Understanding dentatorubral-pallidoluysian atrophy (DRPLA) symptoms and impacts on daily life: a qualitative interview study with patients and caregivers.

Background: Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare, neurodegenerative disorder with no disease-modifying treatments. There is a dearth of information in the literature about the patient and caregiver experience living with DRPLA. Objectives: This study aimed to (1) understand symptoms experienced by adult- and juvenile-onset DRPLA populations and their impact on daily life and (2) explore patient and caregiver treatment goals and clinical trial participation preferences. Design: The study was a qualitative interview study. Methods: Interviews were conducted remotely with adult patients with DRPLA and caregivers. Participants described patient symptoms and the impact of those symptoms on daily life, and they discussed treatment goals and potential clinical trial participation. There were 18 patients described in the interviews with two patients and seven caregivers. Some participants were caregivers to multiple patients with DRPLA. Results: Interview transcripts were coded for themes, and reported symptoms were summarized with descriptive statistics. Adult-onset patients (N = 7) experienced difficulty with ataxia (100%), cognition (100%), fine motor skills (100%), gross motor skills (100%), speech (100%), personality changes (100%), and seizures (57%). Juvenile-onset patients (N = 11) experienced difficulty with ataxia (100%), sleep (100%), speech (100%), jerking/twitching (83%), behavior (82%), cognition (82%), fine motor skills (82%), gross motor skills (82%), sensory sensitivity (75%), and seizures (64%). When considering aspects of DRPLA to target for future treatment, patients prioritized ataxia/mobility (100%), juvenile-onset caregivers prioritized ataxia/mobility (60%) and independence (60%), and adult-onset caregivers prioritized personality (60%). Almost all patients (93%) would participate in a clinical trial if given the opportunity, but travel to a clinical site could pose a participation barrier for half. Conclusion: This study found that there are symptom domains that are relevant across the DRPLA population, but there is heterogeneity within each domain based on the age of symptom onset and disease stage, which has implications for clinical trial design.

Understanding dentatorubral-pallidoluysian atrophy (DRPLA) symptoms and impacts on daily life through interviews with patients and caregivers Why was the study done? Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare and progressive brain disorder. Little is known about the patient and caregiver experience living with DRPLA and this lack of information has hindered the development of patient-focused treatments and the measurement of outcomes that are most meaningful to caregivers and patients. What did the researchers do? To address this problem, researchers conducted interviews with patients and caregivers of DRPLA to (1) better understand symptoms experienced by adult- and juvenile-onset DRPLA populations and their impact on daily life and (2) explore patient and caregiver treatment goals and clinical trial participation preferences. What did the researchers find? Eighteen patients were described in the interviews. Adult-onset patients (onset at age 20 or older) experienced difficulty with coordination, cognition, motor skills, speech, personality changes, and seizures. Juvenile-onset patients (onset before age 20) experienced difficulty with coordination, sleep, speech, jerking/twitching, behavior, cognition, motor skills, sensory sensitivity, and seizures. When considering symptoms to prioritize for future treatment, patients and caregivers identified coordination/mobility, independence, and personality as important. Nearly all participants indicated they would participate in a clinical trial if given an opportunity, however half expressed that travel to a clinical site could pose a barrier. What do the findings mean? This study provides a better understanding of the symptoms experienced by DRPLA patients and their impact on daily life. Additionally, it identifies important targets for treatment and considerations when designing clinical trials for DRPLA such as the barrier caused by travel to a clinical site.

Postoperative decline in renal function after rectal resection and all-cause mortality: a retrospective cohort study.

