Lower Relative Activity Research Articles

Tectonic evolution of Bursa Yenişehir Basin, Turkey from the Neogene to the Quaternary using a morphotectonic approach

In this study, the morphotectonic features of the Yenişehir pull‐apart basin in Bursa in northwestern Turkey were analysed. The faults in the region are the most important structural elements that characterize the morphology of the Yenişehir pull‐apart basin. The aim of this study is to show the deformation effects of these active faults on the geomorphology with some basic morphometric indices. The morphotectonic features were evaluated using the hypsometric curve and hypsometric integral (Hi), drainage basin asymmetry (the asymmetry factor (AF) and the transverse topographic symmetry factor (T)), river length gradient index, mountain front sinuosity, and valley floor ratio. The morphometric indices that play an important role in the analysis of catchment areas are the Hi, AF, and T indices, which indicate tilting and erosion activities. According to the results of the hypsometric curve and hypsometric integral, the Yenişehir Basin is a young basin with a uniform topography as expected in an active pull‐apart basin formed by faulting in the Quaternary. The relative tectonic activity index (Iat) of the study area was calculated using the values of hypsometric integral, transverse topographic symmetry factor, asymmetry factor, mountain front sinuosity, valley floor ratio and stream length gradient index. The Iat values indicate the tectonic activity of the basin from Pliocene to Recent. Three different tectonic classes were identified in the study area. These are class 1 (high relative tectonic activity), class 2 (moderate relative tectonic activity), and class 3 (low relative tectonic activity). The Iat classification data show that the impact of tectonic activity on the geomorphology is lower in the Iat class 3 indices than in the others. The Iat data show high tectonic activity in the region where active faults of the North Anatolian Fault Zone southern branch are located.

Strain rate and anisotropic effects on incipient plastic deformation of Zn–Cu–Ti alloy sheets

Zinc alloys shows strong strain rate dependent and anisotropic mechanical behaviours, the mechanistic origin of which is however not fully understood. In this work, a combination of the experiments and crystal plasticity finite element simulations were used to gain an insight into the relation between deformation mechanisms, tensile deformation behaviour and texture evolution, especially for the incipient plastic deformation stage. To this end, specimens were cut from Zn–Cu–Ti alloy sheets at various orientations with respect to the rolling direction, and uniaxial tensile tests were conducted at different strain rates ranging from 10−3 to 5 × 10−2 s−1. The microstructure evolution with the deformation was examined by the electron backscatter diffraction technique. Crystal plasticity model was calibrated considering the effect of strain rate on the flow stress, and finite element simulations were carried out based on a representative volume element of the polycrystal zinc alloy. It is found out that the flow stress increases significantly, as the loading direction approaches the transverse direction, which results in a lower relative activity of basal slip and higher relative activity of non-basal ones. This, in turn, reduces the rotation of the c-axis of the crystallites towards ND during tensile tests. On the other hand, a positive strain rate sensitivity is found in the zinc alloy. Meanwhile, increasing strain rate leads to an obvious decrease in the activity of the pyramidal π-II slip systems, accompanied by more activated twinning systems. The lower activity of the pyramidal π-II slip at a higher strain rate probably hinders the development of CDRX and grain fragmentation at large strain levels.

Mechanistic study of nucleotide‐sugar binding and catalysis in SECRET AGENT O‐GlcNAc Transferase

