Higher brain function relies upon the ability to flexibly integrate information across specialized communities of brain regions; however, it is unclear how this mechanism manifests over time. In this ...study, we used time-resolved network analysis of fMRI data to demonstrate that the human brain traverses between functional states that maximize either segregation into tight-knit communities or integration across otherwise disparate neural regions. Integrated states enable faster and more accurate performance on a cognitive task, and are associated with dilations in pupil diameter, suggesting that ascending neuromodulatory systems may govern the transition between these alternative modes of brain function. Together, our results confirm a direct link between cognitive performance and the dynamic reorganization of the network structure of the brain.
•The human brain network traverses segregated and integrated states over time•Integrated states enable fast, effective performance on an N-back task•Integrated states track with fluctuations in pupil diameter•Cognitive performance relates to the dynamic reorganization of brain architecture
Shine et al. use dynamic analyses of fMRI data to demonstrate that the network architecture of the human brain fluctuates between states of high and low global integration that track with effective task performance and may relate to fluctuations in arousal.
Gravity waves are one of the main drivers of atmospheric dynamics. The
spatial resolution of most global atmospheric models, however, is too coarse
to properly resolve the small scales of gravity ...waves, which range from tens
to a few thousand kilometers horizontally, and from below 1 km to tens of
kilometers vertically. Gravity wave source processes involve even smaller
scales. Therefore, general circulation models (GCMs) and chemistry climate
models (CCMs) usually parametrize the effect of gravity waves on the global
circulation. These parametrizations are very simplified. For this reason,
comparisons with global observations of gravity waves are needed for an
improvement of parametrizations and an alleviation of model biases. We present a gravity wave climatology based on atmospheric infrared limb
emissions observed by satellite (GRACILE). GRACILE is a global data set of
gravity wave distributions observed in the stratosphere and the mesosphere by
the infrared limb sounding satellite instruments High Resolution Dynamics
Limb Sounder (HIRDLS) and Sounding of the Atmosphere using Broadband Emission
Radiometry (SABER). Typical distributions (zonal averages and global maps) of
gravity wave vertical wavelengths and along-track horizontal wavenumbers are
provided, as well as gravity wave temperature variances, potential energies
and absolute momentum fluxes. This global data set captures the typical
seasonal variations of these parameters, as well as their spatial variations.
The GRACILE data set is suitable for scientific studies, and it can serve for
comparison with other instruments (ground-based, airborne, or other satellite
instruments) and for comparison with gravity wave distributions, both
resolved and parametrized, in GCMs and CCMs. The GRACILE data set is
available as supplementary data at
https://doi.org/10.1594/PANGAEA.879658.
In humans, the cGAS-STING immunity pathway signals in response to cytosolic DNA via 2′,3′ cGAMP, a cyclic dinucleotide (CDN) second messenger containing mixed 2′–5′ and 3′–5′ phosphodiester bonds. ...Prokaryotes also produce CDNs, but these are exclusively 3′ linked, and thus the evolutionary origins of human 2′,3′ cGAMP signaling are unknown. Here we illuminate the ancient origins of human cGAMP signaling by discovery of a functional cGAS-STING pathway in Nematostella vectensis, an anemone species >500 million years diverged from humans. Anemone cGAS appears to produce a 3′,3′ CDN that anemone STING recognizes through nucleobase-specific contacts not observed in human STING. Nevertheless, anemone STING binds mixed-linkage 2′,3′ cGAMP indistinguishably from human STING, trapping a unique structural conformation not induced by 3′,3′ CDNs. These results reveal that human mixed-linkage cGAMP achieves universal signaling by exploiting a deeply conserved STING conformational intermediate, providing critical insight for therapeutic targeting of the STING pathway.
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•Binding of CDNs is an evolutionarily ancient STING function, predating interferons•cGAS-STING function is conserved in anemone, >500 million years diverged from humans•Anemone cGAS produces a canonical 3′,3′ linked CDN similar to those in bacteria•Vertebrate 2′,3′ cGAMP signaling exploits a deeply conserved STING conformation
Kranzusch and Wilson et al. use structural and biochemical approaches to characterize human and anemone cGAS-STING immune pathways, demonstrating that the product of human cGAS is a potent STING activator because it targets an ancient, conserved, intermediate conformation of STING.
