Novel modeling of task versus rest brain state predictability using a dynamic time warping spectrum: comparisons and contrasts with other standard measures of brain dynamics

Dynamic time warping, or DTW, is a powerful and domain-general sequence alignment method for computing a similarity measure. Such dynamic programming-based techniques like DTW are now the backbone and driver of most bioinformatics methods and discoveries. In neuroscience it has had far less use, though this has begun to change. We wanted to explore new ways of applying DTW, not simply as a measure with which to cluster or compare similarity between features but in a conceptually different way. We have used DTW to provide a more interpretable spectral description of the data, compared to standard approaches such as the Fourier and related transforms. The DTW approach and standard discrete Fourier transform (DFT) are assessed against benchmark measures of neural dynamics. These include EEG microstates, EEG avalanches, and the sum squared error (SSE) from a multilayer perceptron (MLP) prediction of the EEG time series, and simultaneously acquired FMRI BOLD signal. We explored the relationships between these variables of interest in an EEG-FMRI dataset acquired during a standard cognitive task, which allowed us to explore how DTW differentially performs in different task settings. We found that despite strong correlations between DTW and DFT-spectra, DTW was a better predictor for almost every measure of brain dynamics. Using these DTW measures, we show that predictability is almost always higher in task than in rest states, which is consistent to other theoretical and empirical findings, providing additional evidence for the utility of the DTW approach

Homology of Distributive Lattices

We outline the theory of sets with distributive operations: multishelves and multispindles, with examples provided by semi-lattices, lattices and skew lattices. For every such a structure we define multi-term distributive homology and show some of its properties. The main result is a complete formula for the homology of a finite distributive lattice. We also indicate the answer for unital spindles and conjecture the general formula for semi-lattices and some skew lattices. Then we propose a generalization of a lattice as a set with a number of idempotent operations satisfying the absorption law.Comment: 30 pages, 3 tables, 3 figure

Modeling uncertainties in EEG microstates: analysis of real and imagined motor movements using probabilistic clustering-driven training of probabilistic neural networks

Part of the process of EEG microstate estimation involves clustering EEG channel data at the global field power (GFP) maxima, very commonly using a modified K-means approach. Clustering has also been done deterministically, despite there being uncertainties in multiple stages of the microstate analysis, including the GFP peak definition, the clustering itself and in the post-clustering assignment of microstates back onto the EEG timecourse of interest. We perform a fully probabilistic microstate clustering and labeling, to account for these sources of uncertainty using the closest probabilistic analogue to KM called Fuzzy C-means (FCM). We train softmax multi-layer perceptrons (MLPs) using the KM and FCM-inferred cluster assignments as target labels, to then allow for probabilistic labeling of the full EEG data instead of the usual correlation-based deterministic microstate label assignment typically used. We assess the merits of the probabilistic analysis vs the deterministic approaches in EEG data recorded while participants perform real or imagined motor movements from a publicly available data set of 109 subjects. Though FCM group template maps that are almost topographically identical to KM were found, there is considerable uncertainty in the subsequent assignment of microstate labels. In general, imagined motor movements are less predictable on a time point-by-time point basis, possibly reflecting the more exploratory nature of the brain state during imagined, compared to during real motor movements. We find that some relationships may be more evident using FCM than using KM and propose that future microstate analysis should preferably be performed probabilistically rather than deterministically, especially in situations such as with brain computer interfaces, where both training and applying models of microstates need to account for uncertainty. Probabilistic neural network-driven microstate assignment has a number of advantages that we have discussed, which are likely to be further developed and exploited in future studies. In conclusion, probabilistic clustering and a probabilistic neural network-driven approach to microstate analysis is likely to better model and reveal details and the variability hidden in current deterministic and binarized microstate assignment and analyses

Staphylococcus aureus Colonization: Modulation of Host Immune Response and Impact on Human Vaccine Design

In apparent contrast to its invasive potential Staphylococcus aureus colonizes the anterior nares of 20–80% of the human population. The relationship between host and microbe appears particularly individualized and colonization status seems somehow predetermined. After decolonization, persistent carriers often become re-colonized with their prior S. aureus strain, whereas non-carriers resist experimental colonization. Efforts to identify factors facilitating colonization have thus far largely focused on the microorganism rather than on the human host. The host responds to S. aureus nasal colonization via local expression of anti-microbial peptides, lipids, and cytokines. Interplay with the co-existing microbiota also influences colonization and immune regulation. Transient or persistent S. aureus colonization induces specific systemic immune responses. Humoral responses are the most studied of these and little is known of cellular responses induced by colonization. Intriguingly, colonized patients who develop bacteremia may have a lower S. aureus-attributable mortality than their non-colonized counterparts. This could imply a staphylococcal-specific immune “priming” or immunomodulation occurring as a consequence of colonization and impacting on the outcome of infection. This has yet to be fully explored. An effective vaccine remains elusive. Anti-S. aureus vaccine strategies may need to drive both humoral and cellular immune responses to confer efficient protection. Understanding the influence of colonization on adaptive response is essential to intelligent vaccine design, and may determine the efficacy of vaccine-mediated immunity. Clinical trials should consider colonization status and the resulting impact of this on individual patient responses. We urgently need an increased appreciation of colonization and its modulation of host immunity

