Continuity in mental development from infancy

Infant circulating MicroRNAs as biomarkers of effect in fetal alcohol spectrum disorders

Prenatal alcohol exposure (PAE) can result in cognitive and behavioral disabilities and growth deficits. Because alcohol-related neurobehavioral deficits may occur in the absence of overt dysmorphic features or growth deficits, there is a need to identify biomarkers of PAE that can predict neurobehavioral impairment. In this study, we assessed infant plasma extracellular, circulating miRNAs (exmiRNAs) obtained from a heavily exposed Cape Town cohort to determine whether these can be used to predict PAE-related growth restriction and cognitive impairment. PAE, controlling for smoking as a covariate, altered 27% of expressed exmiRNAs with clinically-relevant effect sizes (Cohen's d ≥ 0.4). Moreover, at 2 weeks, PAE increased correlated expression of exmiRNAs across chromosomes, suggesting potential co-regulation. In confirmatory factor analysis, the variance in expression for PAE-altered exmiRNAs at 2 weeks and 6.5 months was best described by three-factor models. Pathway analysis found that factors at 2 weeks were associated with (F1) cell maturation, cell cycle inhibition, and somatic growth, (F2) cell survival, apoptosis, cardiac development, and metabolism, and (F3) cell proliferation, skeletal development, hematopoiesis, and inflammation, and at 6.5 months with (F1) neurodevelopment, neural crest/mesoderm-derivative development and growth, (F2) immune system and inflammation, and (F3) somatic growth and cardiovascular development. Factors F3 at 2 weeks and F2 at 6.5 months partially mediated PAE-induced growth deficits, and factor F3 at 2 weeks partially mediated effects of PAE on infant recognition memory at 6.5 months. These findings indicate that infant exmiRNAs can help identify infants who will exhibit PAE-related deficits in growth and cognition.

Prenatal Risk Predicts Preschooler Executive Function: A Cascade Model

Little research has considered whether prenatal experience contributes to executive function (EF) development above and beyond postnatal experience. This study tests direct, mediated, and moderated associations between prenatal risk factors and preschool EF and IQ in a longitudinal sample of 1,292 children from the Family Life Project. A composite of prenatal risk factors (i.e., low birth weight, prematurity, maternal emotional problems, maternal prepregnancy obesity, and obstetric complications) significantly predicted EF and IQ at age 3, above quality of the postnatal environment. This relationship was indirect, mediated through infant general cognitive abilities. Quality of the postnatal home and child-care environments did not moderate the cascade model. These findings highlight the role of prenatal experience as a contributor to individual differences in cognitive development.

The Novelty Effect as a Predictor of Language Outcome

A controversial issue in the field of language acquisition is the extent to which general attentional or cognitive abilities play a role in individual differences in early language outcomes. Here we report a longitudinal study where we examined whether processing efficiency in a novelty detection task predicted later vocabulary size in a stable manner across time. We found that the novelty detection ability measured at 9 months was significantly predictive of later vocabulary size at 12, 14, 18, and 24 months. This study, therefore, emphasizes the importance of controlling for non-linguistic factors when assessing individual variability in language development. A more accurate assessment of language development may be obtained if general attentional and cognitive abilities are also taken into account in addition to linguistic factors.

Visual habituation in deaf and hearing infants

Early cognitive development relies on the sensory experiences that infants acquire as they explore their environment. Atypical experience in one sensory modality from birth may result in fundamental differences in general cognitive abilities. The primary aim of the current study was to compare visual habituation in infants with profound hearing loss, prior to receiving cochlear implants (CIs), and age-matched peers with typical hearing. Two complementary measures of cognitive function and attention maintenance were assessed: the length of time to habituate to a visual stimulus, and look-away rate during habituation. Findings revealed that deaf infants were slower to habituate to a visual stimulus and demonstrated a lower look-away rate than hearing infants. For deaf infants, habituation measures correlated with language outcomes on standardized assessments before cochlear implantation. These findings are consistent with prior evidence suggesting that habituation and look-away rates reflect efficiency of information processing and may suggest that deaf infants take longer to process visual stimuli relative to the hearing infants. Taken together, these findings are consistent with the hypothesis that hearing loss early in infancy influences aspects of general cognitive functioning.

Assessing whether early attention of very preterm infants can be improved by an omega-3 long-chain polyunsaturated fatty acid intervention: a follow-up of a randomised controlled trial

INTRODUCTION

Docosahexaenoic acid (DHA) accumulates in the frontal lobes (responsible for higher-order cognitive skills) of the fetal brain during the last trimester of pregnancy. Infants born preterm miss some of this in utero provision of DHA, and have an increased risk of suboptimal neurodevelopment. It is thought that supplementing infants born preterm with DHA may improve developmental outcomes. The aim of this follow-up is to determine whether DHA supplementation in infants born preterm can improve areas of the brain associated with frontal lobe function, namely attention and distractibility.