O‐linked β‐N‐acetylglucosamine (O‐GlcNAc) transferase (OGT) is an essential protein that is highly conserved across all eukaryotes. Misregulation of OGT’s activity has been implicated in cancers and neurodegenerative diseases. OGT is unique in that it transfers a GlcNAc sugar from UDP‐GlcNAc to over 1,000 nuclear and cytoplasmic proteins in almost every cellular process. The mechanisms of nucleotide‐sugar binding and sugar transfer have been well characterized in human OGT. Secret Agent (SEC), an OGT structural homolog in Arabidopsis thaliana, also uses UDP‐GlcNAc as its sugar donor, but the mechanisms of nucleotide‐sugar binding and catalysis are not well characterized. We investigated how the SEC homolog selects UDP‐GlcNAc, looking particularly at the residues that are hypothesized to interact with the GlcNAc portion of UDP‐GlcNAc in OGT and drive deprotonation of protein substrates. However, it is unknown if the function of these residues is conserved in SEC. Active site residues in SEC corresponding to known essential residues in OGT were mutated using site‐directed mutagenesis and expressed and purified from E. coli. Their catalytic activities were analyzed using glycosyltransferase activity assays and compared to the wildtype enzyme. These mutations led to lower relative activity, similar to OGT studies, suggesting that the binding and orientation mechanism of UDP‐GlcNAc required for sugar transfer is conserved between SEC and OGT.

Disease Burden Affects Aging Brain Function.

Most older adults live with multiple chronic disease conditions, yet the effect of multiple diseases on brain function remains unclear. We examine the relationship between disease multimorbidity and brain activity using regional cerebral blood flow (rCBF) 15O-water PET scans from 97 cognitively normal participants (mean baseline age 76.5) in the Baltimore Longitudinal Study of Aging (BLSA). Multimorbidity index scores, generated from the presence of 13 health conditions, were correlated with PET data at baseline and in longitudinal change (n = 74) over 5.05 (2.74 SD) years. At baseline, voxel-based analysis showed that higher multimorbidity scores were associated with lower relative activity in orbitofrontal, superior frontal, temporal pole and parahippocampal regions, and greater activity in lateral temporal, occipital, and cerebellar regions. Examination of the individual health conditions comprising the index score showed hypertension and chronic kidney disease individually contributed to the overall multimorbidity pattern of altered activity. Longitudinally, both increases and decreases in activity were seen in relation to increasing multimorbidity over time. These associations were identified in orbitofrontal, lateral temporal, brainstem, and cerebellar areas. Together, these results show that greater multimorbidity is associated with widespread areas of altered brain activity, supporting a link between health and changes in aging brain function.

Tectonic activity level evaluation using geomorphic indices in the Shekarab Mountains, Eastern Iran

In order to evaluate the level of tectonic activities in the Shekarab Mountains, several geomorphic indices such as stream length gradient index (SL), valley floor width to valley height ratio (Vf), hypsometric curve (Hc), hypsometric integral (Hi), drainage basin shape (Bs), and relative tectonic activity (Iat) were calculated. Vf values show fastest uplift, deepest valleys, and highest river incision are associated with the basin 24. The high values of SL in the range of 900 to 3250 on the high resistance rocks related to the western basins indicate that the western part of the Shekarab Mountains has had recent tectonic activities. Moreover, distribution of high Hc and Hi values are related to the highest tectonic activity in the western and northeastern basins. Accordingly, the study area was divided into four subareas based on Iat values, which are the following: class 1, very high relative tectonic activity (10.17%); class 2, high relative tectonic activity (11.77%); class 3, moderate relative tectonic activity (29.96%); and class 4, low relative tectonic activity (48.10%). It can be concluded from the Iat values that different parts of the study area had undergone unequal uplift and tectonic activities in the NE-SW direction are showing the highest uplift rate, which is in consistency with the present time compression direction in the Shekarab Mountains.