AIM: Fluid loss, dehydration and resultant kidney injury are common when a diverting ileostomy is formed during rectal cancer surgery, the consequences of which are unknown. The aim of this retrospective single-site cohort study is to evaluate the impact of sustained postoperative renal dysfunction after rectal resection on long-term renal impairment and survival. METHOD: All patients with rectal adenocarcinoma undergoing resection between January 2003 and March 2017 were included, with follow-up to June 2020. The primary outcome was impact on long-term mortality attributed to a 25% or greater drop in estimated glomerular filtration rate (eGFR) following rectal resection. Secondary outcomes were the long-term effect on renal function resulting from the same drop in eGFR and the effect on long-term mortality and renal function of a 50% drop in eGFR. We also calculated the effect on mortality of a 1% drop in eGFR. RESULTS: A total of 1159 patients were identified. Postoperative reductions in eGFR of 25% and 50% were associated with long-term overall mortality with adjusted hazard ratios of 1.84 (1.22-2.77) (p = 0.004) and 2.88 (1.45-5.71) (p = 0.002). The median survival of these groups was 86.0 (64.0-108.0) months and 53.3 (7.8-98.8) months compared with 144.5 (128.1-160.9) months for controls. Long-term effects on renal function were demonstrated, with those who sustained a >25% drop in renal function having a 38.8% mean decline in eGFR at 10 years compared with 10.2% in controls. CONCLUSION: Persistent postoperative declines in renal function may be linked to long-term mortality. Further research is needed to assess causal relationships and prevention.

Maternal immune activation and role of placenta in the prenatal programming of neurodevelopmental disorders.

Maternal infection during pregnancy, leading to maternal immune activation (mIA) and cytokine release, increases the offspring risk of developing a variety of neurodevelopmental disorders (NDDs), including schizophrenia. Animal models have provided evidence to support these mechanistic links, with placental inflammatory responses and dysregulation of placental function implicated. This leads to changes in fetal brain cytokine balance and altered epigenetic regulation of key neurodevelopmental pathways. The prenatal timing of such mIA-evoked changes, and the accompanying fetal developmental responses to an altered in utero environment, will determine the scope of the impacts on neurodevelopmental processes. Such dysregulation can impart enduring neuropathological changes, which manifest subsequently in the postnatal period as altered neurodevelopmental behaviours in the offspring. Hence, elucidation of the functional changes that occur at the molecular level in the placenta is vital in improving our understanding of the mechanisms that underlie the pathogenesis of NDDs. This has notable relevance to the recent COVID-19 pandemic, where inflammatory responses in the placenta to SARS-CoV-2 infection during pregnancy and NDDs in early childhood have been reported. This review presents an integrated overview of these collective topics and describes the possible contribution of prenatal programming through placental effects as an underlying mechanism that links to NDD risk, underpinned by altered epigenetic regulation of neurodevelopmental pathways.

Maternal Immune Activation Induces Adolescent Cognitive Deficits Preceded by Developmental Perturbations in Cortical Reelin Signalling.

Exposure to maternal immune activation (MIA) in utero significantly elevates the risk of developing schizophrenia and other neurodevelopmental disorders. To understand the biological mechanisms underlying the link between MIA and increased risk, preclinical animal models have focussed on specific signalling pathways in the brain that mediate symptoms associated with neurodevelopmental disorders such as cognitive dysfunction. Reelin signalling in multiple brain regions is involved in neuronal migration, synaptic plasticity and long-term potentiation, and has been implicated in cognitive deficits. However, how regulation of Reelin expression is affected by MIA across cortical development and associated cognitive functions remains largely unclear. Using a MIA rat model, here we demonstrate cognitive deficits in adolescent object-location memory in MIA offspring and reductions in Reln expression prenatally and in the adult prefrontal cortex. Further, developmental disturbances in gene/protein expression and DNA methylation of downstream signalling components occurred subsequent to MIA-induced Reelin dysregulation and prior to cognitive deficits. We propose that MIA-induced dysregulation of Reelin signalling contributes to the emergence of prefrontal cortex-mediated cognitive deficits through altered NMDA receptor function, resulting in inefficient long-term potentiation. Our data suggest a developmental window during which attenuation of Reelin signalling may provide a possible therapeutic target.

Maternal behaviours and adult offspring behavioural deficits are predicted by maternal TNFα concentration in a rat model of neurodevelopmental disorders.