METHODS AND ANALYSIS

We will assess a subset of children from the N-3 (omega-3) Fatty Acids for Improvement in Respiratory Outcomes (N3RO) multicentre double-blind randomised controlled trial of DHA supplementation. Infants born <29 weeks' completed gestation were randomised to receive an enteral emulsion containing 60 mg/kg/day of DHA or a control emulsion from within the first 3 days of enteral feeding until 36 weeks' postmenstrual age.Children will undergo multiple measures of attention at 18 months' corrected age. The primary outcome is the average time to be distracted when attention is focused on a toy. Secondary outcomes are other aspects of attention, and (where possible) an assessment of cognition, language and motor development with the Bayley Scales of Infant and Toddler Development, Third Edition.A minimum of 72 children will be assessed to ensure 85% power to detect an effect on the primary outcome. Families, and research personnel are blinded to group assignment. All analyses will be conducted according to the intention-to-treat principal.

ETHICS AND DISSEMINATION

All procedures were approved by the relevant institutional ethics committees prior to commencement of the study. Results will be disseminated in peer-reviewed journal publications and academic presentations.

TRIAL REGISTRATION NUMBER

ACTRN12612000503820; Pre-results.

Attention to novelty versus repetition: Contrasting habituation profiles in Autism and Williams syndrome

BACKGROUND

Abnormalities in habituation have been documented in Autism Spectrum Disorder (ASD) and Williams syndrome (WS). Such abnormalities have been proposed to underlie the distinctive social and non-social difficulties that define ASD, including sensory features and repetitive behaviours, and the distinctive social phenotype characterizing WS.

METHODS

We measured habituation in 39 preschoolers with ASD, 20 peers with WS and 19 typically developing (TD) children using an eye-tracking protocol that measured participants' duration of attention in response to a repeating stimulus and a novel stimulus presented side by side across multiple trials.

RESULTS

Participants in the TD group and the WS group decreased their attention toward the repeating stimulus and increased their attention to the novel stimulus over time. Conversely, the ASD group showed a similar attentional response to the novel and repeating stimuli. Habituation was correlated with social functioning in the WS but not in the ASD group. Contrary to predictions, slower habituation in ASD was associated with lower severity of repetitive behaviours.

CONCLUSIONS

Habituation appears to be intact in WS and impaired in ASD. More research is needed to clarify the nature of the syndrome-specific patterns of correlations between habituation and social and non-social functioning in these neurodevelopmental disorders.

Mouse models of 17q21.31 microdeletion and microduplication syndromes highlight the importance of Kansl1 for cognition

Koolen-de Vries syndrome (KdVS) is a multi-system disorder characterized by intellectual disability, friendly behavior, and congenital malformations. The syndrome is caused either by microdeletions in the 17q21.31 chromosomal region or by variants in the KANSL1 gene. The reciprocal 17q21.31 microduplication syndrome is associated with psychomotor delay, and reduced social interaction. To investigate the pathophysiology of 17q21.31 microdeletion and microduplication syndromes, we generated three mouse models: 1) the deletion (Del/+); or 2) the reciprocal duplication (Dup/+) of the 17q21.31 syntenic region; and 3) a heterozygous Kansl1 (Kans1^+/-) model. We found altered weight, general activity, social behaviors, object recognition, and fear conditioning memory associated with craniofacial and brain structural changes observed in both Del/+ and Dup/+ animals. By investigating hippocampus function, we showed synaptic transmission defects in Del/+ and Dup/+ mice. Mutant mice with a heterozygous loss-of-function mutation in Kansl1 displayed similar behavioral and anatomical phenotypes compared to Del/+ mice with the exception of sociability phenotypes. Genes controlling chromatin organization, synaptic transmission and neurogenesis were upregulated in the hippocampus of Del/+ and Kansl1^+/- animals. Our results demonstrate the implication of KANSL1 in the manifestation of KdVS phenotypes and extend substantially our knowledge about biological processes affected by these mutations. Clear differences in social behavior and gene expression profiles between Del/+ and Kansl1^+/- mice suggested potential roles of other genes affected by the 17q21.31 deletion. Together, these novel mouse models provide new genetic tools valuable for the development of therapeutic approaches.

The 17q21.31 deletion syndrome, also named Koolen-de Vries syndrome (KdVS), is a rare copy number variants associated in humans with intellectual disability, friendly behavior, congenital malformations. The syndrome is caused either by microdeletions in the 17q21.31 region or by variants in the KANSL1 gene in human. The reciprocal 17q21.31 microduplication syndrome is not so well characterized. To investigate the pathophysiology of the syndromes, we studied the deletion, the duplication of the syntenic region and a heterozygous Kansl1 mutant in the mouse. We found affected morphology and cognition, similar to human condition, with genes controlling chromatin organization, synaptic transmission and neurogenesis dysregulated in the hippocampus of KdVS models. In addition we found that synaptic transmission was altered in KdVS mice. Our results demonstrate the implication of KANSL1 in the manifestation of KdVS and extend substantially our knowledge about altered biological processes. Nevertheless, phenotypic differences between deletion and Kansl1^+/- models suggested roles of other genes affected by the 17q21.31 deletion.

