Cohesive and coherent connected speech deficits in mild stroke

Spoken language production theories and lesion studies highlight several important prelinguistic conceptual preparation processes involved in the production of cohesive and coherent connected speech. Cohesion and coherence broadly connect sentences with preceding ideas and the overall topic. Broader cognitive mechanisms may mediate these processes. This study aims to investigate (1) whether stroke patients without aphasia exhibit impairments in cohesion and coherence in connected speech, and (2) the role of attention and executive functions in the production of connected speech. Eighteen stroke patients (8 right hemisphere stroke [RHS]; 6 left [LHS]) and 21 healthy controls completed two self-generated narrative tasks to elicit connected speech. A multi-level analysis of within and between-sentence processing ability was conducted. Cohesion and coherence impairments were found in the stroke group, particularly RHS patients, relative to controls. In the whole stroke group, better performance on the Hayling Test of executive function, which taps verbal initiation/suppression, was related to fewer propositional repetitions and global coherence errors. Better performance on attention tasks was related to fewer propositional repetitions, and decreased global coherence errors. In the RHS group, aspects of cohesive and coherent speech were associated with better performance on attention tasks. Better Hayling Test scores were related to more cohesive and coherent speech in RHS patients, and more coherent speech in LHS patients. Thus, we documented connected speech deficits in a heterogeneous stroke group without prominent aphasia. Our results suggest that broader cognitive processes may play a role in producing connected speech at the early conceptual preparation stage.

Building resilience with the Stress Resilience Training System: Design validation and applications

BACKGROUND

Resilience to stress is critical in today's military service. Past work has shown that experts handle stress in more productive ways compared to novices. Training that specifically addresses stress regulation, such as the Graduated Stress Exposure paradigm, can build individual and unit resilience as well as adaptability so that stressors trigger effective stress coping skills rather than stress injury.

OBJECTIVE

We developed the Stress Resilience Training System (SRTS), a product of Perceptronics Solutions Inc., to demonstrate that a software training app can provide an effective individualized method for mitigating the negative effects of situational and mission-related stress, at the same time eliciting potentially positive effects on performance.

METHODS

Seven separate evaluations including a usability study, controlled experiments, and field evaluations have been conducted to date.

RESULTS

These studies have shown that the SRTS program effectively engages users to manage their stress, effectively reduces stress symptoms, and improves job performance.

CONCLUSIONS

The SRTS system is a highly effective method for individualized training to inoculate professionals against the negative consequences of stress, while teaching them to harness its positive effects. SRTS is a technology that can be widely applied to many professions that are concerned with well-being. We discuss applications to law enforcement, athletics, personal fitness and healthcare in the Appendix.

Circadian-scale periodic bursts in theta and gamma-band coherence between hippocampus, cingulate and insular cortices

Previous studies have demonstrated that mean activity levels in the hippocampus oscillate on a circadian timescale, both at the single neuron and EEG level. This oscillation is also entrained by the availability of food, suggesting that the circadian modulation of hippocampal activity might comprise part of the recently discovered food-entrainable circadian oscillator (FEO). In order to determine whether the circadian oscillation in hippocampal activity is linked to activity in other brain regions, we recorded field-potential EEG from hippocampus and two cortical regions known to connect to hippocampus; the anterior cingulate cortex and the agranular insular cortex. These latter regions are involved in executive control (cingulate) and gustatory feedback (insula) and so are in a position where they could usefully contribute to, or benefit from, hippocampal memorial information in order to undertake task-related processing. We recorded EEG from these three regions for 20 m every hour for 58 consecutive hours in one continuous exposure to the recording environment. We found that there are regular and distinct increases in magnitude coherence between hippocampus and both cortical regions for EEG in both theta (6-12 Hz) and gamma (30-48 Hz) bands. These periods of increased coherence are spaced approximately one solar day apart, appear not to be specifically light-entrained, and are most apparent for gamma frequency activity. The gamma association between the two cortical regions shows the same temporal pattern of coherence peaks as the hippocampal-cortical coherences. We propose that these peaks in coherence represent the transient synchronization of temporally tagged memorial information between the hippocampus and other brain regions for which this information may be relevant. These findings suggest that the FEO involves coordinated activity across a number of brain regions and may underlie a mechanism via which an organism can store and recall salient gustatory events on a circadian timescale.

Coherent array of branched filamentary scales along the wing margin of a small moth

In butterflies and moths, the wing margins are fringed with specialized scales that are typically longer than common scales. In the hindwings of some small moths, the posterior margins are fringed with particularly long filamentary scales. Despite the small size of these moth wings, these scales are much longer than those of large moths and butterflies. In the current study, photography of the tethered flight of a small moth, Phthorimaea operculella, revealed a wide array composed of a large number of long filamentary scales. This array did not become disheveled in flight, maintaining a coherent sheet-like structure during wingbeat. Examination of the morphology of individual scales revealed that each filamentary scale consists of a proximal stalk and distal branches. Moreover, not only long scales but also shorter scales of various lengths were found to coexist in each small section of the wing margin. Scale branches were ubiquitously and densely distributed within the scale array to form a mesh-like architecture similar to a nonwoven fabric. We propose that possible mechanical interactions among branched filamentary scales, mediated by these branches, may contribute to maintaining a coherent sheet-like structure of the scale array during wingbeat.

A unique pattern of cortical connectivity characterizes patients with attention deficit disorders: a large electroencephalographic coherence study

BACKGROUND

Attentional disorders (ADD) feature decreased attention span, impulsivity, and over-activity interfering with successful lives. Childhood onset ADD frequently persists to adulthood. Etiology may be hereditary or disease associated. Prevalence is 5% but recognition may be 'overshadowed' by comorbidities (brain injury, mood disorder) thereby escaping formal recognition. Blinded diagnosis by MRI has failed. ADD may not itself manifest a single anatomical pattern of brain abnormality but may reflect multiple, unique responses to numerous and diverse etiologies. Alternatively, a stable ADD-specific brain pattern may be better detected by brain physiology. EEG coherence, measuring cortical connectivity, is used to explore this possibility.

