic databases were systematically searched to identify peer-reviewed articles published between 2017 and 2022 that examined visual processing in older adults with MCI and reported gaze parameters as potential biomarkers. Moreover, following the contemporary trend for remote healthcare technologies, we reviewed studies that implemented non-commercial eye-tracking instrumentation in order to detect information processing impairments among the MCI population. Based on the gathered literature, eye-tracking-based paradigms may ameliorate the screening limitations of traditional cognitive assessments and contribute to early AD detection. However, in order to translate the findings pertaining to abnormal gaze behavior into clinical applications, it is imperative to conduct longitudinal investigations in both laboratory-based and ecologically valid settings.

Acute Inositol-Stabilized Arginine Silicate Improves Cognitive Outcomes in Healthy Adults

Inositol-stabilized arginine silicate (ASI) is an ergogenic aid that upregulates nitric oxide. Acute ASI supplementation improves working memory and processing speed in young adults but there is a lack of data examining other cognitive tasks. Therefore, the purpose of this study was to examine acute ASI effects on young healthy adults by assessing multiple cognitive domains. Nineteen young adults (20.9 ± 3.2 years) completed this randomized, double-blind, crossover study consuming ASI (1.5 g ASI + 12 g dextrose) and placebo (12 g dextrose). The participants completed the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and two digital cognitive assessments before consuming the supplement and then completed the same battery of tests 60 min post-supplementation. Repeated measures ANOVA demonstrated that ASI consumption significantly improved total RBANS and immediate memory scores compared to the placebo (p < 0.05). However, no significant differences were displayed between trials for other cognitive domains (p > 0.05). Acute ASI ingestion increased overall RBANS scores and immediate memory scores in young adults. More research is needed to examine the acute effects of ASI on other domains of cognition, in older populations, and its long-term effects on cognition.

Attentional Measures of Memory in Typically Developing and Hypoxic-Ischemic Injured Infants

Hypoxic–ischemic injury (HII) at birth has been found to relate to differences in development, including decreased memory performance. The current study assessed recognition memory in 6- and 12-month-old HII infants and typically developing (TD) infants using two eye-tracking paradigms well suited to explore explicit memory processes early in life: visual paired comparison (VPC) and relational memory (RM). During the VPC, infants were familiarized to a face and then tested for their novelty preference immediately and after a two-minute delay. At 6 months, neither HII nor TD showed a VPC novelty preference at immediate delay, but at 12 months, both groups did; after the two-minute delay, no group showed a novelty preference. During RM, infants were presented with blocks containing a learning phase with three different scene–face pairs, and a test phase with one of the three scenes and all three faces appearing simultaneously. When there was no interference from other scene–face pairs between learning and test, 6-month-old TD showed evidence of an early novelty preference, but when there was interference, they revealed an early familiarity preference. For 12-month-old TD, some evidence for a novelty preference during RM was seen regardless of interference. Although HII and TD showed similar recognition memory on the VPC, when looking at RM, HII infants showed subtle differences in their attention to the familiar and novel faces as compared to their TD peers, suggesting that there might be subtle differences in the underlying memory processing mechanisms between HII and TD. More work is needed to understand how these attentional patterns might be predictive of later memory outcomes.

Retinopathy of Prematurity: How to Prevent the Third Epidemics in Developing Countries

Retinopathy of prematurity (ROP) is vasoproliferative disease affecting preterm infants and is a leading cause of avoidable childhood blindness worldwide. The world is currently experiencing the third epidemic of ROP, where majority of the cases are from middle-income countries. Over 40% of the world's premature infants were born in India, China, Bangladesh, Pakistan, and Indonesia. Together with other neighboring nations, this region has unique challenges in ROP management. Key aspects of the challenges including heavier and more mature infants developing severe ROP. Current strategies include adoption of national screening guidelines, telemedicine, integrating vision rehabilitation and software innovations in the form of artificial intelligence. This review overviews some of these aspects.

Individual Differences in Infants' Temperament Affect Face Processing

Infants show an advantage in processing female and familiar race faces, but the effect sizes are often small, suggesting individual differences in their discrimination abilities. This research assessed whether differences in 6-10-month-olds' temperament (surgency and orienting) predicted how they scanned individual faces varying in race and gender during familiarization and whether and how long it took them to locate the face during a visual search task. This study also examined whether infants viewing faces posing pleasant relative to neutral expressions would facilitate their discrimination of male and unfamiliar race faces. Results showed that infants' surgency on its own or in conjunction with their orienting regularly interacted with facial characteristics to predict their scanning and location of faces. Furthermore, infants' scanning patterns (dwell times and internal-external fixation shifts) correlated with their ability and time to locate a familiarized face. Moreover, infants who viewed faces with pleasant expressions showed better discrimination of unfamiliar race and male faces compared with infants who viewed neutral faces. Including temperament in the analyses consistently demonstrated its significance for understanding infant face processing. Findings suggest that positive interactions with other-race individuals and men might reduce processing disadvantages for those face types. Locating familiar adults in a timely manner is a crucial skill for infants to develop and these data elucidate factors influencing this ability.

