The Computational Development of Reinforcement Learning during Adolescence

Adolescence is a period of life characterised by changes in learning and decision-making. Learning and decision-making do not rely on a unitary system, but instead require the coordination of different cognitive processes that can be mathematically formalised as dissociable computational modules. Here, we aimed to trace the developmental time-course of the computational modules responsible for learning from reward or punishment, and learning from counterfactual feedback. Adolescents and adults carried out a novel reinforcement learning paradigm in which participants learned the association between cues and probabilistic outcomes, where the outcomes differed in valence (reward versus punishment) and feedback was either partial or complete (either the outcome of the chosen option only, or the outcomes of both the chosen and unchosen option, were displayed). Computational strategies changed during development: whereas adolescents’ behaviour was better explained by a basic reinforcement learning algorithm, adults’ behaviour integrated increasingly complex computational features, namely a counterfactual learning module (enabling enhanced performance in the presence of complete feedback) and a value contextualisation module (enabling symmetrical reward and punishment learning). Unlike adults, adolescent performance did not benefit from counterfactual (complete) feedback. In addition, while adults learned symmetrically from both reward and punishment, adolescents learned from reward but were less likely to learn from punishment. This tendency to rely on rewards and not to consider alternative consequences of actions might contribute to our understanding of decision-making in adolescence.     

Duration of Breastfeeding Associated With Obesity During Adolescence

ELLIOTT, KRISTEN G, CHRIS L KJOLHEDE, EFFIE GOURNIS, KATHLEEN M RASMUSSEN. Duration of breastfeeding associated with obesity during adolescence. The relationship between duration of breastfeeding and obesity (body mass index 85 percentile) at adolescence was investigated in a white, rural population (n=136) in which confounding by race was absent and confounding by socioeconomic status was expected to be minimal. Relevant data were abstracted from hospital charts. When examined independently, minimal (2 months) or no breastfeeding was positively associated with adolescent obesity (p<0. 03). This association was present in the lower but not the higher socioeconomic status group. However, when sex, birthweight, and socioeconomic status were included in a multiple regression model, duration of breastfeeding was no longer significantly associated with obesity during adolescence.     

The Poetics of Purpose

Hackles have been raised in biosemiotic circles by T. L. Short’s assertion that semiosis, as defined by Peirce, entails “acting for purposes” and therefore is not found below the level of the organism (2007a:174–177). This paper examines Short’s teleology and theory of purposeful behavior and offers a remedy to the disagreement. Remediation becomes possible when the issue is reframed in the terms of the complexity sciences, which allows intentionality to be understood as the interplay between local and global aspects of a system within a system. What is called “acting for purposes” is not itself a type of behavior so much as a relationship between a dynamic system that “exists for a purpose” and its microprocesses that “serve purposes.” The “intentional object” of philosophy is recast here as the holistic self-organized dynamics of a system, which exists for the purpose of self-maintenance, and that constrains the parts’ behaviors, which serve the purpose of forming the system. (A “system” can be any emergent, e.g. an abiotic form, an adapted species, a self, a conditioned response, thought, or a set of ideas.) The self-organized whole, which is represented to the parts in their own constrained behaviors, assumes the guiding function so long attributed to the mysterious “intentional object.” If emergent self-causation is not disallowed, creative originality, as well as directionality, becomes part of the definition of purposeful behavior. Thus, key tools used here, required for understanding emergence, come from poetics rather than semoitics. In the microprocesses of self-organization, I find what I call “accidental” indices and icons — which are poetic in the sense that they involve mere metonymic contiguity and metaphoric similarity — and which are preferentially selected under constrained conditions allowing radically new connections to habituate into an “intentional” self-organized system that, not coincidentally, has some of the emergent characteristics of a conventional symbolic system.

The Relationship between Internalising Symptom Development and Academic Attainment in Early Adolescence

Evidence for the longitudinal associations between internalising symptom development and academic attainment is sparse and results from existing studies are largely inconclusive. The approaches that have been used in existing studies examining this relationship have in common the limitation of grouping together all individuals in the sample which makes the assumption that the relationship between time, symptoms and attainment across all individuals is the same. The current study aimed to use heterogeneous trajectories of symptom development to examine the longitudinal associations between internalising symptom development and change in academic attainment over a three years period in early adolescence, a key period for internalising symptom development. Internalising symptoms were assessed for 3 consecutive years in a cohort from age 11–14 years (n = 2647, mean age at T1 = 11.7 years). National standardised test scores prior to the first wave and subsequent to the last wave were used as measures of academic attainment. Heterogeneous symptom development trajectories were identified using latent class growth analysis and socio-demographic correlates, such as gender, SES and ethnicity, of the different trajectory groupings were investigated. Derived trajectory groupings were examined as predictors of subsequent academic attainment, controlling for prior attainment. Results demonstrate that symptom trajectories differentially predicted change in academic attainment with increasing trajectories associated with significantly worse academic outcomes when compared to pupils with low levels of symptoms in all waves. Hence, a trajectory based approach provides a more nuanced breakdown of complexities in symptom development and their differential relationships with academic outcomes and in doing so helps clarify the longitudinal relationship between these two key domains of functioning in early adolescence.     

