Measures of attention in Rett syndrome: Internal consistency reliability.

OBJECTIVE: Rett syndrome (RTT), an x-linked neurodevelopmental disorder caused by spontaneous mutations in the MECP2 gene, is characterized by profound impairments in expressive language and purposeful hand use. We have pioneered the use of gaze-based tasks to by-pass these limitations and developed measures suitable for clinical trials with RTT. Here we estimated internal consistency reliability for three aspects of attention that are key to cognitive growth and that we previously identified as impaired in RTT. METHOD: Using a sample of 66 children with RTT (2-19 years), we assessed Sustained Attention (butterfly task: Butterfly traverses the screen only when fixated and distractors are ignored); Disengaging/Shifting Attention ("gap/overlap" task: Shifts of gaze from central to peripheral targets are compared in conditions where the central stimulus remains or disappears at the onset of the peripheral target); Selective Attention (search task: the target is embedded in arrays differing in size and distractor type). RESULTS: Reliability was acceptable to excellent on almost all key measures from tasks assessing Sustained Attention and Disengaging/Shifting Attention, with split-half coefficients and Cronbach alphas ranging from .70 to .93. Reliability increased as more trials were aggregated, with acceptable levels often reached with as few as six to nine trials. Measures from Selective Attention showed only limited reliability. CONCLUSION: Finding that critical aspects of attention can be reliably assessed in RTT with gaze-based tasks constitutes a major advance in the development of cognitive measures appropriate for clinical and translational work. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Attentional shifting and disengagement in Rett syndrome.

OBJECTIVE: The purpose of the present study was to deepen our understanding of attention (a core cognitive ability) in Rett syndrome (RTT), an x-linked neurodevelopmental disorder caused by mutations in the MECP2 gene. We focused on 2 key aspects of visual orienting-shifting and disengaging attention-both of which are critical for exploring the visual world. We used gaze-based measures and eye-tracking technology to minimize demands on the limited verbal and motor abilities associated with RTT. METHOD: Shifting and disengaging attention were examined in 31 children (2-12 years) with Rett Syndrome (RTT) and 31 age-matched typically developing (TD) controls. Using the gap-overlap paradigm, the frequency and speed of shifting attention from a central to peripheral target were compared on Baseline trials, where the central stimulus disappears as the peripheral target appears, and Overlap trials, where the central stimulus remains, thus requiring disengagement. RESULTS: Our findings revealed that children with RTT had more "sticky fixations" (p < .001). That is, they had fewer saccades to the peripheral target than TD children, and this was true on both baseline (77% vs. 95%), and overlap trials (63% vs. 90%). The younger children in the RTT group also had slower saccadic RTs (SRTs) than their TD counterparts (p = .04). Within the RTT group, SRTs correlated with symptom severity. Surprisingly, disengagement cost (the relative difference between gap and overlap SRTs) did not differ across groups. CONCLUSION: Our results suggest that children with Rett have difficulty shifting attention and, to a lesser extent, disengaging attention, whereas with other disorders, problems with disengagement are paramount. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Impaired Visual Search in Children with Rett Syndrome.

AIM: This study aims to investigate selective attention in Rett syndrome, a severely disabling neurodevelopmental disorder caused by mutations in the X-linked MECP2 gene. METHOD: The sample included 28 females with Rett syndrome (RTT) and 32 age-matched typically developing controls. We used a classic search task, in conjunction with eye-tracking technology. Each trial included the target and several distractors. The distractors varied in number and differed from targets in either a "single feature" (color or shape), creating a pop-out effect, or in a "conjunction of features" (color and shape), requiring serial search. Children searched for the target in arrays containing five or nine objects; trials ended when the target was fixated (or 4000 ms elapsed). RESULTS: Children with Rett syndrome had more difficulty finding the target than typically developing children in both conditions (success rates less than 50% versus 80%) and their success rates were little influenced by display size or age. Even when successful, children with RTT took significantly longer to respond (392 to 574 ms longer), although saccadic latency differences were observed only in the single-feature condition. Both groups showed the expected slowing of saccadic reaction times for larger arrays in the conjunction-feature condition. Search failures in RTT were not related to symptom severity. CONCLUSIONS: Our findings provide the first evidence that selective attention, the ability to focus on or select a particular element or object in the environment, is compromised by Rett syndrome. They reinforce the notion that gaze-based tasks hold promise for quantifying the cognitive phenotype of RTT.

