Changes In Coherence Research Articles

Changes in Cortical Coherence Supporting Complex Visual and Social Processing in Adolescence.

Despite our differences, there is much about the natural visual world that most observers perceive in common. Across adults, approximately 30% of the brain is activated in a consistent fashion while viewing naturalistic input. At what stage of development is this consistency of neural profile across individuals present? Here, we focused specifically on whether this mature profile is present in adolescence, a key developmental period that bridges childhood and adulthood, and in which new cognitive and social challenges are at play. We acquired fMRI data evoked by a movie shown twice to younger (9-14 years old) and older adolescents (15-19 years old) and to adults, and conducted three key analyses. First, we characterized the consistency of the neural response within individuals (across separate runs of the movie), then within individuals of the same age group, and, last, between age groups. The neural consistency within individuals was similar across age groups with reliable activation in largely overlapping but slightly different cortical regions. In contrast, somewhat differing regions exhibited higher within-age correlations in both groups of adolescents than in the adults. Last, across the whole cortex, we identified regions evincing different patterns of maturation across age. Together, these findings provide a fine-grained characterization of functional neural development in adolescence and uncover signatures of widespread change in cortical coherence that supports the emerging mature stereotypical responses to naturalistic stimuli. These results also offer a more nuanced account of development that obeys neither a rigid linear progression nor a large qualitative change over time.

Spatial Coherence of Speckle for Repeat-Pass Synthetic Aperture Sonar Micronavigation

Accurate positioning of autonomous underwater vehicles is a major challenge. The long-term drift is problematic if global position updates are not available, and for applications such as repeat-pass interferometry and coherent change detection, millimeter accuracy is needed. Repeat-pass synthetic aperture sonar (SAS) micronavigation is one potential technique for countering both challenges. While single-pass SAS micronavigation enabled successful coherent processing within one track, the potential is that repeat-pass SAS micronavigation can support coherent processing between passes. Both techniques are based on recognizing the speckle pattern in the seafloor return, but repeat-pass SAS micronavigation has additional challenges with the larger temporal and spatial separations between the observations. In this study, we investigate the spatial correlation of speckle as observed from SAS systems. We divide the different contributions to spatial decorrelation into three groups: 1) speckle decorrelation; 2) footprint mismatch; and 3) stretching. We examine each contribution separately and develop simplified formulas for their decorrelation baselines. When correlating synthetic aperture images, decorrelation from stretching dominates. When correlating single-element data recorded at low grazing angles common to SAS, speckle decorrelation dominates. We validate our findings on experimental data, and by combining elements into larger effective elements, we demonstrate increasing the across-track baseline for repeat-pass SAS micronavigation updates from less than 1 to 10 m.

Cross‐ Coherence of the Outer Radiation Belt During Storms and the Role of the Plasmapause

AbstractThe high energy electron population in Earth's outer radiation belt is extremely variable, changing by multiple orders of magnitude on timescales that vary from under an hour to several weeks. These changes are typically linked to geomagnetic activity such as storms and substorms. In this study, we seek to understand how coherent changes in the radiation belt are across all radial distances, in order to provide a spatial insight into apparent global variations. We do this by calculating the correlation between fluxes on differentmeasured by the PET instrument aboard the SAMPEX spacecraft for times associated with 15 large storms. Our results show that during these times, variations in the0.63 MeV electron flux are coherent outside the minimum plasmapause location and also coherent inside the minimum plasmapause location, when flux is present. However, variations in the electron fluxes inside the plasmapause show little correlation with those outside the plasmapause. During storm recovery and possibly main phases, flux variations are coherent across allregardless of plasmapause location, due to a rapid decrease, followed by an increase in radiation belt fluxes across all.

