Development during adolescence of the neural processing of social emotion

In this fMRI study, we investigated the development between adolescence and adulthood of the neural processing of social emotions. Unlike basic emotions (such as disgust and fear), social emotions (such as guilt and embarrassment) require the representation of another's mental states. Nineteen adolescents (10–18 years) and 10 adults (22–32 years) were scanned while thinking about scenarios featuring either social or basic emotions. In both age groups, the anterior rostral medial prefrontal cortex (MPFC) was activated during social versus basic emotion. However, adolescents activated a lateral part of the MPFC for social versus basic emotions, whereas adults did not. Relative to adolescents, adults showed higher activity in the left temporal pole for social versus basic emotions. These results show that, although the MPFC is activated during social emotion in both adults and adolescents, adolescents recruit anterior (MPFC) regions more than do adults, and adults recruit posterior (temporal) regions more than do adolescents

Dipole trap model for the metallic state in gated silicon-inversion layers

In order to investigate the metallic state in high-mobility Si-MOS structures, we have further developed and precised the dipole trap model which was originally proposed by B.L. Altshuler and D.L. Maslov [Phys. Rev. Lett.\ 82, 145 (1999)]. Our additional numerical treatment enables us to drop several approximations and to introduce a limited spatial depth of the trap states inside the oxide as well as to include a distribution of trap energies. It turns out that a pronounced metallic state can be caused by such trap states at appropriate energies whose behavior is in good agreement with experimental observations.Comment: 16 pages, 10 figures, submitte

Avoiding Social Risk in Adolescence

Adolescence is a period of life often characterized by behaviors that, prima facie, are irrational, such as seemingly excessive risk taking and impulsivity. However, these behaviors can be interpreted as adaptive and rational if one considers that a key developmental goal of this period of life is to mature into an independent adult in the context of a social world that is unstable and changing. It is proposed that for adolescents, the social risk of being rejected by peers outweighs other potentially negative outcomes of decisions, such as threats to one’s health or the prospect of getting caught. Furthermore, peer influence in adolescence can lead to prosocial as well as antisocial behaviors. Neurocognitive mechanisms of peer influence include the social reward of being accepted by one’s peer group, arousal, and increased mentalizing, which is associated with development of the social brain network. The findings from cognitive neuroscience and developmental psychology studies fit with recent public health evidence that the opinions of peers are particularly important to adolescents in areas such as school antibullying and antismoking campaigns

Sexual Selection and Bacteria

The role of symbiotic bacteria in determining their host’s phenotype has become increasingly apparent in recent times. These bacterial communities can influence a range of host traits and fitness correlates. Symbiotic bacteria can alter their host’s immune function, metabolism, reproductive fitness, sexual and social signals as well as behaviour. The amount of research into the host fitness effects of symbiotic bacterial is rapidly increasing, however; few studies are investigating how these effects vary across different host genotypes. This thesis investigates the relationship between host genetic background and bacterial symbionts across a range of sexually selected fitness measures in Drosophila simulans. We focused on two main types of bacterial symbionts; exosymbionts, that consisted of gut bacterial communities and surface bacteria that inhabit the fly cuticle, along with the bacterial endosymbiont Wolbachia pipentis. Wolbachiais known to influence host fitness in a range of ways that vary from parasitic to mutualistic. The nature of these effects has previously been found to depend on both the host and the strain of Wolbachia.Previous work has attributed fitness effects found when curing Wolbachia infection with antibiotics to the change in the Wolbachia infection status. Antibiotic treatment is likely to change other bacterial components of the microbiota alongside removing Wolbachia infection. In chapter 2 I found that antibiotic-caused male sexual-fitness rank changes across genotypes were caused by Wolbachia curing and not altering exosymbiotic bacterialcommunities. In Chapter 3 I found that the level of bidirectional cytoplasmic incompatibility suffered when mating with a standardised tester mate, was dependant on the genotype of the focal host. This effect was true for both focal males and females. In Chapter 4 I tested whether D. simulans populations evolving under elevated or relaxed natural and sexual selection for 38 generations differed in their gut bacterial communities. We found evolving under elevated sexual selection resulted in more diverse gut bacteria for males but not females. We also found sexual selection altered the gut bacterial community composition of both males and females. We found no effects of natural selection on gut microbial communities and no interaction between natural and sexual selection intensity on these communities. In Chapter 5 I found that altering exosymbiotic bacterial communities had fitness effects on both 3males and females. In females these effects were only present when the bacterial communities were altered,not if the bacteria were simply removed. In Chapter 6I found that Wolbachia infection affects female choosiness dependent on the females’genotype. Removing the exosymbiotic bacteria from females had no effect on their choosiness and genotype did not interact with this bacterial treatment. I also found that removing the symbiotic bacteria of females reduces their adult body size,however hosts infected withWolbachia did not experience the same body size reduction with exosymbiont removal. Symbiotic bacteria are playing an important role in many sexually selected fitness traits. The direction and scale of these fitness effects depend on the host’s genetic background. Sexual selection is also able to act on a host’s gut bacteria. This means that a host’s symbiotic bacteria are likely to play an important role in the evolutionary outcomes ofsexual selection. This thesis increases our understanding of the role symbiotic bacteria playinsexual selection.Natural Environment Research Council (NERC