A Micrometeorological Analysis of the Vento Norte Phenomenon in Southern Brazil

A sonic anemometer is employed to investigate turbulent statistical characteristics and meteorological properties associated with a local windstorm known as the Vento Norte (Portuguese for north wind), which is observed in central Rio Grande do Sul state situated in southern Brazil. The Vento Norte consists of persistent and warm northerly gusts of moderate to strong magnitude that occur just downstream from a modest zonally-oriented downslope. This flow, which generates a shear-dominated atmospheric boundary layer, is investigated through analysis of turbulent properties of the velocity components and temperature measured over two years from a meteorological tower. The overall micrometeorological analysis highlights the influence of the Vento Norte phenomenon on the daily cycle of turbulent energy and fluxes and on the surface energy budget. A more detailed investigation of Vento Norte characteristics is performed by analyzing an extended Vento Norte event that lasted for approximately 35 h. In this episode, a strong increase in turbulence activity is observed on the vertical velocity component and in the absolute turbulent heat flux, as well as a reduction in the relative humidity. Further, the cospectra of the heat-flux wavelet suggest that the Vento Norte flow perturbs the boundary-layer turbulence in both daytime and night-time conditions. The surface energy budget shows a positive night-time soil heat flux and an enhanced positive latent heat flux, induced by the low relative humidity and intense turbulent activity during the Vento Norte event. The onset and demise of the Vento Norte event are characterized by sub-mesoscale activity in the velocity components and temperature field.

Μorphometric Analysis for the Assessment of Relative Tectonic Activity in Evia Island, Greece

The aim of this study is to evaluate the relative tectonic activity in the north part of the Evia Island, located in Central Greece, and to investigate the contribution of neotectonic processes in the development of the fluvial landscape. Five morphometric parameters, including Drainage Basin Slope (Sb), Hypsometric Integral (Hi), Asymmetry Factor (Af), Relief Ratio (Rh), and Melton’s Ruggedness Number (M), were estimated for a total of 189 drainage basins. The catchments were classified into two groups, according to the estimated values of each morphometric parameter, and maps showing their spatial distribution were produced. The combination of the calculated morphometric parameters led to a new single integrated Index of relative tectonic activity (named Irta). Following this indexing, the basins were characterized as of low, moderate, or high relative tectonic activity. The quantitative analysis showed that the development of the present drainage systems and the geometry of the basins of the study area have been influenced by the tectonic uplift caused by the activity of two NW-SE trending offshore active normal fault systems: the north Gulf of Evia fault zone (Kandili-Telethrion) and the Aegean Sea fault zone (Dirfis), respectively. The spatial distribution of the values of the new integrated index Irta showed significant differences among the drainage basins that reflect differences in relative tectonic activity related to their location with regard to the normal fault systems of the study area.

Role of Peptidases of the Enteric Microbiota and Prey in Temperature Adaptations of the Digestive System in Boreal Carnivorous Fish

For the first time the activity of casein-lytic and hemoglobin-lytic peptidases of intestinal mucosa, chyme and enteric microflora of carnivorous boreal fish (pike, zander, burbot, perch) was investigated across a wide temperature range (0–70°С) to reveal the role of the enzymes of the enteric microbiota and the prey in the temperature adaptations of the digestive system of these fish. It was shown that in summer at 0°С, the relative activity of peptidases of intestinal mucosa (less than 20%) is usually considerably less than that of chyme and enteric microflora peptidases (up to 40% of maximal activity). In winter, on the background of low relative activity of mucosa and enteric microbiota peptidases at 0°C revealed a high level of the relative activity of burbot and pike chyme peptidases (45 and 80% of maximal activity). The role of enteric microbiota and prey peptidases in digestive system adaptations of piscivorous fish to low temperatures is discussed.

Effect of Roundup Herbicide on the Temperature Characteristics of Maltase of the Intestinal Mucosa in Juvenile Fish

The in vitro effect of Roundup herbicide at a concentration of 25 μg/L on the activity and temperature characteristics (temperature dependence, activation energy Eact, and Q10 temperature coefficient) of maltase in the intestinal mucosa of the juvenile sander, perch, roach, and common carp has been studied. The magnitude and direction of the effect depends on the fish species and the incubation temperature. Roundup does not affect the temperature optimum for maltase (60°C for perch and sander; 50°C for roach and carp). The lower relative activity of the enzyme in the temperature range of 0–30°C indicates a decrease in the efficiency of maltose hydrolysis, while lower Eact values indicate adaptive changes in this parameter in the presence of Roundup.