Changes in Electrical Brain Activity Due to tDCS in Post-Stroke Chronic Aphasia: a Double-Blind Randomized Controlled Study

<h3>Research Objectives</h3> To better understand changes in brain activity related to transcranial direct current stimulation (tDCS) in post-stroke chronic aphasia. <h3>Design</h3> Double-blind randomized placebo controlled study design. <h3>Setting</h3> Casa Colina Research Institute. <h3>Participants</h3> Forty three post-stroke outpatients with chronic aphasia (32 males; age: 61±13y; 0.9-18years post-injury; 32 ischemic stroke; 19 non-fluent aphasia). Twenty patients were in the tDCS group. <h3>Interventions</h3> Participants were randomly assigned either to the tDCS group (cathode on Broca, left side) or to the sham/placebo group. Both groups had five consecutive days of 20 minutes session, using a FDA approved tDCS device (soterixmedical.com). Resting state electrophysiological recordings (5 minutes) and behavioral assessments were performed the week before/after tDCS/sham intervention. <h3>Main Outcome Measures</h3> 1) EEG data: power spectrum as well as coherence in delta, theta, alpha and beta frequencies in fronto-temporal electrodes; 2) Behavioral data: the Western Aphasia Battery-Revised (WAB-R total scores and subscores). <h3>Results</h3> For the behavioral data, groups differed, pre/post intervention, on the WAB-R total score (F=5.22; p=0.028) as well as for the Auditory-Verbal Comprehension (F=4.657; p=0.038) and Repetition (F=4.56; p=0.04) subscores. For the EEG, groups also differed, pre/post intervention, when looking at changes in coherence between Broca and Wernicke on the contralateral side (F8T4, alpha and beta) as well as between Broca area on bilateral sides (F7F8, beta) and other fronto-temporal electrodes (F3T3, beta; FzT5, alpha; F4T5, beta). Post-hoc analyses revealed a significant increase in coherence for the tDCS group (but not for the sham group) for the following electrodes: F8T4 (alpha), F3T3 (beta) and F4T5 (beta). <h3>Conclusions</h3> In this double-blind randomized placebo controlled trial, our findings show a higher improvement in language functions (for both receptive and expressive language skills) in response to treatment as compared to sham. These improvements seem related to an increase in coherence not only in ipsilateral but also contralateral fronto-temporal electrodes, suggesting a higher functional connectivity within the language network due to tDCS in post-stroke chronic aphasia. <h3>Author(s) Disclosures</h3> The authors have nothing to declare.

Phase-Based GLRT Detection of Moving Targets with Pixel Tracking in Low-Resolution SAR Image Sequences

Spaceborne synthetic aperture radar (SAR) can provide ground area monitoring with large coverage. However, achieving a wide observation scope comes at the cost of resolution reduction owing to the trade-off between these parameters in conventional SAR. In low-resolution imaging, the moving target appears unresolved, weakly scattered, and slow moving in the image sequence, which can be generated by the subaperture technique. This article proposes a novel moving target detection method. First, interferometric phase statistics are combined with the generalized likelihood ratio test detector. A pixel tracking strategy is further exploited to determine whether a motion signal is present. These methods rely on the approximation of both clutter and noise statistics using Gaussian distributions in a low-resolution scenario. In addition, the motion signals are imaged with a subpixel offset. The proposed method is primarily validated using four real image sequences from TerraSAR-X data, which represent two types of homogeneous areas. The results reveal that moving targets can be detected in nearby areas using this strategy. The method is compared with the stack averaged coherence change detection and particle-filter-based tracking strategies.

Different binaural processing of the envelope component and the temporal fine structure component of a narrowband noise in rat inferior colliculus

Complex broadband sounds are decomposed by peripheral auditory filters into a series of relatively narrowband signals, each with a slowly varying envelope (ENV) and a rapidly fluctuating temporal fine structure (TFS). ENV and TFS information at the bilateral ears contribute differentially to auditory perception. However, whether the difference could attribute to mechanisms of binaural integration remains an open question. As a potential neural correlate, subsets of neurons in the central nucleus of the inferior colliculus (ICC) are known to integrate binaural information with binaural inhibition or binaural summation. Therefore, we recorded the frequency-following responses (FFRs) to the ENV and TFS components of narrowband noises in the ICC of anesthetized rats and examined changes in FFR amplitude and stimulus-response coherence under various sound-delivery settings. We showed that binaural FFRENV was predominantly elicited by contralateral inputs and inhibited by ipsilateral inputs, exhibiting a “binaural-inhibition” like property. On the other hand, binaural FFRTFS received a balanced contribution from both sides, echoing the “binaural-summation” mechanism. What is more, binaural FFRENV was significantly correlated with contralateral-evoked but not ipsilateral-evoked FFRENV, while binaural FFRTFS correlated with both contralateral- and ipsilateral-evoked FFRTFS. Overall, these results suggest distinct binaural processing of ENV and TFS information at the midbrain level.