Mechanistic Pathways From Early Gestation Through Infancy and Neurodevelopment

OBJECTIVE

To identify pathways through which pre- and postnatal factors directly or indirectly affect infant neurodevelopment at 12 months of age among Filipino infants.

METHODS

The Bayley Scales of Infant Development, third edition was used to assess the development of 314 infants of mothers enrolled in a trial examining the safety and efficacy of praziquantel during pregnancy. Maternal covariates included socioeconomic status, iron and nutritional status, cognitive performance, and alcohol intake. Infant covariates included birth weight and feeding practices, longitudinal growth and nutritional status, hemoglobin and iron status captured at birth, and 6 and 12 months of age. Multivariable regression and structural equation modeling were used to identify significant factors associated with infant development.

RESULTS

In regression models, maternal education, cognition, and iron status as well as infant weight-for-age z-score (WAZ), weight-for-length z-score, and WAZ gains were significantly associated with infant development at 12 months of age. Structural equation modeling demonstrated a direct effect of maternal cognition on most subscales of infant development and indirect effects on expressive language through effects on infant WAZ. Maternal iron status was a stronger predictor of infant cognition subscale scores than was infant iron status. Exclusive breastfeeding had a direct influence on expressive language rather than acting through improved infant iron or nutritional status.

CONCLUSIONS

We identified key modifiable risk factors for impaired neurodevelopment, including prenatal risk factors such as maternal iron status. Integrated nutritional interventions that impact both maternal and infant nutritional status are likely to positively affect infant neurodevelopment through identified pathways.

MAOA Influences the Trajectory of Attentional Development

Attention is vital to success in all aspects of life (Meck and Benson, 2002; Erickson et al., 2015), hence it is important to identify biomarkers of later attentional problems early enough to intervene. Our objective was to determine if any of 11 genes (APOE, BDNF, HTR4, CHRNA4, COMT, DRD4, IGF2, MAOA, SLC5A7, SLC6A3, and SNAP25) predicted the trajectory of attentional development within the same group of children between infancy and childhood. We recruited follow up participants from children who participated as infants in visual attention studies and used a similar task at both time points. Using multilevel modeling, we associated changes in the participant’s position in the distribution of scores in infancy to his/her position in childhood with genetic markers on each of 11 genes. While all 11 genes predicted reaction time (RT) residual scores, only Monoamine oxidase A (MAOA) had a significant interaction including time point. We conclude that the MAOA single nucleotide polymorphism (SNP) rs1137070 is useful in predicting which girls are likely to develop slower RTs on an attention task between infancy and childhood. This early identification is likely to be helpful in early intervention.

Reduced DHA transfer in diabetic pregnancies: mechanistic basis and long-term neurodevelopmental implications

Infants born to diabetic mothers have a higher frequency of impaired neurodevelopment. The omega-3 or n-3 fatty acid docosahexaenoic acid (DHA) is an important structural component of neural tissue and is critical for fetal brain development. Maternal DHA supplementation during pregnancy is linked to better infant neurodevelopment; however, maternal-fetal transfer of DHA is reduced in women with diabetes. Evidence of mechanisms explaining altered maternal-fetal DHA transfer in this population is limited. This review explores existing evidence underpinning reduced maternal-fetal DHA transfer in maternal fuel metabolism in this population. Further research is necessary to evaluate the role of peroxisome proliferator-activated receptors in modulating placental fatty acid binding and maternal-fetal DHA transfer. Considerations for clinical practice include a diet high in DHA and/or provision of supplemental DHA to obstetric diabetic patients within minimum guidelines.

Pathways From Toddler Information Processing to Adolescent Lexical Proficiency

This study examined the relation of 3-year core information-processing abilities to lexical growth and development. The core abilities covered four domains-memory, representational competence (cross-modal transfer), processing speed, and attention. Lexical proficiency was assessed at 3 and 13 years with the Peabody Picture Vocabulary Test (PPVT) and verbal fluency. The sample (N = 128) consisted of 43 preterms (< 1750 g) and 85 full-terms. Structural equation modeling indicated concurrent relations of toddler information processing and language proficiency and, independent of stability in language, direct predictive links between (a) 3-year cross-modal ability and 13-year PPVT and (b) 3-year processing speed and both 13-year measures, PPVT and verbal fluency. Thus, toddler information processing was related to growth in lexical proficiency from 3 to 13 years.

Socioeconomic disparities in neurocognitive development in the first two years of life

Socioeconomic status (SES) is strongly associated with cognition and achievement. Socioeconomic disparities in language and memory skills have been reported from elementary school through adolescence. Less is known about the extent to which such disparities emerge in infancy. Here, 179 infants from socioeconomically diverse families were recruited. Using a cohort-sequential design, 90 infants were followed at 9 and 15 months, and 89 were followed at 15 and 21 months. SES disparities in developmental trajectories of language and memory were present such that, at 21 months of age, children of highly educated parents scored approximately .8 standard deviations higher in both language and memory than children of less educated parents. The home language and literacy environment and parental warmth partially accounted for disparities in language, but not memory development.

