Specific differences in visual orienting, critical in social-cognitive development, are associated with differences in white matter microstructure of the splenium.
ObjectiveThe authors sought to ...determine whether specific patterns of oculomotor functioning and visual orienting characterize 7-month-old infants who later meet criteria for an autism spectrum disorder (ASD) and to identify the neural correlates of these behaviors.MethodData were collected from 97 infants, of whom 16 were high-familial-risk infants later classified as having an ASD, 40 were high-familial-risk infants who did not later meet ASD criteria (high-risk negative), and 41 were low-risk infants. All infants underwent an eye-tracking task at a mean age of 7 months and a clinical assessment at a mean age of 25 months. Diffusion-weighted imaging data were acquired for 84 of the infants at 7 months. Primary outcome measures included average saccadic reaction time in a visually guided saccade procedure and radial diffusivity (an index of white matter organization) in fiber tracts that included corticospinal pathways and the splenium and genu of the corpus callosum.ResultsVisual orienting latencies were longer in 7-month-old infants who expressed ASD symptoms at 25 months compared with both high-risk negative infants and low-risk infants. Visual orienting latencies were uniquely associated with the microstructural organization of the splenium of the corpus callosum in low-risk infants, but this association was not apparent in infants later classified as having an ASD.ConclusionsFlexibly and efficiently orienting to salient information in the environment is critical for subsequent cognitive and social-cognitive development. Atypical visual orienting may represent an early prodromal feature of an ASD, and abnormal functional specialization of posterior cortical circuits directly informs a novel model of ASD pathogenesis.
Biologically active, fine‐grained sediment forms abundant sedimentary deposits on Earth's surface, and mixed mud‐sand dominates many coasts, deltas, and estuaries. Our predictions of sediment ...transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt, sand, and gravel. This approach underpins many paleoenvironmental reconstructions of sedimentary successions, which rely on analysis of cross‐stratification and bounding surfaces produced by migrating bed forms. Here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology. The results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships. The findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record.
Key Points
Subaqueous bed form dimensions are controlled more by biological than physical cohesion
Existing predictors require reformulation for combined biophysical cohesive effects
Small amounts of substrate biological cohesion act to reduce bed roughness 2 orders of magnitude
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Normal reading relies on the reader making a series of saccadic eye movements along lines of text, separated by brief fixational pauses during which visual information is acquired from a region of ...text. In English and other alphabetic languages read from left to right, the region from which useful information is acquired during each fixational pause is generally reported to extend further to the right of each fixation than to the left. However, the asymmetry of the perceptual span for alphabetic languages read in the opposite direction (i.e., from right to left) has received much less attention. Accordingly, in order to more fully investigate the asymmetry in the perceptual span for these languages, the present research assessed the influence of reading direction on the perceptual span for bilingual readers of Urdu and English.
Text in Urdu and English was presented either entirely as normal or in a gaze-contingent moving-window paradigm in which a region of text was displayed as normal at the reader's point of fixation and text outside this region was obscured. The windows of normal text extended symmetrically 0.5° of visual angle to the left and right of fixation, or asymmetrically by increasing the size of each window to 1.5° or 2.5° to either the left or right of fixation. When participants read English, performance for the window conditions was superior when windows extended to the right. However, when reading Urdu, performance was superior when windows extended to the left, and was essentially the reverse of that observed for English.