Neural and psychophysiological correlates of social communication development: Evidence from sensory processing, motor, cognitive, language and emotional behavioral milestones across infancy

This article presents a literature review focusing on the neural and psychophysiological correlates associated with social communication development in infancy. Studies presenting evidence on infants' brain activity and developments in infant sensory processing, motor, cognitive, language, and emotional abilities are described in regard to the neuropsychophysiological processes underlying the emergence of these specific behavioral milestones and their associations with social communication development. Studies that consider specific age-related characteristics across the infancy period are presented. Evidence suggests that specific neural and physiological signatures accompany age-related social communication development during the first 18 months of life.

Toward the Understanding of Topographical and Spectral Signatures of Infant Movement Artifacts in Naturalistic EEG

Electroencephalography (EEG) is perhaps the most widely used brain-imaging technique for pediatric populations. However, EEG signals are prone to distortion by motion. Compared to adults, infants' motion is both more frequent and less stereotypical yet motion effects on the infant EEG signal are largely undocumented. Here, we present a systematic assessment of naturalistic motion effects on the infant EEG signal. EEG recordings were performed with 14 infants (12 analyzed) who passively watched movies whilst spontaneously producing periods of bodily movement and rest. Each infant produced an average of 38.3 s (SD = 14.7 s) of rest and 18.8 s (SD = 17.9 s) of single motion segments for the final analysis. Five types of infant motions were analyzed: Jaw movements, and Limb movements of the Hand, Arm, Foot, and Leg. Significant movement-related distortions of the EEG signal were detected using cluster-based permutation analysis. This analysis revealed that, relative to resting state, infants' Jaw and Arm movements produced significant increases in beta (∼15 Hz) power, particularly over peripheral sites. Jaw movements produced more anteriorly located effects than Arm movements, which were most pronounced over posterior parietal and occipital sites. The cluster analysis also revealed trends toward decreased power in the theta and alpha bands observed over central topographies for all motion types. However, given the very limited quantity of infant data in this study, caution is recommended in interpreting these findings before subsequent replications are conducted. Nonetheless, this work is an important first step to inform future development of methods for addressing EEG motion-related artifacts. This work also supports wider use of naturalistic paradigms in social and developmental neuroscience.

Nonhuman primate models of hippocampal development and dysfunction

Nonhuman primates provide highly valuable animal models that have significantly advanced our understanding of numerous behavioral and biological phenomena in humans. Here, we reviewed a series of developmental neuropsychological studies that informed us on the timing of development of the hippocampus and of hippocampal-dependent cognitive functions in primates. Data indicate that, in primates, the emergence of adult-like proficiency on behavioral tasks sensitive to hippocampal dysfunction is a stepwise process and reflects the gradual maturation of different hippocampal circuits and their connections with other neural structures. Profound and persistent memory loss resulting from insult to the hippocampus in infancy was absent in early infancy but became evident later in childhood and persisted in adulthood, indicating very little sparing or recovery of function. Finally, the early hippocampal insult resulted in both adaptive and maladaptive neuroplasticity: i.e., sparing contextual memory, but affecting working memory processes as well as emotional reactivity and hypothalamic-pituitary-adrenal (HPA) axis functioning. The results provide significant information on the emergence of hippocampal-dependent functions in humans, on the time course of memory impairment in human cases with early hippocampal insult, and on the clinical implication of the hippocampus in developmental neuropsychiatric disorders.

Universal Mechanisms and the Development of the Face Network: What You See Is What You Get

Our assignment was to review the development of the face-processing network, an assignment that carries the presupposition that a face-specific developmental program exists. We hope to cast some doubt on this assumption and instead argue that the development of face processing is guided by the same ubiquitous rules that guide the development of cortex in general.

P300 development from infancy to adolescence

This article provides an overview of P300 research from infancy through adolescence. First, a brief historical overview is provided highlighting seminal studies that began exploration of the P300 component in developmental groups. Overall, these studies suggest that the P300 can be detected in children and appears to reflect similar cognitive processes to those in adults; however, it is significantly delayed in its latency to peak. Second, two striking findings from developmental research are the lack of a clear P300 component in infancy and differential electrophysiological responses to novel, unexpected stimuli in children, adolescents, and adults. Third, contemporary questions are described, which include P300-like components in infancy, alteration of P300 in atypically developing groups, relations between P300 and behavior, individual differences of P300, and neural substrates of P300 across development. Finally, we conclude with comments regarding the power of a developmental perspective and suggestions for important issues that should be addressed in the next 50 years of P300 research.

Social Origins of Cortical Face Areas

Recently acquired fMRI data from human and macaque infants provide novel insights into the origins of cortical networks specialized for perceiving faces. Data from both species converge: cortical regions responding preferentially to faces are present and spatially organized early in infancy, although fully selective face areas emerge much later. What explains the earliest cortical responses to faces? We review two proposed mechanisms: proto-organization for simple shapes in visual cortex, and an innate subcortical schematic face template. In addition, we propose a third mechanism: infants choose to look at faces to engage in positively valenced, contingent social interactions. Activity in medial prefrontal cortex during social interactions may, directly or indirectly, guide the organization of cortical face areas.