Night Shift Work Before and During Pregnancy and Offspring Weight Outcomes Through Adolescence

Objective

This study aimed to investigate associations between maternal history of rotating night shift nursing work before pregnancy and number of night shifts worked during pregnancy with offspring weight outcomes from early life through adolescence.

Methods

More than 4,000 children, enrolled in the second phase of the Growing Up Today Study between 2004 and 2013, and their mothers participating in the Nurses' Health Study II were included in our analyses.

Results

Children of women with and without a history of rotating night shift work before pregnancy were similar in birth weight and body size at age 5. However, for mothers with night shift work before pregnancy, their children had a modestly elevated risk of having overweight or obesity (relative risk = 1.11; 95% CI: 1.02‐1.21), which was stronger for persistently having overweight or obesity during adolescence and early adulthood. Longer duration of rotating night shift work was not associated with any of these weight outcomes. Weight outcomes of children of women with versus without night shift work during pregnancy were similar, regardless of frequency of night shifts worked during pregnancy (all P > 0.09).

Conclusions

Overall, nurses' night shift work before or during pregnancy did not affect offspring weight outcomes. Future larger studies should explore these associations in more detail.

     

The Development of Chloroplast Structure During Leaf Ontogeny

Advances achieved during last fifteen years in the understanding the development of chloroplast ultrastructure during natural leaf ontogeny are summarized. Life span of a typical C3 mesophyll cell chloroplast is outlined and placed into the scheme of cyclic plastid interrelationships. Possible modifications of this development by stresses, environmental factors or experimental treatments are also shown.     

Sense of Purpose Scale: Development and initial validation

This study focused on the development of the Sense of Purpose Scale and demonstrated three empirically interpretable subscales: awareness of purpose, awakening to purpose, and altruistic purpose. The results provided initial evidence for all three subscales reliability and validity with a sample of 300 undergraduate students. Future research should focus on the further validation and revision of items to increase all three subscales internal consistency.     

Earlier Development of Analytical than Holistic Object Recognition in Adolescence

Background

Previous research has shown that object recognition may develop well into late childhood and adolescence. The present study extends that research and reveals novel differences in holistic and analytic recognition performance in 7–12 year olds compared to that seen in adults. We interpret our data within a hybrid model of object recognition that proposes two parallel routes for recognition (analytic vs. holistic) modulated by attention.

Methodology/Principal Findings

Using a repetition-priming paradigm, we found in Experiment 1 that children showed no holistic priming, but only analytic priming. Given that holistic priming might be thought to be more ‘primitive’, we confirmed in Experiment 2 that our surprising finding was not because children’s analytic recognition was merely a result of name repetition.

Conclusions/Significance

Our results suggest a developmental primacy of analytic object recognition. By contrast, holistic object recognition skills appear to emerge with a much more protracted trajectory extending into late adolescence.     

Observed Measures of Negative Parenting Predict Brain Development during Adolescence

Limited attention has been directed toward the influence of non-abusive parenting behaviour on brain structure in adolescents. It has been suggested that environmental influences during this period are likely to impact the way that the brain develops over time. The aim of this study was to investigate the association between aggressive and positive parenting behaviors on brain development from early to late adolescence, and in turn, psychological and academic functioning during late adolescence, using a multi-wave longitudinal design. Three hundred and sixty seven magnetic resonance imaging (MRI) scans were obtained over three time points from 166 adolescents (11–20 years). At the first time point, observed measures of maternal aggressive and positive behaviors were obtained. At the final time point, measures of psychological and academic functioning were obtained. Results indicated that a higher frequency of maternal aggressive behavior was associated with alterations in the development of right superior frontal and lateral parietal cortical thickness, and of nucleus accumbens volume, in males. Development of the superior frontal cortex in males mediated the relationship between maternal aggressive behaviour and measures of late adolescent functioning. We suggest that our results support an association between negative parenting and adolescent functioning, which may be mediated by immature or delayed brain maturation.     