These findings provide a novel indication that the perceptual span is modified by the language being read to produce an asymmetry in the direction of reading and show for the first time that such an asymmetry occurs for reading Urdu.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Resting state functional magnetic resonance imaging (rs-fMRI) in infants enables important studies of functional brain organization early in human development. However, rs-fMRI in infants has ...universally been obtained during sleep to reduce participant motion artifact, raising the question of whether differences in functional organization between awake adults and sleeping infants that are commonly attributed to development may instead derive, at least in part, from sleep. This question is especially important as rs-fMRI differences in adult wake vs. sleep are well documented. To investigate this question, we compared functional connectivity and BOLD signal propagation patterns in 6, 12, and 24 month old sleeping infants with patterns in adult wakefulness and non-REM sleep. We find that important functional connectivity features seen during infant sleep closely resemble those seen during adult sleep, including reduced default mode network functional connectivity. However, we also find differences between infant and adult sleep, especially in thalamic BOLD signal propagation patterns. These findings highlight the importance of considering sleep state when drawing developmental inferences in infant rs-fMRI.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Initiating joint attention (IJA), the behavioral instigation of coordinated focus of 2 people on an object, emerges over the first 2 years of life and supports social-communicative functioning ...related to the healthy development of aspects of language, empathy, and theory of mind. Deficits in IJA provide strong early indicators for autism spectrum disorder, and therapies targeting joint attention have shown tremendous promise. However, the brain systems underlying IJA in early childhood are poorly understood, due in part to significant methodological challenges in imaging localized brain function that supports social behaviors during the first 2 years of life. Herein, we show that the functional organization of the brain is intimately related to the emergence of IJA using functional connectivity magnetic resonance imaging and dimensional behavioral assessments in a large semilongitudinal cohort of infants and toddlers. In particular, though functional connections spanning the brain are involved in IJA, the strongest brain-behavior associations cluster within connections between a small subset of functional brain networks; namely between the visual network and dorsal attention network and between the visual network and posterior cingulate aspects of the default mode network. These observations mark the earliest known description of how functional brain systems underlie a burgeoning fundamental social behavior, may help improve the design of targeted therapies for neurodevelopmental disorders, and, more generally, elucidate physiological mechanisms essential to healthy social behavior development.
Reductions in stimulus quality may disrupt the reading performance of older adults more when compared with young adults because of sensory declines that begin early in middle age. However, few ...studies have investigated adult age differences in the effects of stimulus quality on reading, and none have examined how this affects lexical processing and eye movement control. Accordingly, we report two experiments that examine the effects of reduced stimulus quality on the eye movements of young (18-24 years), middle-aged (41-51 years), and older (65+ years) adult readers. In Experiment 1, participants read sentences that contained a high- or low-frequency critical word and that were presented normally or with contrast reduced so that words appeared faint. Experiment 2 further investigated effects of reduced stimulus quality using a gaze-contingent technique to present upcoming text normally or with contrast reduced. Typical patterns of age-related reading difficulty (e.g., slower reading, more regressions) were observed in both experiments. In addition, eye movements were disrupted more for older than younger adults when all text (Experiment 1) or just upcoming text (Experiment 2) appeared faint. Moreover, there was an interaction between stimulus quality and word frequency (Experiment 1), such that readers fixated faint low-frequency words for disproportionately longer. Crucially, this effect was similar across all age groups. Thus, although older readers suffer more from reduced stimulus quality, this additional difficulty primarily affects their visual processing of text. These findings have important implications for understanding the role of stimulus quality on reading behavior across the lifespan.
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CEKLJ, FFLJ, NUK, ODKLJ, PEFLJ, UPUK
As compared to the utility of early emerging social communicative risk markers for predicting a later diagnosis of autism spectrum disorder (ASD), less is known about the relevance of early patterns ...of restricted and repetitive behaviors. We examined patterns of stereotyped motor mannerisms and repetitive manipulation of objects in 12-month-olds at high and low risk for developing ASD, all of whom were assessed for ASD at 24 months.
Observational coding of repetitive object manipulation and stereotyped motor behaviors in digital recordings of the Communication and Symbolic Behavior Scales was conducted using the Repetitive and Stereotyped Movement Scales for 3 groups of 12-month-olds: low-risk infants (LR, n = 53); high-familial-risk infants who did not meet diagnostic criteria for ASD at 24 months (HR-negative, n = 75); and high-familial-risk infants who met diagnostic criteria for ASD at 24 months (HR-ASD, n = 30).
The HR-ASD group showed significantly more stereotyped motor mannerisms than both the HR-negative group (p = .025) and the LR group (p = .001). The HR-ASD and HR-negative groups demonstrated statistically equivalent repetitive object manipulation scores (p = .431), and both groups showed significantly more repetitive object manipulation than the LR group (p < .040). Combining the motor and object stereotypy scores into a Repetitive and Stereotyped Movement Scales (RSMS) composite yielded a disorder-continuum effect such that each group was significantly different from one another (LR < HR-negative < HR-ASD).
These results suggest that targeted assessment of repetitive behavior during infancy may augment early ASD identification efforts.