METHODS

Participants: Ages 2 to 22 years; 347 ADD and 619 neurotypical controls (CON). Following artifact reduction, principal components analysis (PCA) identifies coherence factors with unique loading patterns. Discriminant function analysis (DFA) determines discrimination success differentiating ADD from CON. Split-half and jackknife analyses estimate prospective diagnostic success. Coherence factor loading constitutes an ADD-specific pattern or 'connectome'.  RESULTS: PCA identified 40 factors explaining 50% of total variance. DFA on CON versus ADD groups utilizing all factors was highly significant (p≤0.0001). ADD subjects were separated into medication and comorbidity subgroups. DFA (stepping allowed) based on CON versus ADD without comorbidities or medication treatment successfully classified the correspondingly held out ADD subjects in every instance. Ten randomly generated split-half replications of the entire population demonstrated high-average classification success for each of the left out test-sets (overall: CON, 83.65%; ADD, 90.07%). Higher success was obtained with more restricted age sub-samples using jackknifing: 2-8 year olds (CON, 90.0%; ADD, 90.6%); 8-14 year olds (CON, 96.8%; ADD 95.9%); and 14-20 year-olds (CON, 100.0%; ADD, 97.1%). The connectome manifested decreased and increased coherence. Patterns were complex and bi-hemispheric; typically reported front-back and left-right loading patterns were not observed. Subtemporal electrodes (seldom utilized) were prominently involved.  CONCLUSIONS: Results demonstrate a stable coherence connectome differentiating ADD from CON subjects including subgroups with and without comorbidities and/or medications. This functional 'connectome', constitutes a diagnostic ADD phenotype. Split-half replications support potential for EEG-based ADD diagnosis, with increased accuracy using limited age ranges. Repeated studies could assist recognition of physiological change from interventions (pharmacological, behavioral).

Increased long distance event-related gamma band connectivity in Alzheimer's disease

BACKGROUND

Brain oscillatory responses can be used for non-invasive analyses of cortico-cortical connectivity, local neuronal synchronization, and coherence of oscillations in many neuropsychiatric conditions including Alzheimer's disease (AD). In the present paper, we examine sensory-evoked and event-related gamma coherences elicited by visual stimuli in three sub-gamma bands in two sub-groups of patients with AD (i.e., acetylcholinesterase-inhibitor treated and untreated) and healthy controls.

METHODS

We studied a total of 39 patients with probable mild AD (according to NINCDS-ADRDA criteria) who had been sub-divided into untreated (n = 21) and treated (n = 18) (patients either on cholinergic monotherapy or combined therapy with memantine) AD groups, and 21 age-, gender-, and education-matched healthy elderly controls. A simple flash visual paradigm was applied for the acquisition of sensory-evoked coherences. Event-related coherences were elicited using a classical visual oddball paradigm. Both sensory-evoked and event-related gamma coherences were calculated for long-distance intrahemispheric pairs for three frequency ranges: 25-30 Hz, 30-35 Hz, and 40-48 Hz in post-stimulus 0-800 ms duration. The long-distance intrahemispheric pairs from both sides were fronto-parietal, fronto-temporal, fronto-temporoparietal, fronto-occipital, centro-occipital and parieto-occipital.

RESULTS

The sensory-evoked or event-related gamma coherences revealed that both treated and untreated AD patients had significantly increased values compared to healthy controls in all three sub-gamma bands. Moreover, the treated AD patients demonstrated significantly higher fronto-parietal gamma coherences during both sensory stimulation and oddball paradigm and lower occipito-parietal coherences during oddball paradigm in comparison to untreated AD patients.

CONCLUSION

The present study demonstrated that an increase of gamma coherences was present in response to both visual sensory and cognitive stimulation in AD patients in all gamma sub-bands. Therefore, gamma oscillatory activity seems to be fundamental in brain functions at both the sensory and cognitive levels. The increase of gamma coherence values was not due to cholinergic treatment to any significant extent, as both treated and untreated AD patients had increased gamma coherence values compared to healthy controls. The use of coherence values reflecting brain connectivity holds potential for neuroimaging of AD and understanding brain dynamics related to the effects of medication.

Functional interactions between the macaque dorsal and ventral visual pathways during three-dimensional object vision

The division of labor between the dorsal and the ventral visual stream in the primate brain has inspired numerous studies on the visual system in humans and in nonhuman primates. However, how and under which circumstances the two visual streams interact is still poorly understood. Here we review evidence from anatomy, modelling, electrophysiology, electrical microstimulation (EM), reversible inactivation and functional imaging in the macaque monkey aimed at clarifying at which levels in the hierarchy of visual areas the two streams interact, and what type of information might be exchanged between the two streams during three-dimensional (3D) object viewing. Neurons in both streams encode 3D structure from binocular disparity, synchronized activity between parietal and inferotemporal areas is present during 3D structure categorization, and clusters of 3D structure-selective neurons in parietal cortex are anatomically connected to ventral stream areas. In addition, caudal intraparietal cortex exerts a causal influence on 3D-structure related activations in more anterior parietal cortex and in inferotemporal cortex. Thus, both anatomical and functional evidence indicates that the dorsal and the ventral visual stream interact during 3D object viewing.

Conditional Spectral Analysis of Replicated Multiple Time Series with Application to Nocturnal Physiology

This article considers the problem of analyzing associations between power spectra of multiple time series and cross-sectional outcomes when data are observed from multiple subjects. The motivating application comes from sleep medicine, where researchers are able to non-invasively record physiological time series signals during sleep. The frequency patterns of these signals, which can be quantified through the power spectrum, contain interpretable information about biological processes. An important problem in sleep research is drawing connections between power spectra of time series signals and clinical characteristics; these connections are key to understanding biological pathways through which sleep affects, and can be treated to improve, health. Such analyses are challenging as they must overcome the complicated structure of a power spectrum from multiple time series as a complex positive-definite matrix-valued function. This article proposes a new approach to such analyses based on a tensor-product spline model of Cholesky components of outcome-dependent power spectra. The approach exibly models power spectra as nonparametric functions of frequency and outcome while preserving geometric constraints. Formulated in a fully Bayesian framework, a Whittle likelihood based Markov chain Monte Carlo (MCMC) algorithm is developed for automated model fitting and for conducting inference on associations between outcomes and spectral measures. The method is used to analyze data from a study of sleep in older adults and uncovers new insights into how stress and arousal are connected to the amount of time one spends in bed.

Intermittent bilateral coherence in physiological and essential hand tremor

OBJECTIVE

To investigate the prevalence and the temporal structure of bilateral coherence in physiological (PT) and essential (ET) hand tremor.

METHODS

Triaxial accelerometric recordings from both hands in 30 healthy subjects and 34 ET patients were analyzed using spectral coherence and wavelet coherence methods. In 12 additional healthy subjects, the relation between the hand tremor and the chest wall acceleration was evaluated using partial coherence analysis.

RESULTS

The majority of both PT and ET subjects displayed significant bilateral coherence. While in PT, bilateral coherence was most frequently found in resting hand position (97% of subjects), in ET the prevalence was comparable for resting (54%) and postural (49%-57%) positions. In both PT and ET, epochs of strong coherence lasting several to a dozen seconds were separated by intervals of insignificant coherence. In PT, bilateral coherence at the main tremor frequency (8-12Hz) was coupled with the ballistocardiac rhythm.

