Finite rigid sets in sphere complexes

A subcomplex $X\leq \mathcal{C}$ of a simplicial complex is rigid if every locally injective, simplicial map $X\to\mathcal{C}$ is the restriction of an automorphism of $\mathcal{C}$. Aramayona and the second author proved that the curve complex of an orientable surface can be exhausted by finite rigid sets. The Hatcher sphere complex is an analog of the curve complex for isotopy classes of essential spheres in a connect sum of $n$ copies of $S^1\times S^2$. We show that there is an exhaustion of the sphere complex by finite rigid sets for all $n\ge 3$ and that when $n=2$ the sphere complex does not have finite rigid sets.Comment: 13 pages, 5 figure

UCHIME improves sensitivity and speed of chimera detection

Motivation: Chimeric DNA sequences often form during polymerase chain reaction amplification, especially when sequencing single regions (e.g. 16S rRNA or fungal Internal Transcribed Spacer) to assess diversity or compare populations. Undetected chimeras may be misinterpreted as novel species, causing inflated estimates of diversity and spurious inferences of differences between populations. Detection and removal of chimeras is therefore of critical importance in such experiments

Zika virus tropism and interactions in myelinating neural cell cultures: CNS cells and myelin are preferentially affected

The recent global outbreak of Zika virus (ZIKV) infection has been linked to severe neurological disorders affecting the peripheral and central nervous systems (PNS and CNS, respectively). The pathobiology underlying these diverse clinical phenotypes are the subject of intense research; however, even the principal neural cell types vulnerable to productive Zika infection remain poorly characterised. Here we used CNS and PNS myelinating cultures from wild type and Ifnar1 knockout mice to examine neuronal and glial tropism and short-term consequences of direct infection with a Brazilian variant of ZIKV. Cell cultures were infected pre- or post-myelination for various intervals, then stained with cell-type and ZIKV-specific antibodies. In bypassing systemic immunity using ex vivo culture, and the type I interferon response in Ifnar1 deficient cells, we were able to evaluate the intrinsic infectivity of neural cells. Through systematic quantification of ZIKV infected cells in myelinating cultures, we found that ZIKV infection is enhanced in the absence of the type I interferon responses and that CNS cells are considerably more susceptible to infection than PNS cells. In particular, we demonstrate that CNS axons and myelinating oligodendrocytes are especially vulnerable to injury. These results have implications for understanding the pathobiology of neurological symptoms associated with ZIKV infection. Furthermore, we provide a quantifiable ex vivo infection model that can be used for fundamental and therapeutic studies on viral neuroinvasion and its consequences

Neural correlates of suspiciousness and interactions with anxiety during emotional and neutral word processing

Suspiciousness is usually classified as a symptom of psychosis, but it also occurs in depression and anxiety disorders. Though how suspiciousness overlaps with depression is not obvious, suspiciousness does seem to overlap with anxious apprehension and anxious arousal (e.g., verbal iterative processes and vigilance about environmental threat). However, suspiciousness also has unique characteristics (e.g., concern about harm from others and vigilance about social threat). Given that both anxiety and suspiciousness have been associated with abnormalities in emotion processing, it is unclear whether it is the unique characteristics of suspiciousness or the overlap with anxiety that drive abnormalities in emotion processing. Event-related brain potentials were obtained during an emotion-word Stroop task. Results indicated that suspiciousness interacts with anxious apprehension to modulate initial stimulus perception processes. Suspiciousness is associated with attention to all stimuli regardless of emotion content. In contrast, anxious arousal is associated with a later response to emotion stimuli only. These results suggest that suspiciousness and anxious apprehension share overlapping processes, but suspiciousness alone is associated with a hyperactive early vigilance response. Depression did not interact with suspiciousness to predict response to emotion stimuli. These findings suggest that it may be informative to assess suspiciousness in conjunction with anxiety in order to better understand how these symptoms interact and contribute to dysfunctional emotion processing

Frontal and superior temporal auditory processing abnormalities in schizophrenia

AbstractBackgroundAlthough magnetoencephalography (MEG) studies show superior temporal gyrus (STG) auditory processing abnormalities in schizophrenia at 50 and 100ms, EEG and corticography studies suggest involvement of additional brain areas (e.g., frontal areas) during this interval. Study goals were to identify 30 to 130ms auditory encoding processes in schizophrenia (SZ) and healthy controls (HC) and group differences throughout the cortex.MethodsThe standard paired-click task was administered to 19 SZ and 21 HC subjects during MEG recording. Vector-based Spatial–temporal Analysis using L1-minimum-norm (VESTAL) provided 4D maps of activity from 30 to 130ms. Within-group t-tests compared post-stimulus 50ms and 100ms activity to baseline. Between-group t-tests examined 50 and 100ms group differences.ResultsBilateral 50 and 100ms STG activity was observed in both groups. HC had stronger bilateral 50 and 100ms STG activity than SZ. In addition to the STG group difference, non-STG activity was also observed in both groups. For example, whereas HC had stronger left and right inferior frontal gyrus activity than SZ, SZ had stronger right superior frontal gyrus and left supramarginal gyrus activity than HC.ConclusionsLess STG activity was observed in SZ than HC, indicating encoding problems in SZ. Yet auditory encoding abnormalities are not specific to STG, as group differences were observed in frontal and SMG areas. Thus, present findings indicate that individuals with SZ show abnormalities in multiple nodes of a concurrently activated auditory network