Sustained attention in the face of distractors: A study of children with Rett syndrome.

OBJECTIVE: The object of the present study is to advance our understanding of the cognitive profile of Rett syndrome (RTT), an X-linked neurodevelopmental disorder caused by mutations in the MECP2 gene. We focus on sustained attention, which plays a critical role in driving cognitive growth, and use an innovative, gaze-based task that minimizes demands on the limited verbal and motor abilities associated with RTT. METHOD: The task required the ability to sustain attention on a visual target (a butterfly) while inhibiting a prepotent response to look to moving distractors (trees and clouds) presented in the peripheral visual field. The sample included children with RTT (N = 32) and their typically developing (TD) counterparts (N = 32), aged 2-12 years. RESULTS: Our findings revealed that children with RTT had more difficulty sustaining attention (with the TD group averaging 60% looking at the butterfly vs. only 25% for the RTT group). Furthermore, RTT was associated with difficulties in 3 fundamental factors influencing sustained attention: engagement, distractibility, and reengagement. The RTT group was slower to engage, more distractible, and slower to reengage. CONCLUSION: Our findings identify a fundamental disruption to sustained attention in RTT, determine factors related to this impairment, and pinpoint cognitive areas that could serve as markers for evaluating the effectiveness of pharmacological and behavioral interventions. (PsycINFO Database Record

Aspects of Attention in Rett Syndrome.

BACKGROUND: We sought to examine fundamental aspects of attention in children with Rett syndrome, a severely disabling neurodevelopmental disorder caused by spontaneous mutations in the X-linked MECP2 gene. To gauge their attention, we used eye tracking, which bypasses the profound impairments in expressive language and hand use in Rett syndrome. We report two aspects of attention-shifting and sustaining-basic abilities known to drive cognitive growth. METHODS: Two groups were compared: those with Rett syndrome (N = 20; 3-15 years) and a typically developing comparison group (N = 14; 3-16 years), using a task in which an attractive central stimulus was followed, after a short gap, by a dynamic target presented to one side. Time to shift to the target location (reactive and anticipatory saccades) and time fixating the target were assessed. RESULTS: Children with Rett syndrome were consistently slower to shift (largely because of fewer anticipations); their reactive saccades were also slower than those of typically developing children, but not significantly so. The Rett syndrome group spent considerable time looking at the target (over 75% of available time), although significantly less so than the typically developing group. CONCLUSIONS: These findings indicate that children with Rett syndrome could maintain attention on a stimulus and orient relatively quickly to the appearance of a target in the visual field. However, they had difficulty in anticipating predictable events, a difficulty in endogenous attention that is likely to have deleterious implications for executive functioning.

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.

Rett syndrome: recognition of facial expression and its relation to scanning patterns.