CONCLUSION

The oscillations of the two hands are intermittently synchronized in both PT and ET. We propose that in postural PT, bilateral coherence at the main tremor frequency arises from transient simultaneous entrainment of the left and right hand oscillations to ballistocardiac forcing.

SIGNIFICANCE

Bilateral coherence of hand kinematics provides a sensitive measure of synchronizing influences on the left and right tremor oscillators.

Spin polarisation with electron Bessel beams

The theoretical possibility to use an electron microscope as a spin polarizer is studied. It turns out that a Bessel beam passing a standard magnetic objective lens is intrinsically spin polarized when post-selected on-axis. In the limit of infinitely small detectors, the spin polarisation tends to 100%. Increasing the detector size, the polarisation decreases rapidly, dropping below 10^-4 for standard settings of medium voltage microscopes. For extremely low voltages, the Figure of Merit increases by two orders of magnitude, approaching that of existing Mott detectors. Our findings may lead to new desings of spin filters, an attractive option in view of its inherent combination with the electron microscope, especially at low voltage.

Individual difference in β-band corticomuscular coherence and its relation to force steadiness during isometric voluntary ankle dorsiflexion in healthy humans

OBJECTIVE

Magnitude of β-band coherent neural activities between the sensorimotor cortex and contracting muscle is known to vary across healthy individuals. To clarify how this variance affects actual motor function, this study examined associations between the corticomuscular coherence (CMC) and force steadiness.

METHODS

CMC was calculated between scalp electroencephalograms (EEGs) over the sensorimotor cortex and surface electromyograms (EMGs) from the tibialis anterior muscle during tonic isometric voluntary ankle dorsiflexion at 30% of maximal effort in 22 healthy individuals. We calculated the maximal peak of CMC (CMCmax), and examined its relations to some measures of force fluctuation, such as the coefficient of variation (ForceCV), the sum of the power spectral density within 1-4Hz (Forceδ-PSD), 5-14Hz (Forceα-PSD), and 15-35Hz (Forceβ-PSD) bands of force signal.

RESULTS

In all participants showing significant CMC, CMCmax was observed within the β-band. CMCmax was varied across participants (range, 0.084-0.451), and was correlated significantly and positively with ForceCV (r=0.602, p=0.003), Forceβ-PSD (r=0.637, p=0.001), Forceα-PSD (r=0.647, p=0.001), and Forceδ-PSD (r=0.518, p=0.014).

CONCLUSION

The magnitude of the CMC between EEG over the sensorimotor cortex and EMG of contracting muscle is associated with the amount of force fluctuation during tonic isometric voluntary ankle dorsiflexion in healthy humans.

SIGNIFICANCE

CMC may influence an individual's ability to stabilize their muscle force output.

Spatial coherence of electron beams from field emitters and its effect on the resolution of imaged objects

Sub-nanometer and nanometer-sized tips provide high coherence electron sources. Conventionally, the effective source size is estimated from the extent of the experimental biprism interference pattern created on the detector by applying the van Cittert Zernike theorem. Previously reported experimental intensity distributions on the detector exhibit Gaussian distribution and our simulations show that this is an indication that such electron sources must be at least partially coherent. This, in turn means that strictly speaking the Van Cittert Zernike theorem cannot be applied, since it assumes an incoherent source. The approach of applying the van Cittert Zernike theorem is examined in more detail by performing simulations of interference patterns for the electron sources of different size and different coherence length, evaluating the effective source size from the extent of the simulated interference pattern and comparing the obtained result with the pre-defined value. The intensity distribution of the source is assumed to be Gaussian distributed, as it is observed in experiments. The visibility or the contrast in the simulated holograms is found to be always less than 1 which agrees well with previously reported experimental results and thus can be explained solely by the Gaussian intensity distribution of the source. The effective source size estimated from the extent of the interference pattern turns out to be of about 2-3 times larger than the pre-defined size, but it is approximately equal to the intrinsic resolution of the imaging system. A simple formula for estimating the intrinsic resolution, which could be useful when employing nano-tips in in-line Gabor holography or point-projection microscopy, is provided.

Does the recent intensification of nationalistic and xenophobic attitudes in Eastern European countries adversely affect public mental health?

Background

The authors postulate that the recent intensification of the nationalist and xenophobic attitude in Poland and other Eastern European countries is detrimental to public mental health. The xenophobic attitude is accompanied by a higher incidence of anxiety and depression, disputes due to the polarization of opinions, a sense of embarrassment and a sense of contradictions with so-called Christian values, unfavorable demographic predictions and reduced life satisfaction.

Discussion

The authors attempt to describe the sequence of adverse events that led to the intensification of xenophobia and characterize the current state of public mental health in European countries. They formulate and propose possible actions which could counteract the consequences of that transformation.

Short conclusion

The actions which may be undertaken to counteract the deterioration of public mental health can be based on the recommendations of so-called ‘positive psychology’ and ‘positive psychiatry’ as well as the principles of strengthening local social capital.

Drawing Firmer Conclusions: Autistic Children Show No Evidence of a Local Processing Bias in a Controlled Copying Task

Drawing tasks are frequently used to test competing theories of visuospatial skills in autism. Yet, methodological differences between studies have led to inconsistent findings. To distinguish between accounts based on local bias or global deficit, we present a simple task that has previously revealed dissociable local/global impairments in neuropsychological patients. Autistic and typical children copied corner elements, arranged in a square configuration. Grouping cues were manipulated to test whether global properties affected the accuracy of reproduction. All children were similarly affected by these manipulations. There was no group difference in the reproduction of local elements, although global accuracy was negatively related to better local processing for autistic children. These data speak against influential theories of visuospatial differences in autism.

Electrical Activity of the Cerebral Cortex during the Low-Frequency Acoustic Stimulation in Women with Different Characteristics of Alpha Rhythm

BACKGROUND

Human functional capabilities, to a certain extent, depend on an individual's nervous system. The recording of the spontaneous electroencephalogram (EEG) makes it possible to estimate specific features of the nervous system, and in particular the activity of the human brain.

PURPOSE

This study is aimed at investigating the brain in women with a high or a low individual α-frequency (ІαF), determined in a quiescent state during low-frequency acoustic stimulation.