Device-Embedded Cameras for Eye Tracking-Based Cognitive Assessment: Validation With Paper-Pencil and Computerized Cognitive Composites

BACKGROUND

As eye tracking-based assessment of cognition becomes more widely used in older adults, particularly those at risk for dementia, reliable and scalable methods to collect high-quality data are required. Eye tracking-based cognitive tests that utilize device-embedded cameras have the potential to reach large numbers of people as a screening tool for preclinical cognitive decline. However, to fully validate this approach, more empirical evidence about the comparability of eyetracking-based paradigms to existing cognitive batteries is needed.

OBJECTIVE

Using a population of clinically normal older adults, we examined the relationship between a 30-minute Visual Paired Comparison (VPC) recognition memory task and cognitive composite indices sensitive to a subtle decline in domains associated with Alzheimer disease. Additionally, the scoring accuracy between software used with a commercial grade eye tracking camera at 60 frames per second (FPS) and a manually scored procedure used with a laptop-embedded web camera (3 FPS) on the VPC task was compared, as well as the relationship between VPC task performance and domain-specific cognitive function.

METHODS

A group of 49 clinically normal older adults completed a 30-min VPC recognition memory task with simultaneous recording of eye movements by a commercial-grade eye-tracking camera and a laptop-embedded camera. Relationships between webcam VPC performance and the Preclinical Alzheimer Cognitive Composite (PACC) and National Institutes of Health Toolbox Cognitive Battery (NIHTB-CB) were examined. Inter-rater reliability for manually scored tests was analyzed using Krippendorff's kappa formula, and we used Spearman's Rho correlations to investigate the relationship between VPC performance scores with both cameras. We also examined the relationship between VPC performance with the device-embedded camera and domain-specific cognitive performance.

RESULTS

Modest relationships were seen between mean VPC novelty preference and the PACC (r=.39, P=.007) and NIHTB-CB (r=.35, P=.03) composite scores, and additional individual neurocognitive task scores including letter fluency (r=.33, P=.02), category fluency (r=.36, P=.01), and Trail Making Test A (-.40, P=.006). Robust relationships were observed between the 60 FPS eye tracker and 3 FPS webcam on both trial-level VPC novelty preference (r=.82, P<.001) and overall mean VPC novelty preference (r=.92 P<.001). Inter-rater agreement of manually scored web camera data was high (kappa=.84).

CONCLUSIONS

In a sample of clinically normal older adults, performance on a 30-minute VPC task correlated modestly with computerized and paper-pencil based cognitive composites that serve as preclinical Alzheimer disease cognitive indices. The strength of these relationships did not differ between camera devices. We suggest that using a device-embedded camera is a reliable and valid way to assess performance on VPC tasks accurately and that these tasks correlate with existing cognitive composites.

Detailed Visual Memory Capacity Is Present Early in Childhood

Previous studies have shown that adults are able to remember more than 1,000 images with great detail. However, little is known about the development of this visual capacity, nor its presence early in life. This study tests the level of detail of young children's memory for a large number of items, adapting the method of Brady, Konkle, Alvarez, and Oliva (2008). Four- and six-year-old children were shown more than 100 images of everyday objects. They were then tested for recognition of familiar items in a binary decision task. The identity of the foil test item was manipulated in three conditions (Category, Exemplar, and State). Children demonstrated high accuracy across all conditions, remembering not only the basic-level category (Category), but also unique details (Exemplar), and information about position and arrangement of parts (State). These findings demonstrate that children spontaneously encode a high degree of visual detail. Early in life, visual memory exhibits high fidelity and extends over a large set of items.

Visual attention to meaningful stimuli by 1- to 3-year olds: implications for the measurement of memory

The visual recognition memory (VRM) paradigm has been widely used to measure memory during infancy and early childhood; it has also been used to study memory in human and nonhuman adults. Typically, participants are familiarized with stimuli that have no special significance to them. Under these conditions, greater attention to the novel stimulus during the test (i.e., novelty preference) is used as the primary index of memory. Here, we took a novel approach to the VRM paradigm and tested 1-, 2-, and 3-year olds using photos of meaningful stimuli that were drawn from the participants' own environment (e.g., photos of their mother, father, siblings, house). We also compared their performance to that of participants of the same age who were tested in an explicit pointing version of the VRM task. Two- and 3-year olds exhibited a strong familiarity preference for some, but not all, of the meaningful stimuli; 1-year olds did not. At no age did participants exhibit the kind of novelty preference that is commonly used to define memory in the VRM task. Furthermore, when compared to pointing, looking measures provided a rough approximation of recognition memory, but in some instances, the looking measure underestimated retention. The use of meaningful stimuli raise important questions about the way in which visual attention is interpreted in the VRM paradigm, and may provide new opportunities to measure memory during infancy and early childhood.