BACKGROUND: Rett syndrome is a severely disabling neurodevelopmental disorder caused by mutations in the X-linked MECP2 gene. Very little is known about its cognitive phenotype and nothing about recognition of emotional expression, a key factor for social interaction and communication. Using eye tracking technology, a technique uniquely suited for studying cognition in this disorder, we examined this ability here. METHODS: Rett syndrome female patients (n = 37; 2-31 years) and a typically developing age- and gender-matched comparison group (n =34; 2-30 years) were assessed on recognition of three basic emotions (happy, sad, and fear) using six visual paired-comparison problems. Each problem consisted of a 10-second familiarization, in which two identical faces posing one emotion were presented, followed by a 10-second test, in which the familiar emotion was paired with a novel one posed by the same model. Recognition was inferred from preferential looking to the novel target on test. During familiarization, attention was measured by total looking time, number and/or length of fixations, and gaze dispersion across three key facial features (eyes, nose, and mouth). RESULTS: Individuals with Rett syndrome had difficulty recognizing most emotional expressions, unlike the typically developing comparison group. Also, their scanpaths were atypical-less looking, fewer and/or longer fixations, and less time devoted to all facial features (48% versus 72%), particularly the mouth. Significant correlations between looking to critical features and recognition underscored the importance of scanning. CONCLUSIONS: Our results suggest that individuals with Rett syndrome have difficulty reading emotional expressions and that these problems are linked to atypicalities in scanning.

Rett syndrome: an eye-tracking study of attention and recognition memory.

AIM: The aim of this study was to examine attention and recognition memory for faces and patterns in Rett syndrome, a severely disabling neurodevelopmental disorder caused by mutations in the X-linked MECP2 gene. METHOD: Because Rett syndrome impairs speech and hand use, precluding most neuropsychological testing, the visual paired-comparison paradigm (VPC) was used, together with eye tracking. In the VPC, two identical stimuli are presented for familiarization. On test, the familiar stimulus and a new one are paired, and recognition inferred from preferential looking to the novel target. Attention is measured by looking time, gaze dispersion, and number/length of fixations. Twenty-seven female patients with Rett syndrome (mean age 10y 6mo; SD 6y 8mo, age range 2-22y) from the Rett clinic at a children's hospital were assessed in this study, along with 30 age- and sex-matched typically developing participants (outpatients from the same hospital). RESULTS: Although patients with Rett syndrome showed recognition of both faces and patterns, with novelty scores greater than chance (50%), their performance was significantly poorer than that of the typically developing comparison group. Their attention to both was less mature and marked by a more narrowly focused gaze, with fewer and longer fixations. When inspecting faces, attention to the eyes was similar in both groups; however, patients with Rett syndrome tended to ignore the nose and mouth. INTERPRETATION: This is one of the first studies to characterize attention and memory in individuals with Rett syndrome. Visually based techniques, such as the VPC, open a new avenue for quantifying the cognitive phenotype associated with this syndrome.

Information Processing from Infancy to 11 Years: Continuities and Prediction of IQ.

This study provides the first direct evidence of cognitive continuity for multiple specific information processing abilities from infancy and toddlerhood to pre-adolescence, and provides support for the view that infant abilities and form the basis of later childhood abilities. Data from a large sample of children (N = 131) were obtained at five different time points (7, 12, 24, 36 months, and 11 years) for a large battery of tasks representing four cognitive domains (attention, processing speed, memory, and representational competence). Structural equation models of continuity were assessed for each domain, in which it was assumed that infant abilities → toddler abilities → 11-year abilities. Abilities at each age were represented by latent variables, which minimize task-specific variance and measurement error. The model for each domain fit the data. Moreover, abilities from the three age periods predicted global outcome, with infant, toddler, and contemporaneous 11-year measures, respectively, accounting for 12.3%, 18.5%, and 45.2% of the variance in 11-year IQ. These findings strengthen contentions that specific cognitive abilities that can be identified in infancy show long-term continuity and contribute importantly to later cognitive competence.

Implications of infant cognition for executive functions at age 11.

Recent work suggests that executive functions, the cornerstone of higher-level cognitive operations, are driven by basic information processing abilities. Using structural equation modeling, with latent variables, the present study provides the first evidence that this driving force begins in infancy, such that abilities in infancy predict executive functions at age 11. Information processing abilities in three domains (attention, processing speed, and memory) were assessed when participants were infants (7 and 12 months) and toddlers (24 and 36 months) and were used to predict three executive functions (working memory, inhibition, and shifting) when participants were 11 years old. A model relating infant abilities to age-11 executive functions fit well, and accounted for 9% to 19% of the variance in the executive functions. Paths from both speed and memory in infancy to age-11 working memory were significant, as was the path from Speed in infancy to age-11 Shifting. A model using abilities in toddlerhood as predictors fit similarly. These findings implicate early basic cognitive abilities in the development of executive functions.