Multidecadal variability of the Tonle Sap Lake flood pulse regime

AbstractTonle Sap Lake (TSL) is one of the world's most productive lacustrine ecosystems, driven by the Mekong River's seasonal flood pulse. This flood pulse and its long‐term dynamics under the Mekong River basin's (MRB) fast socio‐economic development and climate change need to be identified and understood. However, existing studies fall short of sufficient time coverage or concentrate only on changes in water level (WL) that is only one of the critical flood pulse parameters influencing the flood pulse ecosystem productivity. Considering the rapidly changing hydroclimatic conditions in the Mekong basin, it is crucial to systematically analyse the changes in multiple key flood pulse parameters. Here, we aim to do that by using observed WL data for 1960–2019 accompanied with several parameters derived from a Digital Bathymetry Model. Results show significant declines of WL and inundation area from the late 1990s in the dry season and for the whole year, on top of increased subdecadal variability. Decreasing (increasing) probabilities of high (low) inundation area for 2000–2019 have been found, in comparison to the return period of inundation area for 1986–2000 (1960–1986). The mean seasonal cycle of daily WL in dry (wet) season for 2000–2019, compared to that for 1986–2000, has shifted by 10 (5) days. Significant correlations and coherence changes between the WL and large‐scale circulations (i.e., El Niño‐Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Indian Ocean Dipole (IOD)), indicate that the atmospheric circulations could have influenced the flood pulse in different time scales. Also, the changes in discharge at the Mekong mainstream suggest that anthropogenic drivers may have impacted the high water levels in the lake. Overall, our results indicate a declining flood pulse since the late 1990s.

Global and intertuberal epileptic networks in tuberous sclerosis based on stereoelectroencephalographic (sEEG) findings: a quantitative EEG analysis in pediatric subjects and surgical implications.

Recent evidence favors a network concept in tuberous sclerosis (TSC) with seizure generation and propagation related to changes in global and regional connectivity between multiple, anatomically distant tubers. Direct exploration of network dynamics in TSC has been made possible through intracranial sampling with stereoelectroencephalography (sEEG). The objective of this study is to define epileptic networks in TSC using quantitative analysis of sEEG recordings. We also discuss the impact of the definition of these epileptic networks on surgical decision-making. Intracranial sEEG recordings were obtained from four pediatric patients who presented with medically refractory epilepsy secondary to TSC and subjected to quantitative signal analysis methods. Cortical connectivity was quantified by calculating pairwise coherence between all contacts and constructing an association matrix. The global coherence, defined as the ratio of the largest eigenvalue to the sum of all the eigenvalues, was calculated for each frequency band (delta, theta, alpha, beta, gamma). Spatial distribution of the connectivity was identified by plotting the leading principal component (product of the largest eigenvalue and its corresponding eigenvector). Four pediatric subjects with TSC underwent invasive intracranial monitoring with sEEG, comprising 31 depth electrodes and 250 contacts, for localization of the epileptogenic focus and guidance of subsequent surgical intervention. Quantitative connectivity analysis revealed a change in global coherence during the ictal period in the beta/low gamma (14-30Hz) and high gamma (31-80Hz) bands. Our results corroborate findings from existing literature, which implicate higher frequencies as a driver of synchrony and desynchrony. Coordinated high-frequency activity in the beta/low gamma and high gamma bands among spatially distant sEEG define the ictal period in TSC. This time-dependent change in global coherence demonstrates evidence for intra-tuberal and inter-tuberal connectivity in TSC. This observation has surgical implications. It suggests that targeting multiple tubers has a higher chance of seizure control as there is a higher chance of disrupting the epileptic network. The use of laser interstitial thermal therapy (LITT) allowed us to target multiple disparately located tubers in a minimally invasive manner with good seizure control outcomes.