Hemiparesis, defined as unilateral muscle weakness, often occurs in people post-stroke or people with cerebral palsy, however it is difficult to understand how this hemiparesis affects movement ...patterns as it often presents alongside a variety of other neuromuscular impairments. Predictive musculoskeletal modeling presents an opportunity to investigate how impairments affect gait performance assuming a particular cost function. Here, we use predictive simulation to quantify the spatiotemporal asymmetries and changes to metabolic cost that emerge when muscle strength is unilaterally reduced and how reducing spatiotemporal symmetry affects metabolic cost. We modified a 2-D musculoskeletal model by uniformly reducing the peak isometric muscle force unilaterally. We then solved optimal control simulations of walking across a range of speeds by minimizing the sum of the cubed muscle excitations. Lastly, we ran additional optimizations to test if reducing spatiotemporal asymmetry would result in an increase in metabolic cost. Our results showed that the magnitude and direction of effort-optimal spatiotemporal asymmetries depends on both the gait speed and level of weakness. Also, the optimal speed was 1.25 m/s for the symmetrical and 20% weakness models but slower (1.00 m/s) for the 40% and 60% weakness models, suggesting that hemiparesis can account for a portion of the slower gait speed seen in people with hemiparesis. Modifying the cost function to minimize spatiotemporal asymmetry resulted in small increases (~4%) in metabolic cost. Overall, our results indicate that spatiotemporal asymmetry may be optimal for people with hemiparesis. Additionally, the effect of speed and the level of weakness on spatiotemporal asymmetry may help explain the well-known heterogenous distribution of spatiotemporal asymmetries observed in the clinic. Future work could extend our results by testing the effects of other neuromuscular impairments on optimal gait strategies, and therefore build a more comprehensive understanding of the gait patterns observed in clinical populations.
Little is currently known about the coordination of neural activity over longitudinal timescales and how these changes relate to behavior. To investigate this issue, we used resting-state fMRI data ...from a single individual to identify the presence of two distinct temporal states that fluctuated over the course of 18 mo. These temporal states were associated with distinct patterns of time-resolved blood oxygen level dependent (BOLD) connectivity within individual scanning sessions and also related to significant alterations in global efficiency of brain connectivity as well as differences in self-reported attention. These patterns were replicated in a separate longitudinal dataset, providing additional supportive evidence for the presence of fluctuations in functional network topology over time. Together, our results underscore the importance of longitudinal phenotyping in cognitive neuroscience.
As observed by the Sounding of the Atmosphere using Broadband Emission
Radiometry (SABER), the migrating diurnal tide (DW1) in the upper mesosphere
and lower thermosphere (MLT) region decreased by ∼ ...10 %
during El Niño in the Northern Hemisphere (NH) winter
(December–January–February) from 2002 to 2020. According to the multiple
linear regression (MLR) analysis, the linear effects of El Niño on the
tropical MLT DW1 are significantly negative in both SABER observations and
SD-WACCM (the Specified-Dynamics version of the Whole Atmosphere Community
Climate Model) simulations. The DW1 response to El Niño in NH winter is
much stronger than its annual mean response. As suggested by SD-WACCM
simulation, Hough mode (1, 1) dominates the DW1 tidal variation in the
tropical MLT region. The consistency between the (1, 1) mode in the
tropopause region and the MLT region and the downward phase progression from
15 to 100 km indicates the direct upward propagation of DW1 from the
excitation source in the troposphere. The suppressed DW1 heating rates in
the tropical troposphere (averaged over ∼ 0–16 km and
35∘ S–35∘ N) during El Niño winter contribute to the
decreased DW1 tide. To evaluate the effect of the gravity waves (GWs) on the
tide, the GW forcing is calculated as the GW drag weighted by the phase
relation between DW1 GW drag and DW1 wind. The negative GW forcing in the
tropical upper mesosphere would significantly suppress the MLT DW1 tide
during El Niño winter. This tide–GW interaction could be a dominant
mechanism for DW1 response in the MLT to El Niño. During El Niño
winter, the increased ratio of the absolute and planetary vorticity (R)
suppresses the waveguide and thus the DW1 amplitude in the subtropical
mesosphere. However, the effect of the waveguide might play a secondary role
due to its relatively weak response.
Microwave Limb Sounder and Sounding of the Atmosphere with Broadband Emission Radiometry data provide the first opportunity to characterize the four-dimensional stratopause evolution throughout the ...life-cycle of a major stratospheric sudden warming (SSW). The polar stratopause, usually higher than that at midlatitudes, dropped by 30 km and warmed during development of a major "wave 1" SSW in January 2006, with accompanying mesospheric cooling. When the polar vortex broke down, the stratopause cooled and became ill-defined, with a nearly isothermal stratosphere. After the polar vortex started to recover in the upper stratosphere/lower mesosphere (USLM), a cool stratopause reformed above 75 km, then dropped and warmed; both the mesosphere above and the stratosphere below cooled at this time. The polar stratopause remained separated from that at midlatitudes across the core of the polar night jet. In the early stages of the SSW, the strongly tilted (westward with increasing altitude) polar vortex extended into the mesosphere, and enclosed a secondary temperature maximum extending westward and slightly equatorward from the highest altitude part of the polar stratopause over the cool stratopause near the vortex edge. The temperature evolution in the USLM resulted in strongly enhanced radiative cooling in the mesosphere during the recovery from the SSW, but significantly reduced radiative cooling in the upper stratosphere. Assimilated meteorological analyses from the European Centre for Medium-Range weather Forecasts (ECMWF) and Goddard Earth Observing System Version 5.0.1 (GEOS-5), which are not constrained by data at polar stratopause altitudes and have model tops near 80 km, could not capture the secondary temperature maximum or the high stratopause after the SSW; they also misrepresent polar temperature structure during and after the stratopause breakdown, leading to large biases in their radiative heating rates. ECMWF analyses represent the stratospheric temperature structure more accurately, suggesting a better representation of vertical motion; GEOS-5 analyses more faithfully describe stratopause level wind and wave amplitudes. The high-quality satellite temperature data used here provide the first daily, global, multiannual data sets suitable for assessing and, eventually, improving representation of the USLM in models and assimilation systems.