High‐quality communicative interactions between caregivers and children provide a foundation for children's social and cognitive skills. Although most studies examining these types of interactions ...focus on child language outcomes, this paper takes another tack. It examines whether communicative, dyadic interactions might also relate to child executive function (EF) skills and whether child language might mediate this relation. Using a subset of data from the NICHD Study of Early Child Care and Youth Development, dyadic interactions between 2‐year‐olds and their mothers were coded for three behaviors: symbol‐infused joint engagement, routines and rituals, and fluency and connectedness. Child language was assessed at age 3 and three facets of EF (self‐regulation, sustained attention, and verbal working memory) were assessed at age 4.5. Structural equation modeling showed that dyadic interaction related to later child sustained attention and verbal working memory, indirectly through child language and directly related with child self‐regulation. This suggests that communicative interactions with caregivers that include both verbal and non‐verbal elements relate to child EF, in part through child language. Our findings have implications for the role of caregiver interactions in the development of language and cognitive skills more broadly.
Research Highlights
Using structural equation modeling, we examined how communicative interactions between caregivers and toddlers relate to preschool executive function skills
Communicative interactions relate to later language which in turn relates to sustained attention and verbal working memory in preschool
Communicative interactions relate directly to self‐regulation in preschool
Associations between communicative interactions, language, and executive function vary across facets of executive function and may not be unidirectional
Communicative interactions between caregivers and children provide a foundation for children's language skills, but less is known about how these interactions relate to executive function skills. Using structural equation modeling, this study found that communicative interactions at age 2 related directly to preschool self‐regulation and indirectly to preschool sustained attention and verbal working memory through child language. These findings have implications for the role of communicative interactions in the development of language and cognitive skills more broadly.
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DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Children who developed autism spectrum disorders (ASDs) by age 2 had greater development of cerebral white matter fiber tracts by 6 months than unaffected children. After the initial accelerated ...white matter development, the children who developed ASDs had slower development, so that by age 2 their white matter development was less than that in the unaffected children.
Objective:Evidence from prospective studies of high-risk infants suggests that early symptoms of autism usually emerge late in the first or early in the second year of life after a period of relatively typical development. The authors prospectively examined white matter fiber tract organization from 6 to 24 months in high-risk infants who developed autism spectrum disorders (ASDs) by 24 months.
Method:The participants were 92 high-risk infant siblings from an ongoing imaging study of autism. All participants had diffusion tensor imaging at 6 months and behavioral assessments at 24 months; a majority contributed additional imaging data at 12 and/or 24 months. At 24 months, 28 infants met criteria for ASDs and 64 infants did not. Microstructural properties of white matter fiber tracts reported to be associated with ASDs or related behaviors were characterized by fractional anisotropy and radial and axial diffusivity.
Results:The fractional anisotropy trajectories for 12 of 15 fiber tracts differed significantly between the infants who developed ASDs and those who did not. Development for most fiber tracts in the infants with ASDs was characterized by higher fractional anisotropy values at 6 months followed by slower change over time relative to infants without ASDs. Thus, by 24 months of age, those with ASDs had lower values.
Conclusions:These results suggest that aberrant development of white matter pathways may precede the manifestation of autistic symptoms in the first year of life. Longitudinal data are critical to characterizing the dynamic age-related brain and behavior changes underlying this neurodevelopmental disorder.
Background
Recent evidence suggests that restricted and repetitive behaviors may differentiate children who develop autism spectrum disorder (ASD) by late infancy. How these core symptoms manifest ...early in life, particularly among infants at high risk for the disorder, is not well characterized.
Methods
Prospective, longitudinal parent‐report data (Repetitive Behavior Scales‐Revised) were collected for 190 high‐risk toddlers and 60 low‐risk controls from 12 to 24 months of age. Forty‐one high‐risk children were classified with ASD at age 2. Profiles of repetitive behavior were compared between groups using generalized estimating equations.
Results
Longitudinal profiles for children diagnosed with ASD differed significantly from high‐ and low‐risk children without the disorder on all measures of repetitive behavior. High‐risk toddlers without ASD were intermediate to low risk and ASD positive counterparts. Toddlers with ASD showed significantly higher rates of repetitive behavior across subtypes at the 12‐month time point. Repetitive behaviors were significantly correlated with adaptive behavior and socialization scores among children with ASD at 24 months of age, but were largely unrelated to measures of general cognitive ability.
Conclusions
These findings suggest that as early as 12 months of age, a broad range of repetitive behaviors are highly elevated in children who go on to develop ASD. While some degree of repetitive behavior is elemental to typical early development, the extent of these behaviors among children who develop ASD appears highly atypical.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
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