Circadian Rhythms in Visual Responsiveness in the Behaviorally Arrhythmic Drosophila Clock Mutant ClkJrk

An organism's biological day is characterized by a pattern of anticipatory physiological and behavioral changes that are governed by circadian clocks to align with the 24-h cycling environment. Here, we used flash electroretinograms (ERGs) and steady-state visually evoked potentials (SSVEPs) to examine how visual responsiveness in wild-type Drosophila melanogaster and the circadian clock mutant ClkJrk varies over circadian time. We show that the ERG parameters of wild-type flies vary over the circadian day, with a higher luminance response during the subjective night. The SSVEP response that assesses contrast sensitivity also showed a time-of-day dependence, including 2 prominent peaks within a 24-h period and a maximal response at the end of the subjective day, indicating a tradeoff between luminance and contrast sensitivity. Moreover, the behaviorally arrhythmic ClkJrk mutants maintained a circadian profile in both luminance and contrast sensitivity, but unlike the wild-types, which show bimodal profiles in their visual response, ClkJrk flies show a weakening of the bimodal character, with visual responsiveness tending to peak once a day. We conclude that the ClkJrk mutation mainly affects 1 of 2 functionally coupled oscillators and that the visual system is partially separated from the locomotor circadian circuits that drive bouts of morning and evening activity. As light exposure is a major mechanism for entrainment, our work suggests that a detailed temporal analysis of electrophysiological responses is warranted to better identify the time window at which circadian rhythms are most receptive to light-induced phase shifting

Исследование возможностей фреймворка TensorFlow для прогнозирования временных рядов

Purpose:To present online scanner noise cancellation for speech acquired in functional magnetic resonance imaging (fMRI) studies.Materials and Methods:An online active noise cancellation method for speech acquired in fMRI studies was developed. The approach consists of two automated steps: 1) creation of an MR noise template in a short “test” fMRI scan; 2) application of the template for automatic recognition and subtraction of the MR noise from the acquired microphone signal during an fMRI study. The method was applied in an experimental paradigm where a subject and an investigator communicated in an interactive verbal generation task during fMRI.Results:By applying online active noise cancellation, the quality of the subject's speech was substantially improved. The present approach was found to be flexible, reliable, and easy to implement, providing a method for fMRI studies that investigate the neural correlates of interactive speech communication.Conclusion:Using online noise cancellation it is possible to improve the quality of acquired speech in fMRI. This approach may be recommended for interactive fMRI studies

Extraformational sediment recycling on Mars

Extraformational sediment recycling (old sedimentary rock to new sedimentary rock) is a fundamental aspect of Earth's geological record; tectonism exposes sedimentary rock, whereupon it is weathered and eroded to form new sediment that later becomes lithified. On Mars, tectonism has been minor, but two decades of orbiter instrument-based studies show that some sedimentary rocks previously buried to depths of kilometers have been exposed, by erosion, at the surface. Four locations in Gale crater, explored using the National Aeronautics and Space Administration's Curiosity rover, exhibit sedimentary lithoclasts in sedimentary rock: At Marias Pass, they are mudstone fragments in sandstone derived from strata below an erosional unconformity; at Bimbe, they are pebble-sized sandstone and, possibly, laminated, intraclast-bearing, chemical (calcium sulfate) sediment fragments in conglomerates; at Cooperstown, they are pebble-sized fragments of sandstone within coarse sandstone; at Dingo Gap, they are cobble-sized, stratified sandstone fragments in conglomerate derived from an immediately underlying sandstone. Mars orbiter images show lithified sediment fans at the termini of canyons that incise sedimentary rock in Gale crater; these, too, consist of recycled, extraformational sediment. The recycled sediments in Gale crater are compositionally immature, indicating the dominance of physical weathering processes during the second known cycle. The observations at Marias Pass indicate that sediment eroded and removed from craters such as Gale crater during the Martian Hesperian Period could have been recycled to form new rock elsewhere. Our results permit prediction that lithified deltaic sediments at the Perseverance (landing in 2021) and Rosalind Franklin (landing in 2023) rover field sites could contain extraformational recycled sediment.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737