Exposure to inflammatory stressors during fetal development is a major risk factor for neurodevelopmental disorders (NDDs) in adult offspring. Maternal immune activation (MIA), induced by infection, causes an acute increase in pro-inflammatory cytokines which can increase the risk for NDDs directly by inducing placental and fetal brain inflammation, or indirectly through affecting maternal care behaviours thereby affecting postnatal brain development. Which of these two potential mechanisms dominates in increasing offspring risk for NDDs remains unclear. Here, we show that acute systemic maternal inflammation induced by the viral mimetic polyinosinic:polycytidylic acid (poly I:C) on gestational day 15 of rat pregnancy affects offspring and maternal behaviour, offspring cognition, and expression of NDD-relevant genes in the offspring brain. Dams exposed to poly I:C elicited an acute increase in the pro-inflammatory cytokine tumour necrosis factor (TNF; referred to here as TNFα), which predicted disruption of key maternal care behaviours. Offspring of poly I:C-treated dams showed early behavioural and adult cognitive deficits correlated to the maternal TNFα response, but, importantly, not with altered maternal care. We also found interacting effects of sex and treatment on GABAergic gene expression and DNA methylation in these offspring in a brain region-specific manner, including increased parvalbumin expression in the female adolescent frontal cortex. We conclude that the MIA-induced elevation of TNFα in the maternal compartment affects fetal neurodevelopment leading to altered offspring behaviour and cognition. Our results suggest that a focus on prenatal pathways affecting fetal neurodevelopment would provide greater insights into the mechanisms underpinning the TNFα-mediated genesis of altered offspring behaviour and cognition following maternal inflammation.

Clustering of cognitive phenotypes identifies susceptible and resilient offspring in a rat model of maternal immune activation and early-life stress.

Schizophrenia and other neurodevelopmental disorders often have very heterogeneous symptoms, especially regarding cognition: while some individuals may exhibit deficient cognition, others are relatively unaffected. Studies using developmental animal models often ignore phenotypic heterogeneity in favour of traditional treatment/control comparisons. This may result in resilient or unaffected individuals masking the effects of susceptible individuals if grouped together. Here, we used maternal immune activation and limited bedding and nesting, respectively, as a two-hit neurodevelopmental model for schizophrenia. Both factors reduced cognitive function in a novel object recognition (NOR) task. While we found treatment group effects on cognitive phenotypes, behavioural clustering identified three subpopulations exposed to either insult: those exhibiting 'typical' cognitive performance on the NOR, an intermediate phenotype, or a marked deficit. These clusters included offspring from each treatment group, although both intermediate and marked deficit clusters were composed primarily of offspring from treated groups. Clustering allowed stratification within treatment groups into 'susceptible' and 'resilient' individuals, while also identifying conserved phenotypes across treatment groups. Using unbiased cluster analyses in preclinical models can better characterize phenotypes and enables a better understanding of both face and construct validity of phenotypic heterogeneity. The use of unbiased clustering techniques may help identify potential markers associated with individual susceptibility and resilience in neurodevelopmental disorder models.

Maternal immune activation in rats induces dysfunction of placental leucine transport and alters fetal brain growth.