Modeling a cascade of effects: the role of speed and executive functioning in preterm/full-term differences in academic achievement.

This study identified deficits in executive functioning in pre-adolescent preterms and modeled their role, along with processing speed, in explaining preterm/full-term differences in reading and mathematics. Preterms (< 1750 g) showed deficits at 11 years on a battery of tasks tapping the three basic executive functions identified by Miyake - updating/working memory, inhibition, and shifting. Confirmatory factor analysis showed that these executive functions, though correlated, were distinct from one another and from processing speed, which later proved to account for much of the intercorrelation among executive functions. In the best-fitting structural equation model, the negative effects of prematurity on achievement were completely mediated by the three executive functions and speed in a cascade of effects: prematurity → slower processing speed → poorer executive functioning (working memory) → lower achievement in math and reading.

Basic Information Processing Abilities at 11 years Account for Deficits in IQ Associated with Preterm Birth.

Although it is well established that preterms as a group do poorly relative to their full-term peers on tests of global cognitive functioning, the basis for this relative deficiency is less understood. The present paper examines preterm deficits in core cognitive abilities and determines their role in mediating preterm/full-term differences in IQ. The performance of 11-year-old children born preterm (birth weight <1750g) and their full-term controls were compared on a large battery of 15 tasks, covering four basic cognitive domains -- memory, attention, speed of processing and representational competence. The validity of these four domains was established using latent variables and confirmatory factor analysis (CFA). Preterms showed pervasive deficits within and across domains. Additionally, preterm deficits in IQ were completely mediated by these four cognitive domains in a structural equation model involving a cascade from elementary abilities (attention and speed), to more complex abilities (memory and representational competence), to IQ. The similarity of findings to those obtained with this cohort in infancy and toddlerhood suggest that preterm deficits persist - across time, across task, and from the non-verbal to the verbal period.

The structure of memory in infants and toddlers: an SEM study with full-terms and preterms.

There is considerable dispute about the nature of infant memory. Using SEM models, we examined whether popular characterizations of the structure of adult memory, including the two-process theory of recognition, are applicable in the infant and toddler years. The participants were a cohort of preterms and full-terms assessed longitudinally--at 1, 2, and 3 years--on a battery containing tasks of immediate and delayed recognition, recall, and memory span (a measure of short-term capacity). Results were in accord with adult models which assume that short- and long-term memory are distinct, and that two processes--familiarity and recollection--underlie recognition memory, while one alone--recollection--supports recall. The finding that prematurity, which entails risk of hippocampal compromise, affected recollection, but not familiarity, accords well with adult findings that hippocampal damage selectively affects recollection. These findings reveal striking similarity between the structure and theoretical underpinnings of infant and adult memory.

A cognitive approach to the development of early language.

A controversial issue in the field of language development is whether language emergence and growth is dependent solely on processes specifically tied to language or could also depend on basic cognitive processes that affect all aspects of cognitive competence (domain-general processes). The present article examines this issue using a large battery of infant information-processing measures of memory, representational competence, processing speed, and attention, many of which have been shown to predict general cognition in a cohort of full-terms and preterms. Results showed that various aspects of infant memory and representational competence (a) related to language at both 12 and 36 months, (b) predicted similarly for the two groups, and (c) predicted 36-month language, independently of birth status, 12-month language, and the 12-month Bayley Mental Development Index. Additionally, the results established predictive validity for the MacArthur 12-month language measure. These findings support a domain-general view of language.

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.

The inversion effect in infancy: the role of internal and external features.