The Frequency of Active and Quiescent Galaxies with Companions: Implications for the Feeding of the Nucleus

We analyze the idea that nuclear activity, either AGN or star formation, can be triggered by interactions, studying the percentage of active, HII and quiescent galaxies with companions. Our sample was selected from the Palomar survey, and avoids selection biases faced by previous studies. The comparison between the local galaxy density distributions showed that in most cases there is no statistically significant difference among galaxies of different activity types. The comparison of the percentage of galaxies with nearby companions showed that there is a higher percentage of LINERs, transition, and absorption line galaxies with companions than Seyferts and HII galaxies. However, we find that when we consider only galaxies of similar morphological types (ellipticals or spirals), there is no difference in the percentage of galaxies with companions among different activity types, indicating that the former result was due to the morphology-density effect. Also, only small differences are found when we consider galaxies with similar Halpha luminosities. The comparison between HII galaxies of different Halpha luminosities shows that there is a significantly higher percentage of galaxies with companions among the higher luminosity HII galaxies, indicating that interactions increase the amount of circumnuclear star formation, in agreement with previous results. The fact that we find that galaxies of different activity types have the same percentage of companions, suggests that interactions between galaxies is not a necessary condition to trigger the nuclear activity in AGNs. We compare our results with previous ones and discuss their implications. (abridged)Comment: 30 pages, including 6 figures and 3 tables. To appear in The Astronomical Journal, November issu

Stimulating Multiple-Demand Cortex Enhances Vocabulary Learning

It is well established that networks within multiple-demand cortex (MDC) become active when diverse skills and behaviors are being learnt. However, their causal role in learning remains to be established. In the present study, we first performed functional magnetic resonance imaging on healthy female and male human participants to confirm that MDC was most active in the initial stages of learning a novel vocabulary, consisting of pronounceable nonwords (pseudowords), each associated with a picture of a real object. We then examined, in healthy female and male human participants, whether repetitive transcranial magnetic stimulation of a frontal midline node of the cingulo-opercular MDC affected learning rates specifically during the initial stages of learning. We report that stimulation of this node, but not a control brain region, substantially improved both accuracy and response times during the earliest stage of learning pseudoword– object associations. This stimulation had no effect on the processing of established vocabulary, tested by the accuracy and response times when participants decided whether a real word was accurately paired with a picture of an object. These results provide evidence that noninvasive stimulation to MDC nodes can enhance learning rates, thereby demonstrating their causal role in the learning process. We propose that this causal role makes MDC candidate target for exper- imental therapeutics; for example, in stroke patients with aphasia attempting to reacquire a vocabulary

Design and performance of ropes for climbing and sailing

Ropes are an important part of the equipment used by climbers, mountaineers, and sailors. On first inspection, most modern polymer ropes appear similar, and it might be assumed that their designs, construction, and properties are governed by the same requirements. In reality, the properties required of climbing ropes are dominated by the requirement that they effectively absorb and dissipate the energy of the falling climber, in a manner that it does not transmit more than a critical amount of force to his body. This requirement is met by the use of ropes with relatively low longitudinal stiffness. In contrast, most sailing ropes require high stiffness values to maximize their effectiveness and enable sailors to control sails and equipment precisely. These conflicting requirements led to the use of different classes of materials and different construction methods for the two sports. This paper reviews in detail the use of ropes, the properties required, manufacturing techniques and materials utilized, and the effect of service conditions on the performance of ropes. A survey of research that has been carried out in the field reveals what progress has been made in the development of these essential components and identifies where further work may yield benefits in the future

Prioritizing patients for renal transplantation?: Analysis of patient preferences for kidney allocation according to ethnicity and gender

Revisions to UK transplant allocation policy in 2006 marked a policy shift towards ascribing higher priority to people who had been waiting for a long time for transplants, and to young adults, at the expense of emphasising tissue match between donor and recipient. This benefited members of ethnic minorities because of a shortage of donors from some ethnic groups. However, the change was informed by dated research which was not specific to the UK, and which failed to address ethnic or gender-related differences in preferences. Preference information was elicited using discrete choice experiment (DCE) questionnaires (in English, Punjabi, Hindi, Bengali, Gujarati and Urdu) from 908 patients (508 males and 397 females). Of the 908 repondents, 96 were members of ethnicminority groups, namely white ethnic minorities (27/908) and non-white ethnic minorities (69/908), including 50 South Asians. Priority criteria included length of time spent waiting for a transplant, quality of the donor-recipient tissue match, number of adult and/or child dependants of the recipient, and whether the recipient had diseases that affected their life expectancy or quality of life. Econometric results provided evidence that preferences differed slightly according to gender, but differed to a greater extent according to ethnic origin. In significant contrast to other patients, members of non-white and South Asian ethnic minorities did not tend to prioritise recipients with a good tissue match, nor, unlike patients more generally, did they tend to prioritise younger recipients. Non-white and South Asian ethnic minorities were also less likely to prioritise those with moderate rather than severe diseases affecting life expectancy. These results reinforce the case for recognising differences in ethnic-minority group preferences in transplant allocation policy