Maternal infection during pregnancy increases the offspring risk of developing a variety of neurodevelopmental disorders (NDDs), including schizophrenia. While the mechanisms remain unclear, dysregulation of placental function is implicated. We hypothesised that maternal infection, leading to maternal immune activation and stimulated cytokine production, alters placental and yolk sac amino acid transport, affecting fetal brain development and thus NDD risk. Using a rat model of maternal immune activation induced by the viral mimetic polyinosinic:polycytidylic acid (poly(I:C)), we investigated placental and yolk sac expression of system L amino acid transporter subtypes which transport several essential amino acids including branched-chain amino acids (BCAA), maternal and fetal BCAA concentration, placental 14C-leucine transport activity and associated impacts on fetal growth and development. Poly(I:C) treatment increased acutely maternal IL-6 and TNFα concentration, contrasting with IL-1ß. Transcriptional responses for these pro-inflammatory cytokines were found in placenta and yolk sac following poly(I:C) treatment. Placental and yolk sac weights were reduced by poly(I:C) treatment, yet fetal body weight was unaffected, while fetal brain weight was increased. Maternal plasma BCAA concentration was reduced 24 h post-poly(I:C) treatment, yet placental, but not yolk sac, BCAA concentration was increased. Placental and yolk sac gene expression of Slc7a5, Slc7a8 and Slc43a2 encoding LAT1, LAT2 and LAT4 transporter subtypes, respectively, was altered by poly(I:C) treatment. Placental 14C-leucine transport was significantly reduced 24 h post-treatment, contrasting with a significant increase 6 days following poly(I:C) treatment. Maternal immune activation induces dysregulated placental transport of amino acids affecting fetal brain development, and NDD risk potential in offspring.

Explaining Adherence to American Academy of Pediatrics Screen Time Recommendations With Caregiver Awareness and Parental Motivation Factors: Mixed Methods Study.

BACKGROUND: With the increasing integration of technology into society, it is advisable that researchers explore the effects of repeated digital media exposure on our most vulnerable population-infants. Excessive screen time during infancy has been linked to delays in language, literacy, and self-regulation. OBJECTIVE: This study explores the awareness of and adherence to the American Academy of Pediatrics' (AAP) recommendations related to avoiding screen time for infants younger than 2 years and the motivational factors associated with screen time exposure. METHODS: A mixed methods survey design was used to gather responses from 178 mothers of infants younger than 2 years. The measures included infant screen time use and duration, maternal awareness of screen time use recommendations, and motivations related to screen time exposure. A variety of statistical procedures were used to explore associations between caregiver awareness of and adherence to AAP guidelines for screen time exposure, motivations related to screen time for infants, and the duration of infant screen time exposure. RESULTS: The results indicated that 62.2% (111/178) of mothers were aware of the AAP screen time recommendations, but only 46.1% (82/178) could cite them accurately, and most mothers learned of them via the internet or from a medical professional. Mothers who were aware of the guidelines allowed significantly less screen time for infants than those who were unaware (P=.03). In addition, parents who adhered to the AAP guidelines reported significantly less infant screen time per day than those who did not adhere (P<.001). Among mothers who reported not adhering to the guidelines, the greatest motivation for allowing screen time was perceived educational benefits. Less educated mothers rated an infant's relaxation as a motivational factor in allowing screen time significantly higher than more highly educated mothers (P=.048). The regression analysis indicated that none of the parental motivation factors predicted daily infant screen time. CONCLUSIONS: These results indicate 2 key approaches to improving adherence to screen time recommendations. First, the awareness of the AAP recommendations needs to be increased, which tends to improve adherence. Second, the myth that screen time can be educational for infants needs to be dispelled.

The tipping point of antenatal engagement: A qualitative grounded theory in Tanzania and Zambia.

BACKGROUND: Effective antenatal care is fundamental to the promotion of positive maternal and new-born outcomes. International guidance recommends an initial visit in the first trimester of pregnancy, with a minimum of four antenatal visits in total: the optimum schedule being eight antenatal contacts. In low- and middle-income countries, many women do not access antenatal care until later in pregnancy and few have the recommended number of contacts. AIM: To gain understanding of women's antenatal experiences in Tanzania and Zambia, and the factors that influence antenatal engagement. METHODS: The study was underpinned by Strauss's grounded theory methodology. Interviews were conducted with 48 women, 16 partners, 21 health care providers and 11 stakeholders, and analysed using constant comparison. FINDINGS: The core category was 'The tipping point of antenatal engagement', supported by four categories: awareness of health benefits, experiential motivators, influential support, and environmental challenges. Although participants recognised the importance of antenatal care to health outcomes, individual motivations and external influences determined attendance or non-attendance. The 'tipping point' for antenatal engagement occurred when women believed that any negative impact could be offset by tangible gain. For some women non-attendance was a conscious decision, for others it was an unchallenged cultural norm. CONCLUSION: A complex interplay of factors determines antenatal engagement. Short-term modifiable factors to encourage attendance include the development of strategies for increasing respectful care; use of positive women's narratives, and active community engagement. Further research is required to develop innovative, cost-effective care models that improve health literacy and meet women's needs.