Projected Changes to Hydroclimate Seasonality in the Continental United States

AbstractFuture changes to the hydrological cycle are projected in a warming world, and any shifts in drought risk may prove extremely consequential for natural and human systems. In addition to long‐term moistening, drying, or warming trends, perturbations to the annual cycle of regional hydroclimate variables may also have substantial impacts. We analyze projected changes in several hydroclimate variables across the continental United States, along with shifts in the amplitude and phase of their annual cycles. We find that even in regions where no robust change in the annual mean is expected, coherent changes to the annual cycle are projected. In particular, we identify robust regional phase shifts toward earlier arrival of peak evaporation in the northern regions, and peak runoff and total soil moisture in the western regions. Changes in the amplitude of the annual cycle of total and surface soil moisture are also projected, and reflect changes to the annual cycle in surface water supply and demand. Whether changes become detectable above the background noise of internal variability depends strongly on the future scenario considered, and significant changes to the annual cycle are largely avoided in the lowest‐forcing scenario.

Individual Differences in Developmental Psychology Early Childhood Mentality

As long as human life is never static, from birth to death, humans always experience changes; these changes are known as two kinds of changes: growth, which is increasing size and structure, and second, a development which means progressive, coherent, and orderly changes. Differences influence individual differences in early childhood mental development psychology in cognitive, language skills, motor skills, backgrounds, talents, and learning readiness. Parents who directly educate and shape children's social behavior early tend to continue to survive until the child reaches the next stage of development. Individual attitudes toward others and towards social activities are consistent at every age level. Individual development is a functional change that is qualitative, both from physical and mental functions, as a result of its association with environmental influences. Individual development is indicated by changes that are systematic, progressive, and continuous.

Period‐Lengthening of the Mindanao Current Variability From the Long‐Term Tide Gauge Sea Level Measurements

AbstractLong‐term tide gauge sea level data from 1969 to 2014 at Davao (7.08°N, 125.63°E) and Malakal (7. 33°N, 134.46°E) are analyzed to examine the decadal frequency modulations embedded in the Mindanao Current (MC) variability. The MC variability inferred from the Davao–Malakal sea level was predominantly biennial in the 1970s. This prevailing period switched to interannual in the 1980s and lengthened to decadal during the last two decades. With the aid of the basin‐scale sea level information from satellite altimeter measurements, it is found that the sea level‐inferred MC variability represents the coherent changes of the wind‐driven tropical gyre in the western North Pacific. An investigation into the long‐term wind stress curl data reveals that its prevailing period underwent similar biennial→interannual→decadal transitions in the western tropical Pacific, implying the forced nature of the period‐lengthening of the MC variability during the past half‐a‐century. While the sign of the MC variability is largely determined by the Malakal sea level signals on the interannual and decadal time scales, the Davao sea level change becomes important when the time scale extends to multi‐decades.

Alpha oscillations modulate premotor-cerebellar connectivity in motor learning: Insights from transcranial alternating current stimulation

Alpha oscillations (8-13 Hz) have been suggested to play an important role in dynamic neural processes underlying learning and memory. The goal of this study was to scrutinize the role of alpha oscillations in communication within a cortico-cerebellar network implicated in motor sequence learning. To this end, we conducted two EEG experiments using a serial reaction time task. In the first experiment, we explored changes in alpha power and cross-channel alpha coherence as subjects learned a motor sequence. We found a gradual decrease in spectral alpha power over left premotor cortex (PMC) and sensorimotor cortex (SM1) during learning blocks. In addition, alpha coherence between left PMC/SM1 and left cerebellar crus I was specifically decreased during sequence learning, possibly reflecting a functional decoupling in the broader motor learning network. In the second experiment in a different cohort, we applied 10Hz transcranial alternating current stimulation (tACS), a method shown to entrain local oscillatory activity, to left M1 (lM1) and right cerebellum (rCB) during sequence learning. We observed a tendency for diminished learning following rCB tACS compared to sham, but not following lM1 tACS. Learning-related alpha power following rCB tACS was increased in left PMC, possibly reflecting increase in local inhibitory neural activity. Importantly, learning-specific alpha coherence between left PMC and right cerebellar lobule VIIb was enhanced following rCB tACS. These findings provide strong evidence for a causal role of alpha oscillations in controlling information transfer in a premotor-cerebellar loop during motor sequence learning. Our findings are consistent with a model in which sequence learning may be impaired by enhancing premotor cortical alpha oscillation via external modulation of cerebellar oscillations.