METHODS

The study group consisted of 113 right-handed healthy women in the age group 19-21 years. The study group was divided into 2 categories in terms of the average magnitude of ІαF - groups with high (n = 59, IαF ≥10.25 Hz) and low (n = 54, IαF ≤10.25 Hz) values of ІαF. The power and coherence of electrical activity of the cerebral cortex as well as the differences between the groups were evaluated in a quiescent state during low-frequency acoustic stimulation.

RESULTS

In case of low-frequency acoustic stimulation, a high rate of EEG θ-, β2-power, γ-waves in the cortex, α1-oscillations - in frontal areas were registered in women with a high α-frequency, while the power α2-, α3- and β1-activity became lower in the cortex. Women with a low α-frequency had a decrease of the cerebral cortex α-θ-, α- and β-activity. This was recorded as more generalized, and the expression of γ-waves was more localized. All the participants had increased values of coherence of the EEG frequency components in the cortex. Some overexertion on the right side was detected in the right hemisphere posterior structures. Some local reduction of the coherence of θ-, α1-, α3-oscillations was found in women with a high α-frequency and α1-activity among the study group members with a low α-frequency in the frontal and anterior temporal areas.

CONCLUSION

The establishment of common factors in the study group is an important step towards defining clear prognostic criteria for the physiological capabilities of people based on the congenital features of brain function.

Name recognition in autism: EEG evidence of altered patterns of brain activity and connectivity

BACKGROUND

Impaired orienting to social stimuli is one of the core early symptoms of autism spectrum disorder (ASD). However, in contrast to faces, name processing has rarely been studied in individuals with ASD. Here, we investigated brain activity and functional connectivity associated with recognition of names in the high-functioning ASD group and in the control group.

METHODS

EEG was recorded in 15 young males with ASD and 15 matched one-to-one control individuals. EEG data were analyzed with the event-related potential (ERP), event-related desynchronization and event-related synchronization (ERD/S), as well as coherence and direct transfer function (DTF) methods. Four categories of names were presented visually: one's own, close-other's, famous, and unknown.

RESULTS

Differences between the ASD and control groups were found for ERP, coherence, and DTF. In individuals with ASD, P300 (a positive ERP component) to own-name and to a close-other's name were similar whereas in control participants, P300 to own-name was enhanced when compared to all other names. Analysis of coherence and DTF revealed disruption of fronto-posterior task-related connectivity in individuals with ASD within the beta range frequencies. Moreover, DTF indicated the directionality of those impaired connections-they were going from parieto-occipital to frontal regions. DTF also showed inter-group differences in short-range connectivity: weaker connections within the frontal region and stronger connections within the occipital region in the ASD group in comparison to the control group.

CONCLUSIONS

Our findings suggest a lack of the self-preference effect and impaired functioning of the attentional network during recognition of visually presented names in individuals with ASD.

Name recognition in autism: EEG evidence of altered patterns of brain activity and connectivity

Background

Impaired orienting to social stimuli is one of the core early symptoms of autism spectrum disorder (ASD). However, in contrast to faces, name processing has rarely been studied in individuals with ASD. Here, we investigated brain activity and functional connectivity associated with recognition of names in the high-functioning ASD group and in the control group.

Methods

EEG was recorded in 15 young males with ASD and 15 matched one-to-one control individuals. EEG data were analyzed with the event-related potential (ERP), event-related desynchronization and event-related synchronization (ERD/S), as well as coherence and direct transfer function (DTF) methods. Four categories of names were presented visually: one’s own, close-other’s, famous, and unknown.

Results

Differences between the ASD and control groups were found for ERP, coherence, and DTF. In individuals with ASD, P300 (a positive ERP component) to own-name and to a close-other’s name were similar whereas in control participants, P300 to own-name was enhanced when compared to all other names. Analysis of coherence and DTF revealed disruption of fronto-posterior task-related connectivity in individuals with ASD within the beta range frequencies. Moreover, DTF indicated the directionality of those impaired connections—they were going from parieto-occipital to frontal regions. DTF also showed inter-group differences in short-range connectivity: weaker connections within the frontal region and stronger connections within the occipital region in the ASD group in comparison to the control group.

Conclusions

Our findings suggest a lack of the self-preference effect and impaired functioning of the attentional network during recognition of visually presented names in individuals with ASD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13229-016-0102-z) contains supplementary material, which is available to authorized users.

Quorum sensing: a quantum perspective

Quorum sensing is the efficient mode of communication in the bacterial world. After a lot of advancements in the classical theory of quorum sensing few basic questions of quorum sensing still remain unanswered. The sufficient progresses in quantum biology demands to explain these questions from the quantum perspective as non trivial quantum effects already have manifested in various biological processes like photosynthesis, magneto-reception etc. Therefore, it's the time to review the bacterial communications from the quantum view point. In this article we carefully accumulate the latest results and arguments to strengthen quantum biology through the addition of quorum sensing mechanism in the light of quantum mechanics.

Sequential designs for individualized dosing in phase I cancer clinical trials

This paper addresses dose finding in clinical trials where individuals exhibit biologic characteristics that alter the toxicity risks of the individuals. In these situations, instead of determining a dose that works for every patient, the trial aims to identify a dosing algorithm that prescribes dose according to the patient's biomarker or pharmacokinetic expression. Specifically, we aim to dose patients around a pre-specified level of area under the curve of irinotecan concentration using the patients' baseline phenotypes that predict drug clearance. We propose least squares recursion procedures to estimate the dosing algorithm sequentially with an aim to treat patients in the trial around the true unknown dosing algorithm, and introduce a novel application of an eigenvalue theory that guarantees convergence to the true dosing algorithms. Our simulation study demonstrates that using an eigenvalue constraint improves the efficiency of the recursion by as large as 40%, while concentrating in-trial patient allocation around the true dosing algorithm. We also provide practical guidance on design calibration, and design future irinotecan studies based on data from our first trial.

EEG slow waves in traumatic brain injury: Convergent findings in mouse and man

Objective

Evidence from previous studies suggests that greater sleep pressure, in the form of EEG-based slow waves, accumulates in specific brain regions that are more active during prior waking experience. We sought to quantify the number and coherence of EEG slow waves in subjects with mild traumatic brain injury (mTBI).

Methods

We developed a method to automatically detect individual slow waves in each EEG channel, and validated this method using simulated EEG data. We then used this method to quantify EEG-based slow waves during sleep and wake states in both mouse and human subjects with mTBI. A modified coherence index that accounts for information from multiple channels was calculated as a measure of slow wave synchrony.