Morphotectonic analysis of the East Anatolian Fault, Turkey

The East Anatolian Fault (EAF) is a morphologically distinct and seismically active left-lateral strike-slip fault that extends for ~400 km and forms the Arabian/Anatolian plate boundary in southeastern Turkey. The EAF together with its conjugate fault, the North Anatolian Fault, help accommodate the westward escape of the Anatolian plate from the Arabian/Eurasian collision zone. Morphotectonic features along the EAF provide insights into the nature of landscape development and aid in understanding variations in tectonic activity and fault evolution. Several geomorphic indices, namely stream length-gradient index, mountain-front sinuosity, valley width to valley height ratio, basin asymmetry factor, and drainage density, and hypsometric analysis were examined using digital elevation models. The EAF can be divided into five segments based on its tectonic geomorphology. The stream length-gradient index values are between 50 and 350 along the five segments. Mountain-front sinuosity varies from 1.01 to 1.46 on the five segments. The mean ratio of valley floor width to valley height along the studied segments ranges from 0.11 to 1.32, which is well correlated with the mountain-front sinuosity values. Basin asymmetry factors for 18 catchments range from 1.88 to 26.25 along the study fault zone. Drainage density values for the studied catchments range from 3.5 to 5.6. Finally, the hypsometric analysis index of the 18 catchments indicates high, intermediate, and low relative tectonic activity. The results show that all geomorphic indices are remarkably uniform along the entire length of the fault, thus indicating that fault development was essentially coeval along its length, which supports the view that the present-day Arabian/Anatolian plate boundary (delimited by the EAF) jumped eastwards from the Malatya-Ovacık Fault at ~3 Ma. This is in good agreement with the nearly uniform geological offsets and the GPS-determined present-day slip rate of ~10 mm/year along the entire fault.

Molecular mechanisms of missense mutations that generate ectopic N-glycosylation sites in coagulation factor VIII.

N-glycosylation is a common posttranslational modification of secreted and membrane proteins, catalyzed by the two enzymatic isoforms of the oligosaccharyltransferase, STT3A and STT3B. Missense mutations are the most common mutations in inherited diseases; however, missense mutations that generate extra, non-native N-glycosylation sites have not been well characterized. Coagulation factor VIII (FVIII) contains five consensus N-glycosylation sites outside its functionally dispensable B domain. We developed a computer program that identified hemophilia A mutations in FVIII that can potentially create ectopic glycosylation sites. We determined that 18 of these ectopic sites indeed become N-glycosylated. These sites span the domains of FVIII and are primarily associated with a severe disease phenotype. Using STT3A and STT3B knockout cells, we determined that ectopic glycosylation exhibited different degrees of dependence on STT3A and STT3B. By separating the effects of ectopic N-glycosylation from those due to underlying amino acid changes, we showed that ectopic glycans promote the secretion of some mutants, but impair the secretion of others. However, ectopic glycans that enhanced secretion could not functionally replace a native N-glycan in the same domain. Secretion-deficient mutants, but not mutants with elevated secretion levels, show increased association with the endoplasmic reticulum chaperones BiP (immunoglobulin heavy chain-binding protein) and calreticulin. Though secreted to different extents, all studied mutants exhibited lower relative activity than wild-type FVIII. Our results reveal differential impacts of ectopic N-glycosylation on FVIII folding, trafficking and activity, which highlight complex disease-causing mechanisms of FVIII missense mutations. Our findings are relevant to other secreted and membrane proteins with mutations that generate ectopic N-glycans.