Electron spin relaxation in bulk GaAs for doping densities close to the metal-to-insulator transition

We have measured the electron spin relaxation rate and the integrated spin noise power in n-doped GaAs for temperatures between 4 K and 80 K and for doping concentrations ranging from 2.7 x 10^{-15} cm^{-3} to 8.8 x 10^{-16} cm^{-3} using spin noise spectroscopy. The temperature dependent measurements show a clear transition from localized to free electrons for the lower doped samples and confirm mainly free electrons at all temperatures for the highest doped sample. While the sample at the metal-insulator-transition shows the longest spin relaxation time at low temperatures, a clear crossing of the spin relaxation rates is observed at 70 K and the highest doped sample reveals the longest spin relaxation time above 70 K.Comment: 6 pages, 4 figure

Social and non-social relational reasoning in adolescence and adulthood

Reasoning during social interactions requires the individual manipulation of mental representations of one’s own traits and those of other people, as well as their joint consideration (relational integration). Research using non-social paradigms has linked relational integration to activity in the rostrolateral prefrontal cortex (RLPFC). Here, we investigated whether social reasoning is supported by the same general system or whether it additionally relies on regions of the social brain network, such as the medial prefrontal cortex (MPFC). We further assessed the development of social reasoning. In the social task, participants evaluated themselves or a friend, or compared themselves with their friend, on a series of traits. In the non-social task, participants evaluated their hometown or another town, or compared the two. In a behavioural study involving 325 participants (11-39 years), we found that integrating relations compared to performing single relational judgements improves during adolescence, both for social and non-social information. Thirty-nine female participants (10-31 years) took part in a neuroimaging study using a similar task. Activation of the relational integration network, including the RLPFC, was observed in the comparison condition of both the social and non-social tasks, while MPFC showed greater activation when participants processed social as opposed to non-social information across conditions. Developmentally, the right anterior insula showed greater activity in adolescents compared with adults during the comparison of non-social vs. social information. This study shows parallel recruitment of the social brain and the relational reasoning network during the relational integration of social information in adolescence and adulthood

Age-related changes in the impact of valence on self-referential processing in female adolescents and young adults

Adolescence is a period of self-concept development. In the current study, females aged 11–30 years (N = 210) completed two self-referential tasks. In a memory task, participants judged the descriptiveness of words for themselves or a familiar other and their recognition of these words was subsequently measured. In an associative-matching task, participants associated neutral shapes to either themselves or a familiar other and the accuracy of their matching judgements was measured. In the evaluative memory task, participants were more likely to remember self-judged than other-judged words and there was an age-related decrease in the size of this self-reference effect. Negative self-judgements showed a quadratic association with age, peaking around age 19. Participants were more likely to remember positive than negative words and there was an age-related increase in the magnitude of this positivity bias. In the neutral shapes task, there were no age-related changes in the self-reference effect. Overall, adolescent girls showed enhanced processing of self-relevant stimuli when it could be used to inform their self-concept and especially when it was negative