Developmental pathways for social understanding: linking social cognition to social contexts

Contemporary research, often with looking-time tasks, reveals that infants possess foundational understandings of their social worlds. However, few studies have examined how these early social cognitions relate to the child’s social interactions and behavior in early development. Does an early understanding of the social world relate to how an infant interacts with his or her parents? Do early social interactions along with social-cognitive understandings in infancy predict later preschool social competencies? In the current paper, we propose a theory in which children’s later social behaviors and their understanding of the social world depend on the integration of early social understanding and experiences in infancy. We review several of our studies, as well as other research, that directly examine the pathways between these competencies to support a hypothesized network of relations between social-cognitive development and social-interactive behaviors in the development from infancy to childhood. In total, these findings reveal differences in infant social competences that both track the developmental trajectory of infants’ understanding of people over the first years of life and provide external validation for the large body of social-cognitive findings emerging from laboratory looking-time paradigms.

Early developmental outcomes of children with congenital HHV-6 infection

OBJECTIVE

The goal of this study was to determine if congenital human herpesvirus-6 (HHV-6) infection influences early neurodevelopment.

METHODS

We enrolled 57 newborns with HHV-6 congenital infection and 242 control newborns without congenital infection into a prospective, double-blind study with 4 visits between 4 and 30 months of age. Assessments included the Fagan Test of Infant Intelligence, the Visual Expectation Paradigm, and the Mental Development Index (MDI) of the Bayley Scales of Infant Development II. Newborn audiology screening and follow-up audiology examinations were completed at 12 to 24 months.

RESULTS

No differences were noted in baseline characteristics between infants with HHV-6 congenital infection and control infants. No clinical syndrome due to congenital infection with HHV-6 was evident at birth. No differences were identified on the Fagan Test of Infant Intelligence or the Visual Expectation Paradigm between the two groups. In 39 infants with HHV-6 congenital infection, the mean ± SD Bayley Scale of Infant Development II MDI score was 103.4 ± 8.9 at 12 months of age. The matched control infants had a mean score of 105.4 ± 12.4. After controlling for covariates, HHV-6 congenital infection was associated with lower scores on the Bayley Scale of Infant Development II MDI at 12 months of age (mean difference: 4.3 [95% confidence interval: 0.4 to 8.1]; P = .03) compared with infants without HHV-6 congenital infection.

CONCLUSIONS

Congenital HHV-6 infection may have a detrimental effect on neurodevelopment at 12 months of age and requires further study given that congenital infection with HHV-6 is present in ∼1 in every 101 births.

The Social Context of Infant Intention Understanding

Traditional looking-time paradigms are often used to assess infants' attention to socio-cognitive phenomena, but the link between these laboratory scenarios and real-world interactions is unclear. The current study investigated hypothesized relations between traditional social-cognitive looking-time paradigms and their real-world counterparts in caregiver-infant social interaction. Seventy-five 10- to 12-month-old infants participated in a structured play session with their caregiver, as well as a traditional looking-time paradigm targeting intentional action. Infants' ability to quickly parse intentional displays correlated with several key qualities of their everyday interactions. In particular, caregiver and infant interaction quality, maternal supportiveness, caregiver and infant joint engagement skill, and social attentiveness in infants correlated with faster habituation to looking-time displays. These results support a linkage between social-cognitive looking-time laboratory paradigms and more naturalistic partner interaction, at this key age. The data both provide external validation for the large body of social-cognitive findings emerging from laboratory looking-time paradigms, and contribute to a growing literature tracking the developmental trajectory of infants' understanding of people over the first two years.

Postoperative electroencephalographic seizures are associated with deficits in executive function and social behaviors at 4 years of age following cardiac surgery in infancy

OBJECTIVE

The occurrence of an electroencephalographic (EEG) seizure after surgery for complex congenital heart defects has been associated with worse neurodevelopmental (ND) outcomes. We previously identified postoperative seizures documented by 48-hour EEG monitoring in 11% of 178 neonates and infants. Evaluation at 1 year of age did not identify an adverse effect of an EEG seizure on ND outcomes. The current study was undertaken to determine if testing in the preschool period would identify deficits that become apparent as children develop.

METHODS

The ND outcomes assessed at 4 years of age included cognition, language, attention, impulsivity, executive function, behavior problems, academic achievement, and visual and fine motor skills.

RESULTS

Developmental evaluations were performed in 132 (87%) of 151 survivors. For the entire cohort, the Full-Scale IQ was 95.0 ± 18.5. IQ was 95.1 ± 18.7 for patients without a history of seizure and 93.6 ± 16.7 for those with a history of seizure. After covariate adjustment, occurrence of an EEG seizure was associated with worse executive function (P = .037) and impaired social interactions/restricted behavior (P = .05). Seizures were not significantly associated with worse performance for cognition, language, attention, impulsivity, academic achievement, or motor skills (all P > .1).

