Action observation and imitation in the healthy brain and in high-functioning adults with autism spectrum conditions

Accurate action perception plays an important role in social interaction enabling us to identify and appropriately respond to the behaviour of others. One such response is automatic imitation, the reflexive copying of observed body movements. Action perception is associated with activity in posterior brain areas, which feed into the Mirror Neuron System (MNS), a network of regions that has been associated with imitation and which is under the regulatory control of frontal brain areas. The fMRI study described in Chapter 2 demonstrated that in healthy adults, action perception can be subdivided into objective and subjective components which are primarily associated with activity in different brain areas. Chapter 3 demonstrated that activity in MNS areas, as measured by MEG, comprises an automatic motoric simulation of the kinematics of observed actions. Chapters 2 and 3 therefore enhance knowledge of the neural mechanisms of action perception in the typical brain. Previous studies have linked Autism Spectrum Conditions (ASC) with action perception and imitation impairments. Chapters 4 and 5 demonstrated that adults with ASC exhibit atypical action perception which is likely due to difficulties with subjective processing (i.e. knowing what a ‘natural’ human movement should look like) rather than with objective visual processing of human motion. Chapter 6 reported a lack of imitation in ASC: whereas typical adults imitated human movements more than robot movements, individuals with ASC failed to imitate. Chapter 7 suggested that problems with imitation in ASC may relate to difficulties with the control of imitation: whereas control participants show increased levels of imitation when in a positive social frame-of-mind individuals with ASC did not. Chapters 4 to 7 have implications for ASC. They suggest that atypical imitation may be due to atypical sensory input to the MNS (i.e. impaired action perception) and/or atypical control of imitation

Fixing DNA breaks during class switch recombination

Immunoglobulin (Ig) class switch recombination (CSR) involves the breakage and subsequent repair of two DNA sequences, known as switch (S) regions, which flank IgH constant region exons. The resolution of CSR-associated breaks is thought to require the nonhomologous end-joining (NHEJ) DNA repair pathway, but the role of the NHEJ factor DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in this process has been unclear. A new study, in which broken IgH-containing chromosomes in switching B cells were visualized directly, clearly demonstrated that DNA-PKcs and, unexpectedly, the nuclease Artemis are involved in the resolution of switch breaks

A Tight Karp-Lipton Collapse Result in Bounded Arithmetic

Cook and Krajíček [9] have obtained the following Karp-Lipton result in bounded arithmetic: if the theory proves , then collapses to , and this collapse is provable in . Here we show the converse implication, thus answering an open question from [9]. We obtain this result by formalizing in a hard/easy argument of Buhrman, Chang, and Fortnow [3]. In addition, we continue the investigation of propositional proof systems using advice, initiated by Cook and Krajíček [9]. In particular, we obtain several optimal and even p-optimal proof systems using advice. We further show that these p-optimal systems are equivalent to natural extensions of Frege systems

Characterizing the Existence of Optimal Proof Systems and Complete Sets for Promise Classes.

In this paper we investigate the following two questions: Q1: Do there exist optimal proof systems for a given language L? Q2: Do there exist complete problems for a given promise class C? For concrete languages L (such as TAUT or SAT) and concrete promise classes C (such as NP∩coNP, UP, BPP, disjoint NP-pairs etc.), these ques-tions have been intensively studied during the last years, and a number of characterizations have been obtained. Here we provide new character-izations for Q1 and Q2 that apply to almost all promise classes C and languages L, thus creating a unifying framework for the study of these practically relevant questions. While questions Q1 and Q2 are left open by our results, we show that they receive affirmative answers when a small amount on advice is avail-able in the underlying machine model. This continues a recent line of research on proof systems with advice started by Cook and Kraj́ıček [6]

First evidence of cryptotephra in palaeoenvironmental records associated with Norse occupation sites in Greenland

