The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu.
Event-related potentials (ERPs) have been proposed as biomarkers capable of reflecting individual differences in neural processing not necessarily detectable at the behavioral level. However, the role of ERPs in developmental research could be hampered by current methodological approaches to quantification. ERPs are extracted as an average waveform over many trials, however, actual amplitudes would be misrepresented by an average if there was high trial-to-trial variability in signal latency. Low signal temporal consistency is thought to be a characteristic of immature neural systems, although consistency is not routinely measured in ERP research. The present study examined the differential contributions of signal strength and temporal consistency across trials in the error-related negativity (ERN) in 6-year-old children, as well as the developmental changes that occur in these measures. The 234 children were assessed annually in kindergarten, 1st, and 2nd grade. At all assessments signal strength and temporal consistency were highly correlated with the average ERN amplitude, and were not correlated with each other. Consistent with previous findings, ERN deflections in the averaged waveform increased with age. This was found to be a function of developmental increases in signal temporal consistency, whereas signal strength showed a significant decline across this time period. Additionally, average ERN amplitudes showed low-to-moderate stability across the three assessments whereas signal strength was highly stable. In contrast, signal temporal consistency did not evidence rank order stability across these ages. Signal strength appears to reflect a stable individual trait whereas developmental changes in temporal consistency may be experientially influenced.
Over the past fifteen years northwest Cambodia has seen dramatic agrarian expansion away from the central rice plain into the peripheral uplands fuelled by peasant in-migration. Against this background, we examine the nature of relations between the peasantry and the state. We first show the historical continuities of land control processes and how the use of violence in a post-conflict neoliberal context has legitimised ex-Khmer Rouge in controlling land distribution. Three case studies show the heterogeneity of local level sovereignties, which engage the peasants in different relations with authority. We examine how these processes result in the construction of different rural territories along the agricultural frontier and argue that, in this region of Cambodia, the struggles between Khmer Rouge and neoliberal modes of land control are central to state formation processes.
Frustration is a normative affective response with adaptive value in motivating behavior. However, excessive anger in response to frustration characterizes multiple forms of externalizing psychopathology. How a given trait subserves both normative and pathological behavioral profiles is not entirely clear. One hypothesis is that the magnitude of response to frustration differentiates normative versus maladaptive reactivity. Disproportionate increases in arousal in response to frustration may exceed normal regulatory capacity, thus precipitating aggressive or antisocial responses. Alternatively, pathology may arise when reactivity to frustration interferes with other cognitive systems, impairing the individual’s ability to respond to frustration adaptively. In this paper we examine these two hypotheses in a sample of kindergarten children. First we examine whether children with conduct problems (CP; n = 105) are differentiated from comparison children (n = 135) with regard to magnitude of autonomic reactivity (cardiac and electrodermal) across a task that includes a frustrative non-reward block flanked by two reward blocks. Second we examine whether cognitive processing, as reflected by magnitude of the P3b brain response, is disrupted in the context of frustrative non-reward. Results indicate no differences in skin conductance, but a greater increase in heart rate during the frustration block among children in the CP group. Additionally, the CP group was characterized by a pronounced decrement in P3b amplitude during the frustration condition compared with both reward conditions. No interaction between cardiac and P3b measures was observed, suggesting that each system independently reflects a greater sensitivity to frustration in association with externalizing symptom severity.
Many behavioral paradigms used to study individuals' decision-making tendencies do not capture the decision components that contribute to behavioral outcomes, such as differentiating decisions driven toward a reward from decisions driven away from a cost. This study tested a novel decision-making task in a sample of 403 children (age 9 years) enrolled in an ongoing longitudinal study. The task consisted of three blocks representing distinct cost domains (delay, probability, and effort), wherein children were presented with a deck of cards, each of which consisted of a reward and a cost. Children elected whether to accept or skip the card at each trial. Reward-cost pairs were selected by using an adaptive algorithm to strategically sample the decision space in the fewest number of trials. Using person-specific regression models, decision preferences were quantified for each cost domain with respect to general tolerance (intercept), as well as parameters estimating the effect of incremental increases in reward or cost on the probability of accepting a card. Results support the relative independence of decision-making tendencies across cost domains, with moderate correlations observed between tolerance for delay and effort. Specific decision parameters showed unique associations with cognitive and behavioral measures including executive function, academic motivation, anxiety, and hyperactivity. Evidence indicates that sensitivity to reward is an important factor in incentivizing decisions to work harder or wait longer. Dissociating the relative contributions of reward and cost sensitivity in multiple domains may facilitate the identification of heterogeneity in suboptimal decision making.
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