Web Camera Based Eye Tracking to Assess Visual Memory on a Visual Paired Comparison Task

Background: Web cameras are increasingly part of the standard hardware of most smart devices. Eye movements can often provide a noninvasive "window on the brain," and the recording of eye movements using web cameras is a burgeoning area of research. Objective: This study investigated a novel methodology for administering a visual paired comparison (VPC) decisional task using a web camera.To further assess this method, we examined the correlation between a standard eye-tracking camera automated scoring procedure [obtaining images at 60 frames per second (FPS)] and a manually scored procedure using a built-in laptop web camera (obtaining images at 3 FPS). Methods: This was an observational study of 54 clinically normal older adults.Subjects completed three in-clinic visits with simultaneous recording of eye movements on a VPC decision task by a standard eye tracker camera and a built-in laptop-based web camera. Inter-rater reliability was analyzed using Siegel and Castellan's kappa formula. Pearson correlations were used to investigate the correlation between VPC performance using a standard eye tracker camera and a built-in web camera. Results: Strong associations were observed on VPC mean novelty preference score between the 60 FPS eye tracker and 3 FPS built-in web camera at each of the three visits (r = 0.88-0.92). Inter-rater agreement of web camera scoring at each time point was high (κ = 0.81-0.88). There were strong relationships on VPC mean novelty preference score between 10, 5, and 3 FPS training sets (r = 0.88-0.94). Significantly fewer data quality issues were encountered using the built-in web camera. Conclusions: Human scoring of a VPC decisional task using a built-in laptop web camera correlated strongly with automated scoring of the same task using a standard high frame rate eye tracker camera.While this method is not suitable for eye tracking paradigms requiring the collection and analysis of fine-grained metrics, such as fixation points, built-in web cameras are a standard feature of most smart devices (e.g., laptops, tablets, smart phones) and can be effectively employed to track eye movements on decisional tasks with high accuracy and minimal cost.

What three-year-olds remember from their past

From birth on, infants show long-term recognition memory for persons. Furthermore, infants from six months onwards are able to store and retrieve demonstrated actions over long-term intervals in deferred imitation tasks. Thus, information about the model demonstrating the object-related actions is stored and recognition memory for the objects as well as memory for the actions is retrieved. To study the development of long-term retention for different memory contents systematically, the present study investigated the recognition of person- and object-related information as well as the retention of actions in two samples of three-year-olds who had participated in a deferred imitation task at either nine or 18 months of age. Results showed that three-year-olds who had participated at nine months of age retained actions in a re-enactment task; however, they neither indicated person- nor object-recognition in a picture-choice task (recognition task). Children who had participated at 18 months of age demonstrated person- and object-recognition but no re-enactment at three years of age. Findings are discussed against the background of memory development from a preverbal to a verbal age and in regard to the characteristics of the recognition vs re-enactment tasks and the stimuli used.

Face perception and learning in autism spectrum disorders

Autism Spectrum Disorder (ASD) is characterized by impairment in social communication and restricted and repetitive interests. While not included in the diagnostic characterization, aspects of face processing and learning have shown disruptions at all stages of development in ASD, although the exact nature and extent of the impairment vary by age and level of functioning of the ASD sample as well as by task demands. In this review, we examine the nature of face attention, perception, and learning in individuals with ASD focusing on three broad age ranges (early development, middle childhood, and adolescence/adulthood). We propose that early delays in basic face processing contribute to the atypical trajectory of social communicative skills in individuals with ASD and contribute to poor social learning throughout development. Face learning is a life-long necessity, as the social world of individual only broadens with age, and thus addressing both the source of the impairment in ASD as well as the trajectory of ability throughout the lifespan, through targeted treatments, may serve to positively impact the lives of individuals who struggle with social information and understanding.

Plasticity may change inputs as well as processes, structures, and responses

Significant work has documented neuroplasticity in development, demonstrating that developmental pathways are shaped by experience. Plasticity is often discussed in terms of the results of differences in input; differences in brain structures, processes, or responses reflect differences in experience. In this paper, I discuss how developmental plasticity also effectively changes input into the system. That is, structures and processes change in response to input, and those changed structures and processes influence future inputs. For example, plasticity may change the pattern of eye movements to a stimulus, thereby changing which part of the scene becomes the input. Thus, plasticity is not only seen in the structures and processes that result from differences in experience, but also is seen in the changes in the input as those structures and processes adapt. The systematic study of the nature of experience, and how differences in experience shape learning, can contribute to our understanding of neuroplasticity in general.

Development of long-term event memory in preverbal infants: an eye-tracking study

The development of long-term event memory in preverbal infants remains elusive. To address this issue, we applied an eye-tracking method that successfully revealed in great apes that they have long-term memory of single events. Six-, 12-, 18- and 24-month-old infants watched a video story in which an aggressive ape-looking character came out from one of two identical doors. While viewing the same video again 24 hours later, 18- and 24-month-old infants anticipatorily looked at the door where the character would show up before it actually came out, but 6- and 12-month-old infants did not. Next, 12-, 18- and 24-month-old infants watched a different video story, in which a human grabbed one of two objects to hit back at the character. In their second viewing after a 24-hour delay, 18- and 24-month-old infants increased viewing time on the objects before the character grabbed one. In this viewing, 24-month-old infants preferentially looked at the object that the human had used, but 18-month-old infants did not show such preference. Our results show that infants at 18 months of age have developed long-term event memory, an ability to encode and retrieve a one-time event and this ability is elaborated thereafter.

Behavioral and Neural Foundations of Multisensory Face-Voice Perception in Infancy

In this article, we describe behavioral and neurophysiological evidence for infants' multimodal face-voice perception. We argue that the behavioral development of face-voice perception, like multimodal perception more broadly, is consistent with the intersensory redundancy hypothesis (IRH). Furthermore, we highlight that several recently observed features of the neural responses in infants converge with the behavioral predictions of the intersensory redundancy hypothesis. Finally, we discuss the potential benefits of combining brain and behavioral measures to study multisensory processing, as well as some applications of this work for atypical development.