Results

Brain-injured mice showed significantly higher theta:alpha amplitude ratios and significantly more slow waves during spontaneous wakefulness and during prolonged sleep deprivation, compared to sham-injured control mice. Human subjects with mTBI showed significantly higher theta:beta amplitude ratios and significantly more EEG slow waves while awake compared to age-matched control subjects. We then quantified the global coherence index of slow waves across several EEG channels in human subjects. Individuals with mTBI showed significantly less EEG global coherence compared to control subjects while awake, but not during sleep. EEG global coherence was significantly correlated with severity of post-concussive symptoms (as assessed by the Neurobehavioral Symptom Inventory scale).

Conclusion and implications

Taken together, our data from both mouse and human studies suggest that EEG slow wave quantity and the global coherence index of slow waves may represent a sensitive marker for the diagnosis and prognosis of mTBI and post-concussive symptoms.

MEG Coherence and DTI Connectivity in mTLE

Magnetoencephalography (MEG) is a noninvasive imaging method for localization of focal epileptiform activity in patients with epilepsy. Diffusion tensor imaging (DTI) is a noninvasive imaging method for measuring the diffusion properties of the underlying white matter tracts through which epileptiform activity is propagated. This study investigates the relationship between the cerebral functional abnormalities quantified by MEG coherence and structural abnormalities quantified by DTI in mesial temporal lobe epilepsy (mTLE). Resting state MEG data was analyzed using MEG coherence source imaging (MEG-CSI) method to determine the coherence in 54 anatomical sites in 17 adult mTLE patients with surgical resection and Engel class I outcome, and 17 age- and gender- matched controls. DTI tractography identified the fiber tracts passing through these same anatomical sites of the same subjects. Then, DTI nodal degree and laterality index were calculated and compared with the corresponding MEG coherence and laterality index. MEG coherence laterality, after Bonferroni adjustment, showed significant differences for right versus left mTLE in insular cortex and both lateral orbitofrontal and superior temporal gyri (p < 0.017). Likewise, DTI nodal degree laterality, after Bonferroni adjustment, showed significant differences for right versus left mTLE in gyrus rectus, insular cortex, precuneus and superior temporal gyrus (p < 0.017). In insular cortex, MEG coherence laterality correlated with DTI nodal degree laterality ([Formula: see text] in the cases of mTLE. None of these anatomical sites showed statistically significant differences in coherence laterality between right and left sides of the controls. Coherence laterality was in agreement with the declared side of epileptogenicity in insular cortex (in 82 % of patients) and both lateral orbitofrontal (88 %) and superior temporal gyri (88 %). Nodal degree laterality was also in agreement with the declared side of epileptogenicity in gyrus rectus (in 88 % of patients), insular cortex (71 %), precuneus (82 %) and superior temporal gyrus (94 %). Combining all significant laterality indices improved the lateralization accuracy to 94 % and 100 % for the coherence and nodal degree laterality indices, respectively. The associated variations in diffusion properties of fiber tracts quantified by DTI and coherence measures quantified by MEG with respect to epileptogenicity possibly reflect the chronic microstructural cerebral changes associated with functional interictal activity. The proposed methodology for using MEG and DTI to investigate diffusion abnormalities related to focal epileptogenicity and propagation may provide a further means of noninvasive lateralization.

Incoherent dose-escalation in phase I trials using the escalation with overdose control approach

A desirable property of any dose-escalation strategy for phase I oncology trials is coherence: if the previous patient experienced a toxicity, a higher dose is not recommended for the next patient; similarly, if the previous patient did not experience a toxicity, a lower dose is not recommended for the next patient. The escalation with overdose control (EWOC) approach is a model-based design that has been applied in practice, under which the dose assigned to the next patient is the one that, given all available data, has a posterior probability of exceeding the maximum tolerated dose equal to a pre-specified value known as the feasibility bound. Several methodological and applied publications have considered the EWOC approach with both feasibility bounds fixed and increasing throughout the trial. Whilst the EWOC approach with fixed feasibility bound has been proven to be coherent, some proposed methods of increasing the feasibility bound regardless of toxicity outcomes of patients can lead to incoherent dose-escalation. This paper formalises a proof that incoherent dose-escalation can occur if the feasibility bound is increased without consideration of preceding toxicity outcomes, and shows via simulation studies that only small increases in the feasibility bound are required for incoherent dose-escalations to occur.

Effect of electrocardiogram interference on cortico-cortical connectivity analysis and a possible solution

BACKGROUND

Electroencephalogram (EEG) signals are often contaminated by the electrocardiogram (ECG) interference, which affects quantitative characterization of EEG.

NEW METHOD

We propose null-coherence, a frequency-based approach, to attenuate the ECG interference in EEG using simultaneously recorded ECG as a reference signal. After validating the proposed approach using numerically simulated data, we apply this approach to EEG recorded from six newborns receiving therapeutic hypothermia for neonatal encephalopathy. We compare our approach with an independent component analysis (ICA), a previously proposed approach to attenuate ECG artifacts in the EEG signal. The power spectrum and the cortico-cortical connectivity of the ECG attenuated EEG was compared against the power spectrum and the cortico-cortical connectivity of the raw EEG.

RESULTS

The null-coherence approach attenuated the ECG contamination without leaving any residual of the ECG in the EEG.

COMPARISON WITH EXISTING METHOD

We show that the null-coherence approach performs better than ICA in attenuating the ECG contamination without enhancing cortico-cortical connectivity.

CONCLUSION

Our analysis suggests that using ICA to remove ECG contamination from the EEG suffers from redistribution problems, whereas the null-coherence approach does not. We show that both the null-coherence and ICA approaches attenuate the ECG contamination. However, the EEG obtained after ICA cleaning displayed higher cortico-cortical connectivity compared with that obtained using the null-coherence approach. This suggests that null-coherence is superior to ICA in attenuating the ECG interference in EEG for cortico-cortical connectivity analysis.

Linguistic Markers of Inference Generation While Reading

Words can be informative linguistic markers of psychological constructs. The purpose of this study is to examine associations between word use and the process of making meaningful connections to a text while reading (i.e., inference generation). To achieve this purpose, think-aloud data from third-fifth grade students ([Formula: see text]) reading narrative texts were hand-coded for inferences. These data were also processed with a computer text analysis tool, Linguistic Inquiry and Word Count, for percentages of word use in the following categories: cognitive mechanism words, nonfluencies, and nine types of function words. Findings indicate that cognitive mechanisms were an independent, positive predictor of connections to background knowledge (i.e., elaborative inference generation) and nonfluencies were an independent, negative predictor of connections within the text (i.e., bridging inference generation). Function words did not provide unique variance towards predicting inference generation. These findings are discussed in the context of a cognitive reflection model and the differences between bridging and elaborative inference generation. In addition, potential practical implications for intelligent tutoring systems and computer-based methods of inference identification are presented.