CONCLUSIONS

The occurrence of a postoperative seizure is a biomarker of brain injury. This study confirms that postoperative EEG seizures are associated with worse ND outcomes, characterized by impairments of executive function and a higher prevalence of deficits in social interactions and repetitive/restricted behaviors in preschool survivors of cardiac surgery in infancy. However, EEG seizures were not associated with worse cognitive, language, or motor skills.

Infant attention and early childhood executive function

Individual differences in infant attention are theorized to reflect the speed of information processing and are related to later cognitive abilities (i.e., memory, language, and intelligence). This study provides the first systematic longitudinal analysis of infant attention and early childhood executive function (EF; e.g., working memory, inhibitory control, cognitive flexibility). A group of 5-month-olds (n = 201) were classified as short or long lookers. At 24, 36, and 48 months of age, children completed age-appropriate EF tasks. Infant short lookers (i.e., more efficient information processors) exhibited higher EF throughout early childhood as compared to infant long lookers, even after controlling for verbal ability (a potential indicator of intelligence). These findings are discussed in relation to the emergence of executive attention.

Simulating the role of visual selective attention during the development of perceptual completion

We recently proposed a multi-channel, image-filtering model for simulating the development of visual selective attention in young infants (Schlesinger, Amso & Johnson, 2007). The model not only captures the performance of 3-month-olds on a visual search task, but also implicates two cortical regions that may play a role in the development of visual selective attention. In the current simulation study, we used the same model to simulate 3-month-olds' performance on a second measure, the perceptual unity task. Two parameters in the model - corresponding to areas in the occipital and parietal cortices - were systematically varied while the gaze patterns produced by the model were recorded and subsequently analyzed. Three key findings emerged from the simulation study. First, the model successfully replicated the performance of 3-month-olds on the unity perception task. Second, the model also helps to explain the improved performance of 2-month-olds when the size of the occluder in the unity perception task is reduced. Third, in contrast to our previous simulation results, variation in only one of the two cortical regions simulated (i.e. recurrent activity in posterior parietal cortex) resulted in a performance pattern that matched 3-month-olds. These findings provide additional support for our hypothesis that the development of perceptual completion in early infancy is promoted by progressive improvements in visual selective attention and oculomotor skill.

General learning ability regulates exploration through its influence on rate of habituation

"General intelligence" is purported to influence diverse domain-specific learning abilities in humans, and previous research indicates that an analogous trait is expressed in CD-1 outbred mice. In humans and mice, exploratory tendencies are predictive of general cognitive abilities, such that higher cognitive abilities are associated with elevated levels of exploration. However, in mice, repeated exposure to novel environments outside the home cage has been found to up-regulate exploratory tendencies but has no commensurate effect on general learning abilities, suggesting that exploratory tendencies do not causally influence general cognitive performance. This leaves open the question of what is responsible for the robust relationship observed between exploration and general learning abilities? In the present experiments, we find that differential rates of habituation (e.g., to a novel open field) between animals of high and low general learning abilities accounts for the relationship between exploration and learning abilities. First, we up-regulated exploration by exposing mice to a series of novel environments. Similar to its lack of effect on learning tasks, this up-regulation of exploration had no commensurate effect on habituation to novel objects or stimuli. Next we examined the relationship between general learning abilities and exploration under conditions where habituation had a high or low impact on exploratory behaviors. A strong correlation between general learning abilities and exploration was observed under conditions where the levels of habituation (to a novel object or an open field) between animals of high and low general learning abilities were allowed to vary. However, this same correlation was attenuated when the level of habituation attained by animals of high and low general learning abilities was asymptotic or held constant across animals. In total, these results indicate that the relationship between exploration and general learning abilities is accounted for by the impact of habituation (itself a form of learning) on behaviors indicative of exploration.

Long-chain polyunsaturated fatty acid supplementation in infancy reduces heart rate and positively affects distribution of attention

A double-blind, randomized, controlled, parallel-group prospective trial was conducted to determine whether a dose-response existed for four different levels of docosahexaenoic acid (DHA) supplementation on the cognitive performance of infants. A total of 122 term infants were fed one of four different formulas varying in their DHA composition (0.00, 0.32, 0.64, and 0.96% of total fatty acids as DHA) from birth to 12 mo. The three DHA-supplemented formulas also contained 0.64% of total fatty acids as arachidonic acid (ARA, 20:4n-6). Infants were tested at 4, 6, and 9 mo of age on a visual habituation protocol that yielded both behavioral and psychophysiological indices of attention. Infants in all DHA+ARA-supplemented conditions had lower heart rates than those in the unsupplemented condition; there was no dose-response for this effect. The distribution of time that infants spent in different phases of attention (a cognitive index derived from the convergence of behavioral and cardiac responses) varied as a function of dosage. Infants supplemented at the two lower DHA doses spent proportionately more time engaged in active stimulus processing than infants fed the unsupplemented formula, whereas infants fed the highest dose were intermediate and did not differ from any other group.