Young pigs exhibit differential exploratory behavior during novelty preference tasks in response to age, sex, and delay

Novelty preference paradigms have been widely used to study recognition memory and its neural substrates. The piglet model continues to advance the study of neurodevelopment, and as such, tasks that use novelty preference will serve especially useful due to their translatable nature to humans. However, there has been little use of this behavioral paradigm in the pig, and previous studies using the novel object recognition paradigm in piglets have yielded inconsistent results. The current study was conducted to determine if piglets were capable of displaying a novelty preference. Herein a series of experiments were conducted using novel object recognition or location in 3- and 4-week-old piglets. In the novel object recognition task, piglets were able to discriminate between novel and sample objects after delays of 2min, 1h, 1 day, and 2 days (all P<0.039) at both ages. Performance was sex-dependent, as females could perform both 1- and 2-day delays (P<0.036) and males could perform the 2-day delay (P=0.008) but not the 1-day delay (P=0.347). Furthermore, 4-week-old piglets and females tended to exhibit greater exploratory behavior compared with males. Such performance did not extend to novel location recognition tasks, as piglets were only able to discriminate between novel and sample locations after a short delay (P>0.046). In conclusion, this study determined that piglets are able to perform the novel object and location recognition tasks at 3-to-4 weeks of age, however performance was dependent on sex, age, and delay.

Population Coding of Facial Information in the Monkey Superior Colliculus and Pulvinar

The superior colliculus (SC) and pulvinar are thought to function as a subcortical visual pathway that bypasses the striate cortex and detects fundamental facial information. We previously investigated neuronal responses in the SC and pulvinar of monkeys during a delayed nonmatching-to-sample task, in which the monkeys were required to discriminate among 35 facial photos of five models and other categories of visual stimuli, and reported that population coding by multiple SC and pulvinar neurons well discriminated facial photos from other categories of stimuli (Nguyen et al., 2013, 2014). However, it remains unknown whether population coding could represent multiple types of facial information including facial identity, gender, facial orientation, and gaze direction. In the present study, to investigate population coding of multiple types of facial information by the SC and pulvinar neurons, we reanalyzed the same neuronal responses in the SC and pulvinar; the responses of 112 neurons in the SC and 68 neurons in the pulvinar in serial 50-ms epochs after stimulus onset were reanalyzed with multidimensional scaling (MDS). The results indicated that population coding by neurons in both the SC and pulvinar classified some aspects of facial information, such as face orientation, gender, and identity, of the facial photos in the second epoch (50–100 ms after stimulus onset). The Euclidean distances between all the pairs of stimuli in the MDS spaces in the SC were significantly correlated with those in the pulvinar, which suggested that the SC and pulvinar function as a unit. However, in contrast with the known population coding of face neurons in the temporal cortex, the facial information coding in the SC and pulvinar was coarse and insufficient. In these subcortical areas, identity discrimination was face orientation-dependent and the left and right profiles were not discriminated. Furthermore, gaze direction information was not extracted in the SC and pulvinar. These results suggest that the SC and pulvinar, which comprise the subcortical visual pathway, send coarse and rapid information on faces to the cortical system in a bottom-up process.

From Sensory Perception to Lexical-Semantic Processing: An ERP Study in Non-Verbal Children with Autism

This study examines electrocortical activity associated with visual and auditory sensory perception and lexical-semantic processing in nonverbal (NV) or minimally-verbal (MV) children with Autism Spectrum Disorder (ASD). Currently, there is no agreement on whether these children comprehend incoming linguistic information and whether their perception is comparable to that of typically developing children. Event-related potentials (ERPs) of 10 NV/MV children with ASD and 10 neurotypical children were recorded during a picture-word matching paradigm. Atypical ERP responses were evident at all levels of processing in children with ASD. Basic perceptual processing was delayed in both visual and auditory domains but overall was similar in amplitude to typically-developing children. However, significant differences between groups were found at the lexical-semantic level, suggesting more atypical higher-order processes. The results suggest that although basic perception is relatively preserved in NV/MV children with ASD, higher levels of processing, including lexical- semantic functions, are impaired. The use of passive ERP paradigms that do not require active participant response shows significant potential for assessment of non-compliant populations such as NV/MV children with ASD.

The extended trajectory of hippocampal development: Implications for early memory development and disorder

Hippocampus has an extended developmental trajectory, with refinements occurring in the trisynaptic circuit until adolescence. While structural change should suggest a protracted course in behavior, some studies find evidence of precocious hippocampal development in the first postnatal year and continuity in memory processes beyond. However, a number of memory functions, including binding and relational inference, can be cortically supported. Evidence from the animal literature suggests that tasks often associated with hippocampus (visual paired comparison, binding of a visuomotor response) can be mediated by structures external to hippocampus. Thus, a complete examination of memory development will have to rule out cortex as a source of early memory competency. We propose that early memory must show properties associated with full function of the trisynaptic circuit to reflect "adult-like" memory function, mainly (1) rapid encoding of contextual details of overlapping patterns, and (2) retention of these details over sleep-dependent delays. A wealth of evidence suggests that these functions are not apparent until 18-24 months, with behavioral discontinuities reflecting shifts in the neural structures subserving memory beginning approximately at this point in development. We discuss the implications of these observations for theories of memory and for identifying and measuring memory function in populations with typical and atypical hippocampal function.