EEG power and glucose fluctuations are coupled during sleep in young adults with type 1 diabetes

OBJECTIVE

To determine the coupling between brain activity and glucose variations during sleep in young adults with type 1 diabetes mellitus (T1DM).

METHODS

27 participants, age 18-30, wore a continuous glucose monitoring system (CGMS) and underwent in-laboratory overnight polysomnography (PSG). Quantitative electroencephalogram (qEEG) metrics were determined from the PSG and included Delta, Theta, Alpha, Sigma, Beta and Gamma Band power at 5-min intervals. Wavelet Coherence Analysis was employed to determine the time varying and frequency specific coupling between glucose and EEG Band power. ANOVA was used to compare differences across fluctuation speeds and EEG bands.

RESULTS

There was a high degree of time varying and frequency specific coupling between glucose variations and EEG power in all EEG Bands during sleep. The average number of intervals of statistically significant coherence was highest for fluctuations periods between 10 and 30min in all Bands (p<0.0001 for each). Mean significant coherence was negatively correlated with hemoglobin A1c, a marker of glycemic control.

CONCLUSIONS

The relationship between glucose and EEG power during sleep is time varying and frequency dependent in young adults with T1DM.

SIGNIFICANCE

Understanding the time varying mutual relationship between glucose changes and brain activity during sleep may have implications for disease management in T1DM.

Human subthalamic nucleus-medial frontal cortex theta phase coherence is involved in conflict and error related cortical monitoring

The medial prefrontal cortex (mPFC) is thought to control the shift from automatic to controlled action selection when conflict is present or when mistakes have been recently committed. Growing evidence suggests that this process involves frequency specific communication in the theta (4-8Hz) band between the mPFC and the subthalamic nucleus (STN), which is the main target of deep brain stimulation (DBS) for Parkinson's disease. Key in this hypothesis is the finding that DBS can lead to impulsivity by disrupting the correlation between higher mPFC oscillations and slower reaction times during conflict. In order to test whether theta band coherence between the mPFC and the STN underlies adjustments to conflict and to errors, we simultaneously recorded mPFC and STN electrophysiological activity while DBS patients performed an arrowed flanker task. These recordings revealed higher theta phase coherence between the two sites during the high conflict trials relative to the low conflict trials. These differences were observed soon after conflicting arrows were displayed, but before a response was executed. Furthermore, trials that occurred after an error was committed showed higher phase coherence relative to trials that followed a correct trial, suggesting that mPFC-STN connectivity may also play a role in error related adjustments in behavior. Interestingly, the phase coherence we observed occurred before increases in theta power, implying that the theta phase and power may influence behavior at separate times during cortical monitoring. Finally, we showed that pre-stimulus differences in STN theta power were related to the reaction time on a given trial, which may help adjust behavior based on the probability of observing conflict during a task.

Adult attachment representation moderates psychotherapy treatment efficacy in clinically depressed inpatients

BACKGROUND

We explored in a sample of clinically depressed patients the influence of attachment security and unresolved trauma on psychotherapeutic outcome as well as changes in attachment representation through psychotherapeutic intervention.

METHODS

The sample consisted of 85 women (aged 19-52), 43 clinically depressed patients from a psychosomatic inpatient unit, and 42 healthy control subjects matched for age and education. Average length of hospitalization in the patient group was eight weeks. Attachment representations were assessed with the Adult Attachment Interview at the time of admission (baseline) and at discharge. Depressive symptoms were measured using the PHQ-9 at T1 and T2.

RESULTS

Insecure attachment representations were overrepresented in depressed patients. Treatment effects were moderated by baseline attachment representation: patients with higher attachment security scores at admission benefited more from the inpatient treatment and were less depressed at time of discharge than less secure patients (η(2)=.07). Generally, attachment security increased (η(2)=.19) and depressive symptoms decreased (η(2)=.23) after inpatient psychotherapy treatment in the patient group. No significant effects for unresolved symptoms were found.

LIMITATIONS

The study is not a randomized controlled study, but used a quasi-experimental matched control group design with female subjects only.

CONCLUSIONS

Our results suggest that attachment representations play a major role in both the development and treatment of clinical depression. Baseline attachment security may influence psychotherapeutic outcome, perhaps through relational factors such as therapeutic working alliance. Inpatient psychotherapy may also need to address psychological issues associated with depression such as attachment insecurity.

Transcranial Alternating Current Stimulation in Patients with Chronic Disorder of Consciousness: A Possible Way to Cut the Diagnostic Gordian Knot?

Unresponsive wakefulness syndrome (UWS) is a chronic disorder of consciousness (DOC) characterized by a lack of awareness and purposeful motor behaviors, owing to an extensive brain connectivity impairment. Nevertheless, some UWS patients may retain residual brain connectivity patterns, which may sustain a covert awareness, namely functional locked-in syndrome (fLIS). We evaluated the possibility of bringing to light such residual neural networks using a non-invasive neurostimulation protocol. To this end, we enrolled 15 healthy individuals and 26 DOC patients (minimally conscious state-MCS- and UWS), who underwent a γ-band transcranial alternating current stimulation (tACS) over the right dorsolateral prefrontal cortex. We measured the effects of tACS on power and partial-directed coherence within local and long-range cortical networks, before and after the protocol application. tACS was able to specifically modulate large-scale cortical effective connectivity and excitability in all the MCS participants and some UWS patients, who could be, therefore, considered as suffering from fLIS. Hence, tACS could be a useful approach in supporting a DOC differential diagnosis, depending on the level of preservation of the cortical large-scale effective connectivity.

Understanding One's Own Emotions in Cognitively-Able Preadolescents with Autism Spectrum Disorder

There are still no straightforward answers as to whether understanding one's own emotions is impaired in autism spectrum disorder (ASD). This study evaluated the perception of one's own different emotions, based on the relevant section of the Autism Diagnostic Observation Schedule Module 3 test. Forty boys, aged 8-11 years, 20 diagnosed with ASD (IQ ≥ 85) and 20 typically developing children were included. Description of events that elicited specific emotions in ASD was characterized by more 'odd' statements and 'no responses' and less use of content related to 'social situations', 'interpersonal' and 'self-awareness'. More 'no responses' and odd statements were associated with the severity of ASD symptoms. Clinicians should be aware of these differentiating factors during the diagnostic process of ASD.