The present work examined the changing role of inner and outer facial features in the recognition of upright and inverted faces in 5-, 7-, and 9-month-olds. Study 1 established that the "inversion effect" (impaired recognition of an inverted face) was present in infants as young as 5 months. In Study 2, internal and external features were inverted separately. Disrupting the internal configuration by inversion impaired recognition at all ages; disrupting the external configuration impaired recognition only at 5-months. In Study 3, an upright familiar face was paired with one having either novel internal or novel external features. The results confirmed that the 5-month-olds used only the external features to recognize faces, whereas older infants were as adept at using internal features as external ones. These findings suggest a shift, after 5 months, away from dependence on external features for face recognition and toward greater reliance on internal ones.

A Cognitive Cascade in Infancy: Pathways from Prematurity to Later Mental Development.

Using data from a longitudinal study of preterms and full-terms, the present study examined the structure of infant cognition at 12 months, the extent to which five 12-month abilities (attention, speed, recognition, recall, and representational competence) mediated the relation from prematurity to mental development at 2 - 3 years, and how continuity and change in infant information processing from 7 to 12 months affected later outcome. The results indicated that 12-month measures of infant information processing completely mediated the effect of prematurity on outcome and the infant measures form a 'cognitive cascade,' similar to that seen at 7 months, in which the two more elementary abilities (attention and speed) influenced the more complex ones, which in turn influenced later cognition. Additionally, despite cross-age stability, 7- month assessments contribute to outcome independently of their 12-month counterparts, suggesting that infant abilities undergo important developmental transformations in the second half of the first year of life.

Pathways from prematurity and infant abilities to later cognition.

This study examined the relation of information processing in 7-month-old preterms (<1750 g at birth) and full-terms to Bayley Mental Development Indexes (MDIs) at 2 and 3 years. The infant measures were drawn from four cognitive domains: attention, speed, memory, and representational competence. Structural equation modeling showed that these measures of infant information processing mediated the effects of prematurity, and that there was a cascade of effects, with infant processing speed influencing memory and representational competence, which in turn influenced later MDI. This study shows that infant information processing mediates the effect of prematurity on later cognition, and delineates pathways whereby infant abilities relate to one another and to later outcome.

Recall memory in the first three years of life: a longitudinal study of preterm and term children.

This report concerns the development and stability of recall memory at 12, 24, and 36 months of age in preterm (<1750 g birthweight) and term children from a prospective, longitudinal study. There were 56 preterm children (55.4% male; mean birthweight 1119.5 g [SD 279.2], range 551 to 1742 g; mean gestational age 29.7 weeks [SD 2.9], range 25 to 36 wks) and 126 term controls (51.6% male; mean birthweight 3453.8 g [SD 438.2], range 2500 to 4564 g; mean gestational age 40.2 weeks [SD 1.1], range 38 to 42 wks). Recall memory was assessed using an elicited imitation task in which children attempted to reproduce a sequence of actions 15 minutes after they were modeled by the examiner. Relative to term children, the preterm group performed poorly at all three ages: they reproduced fewer actions overall and fewer in the correct order. Lower birthweight and lengthier postnatal hospitalization were associated with poorer performance in preterm children at 24 and 36 months. Although performance improved considerably for both groups with age, there was no evidence of preterm 'catch-up': the deficits detected at 12 months did not diminish with age. Individual differences in recall were modestly stable from one year to the next, with cross-age correlations highest from 24 to 36 months (r=0.43 to 0.49). These results suggest that preterm children have deficits in recall memory that emerge by 12 months and persist into early childhood.

The building blocks of cognition.

This article provides an overview of some innovative ways of examining infant cognition, highlighting several procedures that are likely to prove useful for assessing the effects of interventions in the first year of life. The procedures singled out assess three aspects of cognition in infancy: visual recognition memory, attention, and speed of processing. Assessments of each, while primarily experimental in nature, show strong developmental change over the first year, as well as modest stability, discriminant validity, and predictive validity. The emerging evidence suggests that these three aspects of infant cognition are among the most basic building blocks of mature cognition.