The development of hippocampal-dependent memory functions: Theoretical comments on Jabès and Nelson review (2015)

Studies investigating the development of memory processes and their neural substrates have flourished over the last two decades. The review by Jabès and Nelson (2015) adds an important piece to our understanding of the maturation of different elements and circuits within the hippocampal system and their association with the progressive development of hippocampal-dependent memory processes in humans. In this accompanying commentary, we explore some additional connections between the nonhuman primate work and the human data, and take the opportunity to highlight some common and additional interpretations of the results. This commentary makes three points: (1) the recognition processes present in the first few days of life may be linked to the early maturation of the medial temporal cortical areas instead of, or in addition to, the early maturation of the subiculum; (2) recent findings on the differential protracted maturation of spatial relational memory processes in monkeys further support the notion proposed by Jabès and Nelson that this protracted development may reflect progressive maturation of the CA1 field of the hippocampus followed by further maturation of CA3/dentate gyrus; (3) finally, further considerations of the differential maturation of the longitudinal hippocampal axis and of the diencephalon are proposed as additional contributors to the refinement of episodic memory functions during development.

Memory for complex visual objects but not for allocentric locations during the first year of life

Although human infants demonstrate early competence to retain visual information, memory capacities during infancy remain largely undocumented. In three experiments, we used a Visual Paired Comparison (VPC) task to examine abilities to encode identity (Experiment 1) and spatial properties (Experiments 2a and 2b) of unfamiliar complex visual patterns during the first year of life. In the first experiment, 6- and 9-month-old infants were familiarized with visual arrays composed of four abstract patterns arranged in a square configuration. Recognition memory was evaluated by presenting infants with the familiarized array paired with a novel array composed of four new patterns. The second couple of experiments aimed to examine infant ability to encode the spatial relationships between each pattern of the array (e.g., where is A in the square configuration). The 6-, 9- and 12-month-old infants were tested on a spatial version of the VPC task, in which the novel array was composed of the same patterns than the familiarized array but arranged differently within the square configuration. Results indicated that infants retained the identity of the patterns but not their specific spatial relationships within the square configuration (i.e., allocentric location of the patterns), suggesting either an immaturity of the processes involved in object-to-location binding, or the inappropriateness of unfamiliar complex objects to reveal such early allocentric abilities.

20 years after “The ontogeny of human memory: A cognitive neuroscience perspective,” where are we?

In 1995, Nelson published a paper describing a model of memory development during the first years of life. The current article seeks to provide an update on the original work published 20 years ago. Specifically, we review our current knowledge on the relation between the emergence of explicit memory functions throughout development and the maturation of associated brain regions. It is now well established that the brain regions subserving explicit memory functions (i.e. the hippocampal formation) are far from mature at birth, and exhibit important and gradual structural changes during childhood and beyond. Accordingly, explicit memory functions develop progressively. While some functions are present shortly after birth (formerly proposed as pre-explicit memory), others exhibit protracted developmental profiles during the first years of life. We examine the link between the emergence of different memory functions and the maturation of specific hippocampal circuits.

fNIRS in the developmental sciences

With the introduction of functional near-infrared spectroscopy (fNIRS) into the experimental setting, developmental scientists have, for the first time, the capacity to investigate the functional activation of the infant brain in awake, engaged participants. The advantages of fNIRS clearly outweigh the limitations, and a description of how this technology is implemented in infant populations is provided. Most fNIRS research falls into one of three content domains: object processing, processing of biologically and socially relevant information, and language development. Within these domains, there are ongoing debates about the origins and development of human knowledge, making early neuroimaging particularly advantageous. The use of fNIRS has allowed investigators to begin to identify the localization of early object, social, and linguistic knowledge in the immature brain and the ways in which this changes with time and experience. In addition, there is a small but growing body of research that provides insight into the neural mechanisms that support and facilitate learning during the first year of life. At the same time, as with any emerging field, there are limitations to the conclusions that can be drawn on the basis of current findings. We offer suggestions as to how to optimize the use of this technology to answer questions of theoretical and practical importance to developmental scientists.

Four-month-old infants' long-term memory for a stressful social event

Infants clearly show an early capacity for memory for inanimate emotionally neutral events. However, their memory for social stress events has received far less attention. The aim of the study was to investigate infants' memory for a stressful social event (i.e., maternal unresponsiveness during the Still-Face paradigm) after a 15-day recall interval using changes in behavioral responses and salivary post-stress cortisol reactivity as measures of memory. Thirty-seven infants were exposed to social stress two times (experimental condition); the first time when they were 4 months of age and second exposure after a 2 week interval. Infants in the control condition (N = 37) were exposed to social stress just one time, at the age corresponding to the second exposure for infants in the experimental condition (4 months plus 2 weeks). Given individual differences in infants' reactivity to social stress events, we categorized infants as increasers or decreasers based on their cortisol reactivity after their initial exposure to the stress of the maternal still-face. Infants in the experimental condition, both increasers and decreasers, showed a significant change in cortisol response after the second exposure to the maternal still-face, though change was different for each reactivity group. In contrast, age-matched infants with no prior exposure to the maternal still-face showed similar post-stress cortisol reactivity to the reactivity of the experimental infants at their first exposure. There were no behavioral differences between increasers and decreasers during the Still-Face paradigm and exposures to the social stress. Thus differences between the experimental and control groups' post-stress cortisol reactivity was associated with the experimental group having previous experience with the social stress. These findings indicate long-term memory for social stress in infants as young as 4 months of age.