The difficulty of the postural control task affects multi-muscle control during quiet standing

The aim of this study was to compare the electromyographic (EMG) coherence between the lower limb and the core muscles when carrying out two postural tasks at different difficulty levels. EMG was recorded in 20 healthy male subjects while performing two independent quiet standing tasks. The first one involved a bipedal stance with the eyes open, while the second consisted of a dominant unipedal stance also with the eyes open. The obtained EMG signals were analysed by computing estimations of EMG–EMG coherence between muscle pairs, both singly (single-pair estimations) and combined (pooled estimations). Pooled and single coherence of anterior, posterior, core, antagonist and mixed pairs of muscles were significant in the 0–5 Hz frequency band. The results indicate that core and antagonist muscle groups, such as the anterior and posterior muscles, share low-frequency neural inputs (0–5 Hz) which could be responsible of the M-modes assembly. The core muscles could therefore provide the necessary synergy to maintain spine stability during the balancing exercise. Finally, differences in EMG–EMG coherence suggest that the muscle synergies formed during unipedal stance tasks are different from those established during bipedal stance.

Evaluating interhemispheric cortical responses to transcranial magnetic stimulation in chronic stroke: A TMS-EEG investigation

TMS-evoked cortical responses can be measured using simultaneous electroencephalography (TMS-EEG) to directly quantify cortical connectivity in the human brain. The purpose of this study was to evaluate interhemispheric cortical connectivity between the primary motor cortices (M1s) in participants with chronic stroke and controls using TMS-EEG. Ten participants with chronic stroke and four controls were tested. TMS-evoked responses were recorded at rest and during a typical TMS assessment of transcallosal inhibition (TCI). EEG recordings from peri-central gyral electrodes (C3 and C4) were evaluated using imaginary phase coherence (IPC) analyses to quantify levels of effective interhemispheric connectivity. Significantly increased TMS-evoked beta (15-30Hz frequency range) IPC was observed in the stroke group during ipsilesional M1 stimulation compared to controls during TCI assessment but not at rest. TMS-evoked beta IPC values were associated with TMS measures of transcallosal inhibition across groups. These results suggest TMS-evoked EEG responses can index abnormal effective interhemispheric connectivity in chronic stroke.

Reduced functional connectivity of somatosensory network in writer's cramp patients

BACKGROUND

The involvement of motor cortex and sensorimotor integration in patients with writer's cramp (WC) has been well documented. However, the exact neurophysiological profile within the somatosensory system, including primary somatosensory cortex (SI), contralateral (SIIc), and ipsilateral (SIIi) secondary somatosensory areas remains less understood.

METHODS

This study investigated the neuromagnetic cortical activities of median nerve stimulation in 10 patients with WC and 10 healthy controls (HC). To comprehensively explore all the aspects of somatosensory functioning, we analyzed our data with the minimum norm estimate (MNE), the time-frequency approach with evoked and induced activities, and functional connectivity between SI and SIIc (SI-SIIc), SI and SIIi (SI-SIIi), and SIIc and SIIi (SIIc-SIIi) from theta to gamma oscillations.

RESULTS

No significant between-group differences were found in the MNE cortical amplitudes of SI, SIIc, and SIIi. Power strengths of evoked gamma oscillation and induced beta synchronization were also equivalent between WC and HC groups. However, we found significantly reduced theta coherence of SI-SIIi, alpha coherence of SI-SIIi and SIIc-SIIi, as well as beta coherence of SIIc-SIIi in patients with WC.

CONCLUSION

Our results suggest the involvement of somatosensory abnormalities, primarily with the form of functional connectivity, in patients with WC.

Quantifying synchrony patterns in the EEG of Alzheimer's patients with linear and non-linear connectivity markers

We analyzed the relation of several synchrony markers in the electroencephalogram (EEG) and Alzheimer's disease (AD) severity as measured by Mini-Mental State Examination (MMSE) scores. The study sample consisted of 79 subjects diagnosed with probable AD. All subjects were participants in the PRODEM-Austria study. Following a homogeneous protocol, the EEG was recorded both in resting state and during a cognitive task. We employed quadratic least squares regression to describe the relation between MMSE and the EEG markers. Factor analysis was used for estimating a potentially lower number of unobserved synchrony factors. These common factors were then related to MMSE scores as well. Most markers displayed an initial increase of EEG synchrony with MMSE scores from 26 to 21 or 20, and a decrease below. This effect was most prominent during the cognitive task and may be owed to cerebral compensatory mechanisms. Factor analysis provided interesting insights in the synchrony structures and the first common factors were related to MMSE scores with coefficients of determination up to 0.433. We conclude that several of the proposed EEG markers are related to AD severity for the overall sample with a wide dispersion for individual subjects. Part of these fluctuations may be owed to fluctuations and day-to-day variability associated with MMSE measurements. Our study provides a systematic analysis of EEG synchrony based on a large and homogeneous sample. The results indicate that the individual markers capture different aspects of EEG synchrony and may reflect cerebral compensatory mechanisms in the early stages of AD.

Coherence in children with AD/HD and excess alpha power in their EEG

OBJECTIVE

This study investigated differences in EEG coherence measures between two groups of children with Attention-Deficit/Hyperactivity Disorder (AD/HD) - one with the more common EEG profile (increased theta), and a group with excess alpha activity as the dominant EEG abnormality.

METHODS

26 children (aged 9-13years) with AD/HD were included in each of the excess-theta and excess-alpha groups, and were age- and sex-matched with 26 control subjects. EEG was recorded from 19 electrode sites during an eyes-closed resting condition. Wave-shape coherence was calculated for eight intrahemispheric and eight interhemispheric electrode pairs, for the delta, theta, alpha and beta bands.

RESULTS

In comparison with the controls, the excess-theta AD/HD group had increased theta intrahemispheric coherences at short-medium inter-electrode distances. Frontally, the excess-theta AD/HD group had increased interhemispheric theta and reduced beta coherences. The excess-alpha group primarily showed increased slow wave (delta and theta) intrahemispheric coherence at short-medium inter-electrode distances, and reduced alpha coherence at longer inter-electrode distances, compared with controls. An increase in frontal interhemispheric theta coherence was also found.

CONCLUSIONS

These results suggest that AD/HD children with excess alpha power have an underlying connectivity dysfunction in the frontal lobes, which is found in common with other subjects with the excess-theta EEG profile. However, a number of qualitative differences exist that could be associated with other aspects of the AD/HD diagnosis. The excess-alpha group appeared to have fewer frontal-lobe abnormalities than the excess-theta AD/HD group.

SIGNIFICANCE

This is the first study to investigate coherence in AD/HD children who have the atypical profile of increased alpha power in their EEG.