The Norse/Viking occupation of Greenland is part of a dispersal of communities across the North Atlantic coincident with the supposed Medieval Warm Period of the late 1st millennium AD. The abandonment of the Greenland settlements has been linked to climatic deterioration in the Little Ice Age as well as other possible explanations. There are significant dating uncertainties over the time of European abandonment of Greenland and the potential influence of climatic deterioration. Dating issues largely revolve around radiocarbon chronologies for Norse settlements and associated mire sequences close to settlement sites. Here we show the potential for moving this situation forward by a combination of palynological, radiocarbon and cryptotephra analyses of environmental records close to three ‘iconic’ Norse sites in the former Eastern Settlement of Greenland – Herjolfsnes, Hvalsey and Garðar (the modern Igaliku). While much work remains to be undertaken, our results show that palynological evidence can provide a useful marker for both the onset and end of Norse occupation in the region, while the radiocarbon chronologies for these sequences remain difficult. Significantly, we here demonstrate the potential for cryptotephra to become a useful tool in resolving the chronology of Norse occupation, when coupled with palynology. For the first time, we show that cryptotephra are present within palaeoenvironmental sequences located within or close to Norse settlement ruin-groups, with tephra horizons detected at all three sites. While shard concentrations were small at Herjolfsnes, concentrations sufficient for geochemical analyses were detected at Igaliku and Hvalsey. WDS-EPMA analyses of these tephra indicate that, unlike the predominantly Icelandic tephra sources reported in the Greenland ice core records, the tephra associated with the Norse sites correlate more closely with volcanic centres in the Aleutians and Cascades. Recent investigations of cryptotephra dispersal from North American centres, along with our new findings, point to the potential for cryptotephra to facilitate hypothesis testing, providing a key chronological tool for refining the timing of Norse activities in Greenland (e.g. abandonment) and of environmental contexts and drivers (e.g. climate forcing)

Are adult amateur musicians at ‘high risk’ of experiencing musculoskeletal symptoms?

Musculoskeletal symptoms (MSSs) are a common problem for musicians, but the MSS burden of amateur musicians specifically is under-investigated. For the first time we sought to compare the MSS prevalence and profile (e.g. MSS location, impact) of adult amateur musicians with those of non-musicians. Amateur and non-musicians were asked to complete a questionnaire that collected data on their demographics, musical activities and MSS outcomes. A total of 456 participants were included, 30.9% of whom were amateur musicians. MSSs were common for both amateurs and non-musicians (96.4% and 96.1%, respectively, for the last twelve months). The only significant difference between the two groups was for the twelve-month prevalence of head MSSs with amateur musicians having a higher prevalence than non-musicians (49.6% and 39.8%, respectively, p<0.05). We conclude that amateur musicians do not have a substantially different MSS prevalence and profile compared with non-musicians for this university-based population.Stanhope, Jessica, Cook, Angus, Weinstein, Phili

Equation of state of neutron star cores and spin down of isolated pulsars

We study possible impact of a softening of the equation of state by a phase transition, or appearance of hyperons, on the spin evolution of of isolated pulsars. Numerical simulations are performed using exact 2-D simulations in general relativity. The equation of state of dense matter at supranuclear densities is poorly known. Therefore, the accent is put on the general correlations between evolution and equation of state, and mathematical strictness. General conjectures referring to the structure of the one-parameter families of stationary configurations are formulated. The interplay of the back bending phenomenon and stability with respect to axisymmetric perturbations is described. Changes of pulsar parameters in a corequake following instability are discussed, for a broad choice of phase transitions predicted by different theories of dense matter. The energy release in a corequake, at a given initial pressure, is shown to be independent of the angular momentum of collapsing configuration. This result holds for various types of phases transition, with and without metastability. We critically review observations of pulsars that could be relevant for the detection of the signatures of the phase transition in neutron star cores.Comment: 7 pages, 11 figures, to appear in Astrophysics and Space Science, in the proceedings of "Isolated Neutron Stars: from the Interior to the Surface", edited by D. Page, R. Turolla and S. Zan