Maternal immune activation in rodent models: A systematic review of neurodevelopmental changes in gene expression and epigenetic modulation in the offspring brain.

Maternal immune activation (mIA) during pregnancy is hypothesised to disrupt offspring neurodevelopment and predispose offspring to neurodevelopmental disorders such as schizophrenia. Rodent models of mIA have explored possible mechanisms underlying this paradigm and provide a vital tool for preclinical research. However, a comprehensive analysis of the molecular changes that occur in mIA-models is lacking, hindering identification of robust clinical targets. This systematic review assesses mIA-driven transcriptomic and epigenomic alterations in specific offspring brain regions. Across 118 studies, we focus on 88 candidate genes and show replicated changes in expression in critical functional areas, including elevated inflammatory markers, and reduced myelin and GABAergic signalling proteins. Further, disturbed epigenetic markers at nine of these genes support mIA-driven epigenetic modulation of transcription. Overall, our results demonstrate that current outcome measures have direct relevance for the hypothesised pathology of schizophrenia and emphasise the importance of mIA-models in contributing to the understanding of biological pathways impacted by mIA and the discovery of new drug targets.

Infants distinguish and represent pattern as an object feature from externally generated patterns superimposed on real, 3-dimensional objects' surfaces.

As infants form object representations, the patterns viewed on objects' surfaces may be challenging to decipher because these patterns may be created from the surface reflectance of an object (an object property) or from an external source, such as a cast shadow. We tested 7 ½-month-old infants' use of cues that specify the source of patterns seen on the surfaces of real, 3-dimensional objects to individuate those objects. Results suggest that when forming object representations based on patterns, 7½-month-olds rely heavily on temporal and depth cues to distinguish patterns inherent to the object from other types of patterns.

The Discharge Lounge: A Patient Flow Process Solution.

BACKGROUND: Patient flow, from emergency department admission through to discharge, influences hospital overcrowding. We aimed to improve patient flow by increasing discharge lounge (DL) usage. LOCAL PROBLEM: Patients need to receive a continuum of nursing care to encourage compliance with follow-up care after discharge from the acute care setting. METHODS: Baseline data revealed inefficient use of the DL. We targeted the medical-surgical unit with the lowest DL use and trialed interventions over sequential Plan-Do-Study-Act cycles. INTERVENTIONS: After surveying the nursing staff, we assessed the influence of 3 interventions on DL usage: educating staff on patient eligibility, engaging a recruitment scout, and displaying a visual cue notifying staff when a patient's discharge order was written. RESULTS: The unit's average DL use increased from 18% to 36%, while hospital overcrowding and discharge turnaround time decreased. CONCLUSION: The DL is an effective tool to improve patient flow and decrease hospital overcrowding.

Parents' Influence on Infants' Gender-Typed Toy Preferences.

Gender socialization influences children at early ages, shaping their developing identities. The toys provided by parents deliver some of the earliest gender-based messages by encouraging children to engage in activities associated with, for example, dolls and trucks. In the current study, we measured the influence of parental socialization by assessing 5- and 12 ½-month-old infants' exposure to dolls and trucks and by experimentally manipulating parents' encouragement to play with these toys. We found that infants displayed gender-typical toy preferences at 12 ½, but not 5 months, a pattern characteristic of previous studies. However, brief encouragement by a parent to play with toys from each category was ineffective in altering infants' preferences. Rather, the types of toys present in the home predicted preferences, suggesting that at-home exposure to toys may be influential in the development of toy preferences. These findings reveal that socialization processes may indeed play a role in the formation of early gender-typical toy preferences and highlight the importance of equal toy exposure during infancy to ensure optimal development.