Neural responses to multimodal ostensive signals in 5-month-old infants

Infants' sensitivity to ostensive signals, such as direct eye contact and infant-directed speech, is well documented in the literature. We investigated how infants interpret such signals by assessing common processing mechanisms devoted to them and by measuring neural responses to their compounds. In Experiment 1, we found that ostensive signals from different modalities display overlapping electrophysiological activity in 5-month-old infants, suggesting that these signals share neural processing mechanisms independently of their modality. In Experiment 2, we found that the activation to ostensive signals from different modalities is not additive to each other, but rather reflects the presence of ostension in either stimulus stream. These data support the thesis that ostensive signals obligatorily indicate to young infants that communication is directed to them.

Attentional capture by social stimuli in young infants

We investigated the possibility that a range of social stimuli capture the attention of 6-month-old infants when in competition with other non-face objects. Infants viewed a series of six-item arrays in which one target item was a face, body part, or animal as their eye movements were recorded. Stimulus arrays were also processed for relative salience of each item in terms of color, luminance, and amount of contour. Targets were rarely the most visually salient items in the arrays, yet infants' first looks toward all three target types were above chance, and dwell times for targets exceeded other stimulus types. Girls looked longer at faces than did boys, but there were no sex differences for other stimuli. These results are interpreted in a context of learning to discriminate between different classes of animate stimuli, perhaps in line with affordances for social interaction, and origins of sex differences in social attention.

Brain dynamics in young infants' recognition of faces: EEG oscillatory activity in response to mother and stranger

The brain electrical responses of 3-month-old infants were compared between images of familiar and unfamiliar faces. Infants were shown images of their mothers and of appearance-matched female strangers for 500 ms per trial while their electroencephalography was recorded. Electroencephalographic signals were segmented from stimulus onset through 1200 ms, and segments were analyzed in the time-frequency domain with a continuous wavelet transform. Differentiated responses were apparent in three time windows: 370-480, 610-690, and 830-960 ms. Across response windows, event-related synchronization or desynchronization was observed in beta or gamma frequency bands at the left frontal, midline central, bilateral temporal, and right parietal sites. In conclusion, these findings provide the first evidence of organized brain activity underlying familiar face recognition in very young infants and are discussed in relation to comparable patterns that have been observed in adults.

Sex Differences in Facial Scanning: Similarities and Dissimilarities Between Infants and Adults

When face processing studies find sex differences, male infants appear better at face recognition than female infants, whereas female adults appear better at face recognition than male adults. Both female infants and adults, however, discriminate emotional expressions better than males. To investigate if sex and age differences in facial scanning might account for these processing discrepancies, 3-4-month-olds, 9-10-month-olds, and adults viewed faces presented individually while an eye tracker recorded eye movements. Regardless of age, males shifted fixations between internal and external facial features more than females, suggesting more holistic processing. Females shifted fixations between internal facial features more than males, suggesting more second-order relational processing, which may explain females' emotion discrimination advantage. Older male infants made more fixations than older female infants. Female adults made more fixations for shorter fixation durations than male adults. Male infants and female adults' greater encoding of facial information may explain their face recognition advantage.

Auditory recognition memory in 2-month-old infants as assessed by event-related potentials

Previous studies of auditory recognition memory in sleeping newborns reported 2 event-related potential (ERP) components, P2 and negative slow wave (NSW), reflecting voice discrimination and detection of novelty, respectively. In the present study, using high-density recording arrays, ERPs were acquired from 26 2-month-old awake infants as they were presented with a familiar and unfamiliar voice (i.e., mother and stranger) with equal probability. In addition to P2 and NSW, we observed a positive slow wave (PSW) over the right temporo-parietal scalp, indicating memory updating. Our study suggests that infants appear to have the capacity to encode novel stimuli as early as 2 months of age.

Biracial and monoracial infant own-race face perception: an eye tracking study

We know that early experience plays a crucial role in the development of face processing, but we know little about how infants learn to distinguish faces from different races, especially for non-Caucasian populations. Moreover, it is unknown whether differential processing of different race faces observed in typically studied monoracial infants extends to biracial infants as well. Thus, we investigated 3-month-old Caucasian, Asian and biracial (Caucasian-Asian) infants' ability to distinguish Caucasian and Asian faces. Infants completed two within-subject, infant-controlled habituation sequences and test trials as an eye tracker recorded looking times and scanning patterns. Examination of individual differences revealed significant positive correlations between own-race novelty preference and scanning frequency between eye and mouth regions of own-race habituation stimuli for Caucasian and Asian infants, suggesting that facility in own-race face discrimination stems from active inspection of internal facial features in these groups. Biracial infants, however, showed the opposite effect: An 'own-race' novelty preference was associated with reduced scanning between eye and mouth regions of 'own-race' habituation stimuli, suggesting that biracial infants use a distinct approach to processing frequently encountered faces. Future directions for investigating face processing development in biracial populations are discussed.