Effects of temperature on extracellular hydrolase enzymes from soil microfungi

Soil microbes play important roles in global carbon and nutrient cycling. Soil microfungi are generally amongst the most important contributors. They produce various extracellular hydrolase enzymes that break down the complex organic molecules in the soil into simpler form. In this study, we investigated patterns of amylase and cellulase (which are responsible for breaking down starch and cellulose, respectively) relative activity (RA) on solid media at different culture temperatures in fungal strains from Arctic, Antarctic and tropical soils. Fungal isolates from all three regions were inoculated onto R2A media supplemented with starch for amylase and carboxymethylcellulose and trypan blue for cellulase screening. The isolates were then incubated at 4, 10, 15, 20, 25, 30, 35 and 40 °C and examined for activity after 5 and 10 days, for tropical and polar isolates, respectively. The data obtained indicate that the polar fungal strains exhibited similar patterns of amylase and cellulase RA. Both Arctic and Antarctic fungi showed highest RA for amylase and cellulase at 35 °C, while colony growth was maximised at 15 °C. Colony growth and RA of the polar isolates were negatively correlated suggesting that, as temperatures increase, the cells become stressed and have fewer resources available to invest in growth. Unlike polar isolates, tropical isolates did not exhibit any trend of colony growth with temperature, rather having idiosyncratic patterns in each isolate. The low enzyme production and RA levels in the tropical strains may suggest both a low ability to respond to temperature variation in their natural thermally stable tropical habitats, as well as a level of thermal stress limiting their enzyme production ability.

Avoidant Responses to Interpersonal Provocation Are Associated with Increased Amygdala and Decreased Mentalizing Network Activity.

When intentionally pushed or insulted, one can either flee from the provoker or retaliate. The implementation of such fight-or-flight decisions is a central aspect in the genesis and evolution of aggression episodes, yet it is usually investigated only indirectly or in nonsocial situations. In the present fMRI study, we aimed to distinguish brain regions associated with aggressive and avoidant responses to interpersonal provocation in humans. Participants (thirty-six healthy young women) could either avoid or face a highly (HP) and a lowly (LP) provoking opponent in a competitive reaction time task: the fight-or-escape (FOE) paradigm. Subjects avoided the HP more often, but retaliated when facing her. Moreover, they chose to fight the HP more quickly, and showed increased heart rate (HR) right before confronting her. Orbitofrontal cortex (OFC) and sensorimotor cortex were more active when participants decided to fight, whereas the mentalizing network was engaged when deciding to avoid. Importantly, avoiding the HP relative to the LP was associated with both higher activation in the right basolateral amygdala and lower relative activity in several mentalizing regions [e.g., medial and inferior frontal gyrus (IFG), temporal-parietal junction (TPJ)]. These results suggest that avoidant responses to provocation might result from heightened threat anticipation and are associated with reduced perspective taking. Furthermore, our study helps to reconcile conflicting findings on the role of the mentalizing network, the amygdala, and the OFC in aggression.

Active Tectonics of the Saymareh-Karkheh River Basin (Northwest of Persian Gulf, Iran)

Active tectonics is an indicator of recent movement of mountains and landscapes evolution for regions affected by current tectonic activity. The Saymareh-Karkheh river basin is located on the Zagros Mountain in the west Iran. The Zagros Mountain is an orogenic belt that is formed by the collision between the Eurasian and Arabian plates during Cenozoic. Active tectonics has analyzed by measurement of six geomorphic indices (hypsometric integral, basin asymmetry factor, basin shape, the stream length-gradient, mountain-front sinuosity and valley floor width-height ratio) which they combined to index of active tectonics (Iat). Based on values of this index, the Saymareh-Karkheh river basin was divided into high (Class 2, 18.8%), moderate (Class 3, 70.3%), and low (Class 4, 10.9%) relative tectonic activity parts. The above results confirm the usefulness of geomorphic analyses for regional assessment of active tectonics they are compatible with differential tectonic activity in the High Zagros and Zagros fold and thrust belt. Also, it was revealed that geomorphic indices and using of GIS technics are very useful to investigation of active tectonics in the mountain areas.