Developmental and cognitive characteristics of "high-level potentialities" (highly gifted) children

This study covers the interesting field of the development in gifted children which is often neglected in pediatrics because psychomotor development data are still rare, since "gifted" children are generally noticed towards the end of their primary schooling by IQ measurement. Developmental studies have shown the evidence from several fields that children identified as "high-level potentialities" or "intellectually gifted" develop sensory, locomotor, neuropsychological, and language skills earlier than typically expected. The hypothesis is offered that the earlier development originates from biological processes affecting the physical development of the brain and in turn even intellectual abilities are developed earlier, potentially allowing for advanced development. Further it is discussed how these developmental advances interact with the social environment and in certain circumstances may entail increased risk for developing socioemotional difficulties and learning disabilities that often go unaddressed due to the masking by the advance intellectual abilities.

Neural Correlates of Individual Differences in Infant Visual Attention and Recognition Memory

Past studies have identified individual differences in infant visual attention based upon peak look duration during initial exposure to a stimulus. Colombo and colleagues (e.g., Colombo & Mitchell, 1990) found that infants that demonstrate brief visual fixations (i.e., short lookers) during familiarization are more likely to demonstrate evidence of recognition memory during subsequent stimulus exposure than infants that demonstrate long visual fixations (i.e., long lookers). The current study utilized event-related potentials to examine possible neural mechanisms associated with individual differences in visual attention and recognition memory for 6- and 7.5-month-old infants. Short- and long-looking infants viewed images of familiar and novel objects during ERP testing. There was a stimulus type by looker type interaction at temporal and frontal electrodes on the late slow wave (LSW). Short lookers demonstrated a LSW that was significantly greater in amplitude in response to novel stimulus presentations. No significant differences in LSW amplitude were found based on stimulus type for long lookers. These results indicate deeper processing and recognition memory of the familiar stimulus for short lookers.

Emergence of a Gene x socioeconomic status interaction on infant mental ability between 10 months and 2 years

Recent research in behavioral genetics has found evidence for a Gene × Environment interaction on cognitive ability: Individual differences in cognitive ability among children raised in socioeconomically advantaged homes are primarily due to genes, whereas environmental factors are more influential for children from disadvantaged homes. We investigated the developmental origins of this interaction in a sample of 750 pairs of twins measured on the Bayley Short Form test of infant mental ability, once at age 10 months and again at age 2 years. A Gene × Environment interaction was evident on the longitudinal change in mental ability over the study period. At age 10 months, genes accounted for negligible variation in mental ability across all levels of socioeconomic status (SES). However, genetic influences emerged over the course of development, with larger genetic influences emerging for infants raised in higher-SES homes. At age 2 years, genes accounted for nearly 50% of the variation in mental ability of children raised in high-SES homes, but genes continued to account for negligible variation in mental ability of children raised in low-SES homes.

Toddlers with elevated autism symptoms show slowed habituation to faces

We explored social information processing and its relation to social and communicative symptoms in toddlers with Autism Spectrum Disorder (ASD) and their siblings. Toddlers with more severe symptoms of autism showed slower habituation to faces than comparison groups; slower face learning correlated with poorer social skills and lower verbal ability. Unaffected toddlers who were siblings of children with ASD also showed slower habituation to faces compared with toddlers without siblings with ASD. We conclude that slower rates of face learning may be an endophenotype of ASD and is associated with more severe symptoms among affected individuals.

Infant visual habituation

The use of visual habituation in the study of infant cognition and learning is reviewed. This article traces the history of the technique, underlying theory, and procedural variation in its measurement. In addition, we review empirical findings with respect to the cognitive processes that presumably contribute to habituation, studies of developmental course and long-term prediction, as well as recent attempts to address or explain the phenomenon of visual habituation through the use of mathematical or quantitative models. The review ends with an appeal for a return to the study of habituation per se as a valid measure of infant learning, rather than relegating the phenomenon to its use as a technique for familiarizing infants in procedures testing for discrimination or recognition.

Information Processing in Toddlers: Continuity from Infancy and Persistence of Preterm Deficits

The present report assesses information processing in the toddler years (24 and 36 months), using a cohort of preterms (<1750 g) and full-terms initially seen in infancy. The children received a battery of tasks tapping 11 specific abilities from four domains - memory, processing speed, attention, and representational competence. The same battery had been used earlier - at 7 and 12 months. There were four main findings. (1) Preterms showed no 'catch-up,' but rather persistent deficits in immediate recognition, recall, encoding speed, and attention. (2) There was significant continuity from infancy through the toddler years for most aspects of information processing. (3) These specific abilities combined additively to account for global cognitive ability, consistent with the componential theory of intelligence. (4) Toddler information processing abilities completely mediated the relative deficits of preterms in general cognitive ability. Thus, although the toddler years have often been characterized as a period of discontinuity and transformation, these results indicate that continuity prevails for information processing abilities over the first three years of life.