Resting State EEG Related to Mathematical Improvement After Spatial Training in Children.

Spatial cognitive abilities, including mental rotation (MR) and visuo-spatial working memory (vsWM) are correlated with mathematical performance, and several studies have shown that training of these abilities can enhance mathematical performance. Here, we investigated the behavioral and neural correlates of MR and vsWM training combined with number line (NL) training. Fifty-seven children, aged 6–7, performed 25 days of NL training combined with either vsWM or MR and participated in an Electroencephalography (EEG)-session in school to measure resting state activity and steady-state visual evoked potentials during a vsWM task before and after training. Fifty children, aged 6–7, received usual teaching and acted as a control group. Compared to the control group, both training groups improved on a combined measure of mathematics. Cognitive improvement was specific to the training. Significant pre-post changes in resting state-EEG (rs-EEG), common to both training groups, were found for power as well as for coherence, with no significant differences in rs-EEG-changes between the vsWM and MR groups. Two of the common rs-EEG changes were correlated with mathematical improvement: (1) an increase in coherence between the central frontal lobe and the right parietal lobe in frequencies ranging from 16 to 25 Hz, and (2) an increase in coherence between the left frontal lobe and the right parietal lobe ranging from 23 to 25 Hz. These results indicate that changes in fronto-parietal coherence are related to an increase in mathematical performance, which thus might be a useful measure in further investigations of mathematical interventions in children.

Coeval Drying Across the Central Tropical Pacific Over the Last Millennium

AbstractHydroclimatic variability in the tropical Pacific reflects large‐scale ocean‐atmosphere processes that imprint on global climate, but tropical Pacific hydroclimate variability over the last millennium remains uncertain. Here we present a multi‐proxy reconstruction from a lacustrine sediment record on Kiritimati Atoll that spans the last millennium. A lake salinity reconstruction from the δ2H values of total lipid extracts, combined with changes in sediment mineralogy and the stable isotopic composition of inorganic carbonates, indicate the presence of several distinct hydrologic regimes on Kiritimati, including a period of persistent aridity from 960–1030 CE, shorter episodes of aridity from 1030–1370 CE, and extreme aridity throughout the latter half of the last millennium, from 1370–1970 CE, that drove complete evaporation of the lake. A period of wetter, variable conditions defines recent decades. Compound‐specific lipid biomarker δ2H values indicate that shifts in microbial community structure occurred in the past, from a community dominated by photoautotrophic and chemoautotrophic organisms in more arid periods to a more metabolically diverse community in the recent period. Comparison of this record with nearby sediment records from Washington Island reveals a similar pattern of aridity through the last millennium, followed by wetter conditions in the modern period. These coherent changes in hydroclimate in the central Pacific are inconsistent with a migration of the Pacific Intertropical Convergence Zone within these latitudes. Rather, past aridity was caused by reduced El Niño‐Southern Oscillation variability, observed through the low‐pass filter of lacustrine records, or by multidecadal to multi‐century strengthening of the Pacific Walker Circulation.

Normalized class coherence change-based [formula omitted]NN for classification of imbalanced data

kNN is a widely used machine learning algorithm in many different domains because of its fairly good performance in actual cases and its simplicity. This study aims to enhance the performance of kNN for imbalanced datasets, a topic that has been relatively ignored in kNN research. The proposed kNN algorithm, called normalized class coherence change-based k-nearest neighbor (NCC-NN) algorithm, determines the label of a test sample by computing the normalized class coherence changes at class and sample levels for every possible class and assigning the sample to the class with the maximum value. It considers the tendency that the minority classes usually show the lower-class coherence than the majority class. NCC-kNN also utilizes the adaptive k for the class coherence, which is calculated in a weighted manner to reduce the sensitivity to the selection of k. NCC-kNN was applied to 20 benchmark datasets with varying class imbalance and coherence, and its performance was compared with that of five kNN algorithms, SMOTE and MetaCost with standard kNN as a base classifier. The proposed NCC-kNN outperformed the other kNN algorithms in classification of imbalanced data, especially for imbalanced data with low positive class coherence.

