Alterations in brain connectivity due to plasticity and synaptic delay

Brain plasticity refers to brain's ability to change neuronal connections, as a result of environmental stimuli, new experiences, or damage. In this work, we study the effects of the synaptic delay on both the coupling strengths and synchronisation in a neuronal network with synaptic plasticity. We build a network of Hodgkin-Huxley neurons, where the plasticity is given by the Hebbian rules. We verify that without time delay the excitatory synapses became stronger from the high frequency to low frequency neurons and the inhibitory synapses increases in the opposite way, when the delay is increased the network presents a non-trivial topology. Regarding the synchronisation, only for small values of the synaptic delay this phenomenon is observed

Within-Person Variation in Personality and Psychological Well-Being

Personality is one of the most broad and complex areas in psychology. This has led to many researchers attempting to reduce this complexity by focusing solely on how habitual personality differs between each individual (inter-individual differences). This is important to study, but it has been focused on so heavily that research into how each individual personality varies within the person (intra-individual differences) has been neglected in comparison. Recent research has started to examine intra-individual variation in personality more thoroughly. One research aim of this programme was to establish the nature of several different types of within person variability including inter-item variation (variation within the test responses for a personality trait), and cross-contextual variation in personality (variation according to context), to see whether these types of variability are associated with psychological outcomes. Three research questions were examined to this end: 1) What is the extent of meaningful variability in personality trait test responding? 2) What are the predictors of intra-individual variability in personality? 3) What is the relative importance of the person and situational factors in personality variability? The first question was developed to try and determine whether the individual can display meaningful inter-item variation in ratings of specific behaviours within personality trait measures. Trait questionnaires are usually only analysed at the between subject level, and within subject variation in inter-item ratings have not been extensively examined in relation to meaningful psychological outcomes. The second and third questions were developed to look into the nature of cross-contextual personality, and establish whether within person personality differences are influenced more strongly by the person or situation. The studies conducted towards answering these questions demonstrated a person-based capacity to display intra-individual variability. A second aim of the research programme was to see whether the capacity to display these types of variability can be utilised in behaviour change. The fourth research question was developed to try and understand how a person can display intra-individual variability, yet still be resistant to changing negative habits: 4) How do the different aspects in personality variability help explain why some people are resistant to change, especially with regard to behaviours that are bad for them? This question was answered by theoretically discussing the findings from the three previous studies which proposed that positive or problematic behaviour could be interpreted with a simple path to understand the process of behavioural action: The individual receives feedback from a behaviour response which either validates or invalidates their action in the situation context (does or does not receive a desired outcome). Reinforcement of the behaviour happens if it is validated by positive feedback. Alternately reconstruction of the situation happens if the behaviour is invalidated. This allows for two types of intra-individual variability. One is flexibility in behaviour responses to different situations under the individual’s control. The other is change according to the situation, where the behaviour is invalidated and an alternative is attempted. A problematic behaviour may have benefit in stopping something invalidating, but if repeated it may become a habit needed for psychological functioning. As part of the second research aim a behaviour change strategy was developed and piloted to try and bring the individual closer to their construct of the ideal self. Instructions were provided for the individual to experiment with that differed from their disposition. The programmes had varied degrees of success depending on the participant. The implications for personality research and behaviour change are discussed

Inference of topology and the nature of synapses, and the flow of information in neuronal networks

ACKNOWLEDGEMENTS CAPES, DFG-IRTG 1740/2, Fundacao Araucaria, Newton Fund, CNPq (154705/2016-0, 311467/2014-8), FAPESP (2011/19296-1, 2015/07311-7, 2016/16148-5, 2016/23398-8, 2015/50122-0), EPSRC-EP/I032606.Peer reviewedPublisher PD

On Optimal Two-Impulse Earth-Moon Transfers in a Four-Body Model

In this paper two-impulse Earth-Moon transfers are treated in the restricted four-body problem with the Sun, the Earth, and the Moon as primaries. The problem is formulated with mathematical means and solved through direct transcription and multiple shooting strategy. Thousands of solutions are found, which make it possible to frame known cases as special points of a more general picture. Families of solutions are defined and characterized, and their features are discussed. The methodology described in this paper is useful to perform trade-off analyses, where many solutions have to be produced and assessed

High-dimensional interior crisis in the Kuramoto-Sivashinsky equation

An investigation of interior crisis of high dimensions in an extended spatiotemporal system exemplified by the Kuramoto-Sivashinsky equation is reported. It is shown that unstable periodic orbits and their associated invariant manifolds in the Poincaré hyperplane can effectively characterize the global bifurcation dynamics of high-dimensional systems.A. C.-L. Chian, E. L. Rempel, E. E. Macau, R. R. Rosa, and F. Christianse

Dynamical systems approach to space environment turbulence

Space plasmas are dominated by waves, instabilities and turbulence. Dynamical systems approach offers powerful mathematical and computational techniques to probe the origin and nature of space environment turbulence. Using the nonlinear dynamics tools such as the bifurcation diagram and Poincaré maps, we study the transition from order to chaos, from weak to strong chaos, and the destruction of a chaotic attractor. The characterization of the complex system dynamics of the space environment, such as the Alfvén turbulence, can improve the capability of monitoring Sun-Earth connections and prediction of space weather.A.C.-L. Chian, F.A. Borotto, E.L. Rempel, E.E.N. Macau, R.R. Rosa, F. Christianse

Gravity data on the Central Pyrenees: a step forward to help a better understanding of the Pyrenean structures

In this work, we present new Bouguer and residual Bouguer anomaly maps of the Central Pyrenees calculated from 3590 stations, of which 1141 are new observations acquired from surveys performed between 2018 and 2019. The most prominent feature of the Bouguer anomaly is the long wavelength elongated minimum in its central part that continues to the W and ends towards the E with a positive gradient that seems to envelope the minimum. Other short and medium wavelength minima are superimposed, some placed over the batholithic outcrops. In the residual Bouguer, the main relative minima are related with outcrops of batholiths or interpreted buried granites except for the prominent minimum South of La Maladeta Granite, associated with Triassic evaporitic accumulations. These maps (shown on the Main Map) will help characterizing the Permo-Carboniferous batholiths of the Central Pyrenees, in particular La Maladeta and Andorra Mont-Louis granites in order to add constraints to the mechanism of their emplacement

Blocking Radial Diffusion in a Double-Waved Hamiltonian Model

A non-twist Hamiltonian system perturbed by two waves with particular wave numbers can present Robust Tori, barriers created by the vanishing of the perturbing Hamiltonian at some defined positions. When Robust Tori exist, any trajectory in phase space passing close to them is blocked by emergent invariant curves that prevent the chaotic transport. We analyze the breaking up of the RT as well the transport dependence on the wave numbers and on the wave amplitudes. Moreover, we report the chaotic web formation in the phase space and how this pattern influences the transport