Unaffected perceptual thresholds for biological and non-biological form-from-motion perception in autism spectrum conditions

Background: Perception of biological motion is linked to the action perception system in the human brain, abnormalities within which have been suggested to underlie impairments in social domains observed in autism spectrum conditions (ASC). However, the literature on biological motion perception in ASC is heterogeneous and it is unclear whether deficits are specific to biological motion, or might generalize to form-from-motion perception. Methodology and Principal Findings: We compared psychophysical thresholds for both biological and non-biological form-from-motion perception in adults with ASC and controls. Participants viewed point-light displays depicting a walking person (Biological Motion), a translating rectangle (Structured Object) or a translating unfamiliar shape (Unstructured Object). The figures were embedded in noise dots that moved similarly and the task was to determine direction of movement. The number of noise dots varied on each trial and perceptual thresholds were estimated adaptively. We found no evidence for an impairment in biological or non-biological object motion perception in individuals with ASC. Perceptual thresholds in the three conditions were almost identical between the ASC and control groups. Discussion and Conclusions: Impairments in biological motion and non-biological form-from-motion perception are not across the board in ASC, and are only found for some stimuli and tasks. We discuss our results in relation to other findings in the literature, the heterogeneity of which likely relates to the different tasks performed. It appears that individuals with ASC are unaffected in perceptual processing of form-from-motion, but may exhibit impairments in higher order judgments such as emotion processing. It is important to identify more specifically which processes of motion perception are impacted in ASC before a link can be made between perceptual deficits and the higher-level features of the disorder

Multitasking during social interactions in adolescence and early adulthood

Multitasking is part of the everyday lives of both adolescents and adults. We often multitask during social interactions by simultaneously keeping track of other non-social information. Here, we examined how keeping track of non-social information impacts the ability to navigate social interactions in adolescents and adults. Participants aged 11–17 and 22–30 years old were instructed to carry out two tasks, one social and one non-social, within each trial. The social task involved referential communication, requiring participants to use social cues to guide their decisions, which sometimes required taking a different perspective. The non-social task manipulated cognitive load by requiring participants to remember non-social information in the form of one two-digit number (low load) or three two-digit numbers (high load) presented before each social task stimulus. Participants showed performance deficits when under high cognitive load and when the social task involved taking a different perspective, and individual differences in both trait perspective taking and working memory capacity predicted performance. Overall, adolescents were less adept at multitasking than adults when under high cognitive load. These results suggest that multitasking during social interactions incurs performance deficits, and that adolescents are more sensitive than adults to the effects of cognitive load while multitasking

Amplified Concern for Social Risk in Adolescence: Development and Validation of a New Measure

In adolescence, there is a heightened propensity to take health risks such as smoking, drinking or driving too fast. Another facet of risk taking, social risk, has largely been neglected. A social risk can be defined as any decision or action that could lead to an individual being excluded by their peers, such as appearing different to one’s friends. In the current study, we developed and validated a measure of concern for health and social risk for use in individuals of 11 years and over (N = 1399). Concerns for both health and social risk declined with age, challenging the commonly held stereotype that adolescents are less worried about engaging in risk behaviours, compared with adults. The rate of decline was steeper for social versus health risk behaviours, suggesting that adolescence is a period of heightened concern for social risk. We validated our measure against measures of rejection sensitivity, depression and risk-taking behaviour. Greater concern for social risk was associated with increased sensitivity to rejection and greater depressed mood, and this association was stronger for adolescents compared with adults. We conclude that social risks should be incorporated into future models of risk-taking behaviour, especially when they are pitted against health risks