Monthly tidal temperatures 20–120 km from TIMED/SABER Zhang, Xiaoli; Forbes, Jeffrey M.; Hagan, Maura E. ...
Journal of Geophysical Research - Space Physics,
October 2006, Letnik:
111, Številka:
A10
Journal Article
Recenzirano
Odprti dostop
The SABER instrument on the TIMED satellite provides unprecedented geographical coverage for the determination and study of atmospheric tides. However, the slow local time precession rate of TIMED ...can cause longer‐term temperature variations to alias into the tidal signals. A new method of analyzing satellite data for tides has been developed to circumvent this difficulty, but at the expense of temporal resolution of the tidal fields, i.e., 120‐day mean tidal structures are obtained. In this work, we apply this method to SABER temperature data to derive a series of 120‐day mean tidal structures, extending between 20 and 120 km altitude, 50°S–50°N latitude, and centered on each month from September 2003 to September 2004. In addition to the migrating (Sun‐synchronous) diurnal and semidiurnal tides, a number of nonmigrating tides are revealed in the SABER measurements. Some of these waves are thought to originate via nonlinear coupling between the migrating tides and the stationary planetary wave with zonal wave number s = 1. Other nonmigrating tidal components appear to be forced by latent heating due to deep tropical convection. Of the latter, the eastward propagating diurnal tide with s = 3 is dominant and is as large as the migrating diurnal tide during some months. Of particular interest is the wave‐4 structure with respect to longitude that characterizes both the diurnal and semidiurnal total tidal fields. This feature is a result of the predominant wave‐4 topography/land‐sea longitude dependence at the surface, which is reflected in the diurnal and semidiurnal components of the latent heating rates due to deep tropical convection. The ability of the global‐scale wave model (GSWM) to approximate the observed tidal fields, including the wave‐4 total tidal structures, is also assessed.
Since February 2002, the SABER (sounding of the atmosphere using broadband emission radiometry) satellite instrument has measured temperatures throughout the entire middle atmosphere. Employing the ...same techniques as previously used for CRISTA (cryogenic infrared spectrometers and telescopes for the atmosphere), we deduce from SABER V1.06 data 5 years of gravity wave (GW) temperature variances from altitudes of 20 to 100 km. A typical annual cycle is presented by calculating averages for the individual calendar months. Findings are consistent with previous results from various satellite missions. Based on zonal mean, SABER data for July and zonal mean GW momentum flux from CRISTA, a homogeneous and isotropic launch distribution for the GROGRAT (gravity wave regional or global ray tracer) is tuned. The launch distribution contains different phase speed mesoscale waves, some of very high‐phase speed and extremely low amplitudes, as well as waves with horizontal wavelengths of several thousand kilometers. Global maps for different seasons and altitudes, as well as time series of zonal mean GW squared amplitudes based on this launch distribution, match the observations well. Based on this realistic observation‐tuned model run, we calculate quantities that cannot be measured directly and are speculated to be major sources of uncertainty in current GW parameterization schemes. Two examples presented in this paper are the average cross‐latitude propagation of GWs and the relative acceleration contributions provided by saturation and dissipation, on the one hand, and the horizontal refraction of GWs by horizontal gradients of the mean flow, on the other hand.
The added value of using regional climate models (RCMs) to downscale data from general circulation models (GCMs) has often been questioned and researched. Although several studies have used different ...methods to identify (and in some cases quantify) the added value, there is still a need to find a general metric that quantifies the added value of any variable. This paper builds on past studies to propose a new metric of added value in the simulation of present-day climate which measures the difference in the probability density functions (PDFs) at each grid-cell between a model and an observation source, and then compares the results of the RCM and GCM in order to spatially compute the added value index. The same method is also adapted to quantify the climate change downscaling signal in a way that is consistent with the present-day metric. These new metrics are tested on the daily precipitation output from the EURO-CORDEX and CORDEX-CORE projection ensembles and reveal an overall positive added value of RCMs, especially at the tail-end of the distribution. Higher added value is obtained in areas of complex topography and coast-lines, as well as in tropical regions. Areas with large added value in present-day climate are consistent with areas of significant climate change downscaling signal in the RCP 8.5 far future simulations, and when the analysis is repeated at a low-resolution. The use of different resolution observations shows that the added value tends to decrease when models are compared to low-resolution observation datasets.
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