Caracterização eletroforética e bioquímica das esterases da abelha sem ferrão Tetragonisca weyrauchi (Hymenoptera, Apidae)

The meliponinae are important pollinators of plant species. T. weyrauchi has restricted distribution , is found only in northern Brazil . This study aimed to perform the electrophoretic characterization of esterases from T. weyrauchi and check the expression pattern of total proteins. Adult individuals were collected at the entrance of the nests located in Alto Paraiso, state of Rondonia, Brazil and stored at -20 °C. Individual extracts of head and thorax and abdomen of the workers were subjected to electrophoresis on 10% polyacrylamide gel and 5% stacking gel. Extracts from head and thorax of T. weyrauchi presented six esterase regions. In abdomen extracts it was only one esterase activity region, EST- 4. The heated samples to 52 °C and 54 °C decrease in the relative activity of esterases 1, 2, 3 and 4 and total degradation of esterases 5 and 6. At 58 °C only esterase 4 presented lower relative activity while the others were totally degraded. On the electrophoretic pattern of the proteins, 24 peptides detected, by molecular weight, their size ranged from 10 to 220 kDa. This study revealed , that number found for esterase species is greater than for other species of the same genus , as well as the number of proteins. The thermostability test showed resistance is associated with thermoregulatory capacity , an important characteristic because this species is found in regions with high temperatures.

GIS-Based analysis of relative tectonic activity along the kazerun fault zone, zagros mountains, iran: insights from data mining of Geomorphic Data

This paper tests a data mining method for evaluation of the “IRTA” (Index of Relative Tectonic Activity) to investigate the impact of active tectonics on geomorphic processes and landscape development. Based upon K-means clustering of six basin-related geomorphic indices (the hypsometric integral, basin asymmetric factor, drainage density, basin shape ratio, mean axial slope of the channel and topographic roughness) that represent the relative strength of active tectonic deformation on topography and morphology, the relative tectonic activity along the Kazerun Fault Zone in the Zagros Mountains of Iran may be classified into low, moderate and high relative tectonic activity zones. The results allow the identification of the clusters of similarly deformed areas related to relative tectonic activity. The utilization of geomorphic parameters as well as IRTA with comparison to the field observations exhibit change in relative tectonic activities mostly corresponding to the change in mechanism of the prominent fault zones in the study area.

A New Alkaliphilic Cold-Active Esterase from the Psychrophilic Marine Bacterium Rhodococcus sp.: Functional and Structural Studies and Biotechnological Potential

The special features of cold-adapted lipolytic biocatalysts have made their use possible in several industrial applications. In fact, cold-active enzymes are known to be able to catalyze reactions at low temperatures, avoiding side reactions taking place at higher temperatures and preserving the integrity of products. A lipolytic gene was isolated from the Arctic marine bacterium Rhodococcus sp. AW25M09 and expressed in Escherichia coli as inclusion bodies. The recombinant enzyme (hereafter called RhLip) showed interesting cold-active esterase activity. The refolded purified enzyme displayed optimal activity at 30 °C and was cold-active with retention of 50% activity at 10 °C. It is worth noting that the optimal pH was 11, and the low relative activity below pH 10 revealed that RhLip was an alkaliphilic esterase. The enzyme was active toward short-chain p-nitrophenyl esters (C2-C6), displaying optimal activity with the butyrate (C4) ester. In addition, the enzyme revealed a good organic solvent and salt tolerance. These features make this an interesting enzyme for exploitation in some industrial applications.