Brain connectivity alterations during sleep by closed-loop transcranial neurostimulation predict metamemory sensitivity.

Metamemory involves the ability to correctly judge the accuracy of our memories. The retrieval of memories can be improved using transcranial electrical stimulation (tES) during sleep, but evidence for improvements to metamemory sensitivity is limited. Applying tES can enhance sleep-dependent memory consolidation, which along with metamemory requires the coordination of activity across distributed neural systems, suggesting that examining functional connectivity is important for understanding these processes. Nevertheless, little research has examined how functional connectivity modulations relate to overnight changes in metamemory sensitivity. Here, we developed a closed-loop short-duration tES method, time-locked to up-states of ongoing slow-wave oscillations, to cue specific memory replays in humans. We measured electroencephalographic (EEG) coherence changes following stimulation pulses, and characterized network alterations with graph theoretic metrics. Using machine learning techniques, we show that pulsed tES elicited network changes in multiple frequency bands, including increased connectivity in the theta band and increased efficiency in the spindle band. Additionally, stimulation-induced changes in beta-band path length were predictive of overnight changes in metamemory sensitivity. These findings add new insights into the growing literature investigating increases in memory performance through brain stimulation during sleep, and highlight the importance of examining functional connectivity to explain its effects.

Quantum coherence and ground-state phase transition in a four-chain Bose–Hubbard model

We study the quantum coherence and ground-state phase transition of a four-chain Bose–Hubbard model with the long-range interaction. In a special four-chain Bose–Hubbard model, i.e., each chain only has one optical potential, four types of the ground-state phases are discovered. The effects of the disorder, the on-site interaction and the long-range interaction on the quantum coherence are studied. For the system without the long-range interaction, the quantum coherence changes from one periodic oscillation to two periodic oscillations as the on-site interaction increases. By considering the long-range interaction, the quantum coherence goes back to one periodic oscillation again. The on-site interaction itself suppresses the quantum coherence, both the on-site interaction and long-range interaction together enhance the quantum coherence with the weak disorder. If the disorder strength is increased beyond a critical value, they start to suppress the quantum coherence. In a regular four-chain Bose–Hubbard model, i.e., each chain has many optical potentials, the ground-state phase transitions are obtained by using the cluster Gutzwiller mean-field method. Exotic ground-state phases are found, i.e., superfluid phase, integer Mott insulator phase, supersolid phase and loophole insulator phase. The combination of the loophole insulator phase and the supersolid phase expands the lobes with the half-integer filling per site for the small ratio β = t ∥/t ⊥.

Virtual Reality-Guided Meditation for Chronic Pain in Patients With Cancer: Exploratory Analysis of Electroencephalograph Activity.