Structure and Continuity of Intellectual Development in Early Childhood

We evaluated over 200 participants semiannually from 12 to 48 months of age on measures of intellectual (Bayley Scales, Stanford-Binet Scale) and verbal (MacArthur-Bates Inventory, Peabody Picture Vocabulary Test) status. Structural equation modeling and hierarchical linear (growth curve) analyses were applied to address the nature of development and individual differences during this time. Structural analyses showed a strong and robust simplex model from infancy to the preschool period, with no evidence of qualitative reorganizations or discontinuities. Growth-curve modeling revealed significant associations between level factors across the early and later measures of cognition, providing further evidence of continuity; the growth trajectory from the Bayley through 24 months predicted growth in a nonverbal factor, but not in a verbal factor. Altogether, the findings reveal continuous and stable development in intellectual function from late infancy through the preschool years. Additionally, the high level of continuity demonstrated across these ages was observed to be largely independent of growth in vocabulary.

Individual differences and the development of joint attention in infancy

This study examined the development of joint attention in 95 infants assessed between 9 and 18 months of age. Infants displayed significant test-retest reliability on measures of following gaze and gestures (responding to joint attention, RJA) and in their use of eye contact to establish social attention coordination (initiating joint attention, IJA). Infants displayed a linear, increasing pattern of age-related growth on most joint attention measures. However, IJA was characterized by a significant cubic developmental pattern. Infants with different rates of cognitive development exhibited different frequencies of joint attention acts at each age, but did not exhibit different age-related patterns of development. Finally, 12-month RJA and 18-month IJA predicted 24-month language after controlling for general aspects of cognitive development.

Infant information processing and family history of specific language impairment: converging evidence for RAP deficits from two paradigms

An infant's ability to process auditory signals presented in rapid succession (i.e. rapid auditory processing abilities [RAP]) has been shown to predict differences in language outcomes in toddlers and preschool children. Early deficits in RAP abilities may serve as a behavioral marker for language-based learning disabilities. The purpose of this study is to determine if performance on infant information processing measures designed to tap RAP and global processing skills differ as a function of family history of specific language impairment (SLI) and/or the particular demand characteristics of the paradigm used. Seventeen 6- to 9-month-old infants from families with a history of specific language impairment (FH+) and 29 control infants (FH-) participated in this study. Infants' performance on two different RAP paradigms (head-turn procedure [HT] and auditory-visual habituation/recognition memory [AVH/RM]) and on a global processing task (visual habituation/recognition memory [VH/RM]) was assessed at 6 and 9 months. Toddler language and cognitive skills were evaluated at 12 and 16 months. A number of significant group differences were seen: FH+ infants showed significantly poorer discrimination of fast rate stimuli on both RAP tasks, took longer to habituate on both habituation/recognition memory measures, and had lower novelty preference scores on the visual habituation/recognition memory task. Infants' performance on the two RAP measures provided independent but converging contributions to outcome. Thus, different mechanisms appear to underlie performance on operantly conditioned tasks as compared to habituation/recognition memory paradigms. Further, infant RAP processing abilities predicted to 12- and 16-month language scores above and beyond family history of SLI. The results of this study provide additional support for the validity of infant RAP abilities as a behavioral marker for later language outcome. Finally, this is the first study to use a battery of infant tasks to demonstrate multi-modal processing deficits in infants at risk for SLI.

Infant recall memory and communication predicts later cognitive development

This longitudinal study investigates the relation between recall memory and communication in infancy and later cognitive development. Twenty-six typically developing Swedish children were tested during infancy for deferred imitation (memory), joint attention (JA), and requesting (nonverbal communication); they also were tested during childhood for language and cognitive competence. Results showed that infants with low performance on both deferred imitation at 9 months and joint attention at 14 months obtained a significantly lower score on a test of cognitive abilities at 4 years of age. This long-term prediction from preverbal infancy to childhood cognition is of interest both to developmental theory and to practice.

Infants' attention to patterned stimuli: developmental change from 3 to 12 months of age

To examine the development of look duration as a function of age and stimulus type, 14- to 52-week-old infants were shown static and dynamic versions of faces, Sesame Street material, and achromatic patterns for 20 s of accumulated looking. Heart rate was recorded during looking and parsed into stimulus orienting, sustained attention, and attention termination phases. Infants' peak look durations indicated that prior to 26 weeks there was a linear decrease with age for all stimuli. Older infants' look durations continued to decline for patterns but increased for Sesame Street and faces. Measures of heart rate change during sustained attention and the proportion of time spent in each phase of attention confirmed infants' greater engagement with the more complex stimuli.

Exploring the Relation Between Memory, Gestural Communication, and the Emergence of Language in Infancy: A Longitudinal Study

The relationship between recall memory, visual recognition memory, social communication, and the emergence of language skills was measured in a longitudinal study. Thirty typically developing Swedish children were tested at 6, 9 and 14 months. The result showed that, in combination, visual recognition memory at 6 months, deferred imitation at 9 months and turn-taking skills at 14 months could explain 41% of the variance in the infants' production of communicative gestures as measured by a Swedish variant of the MacArthur Communicative Development Inventories (CDI). In this statistical model, deferred imitation stood out as the strongest predictor.