The Role of Autophagy During Development in Higher Eukaryotes

Autophagy is a lysosome‐mediated degradation pathway used by eukaryotes to recycle cytosolic components in both basal and stress conditions. Several genes have been described as regulators of autophagy, many of them being evolutionarily conserved from yeast to mammals. The study of autophagy‐defective model systems has made it possible to highlight the importance of correctly functioning autophagic machinery in the development of invertebrates as, for example, during the complex events of fly and worm metamorphosis. In vertebrates, on the other hand, autophagy defects can be lethal for the animal if the mutated gene is involved in the early stages of development, or can lead to severe phenotypes if the mutation affects later stages. However, in both lower and higher eukaryotes, autophagy seems to be crucial during embryogenesis by acting in tissue remodeling in parallel with apoptosis. An increase of autophagic cells is, in fact, observed in the embryonic stages characterized by massive cell elimination. Moreover, autophagic processes probably protect cells during metabolic stress and nutrient paucity that occur during tissue remodeling. In light of such evidence, it can be concluded that there is a close interplay between autophagy and the processes of cell death, proliferation and differentiation that determine the development of higher eukaryotes.     

瘦素在脑老化认知发展不同阶段中的作用

脑老化过程中伴随脑结构、功能退化和认知能力减退,其认知发展呈异质性,即发展的不均一性,有成功脑老化、正常脑老化、轻度认知功能障碍和阿尔茨海默病等状态。瘦素在不同认知状态下含量不同。研究发现,无神经病理改变的老年人群瘦素水平高,认知功能减退不明显;多数轻度认知功能障碍者瘦素水平降低;瘦素可改善阿尔茨海默病患者的认知障碍,被认为是一种潜在的认知增强剂。瘦素水平降低在脑老化认知障碍的发展中起重要作用。     

The Determinants of Muscle Fiber Type During Embryonic Development

SYNOPSIS. Most vertebrate skeletal muscles consist of a heterogeneousarray of muscle fiber types that are distinguishable, in part,by differences in their contractile protein isoform content.It is often suggested that the information necessary for directingthe development of these fiber types is derived from interactionswith factors outside the muscle fibers themselves and, in particular,with innervating motoneurons. However, recent data from thisand other laboratories indicate that the emergence of fiberspecialization within developing muscle is not dependent oninnervation at all. These studies recognize two periods of embryonicfiber specialization. The first occurs during early embryonicdevelopment as individual muscles are formed from primary generationfibers expressing different myosin isoform types. The formationof these "early" muscle fiber types and their characteristicdistributions within and among different muscles are not dependenton interactions with innervating motoneurons. Furthermore, myoblastsisolated from "early" embryonic muscle tissue and cultured invitro display the same heterogeneity of myosin expression asthe primary generation fiber types in ovo, suggesting that thedifferences in expression among early muscle fiber types arepreprogrammed within their myoblasts. The second period occurs"late" in development after the major morphological events oflimb formation are complete and the initial pattern of fibertypes has been established. It is during this period that massivegrowth of most muscles occurs which is due, in part, to theformation of a secondary generation of muscle fibers. Thesesecondary generation fibers in ovo and the cultured myotubesderived from "late" embryonic myoblasts exhibit a single myosinphenotype (e.g., fast). The transition from "early" to "late"embryonic phases is accompanied by a change in fast myosin heavychain expression and is blocked by agents that disrupt neuromuscularcontacts.     

Prenatal Exposure to Maternal Cigarette Smoking and Accumulation of Intra‐abdominal Fat During Adolescence

In industrialized countries, prenatal exposure to maternal cigarette smoking (PEMCS) is the most common environmental insult to the fetus. Here, we tested the hypothesis that PEMCS amplifies accumulation of abdominal fat during the accelerated weight gain occurring in late puberty. This hypothesis was tested in 508 adolescents (12–18 years, 237 exposed prenatally to maternal cigarette smoking) in whom subcutaneous and intra‐abdominal fat were quantified with magnetic resonance imaging (MRI). We found that, in early puberty, exposed and nonexposed adolescents did not differ in MRI‐based measures of adiposity. In late puberty, on the other hand, exposed compared with nonexposed adolescents demonstrated markedly higher quantities of both subcutaneous fat (by 26%, P = 0.004) and intra‐abdominal fat (by 33%, P = 0.001). These group differences remained virtually unchanged after adjusting for sex and potential confounders, including birth weight and breastfeeding. As such, our results suggest that PEMCS may represent a major risk factor for the development of abdominal obesity at the later stages of puberty.     

Problems of Adolescence

Adolescence is a period of active growth and development-physical, sexual, social and emotional. There are wide normal variations between the time of onset and the attainment of full maturity. Many adolescents present few if any problems during this potentially turbulent period, and make the necessary adjustments without undue stress to themselves, their family or their friends. Problems in growth and hormonal balance, presenting as short and tall teenagers, menstrual irregularities, obesity and acne are discussed. The impact of chronic disease-diabetes, convulsive disorders and rheumatic carditis-is a challenge to the skills and patience of the practising physician.