Give Me a Hand: Adult Involvement During Object Exploration Affects Object Individuation in Infancy.

The development of object individuation, a fundamental ability that supports identification and discrimination of objects across discrete encounters, has been examined extensively by researchers. There are significant advancements in infants' ability to individuate objects during the first year-and-a-half. Experimental work has established a timeline of object individuation abilities and revealed some mechanisms underlying this ability, however, the influence of adult assistance during object exploration has not yet been explored. The current study investigates the effect of adult involvement during object exploration on infants' object individuation abilities. In Experiment 1a and 1b, we examined 9.5-month-old infants' colour-based object individuation following adult-assisted multisensory object exploration. Two components of adult interaction were of particular interest: facilitation of object manipulation (grasping, rotating, and attention-getting behaviours) and social engagement (smiling, pointing, attention-getting verbalizations, and object-directed gaze). Experiment 2a and 2b assessed these components with 4.5-month-olds to examine their impact across development. The results showed that after adult-guided object exploration, both 9.5- and 4.5-month-old infants successfully individuated previously undifferentiated objects. Results of Experiments 1b and 2b provide implications for the mechanisms underlying the scaffolding influence of adult interaction during infant behaviours.

Experience with malleable objects influences shape-based object individuation by infants.

Infants' ability to accurately represent and later recognize previously viewed objects, and conversely, to discriminate novel objects from those previously seen improves remarkably over the first two years of life. During this time, infants acquire extensive experience viewing and manipulating objects and these experiences influence their physical reasoning. Here we posited that infants' observations of object feature stability (rigid versus malleable) can influence the use of those features to individuate two successively viewed objects. We showed 8.5-month-olds a series of objects that could or could not change shape, then assessed their use of shape as a basis for object individuation. Infants who explored rigid objects later used shape differences to individuate objects; however, infants who explored malleable objects did not. This outcome suggests that the latter infants did not take into account shape differences during the physical reasoning task and provides further evidence that infants' attention to object features can be readily modified based on recent experiences.

Infant Preference for Natural Texture Statistics is Modulated by Contrast Polarity.

Adult observers are sensitive to statistical regularities present in natural images. Developmentally, research has shown that children do not show sensitivity to these natural regularities until approximately 8-10 years of age. This finding is surprising given that even infants gradually encode a range of high-level statistical regularities of their visual environment in the first year of life, We suggest that infants may in fact exhibit sensitivity to natural image statistics under circumstances where images of complex, natural textures, such as a photograph of rocks, are used as experimental stimuli and natural appearance is substantially manipulated. We tested this hypothesis by examining how infants' visual preference for real versus computer-generated synthetic textures was modulated by contrast negation, which produces an image similar to a photographic negative. We observed that older infants' (9-months of age) preferential looking behavior in this task was affected by contrast polarity, suggesting that the infant visual system is sensitive to deviations from natural texture appearance, including (1) discrepancies in appearance that differentiate natural and synthetic textures from one another and (2) the disruption of contrast polarity following negation. We discuss our results in the context of adult texture processing and the "perceptual narrowing" of visual recognition during the first year of life.

Posture support improves object individuation in infants.