Prenatal cocaine exposure and infant cognition

The present study examined the relationship of prenatal cocaine exposure to infant information processing in the first year of life.In a prospective, longitudinal study of 177 cocaine-exposed and 175 non-exposed infants, the Fagan Test of Infant Intelligence (FTII) was used to measure attention, visual recognition memory and information processing speed at 6.5 and 12 months of age. Groups were compared over time using mixed linear model analyses.Prenatal cocaine exposure predicted poorer visual recognition memory at 12 months, with exposed infants obtaining lower mean scores and a higher percentage of scores in the risk range. Across exposure groups, information processing speed increased with age, demonstrating a developmental effect. Tobacco and marijuana exposures were related to faster looking times, which did not relate to visual recognition memory.Cognitive deficits and attentional problems noted in prior studies of cocaine-exposed children at later ages may be detectable in infancy.

Individual differences in the expression of a "general" learning ability in mice

Human performance on diverse tests of intellect are impacted by a "general" regulatory factor that accounts for up to 50% of the variance between individuals on intelligence tests. Neurobiological determinants of general cognitive abilities are essentially unknown, owing in part to the paucity of animal research wherein neurobiological analyses are possible. We report a methodology with which we have assessed individual differences in the general learning abilities of laboratory mice. Abilities of mice on tests of associative fear conditioning, operant avoidance, path integration, discrimination, and spatial navigation were assessed. Tasks were designed so that each made unique sensory, motor, motivational, and information processing demands on the animals. A sample of 56 genetically diverse outbred mice (CD-1) was used to assess individuals' acquisition on each task. Indicative of a common source of variance, positive correlations were found between individuals' performance on all tasks. When tested on multiple test batteries, the overall performance ranks of individuals were found to be highly reliable and were "normally" distributed. Factor analysis of learning performance variables determined that a single factor accounted for 38% of the total variance across animals. Animals' levels of native activity and body weights accounted for little of the variability in learning, although animals' propensity for exploration loaded strongly (and was positively correlated) with learning abilities. These results indicate that diverse learning abilities of laboratory mice are influenced by a common source of variance and, moreover, that the general learning abilities of individual mice can be specified relative to a sample of peers.

The importance of rapid auditory processing abilities to early language development: evidence from converging methodologies

The ability to process two or more rapidly presented, successive, auditory stimuli is believed to underlie successful language acquisition. Likewise, deficits in rapid auditory processing of both verbal and nonverbal stimuli are characteristic of individuals with developmental language disorders such as Specific Language Impairment. Auditory processing abilities are well developed in infancy, and thus such deficits should be detectable in infants. In the studies presented here, converging methodologies are used to examine such abilities in infants with and without a family history of language disorder. Behavioral measures, including assessments of infant information processing, and an EEG/event-related potential (ERP) paradigm are used concurrently. Results suggest that rapid auditory processing skills differ as a function of family history and are predictive of later language outcome. Further, these paradigms may prove to be sensitive tools for identifying children with poor processing skills in infancy and thus at a higher risk for developing a language disorder.

Polychlorinated biphenyls (PCBs) and neurological development in children: a systematic review

BACKGROUND

Polychlorinated biphenyls (PCBs) are complex mixtures of persistent contaminants that are widespread in the environment. Newborns are exposed across the placenta and through breast feeding. Experimental animal studies have indicated that PCBs are neurotoxic. The neurological effects of these compounds on children are not clear.

METHODS

A systematic review of literature on the relation between neurological development in children and exposure to polychlorinated biphenyls.

RESULTS

Seven follow up studies evaluated the effect of prenatal exposure to PCBs. Two of these studies evaluated highly exposed children. In newborns, an increase of the abnormal reflexes was observed in all four studies evaluating it. During the first months of life, a decrease in motor skills was observed in four of the five studies that investigated psychomotor development; deficits in the acquisition of cognitive skills were observed only in one study assessing non-highly exposed populations. At 4 years of age, an effect on the cognitive areas was observed in four of the five studies that evaluated it. Postnatal exposure to PCBs through breast feeding was not clearly related to any effect on neurological development.

CONCLUSIONS

These studies suggest a subtle adverse effect of prenatal PCBs exposure on child neurodevelopment. Differences in study design, inconsistency in some of the results, and the lack of adequate quantitative exposure data, do not allow the derivation of the degree of risk associated with neurodevelopmental effects at current levels of exposure.

Cognitive functioning in 8- to 18-month-old drug-exposed infants

This study examined the cognitive functioning in 236 infants at 8 and 18 months of age. Thirty-seven infants were heavily exposed to cocaine in-utero, 30 were lightly exposed, and 169 were not exposed to cocaine. Cognitive functioning was evaluated with the Bayley Scales of Infant Development (2nd ed.; N. Bayley, 1993) at both ages. Infant information processing was also assessed with an infant-controlled habituation procedure. Results indicated that (a) infants of cocaine-abusing women had higher neonatal medical and environmental risk scores; (b) at 8 months, exposure groups did not differ in Psychomotor Development Index, Mental Development Index (MDI) scores, or recovery to a novel stimulus; and (c) infants heavily exposed to cocaine or high environmental risk had a decrease in MDI scores from 8 to 18 months. These results were obtained when neonatal medical and environmental risk, as well as polydrug exposure, were controlled.