Recognition memory is impaired in children after prolonged febrile seizures

Children with a history of a prolonged febrile seizure show signs of acute hippocampal injury on magnetic resonance imaging. In addition, animal studies have shown that adult rats who suffered febrile seizures during development reveal memory impairments. Together, these lines of evidence suggest that memory impairments related to hippocampal injury may be evident in human children after prolonged febrile seizures. The current study addressed this question by investigating memory abilities in 26 children soon after a prolonged febrile seizure (median: 37.5 days) and compared their results to those of 37 normally developing children. Fifteen patients were reassessed at a mean of 12.5 months after their first assessment to determine the transiency of any observed effects. We used the visual paired comparison task to test memory abilities in our group, as this task does not depend on verbal abilities and also because successful performance on the task has been proven to depend on the presence of functional hippocampi. Our findings show that patients perform as well as controls in the absence of a delay between the learning phase and the memory test, suggesting that both groups are able to form representations of the presented stimulus. However, after a 5-min delay, patients' recognition memory is not different from chance, and comparison of patients and controls points to an accelerated forgetting rate in the prolonged febrile seizure group. The patients' performance was not related to the time elapsed from the acute event or the duration of the prolonged febrile seizure, suggesting that the observed effect is not a by-product of the seizure itself or a delayed effect of medication administered to terminate the seizure. By contrast, performance was related to hippocampal size; participants with the smallest mean hippocampal volumes revealed the biggest drop in performance from the immediate to the delayed paradigm. At follow-up, children were still showing deficiencies in recognizing a face after a 5-min delay. Similarly, this suggests that the observed memory impairments are not a transient effect of the prolonged febrile seizures. This is the first report of such impairments in humans, and it is clinically significant given the links between mesial temporal sclerosis and prolonged febrile seizures. The persistence of these impairments a year onwards signals the potential benefits of intervention in these children who run the risk of developing episodic memory deficits in later childhood.

Recognition memory in tree shrew (Tupaia belangeri) after repeated familiarization sessions

Recognition memories are formed during perceptual experience and allow subsequent recognition of previously encountered objects as well as their distinction from novel objects. As a consequence, novel objects are generally explored longer than familiar objects by many species. This novelty preference has been documented in rodents using the novel object recognition (NOR) test, as well is in primates including humans using preferential looking time paradigms. Here, we examine novelty preference using the NOR task in tree shrew, a small animal species that is considered to be an intermediary between rodents and primates. Our paradigm consisted of three phases: arena familiarization, object familiarization sessions with two identical objects in the arena and finally a test session following a 24-h retention period with a familiar and a novel object in the arena. We employed two different object familiarization durations: one and three sessions on consecutive days. After three object familiarization sessions, tree shrews exhibited robust preference for novel objects on the test day. This was accompanied by significant reduction in familiar object exploration time, occurring largely between the first and second day of object familiarization. By contrast, tree shrews did not show a significant preference for the novel object after a one-session object familiarization. Nonetheless, they spent significantly less time exploring the familiar object on the test day compared to the object familiarization day, indicating that they did maintain a memory trace for the familiar object. Our study revealed different time courses for familiar object habituation and emergence of novelty preference, suggesting that novelty preference is dependent on well-consolidated memory of the competing familiar object. Taken together, our results demonstrate robust novelty preference of tree shrews, in general similarity to previous findings in rodents and primates.

A critical review of the development of face recognition: experience is less important than previously believed

Historically, it has been argued that face individuation develops very slowly, not reaching adult levels until adolescence, with experience being the driving force behind this protracted improvement. Here, we challenge this view based on extensive review of behavioural and neural findings. Results demonstrate qualitative presence of all key phenomena related to face individuation (encoding of novel faces, holistic processing effects, face-space effects, face-selective responses in neuroimaging) at the earliest ages tested, typically 3-5 years of age and in many cases even infancy. Results further argue for quantitative maturity by early childhood, based on an increasing number of behavioural studies that have avoided the common methodological problem of restriction of range, as well as event-related potential (ERP), but not functional magnetic resonance imaging (fMRI) studies. We raise a new possibility that could account for the discrepant fMRI findings-namely, the use of adult-sized head coils on child-sized heads. We review genetic and innate contributions to face individuation (twin studies, neonates, visually deprived monkeys, critical periods, perceptual narrowing). We conclude that the role of experience in the development of the mechanisms of face identification has been overestimated. The emerging picture is that the mechanisms supporting face individuation are mature early, consistent with the social needs of children for reliable person identification in everyday life, and are also driven to an important extent by our evolutionary history.

Brief report: face-specific recognition deficits in young children with autism spectrum disorders

This study used eyetracking to investigate the ability of young children with autism spectrum disorders (ASD) to recognize social (faces) and nonsocial (simple objects and complex block patterns) stimuli using the visual paired comparison (VPC) paradigm. Typically developing (TD) children showed evidence for recognition of faces and simple objects, but not complex block patterns. Children with ASD were successful at recognizing novel objects and block patterns, but showed no evidence for face recognition. These findings suggest that young children with ASD have specific impairments in face recognition, and that they may have advantage over TD controls when processing complex nonsocial stimuli.