A hierarchical progression in infants' ability to use surface features, such as color, as a basis for object individuation in the first year has been well established (Tremoulet, Leslie, & Hall, 2000; Wilcox, 1999). There is evidence, however, that infants' sensitivity to surface features can be increased through multisensory (i.e., visuohaptic) exploration of objects (Wilcox, Woods, Chapa, & McCurry, 2007). Three studies were conducted to investigate the effect of multisensory experience on infants' sensitivity to pattern information. Experiments 1 and 2 confirmed that 5.5- and 6.5-month-olds do not spontaneously use pattern differences to individuate objects and revealed that 6.5- but not 5.5-month-olds can be primed to attend to pattern differences if allowed multisensory experience with the objects prior to the individuation task. However, the 5.5-month-olds also had greater difficulty maintaining a self-sitting posture during the multisensory priming experience. In Experiment 3, 4.5- and 5.5-month-olds were given full postural support during the multisensory exploration period. In this situation, the 5.5-month-olds successfully individuated the objects, but even with full postural support, 4.5-month-old infants did not use the pattern differences to individuate the objects. These results demonstrate that multisensory priming is effective with infants as young as 5.5 months and extends multisensory priming to another surface feature, pattern. Furthermore, these results indicate that constraints are placed on the multisensory experience by the physical and motor development of the infant.

The effectiveness of reminder phone calls on reducing no-show rates in ambulatory care.

The objective of this study was to determine the effectiveness of daily reminder phone calls on reducing no-show rates in the ambulatory care setting. With the initiation of reminder telephone calls over a 6-month period, the no-show rate dropped by 50% from 8% to 4%. The no-show rate with reminder letters over 3 months was reduced by 29% from 8.5% to 6%. Reminding patients by telephone call 1 day prior to their appointment significantly increased the number of patients who arrived. Reminder phone calls also allowed patients to cancel their appointments if they weren't able to attend, rather than not showing up. Patients were given the option of rescheduling their appointments while on the phone at that time or calling back to reschedule. Most patients took the opportunity to reschedule at that time.

Priming infants to use pattern information in an object individuation task: the role of comparison.

There is evidence that 4.5-month-olds do not always use surface pattern to individuate objects but that they can be primed to attend to pattern differences through select experiences. For example, if infants are first shown events in which the pattern of an object predicts its function (dotted containers pound and striped containers pour), they will attend to pattern differences in a subsequent individuation task. However, 4.5-month-olds must see multiple exemplars of the pound and pour events and view the dotted and striped containers together during the events. These results suggest that it is the formation of event categories, in which pattern is linked to object function, that supports pattern priming and that direct comparison of the exemplars facilitates the extraction of event categories. The present research investigated conditions that support the comparison process in 4.5-month-olds. The results revealed that the comparison process was initiated only when the dotted and striped containers were seen directly adjacent to each other; if the containers sat far apart, so that infants had to shift their gaze to compare them, event categories were not extracted. In addition, it was comparison of the two patterned containers, and not comparison of the two function events, that was critical to the formation of event categories. These results join a growing body of research indicating the importance of comparison to category formation in infants and reveal the impact of categorization and comparison processes on object individuation in infancy.

Infants' representations of three-dimensional occluded objects.

Infants' ability to represent objects has received significant attention from the developmental research community. With the advent of eye-tracking technology, detailed analysis of infants' looking patterns during object occlusion have revealed much about the nature of infants' representations. The current study continues this research by analyzing infants' looking patterns in a novel manner and by comparing infants' looking at a simple display in which a single three-dimensional (3D) object moves along a continuous trajectory to a more complex display in which two 3D objects undergo trajectories that are interrupted behind an occluder. Six-month-old infants saw an occlusion sequence in which a ball moved along a linear path, disappeared behind a rectangular screen, and then a ball (ball-ball event) or a box (ball-box event) emerged at the other edge. An eye-tracking system recorded infants' eye-movements during the event sequence. Results from examination of infants' attention to the occluder indicate that during the occlusion interval infants looked longer to the side of the occluder behind which the moving occluded object was located, shifting gaze from one side of the occluder to the other as the object(s) moved behind the screen. Furthermore, when events included two objects, infants attended to the spatiotemporal coordinates of the objects longer than when a single object was involved. These results provide clear evidence that infants' visual tracking is different in response to a one-object display than to a two-object display. Furthermore, this finding suggests that infants may require more focused attention to the hidden position of objects in more complex multiple-object displays and provides additional evidence that infants represent the spatial location of moving occluded objects.