Preparation and properties of adsorption material from corn stalks core when used for enzyme immobilization and the subsequent activities of the adsorbed enzymes

This study investigates the characteristics of core adsorption material (CAM) prepared from corn stalks core (Core) by glycol solvent treatment (high pressure boiling at 120°C for 30min using a 50:3 liquor/solid ratio with 2%, w/w sodium hydroxide). The structures of CAM and Core were compared by FT-IR, SEM and XRD. Maltogenic amylase from Aspergillus awamori var., neutral proteins from Source Organism and lipase from Pseudomonas aeruginosa were selected as model enzymes in order to assess their potential applicability for enzyme immobilization. Adsorption characteristics for the different enzymes on CAM were studied and the activity of the immobilized enzymes was evaluated. The results show that CAM has many hydroxyl groups, more flakes, irregular indentations and grooves and a proportionally larger amount of hemi-cellulose than Core, which results in increased numbers of hydroxyl groups in CAM and increased enzyme accessibility into CAM; CAM has the greatest adsorption capacity (9.84±0.32mg/g) for neutral proteins and the best relative activity (total relative activity of 212.6% after being reused three times) after being immobilized, as well as the lowest adsorption capacity (5.15±0.51mg/g) for lipase and the lowest relative activity (total relative activity is 78.23%). The isotherms of maltogenic amylase and neutral proteinase were found to be linear using the Langmuir equation (R2=0.9974 and 0.9966, respectively, p<0.0001) and lipase was found to be linear using the Freundlich equation (R2=0.9331, p<0.0075) in the studied concentration range; CAM could adsorb neutral proteinase and could be used in the simple and inexpensive production of large quantities of pure industrial neutral proteinase and Core can be used to prepare CAM.

REM and NREM power spectral analysis on two consecutive nights in psychophysiological and paradoxical insomnia sufferers

The objectives of the study were to examine EEG activities using power spectral analysis (PSA) of good sleepers (GS), psychophysiological (PsyI) and paradoxical (ParI) insomnia sufferers on two consecutive nights. Participants completed three nights of PSG recordings in a sleep laboratory following a clinical evaluation. Participants were 26 PsyI, 20 ParI and 21 GS (mean age=40years, SD=9.4). All sleep cycles of Nights 2 and 3 were retained for PSA. The absolute and relative activity in frequency bands (0.00 to 125.00Hz) were computed at multiple frontal, central and parietal sites in REM and NREM sleep. Mixed model ANOVAs were performed with absolute and relative PSA data to assess differences between groups and nights. Over the course of the two nights, more absolute delta activity at F3, C3, and P3 was observed in ParI compared with PsyI suggesting deactivation of the left hemisphere in ParI and/or hyperactivation in PsyI. Further analysis on absolute PSA data revealed that differences between groups relate mostly to NREM. In REM, lower relative activity in slower frequency bands was found in ParI in comparison with GS and less relative theta activity was found in PsyI compared with GS implying higher activation in insomnia. In addition, between nights variability has been found in absolute powers of faster frequency bands (beta to omega). Signs of decreased cortical activity in absolute PSA in NREM combined with increased relative cortical activation in REM were found in ParI which might contribute to the misperception of sleep in ParI.

Dynamical stability of intrinsic connectivity networks

Functional connectivity MRI (fcMRI) has become a widely used technique in recent years for measuring the static correlation of activity between cortical regions. Using a publicly available resting state dataset (n = 961 subjects), we obtained high spatial-resolution maps of functional connectivity between a lattice of 7266 regions covering the gray matter. Average whole brain functional correlations were calculated, with high reproducibility within the dataset and across sites. Since correlation measures not only represent pairwise connectivity information, but also shared inputs from other brain regions, we approximate pairwise connection strength by representing each region as a linear combination of the others by performing a Cholesky decomposition of the pairwise correlation matrix. We then used this weighted connection strength between regions to iterate relative brain activity in discrete temporal steps, beginning both with random initial conditions, and with initial conditions reflecting intrinsic connectivity networks using each region as a seed. In whole brain simulations based on weighted connectivity from healthy adult subjects (mean age 27.3), there was consistent convergence to one of two inverted states, one representing high activity in the default mode network, the other representing low relative activity in the default mode network. Metastable intermediate states in our simulation corresponded to combinations of characterized functional networks. Convergence to a final state was slowest for initial conditions on the borders of the default mode network.