Mindfulness-based stress reduction has demonstrated some efficacy for chronic pain management. More recently, virtual reality (VR)-guided meditation has been used to assist mindfulness-based stress reduction. Although studies have also found electroencephalograph (EEG) changes in the brain during mindfulness meditation practices, such changes have not been demonstrated during VR-guided meditation. This exploratory study is designed to explore the potential for recording and analyzing EEG during VR experiences in terms of the power of EEG waveforms, topographic mapping, and coherence. We examine how these measures changed during a VR-guided meditation experience in participants with cancer-related chronic pain. A total of 10 adult patients with chronic cancer pain underwent a VR-guided meditation experience while EEG signals were recorded during the session using a BioSemi ActiveTwo system (64 channels, standard 10-20 configuration). The EEG recording session consisted of an 8-minute resting condition (pre), a 30-minute sequence of 3 VR-guided meditation conditions (med), and a final rest condition (post). Power spectral density (PSD) was compared between each condition using a cluster-based permutation test and across conditions using multivariate analysis of variance. A topographic analysis, including coherence exploration, was performed. In addition, an exploratory repeated measures correlation was used to examine possible associations between pain scores and EEG signal power. The predominant pattern was for increased β and γ bandwidth power in the meditation condition (P<.025), compared with both the baseline and postexperience conditions. Increased power in the δ bandwidth was evident, although not statistically significant. The pre versus post comparison also showed changes in the θ and α bands (P=.02) located around the frontal, central, and parietal cortices. Across conditions, multivariate analysis of variance tests identified 4 clusters with significant (P<.05) PSD differences in the δ, θ, β, and γ bands located around the frontal, central, and parietal cortices. Topographically, 5 peak channels were identified: AF7, FP2, FC1, CP5, and P5, and verified the changes in power in the different brain regions. Coherence changes were observed primarily between the frontal, parietal, and occipital regions in the θ, α, and γ bands (P<.0025). No significant associations were observed between pain scores and EEG PSD. This study demonstrates the feasibility of EEG recording in exploring neurophysiological changes in brain activity during VR-guided meditation and its effect on pain reduction. These findings suggest that distinct altered neurophysiological brain signals are detectable during VR-guided meditation. However, these changes were not necessarily associated with pain. These exploratory findings may guide further studies to investigate the highlighted regions and EEG bands with respect to VR-guided meditation. ClinicalTrials.gov NCT00102401; http://clinicaltrials.gov/ct2/show/NCT00102401.

Tracking spatial dynamics of functional connectivity during a task

Functional connectivity (FC) measured from functional magnetic resonance imaging (fMRI) provides a powerful tool to explore brain organization. Studies of the temporal dynamics of brain organization have shown a large temporal variability of the functional connectome, which may be associated with mental status transitions and/or adaptive process. Most dynamic studies, e.g. functional connectome and functional network connectivity (FNC), have focused on the macroscopic FC changes, i.e. the changes of temporal coherence across various brain network sources, nodes and/or regions of interest, where it is assumed within the network or node that the FC is static. In this paper, we develop a novel method to examine the spatial dynamics of FC, without the assumption of its intra-network stationarity. We applied our approach to fMRI data during an auditory oddball task (AOD) from twenty-two subjects, in an attempt to capture/validate the approach by evaluating whether spatial connectivity varies with task condition. The results showed that connectivity networks exhibit spatial variability over time, in addition to participating in conventional temporal dynamics, i.e. cross-network variability or dynamic functional network connectivity (dFNC). Furthermore, we studied the relationship of spatial dynamic in FC to cognitive processes, by performing a cluster analysis to evaluate an individual's functional correspondence towards the ‘target’ (oddball) detection from AOD task, and extracting cognitive task correspondence states as well as their dynamic FC spatial maps segregated by such states. We found a clear trend in different task-guided states, particularly, a prominent reduction of task stimulus synchrony state along with strong anticorrelation between default mode network (DMN) and cognitive attentional networks. We also observed an increasing occurrence of the task desynchrony state which showed an absence of DMN anticorrelation. The results highlight the impact of a well-studied cognitive task on the observed spatial dynamic structure. We also showed that the FC spatial dynamic pattern from our method largely corresponds to macroscopic dFNC patterns, but with more details and specifications over space, meanwhile the connectivity within the source itself provides novel information and varies over time. Overall, we demonstrate clear evidence of the presence of the (usually ignored) spatial dynamics of connectivity, its links to the task and implications of cognition/mental status.

Anomalous spatial coherence changes in radiation and scattering.

The superposition of two partially correlated waves is shown to produce fields with drastically altered coherence properties. It is demonstrated, both theoretically and experimentally, that two strongly correlated sources may generate a field with practically zero correlation between certain pairs of points. This anomalous change in coherence is a general phenomenon that takes place in all cases of wave superposition, including Mie scattering, as is shown. Our results are particularly relevant to applications in which it is assumed that highly coherent radiation maintains its spatial coherence on propagation, such as optical systems design and the imaging of extended sources.