Image contrast reduction mechanism in full-field optical coherence tomography

Correct interpretation of image contrast obtained with full-field optical coherence tomography (FFOCT) technique is required for accurate medical diagnosis applications. In this work, first, the characteristics of microscopic structures of tissue that generate the contrast in en-face tomographic image obtained with FFOCT are discussed. Then an overview is given of the parameters that affect image contrast. Finally, the contrast correction factor for correct image interpretation and the contrast limits to practical FFOCT systems are outlined.

Subarray coherence based postfilter for eigenspace based minimum variance beamformer in ultrasound plane-wave imaging

This paper introduces a new beamformer, which combines the eigenspace based minimum variance (ESBMV) beamformer with a subarray coherence based postfilter (SCBP), for improving the quality of ultrasound plane-wave imaging. The ESBMV beamformer has been validated in improving the imaging contrast, but the difficulty in dividing the signal subspace limits the usage of it in the low signal-to-noise ratio (SNR) scenarios. Coherence factor (CF) based methods could optimize the output of a distortionless beamformer to reduce sidelobes, but the influence by the subarray decorrelation technique on the postfilter design has not attracted enough concern before. Accordingly, an ESBMV-SCBP beamformer was proposed in this paper, which used the coherence of the subarray signal to compute an SCBP to optimize the ESBMV results. Simulated and experimental data were used to evaluate the performance of the proposed method. The results showed that the ESBMV-SCBP method achieved an improved imaging quality compared with the ESBMV beamformer. In the simulation study, the contrast ratio (CR) for an anechoic cyst was improved by 9.88 dB and the contrast-to-noise ratio (CNR) was improved by 0.97 over the ESBMV. In the experimental study, the CR improvements for two anechoic cysts were 7.32 dB and 9.45 dB, while the CNRs were improved by 1.27 and 0.66, respectively. The ESBMV-SCBP also showed advantages over the ESBMV-Wiener beamformer in preserving a less grainy speckle, which is closer to that of distortionless beamformers and benefits the imaging contrast. With a relatively small extra computational load, the proposed method has potential to enhance the quality of the ultrasound plane-wave imaging.

Detecting neuromagnetic synchrony in the presence of noise

BACKGROUND

Synchrony between neuroelectric oscillations in distant brain areas is currently used as an indicator of functional connectivity between the involved neural substrates. Coherence measures, which quantify synchrony, are affected by concurrent brain activities, commonly subsumed as noise.

NEW METHOD

Using Monte-Carlo simulation, we analysed the properties of circular statistics and how those are affected by noise. We considered three different models of neuroelectric signal generation, which are an additive model, phase-reset, and reciprocal phase-interaction. Using the receiver-operating characteristic method, we compared the performances of currently implemented algorithms for coherence detection such as phase-coherence or phase-locking factor, magnitude-squared coherence, and phase-lagging index, all based on circular statistics, and a more general approach to synchrony, using measures of mutual information. We compared inter-trial coherence as a method for signal detection with coherence between multiple sources as measure of source interaction and connectivity.

RESULTS

Charts of performance characteristics showed that the choice of methods depend on the underlying signal generation model. Detection of coherence requires in general a higher signal-to-noise ratio than detection of the signal itself, and again, the difference in performance depends strongly on the underlying model of signal generation.

COMPARISON WITH EXISTING METHODS

Previous comparisons of the performances of different algorithms for signal detection and coherence have not considered systematically the underlying neural generation mechanisms.

CONCLUSION

Detection of coherence generated by additive signals or a phase-reset requires largely higher signal-to-noise ratio compared to signal detection. Only in case of true phase interaction, signal detection and coherence measures are similarly sensitive.

Effect of motion coherence on time perception relates to perceived speed

The present study examined the effect of coherence of moving visual objects on time perception. Participants observed stimuli composed of four line segments moving behind or in front of occluders. The line segments appeared to move either coherently as a diamond outline or incoherently, depending on the occlusion. Results from the temporal bisection task indicated that the duration of the coherently moving stimulus was perceived longer or shorter compared to the duration of the incoherently moving stimulus depending on the stimulus configurations. The speed comparison task revealed that the trend of the difference in perceived speed between the coherent and incoherent motions in each stimulus configuration was consistent with that of the difference in perceived duration between them. These results demonstrate the effect of motion coherence on perceived duration, and that this effect may be mediated by changes in perceived speed. Our finding provides evidence supporting the involvement of global motion processing in time perception.

Analysis of coherent activity between retrosplenial cortex, hippocampus, thalamus, and anterior cingulate cortex during retrieval of recent and remote context fear memory

Memory for contextual fear conditioning relies upon the retrosplenial cortex (RSC) regardless of how long ago conditioning occurred, whereas areas connected to the RSC, such as the dorsal hippocampus (DH) and anterior cingulate cortex (ACC) appear to play time-limited roles. To better understand whether these brain regions functionally interact during memory processing and how the passage of time affects these interactions, we simultaneously recorded local field potentials (LFPs) from these three regions as well as anterior dorsal thalamus (ADT), which provides one of the strongest inputs to RSC, and measured coherence of oscillatory activity within the theta (4-12Hz) and gamma (30-80Hz) frequency bands. We identified changes of theta coherence related to encoding, retrieval, and extinction of context fear, whereas changes in gamma coherence were restricted to fear extinction. Specifically, exposure to a novel context and retrieval of recently acquired fear conditioning memory were associated with increased theta coherence between RSC and all three other structures. In contrast, RSC-DH and RSC-ADT theta coherence were decreased in mice that successfully retrieved, relative to mice that failed to retrieve, remote memory. Greater RSC-ADT theta and gamma coherence were observed during recent, compared to remote, extinction of freezing responses. Thus, the degree of coherence between RSC and connected brain areas may predict and contribute to context memory retrieval and retrieval-related phenomena such as fear extinction. Importantly, although theta coherence in this circuit increases during memory encoding and retrieval of recent memory, failure to decrease RSC-DH theta coherence might be linked to retrieval deficit in the long term, and possibly contribute to aberrant memory processing characteristic of neuropsychiatric disorders.

Public Reception of Climate Science: Coherence, Reliability, and Independence

Possible measures to mitigate climate change require global collective actions whose impacts will be felt by many, if not all. Implementing such actions requires successful communication of the reasons for them, and hence the underlying climate science, to a degree that far exceeds typical scientific issues which do not require large-scale societal response. Empirical studies have identified factors, such as the perceived level of consensus in scientific opinion and the perceived reliability of scientists, that can limit people's trust in science communicators and their subsequent acceptance of climate change claims. Little consideration has been given, however, to recent formal results within philosophy concerning the relationship between truth, the reliability of evidence sources, the coherence of multiple pieces of evidence/testimonies, and the impact of (non-)independence between sources of evidence. This study draws on these results to evaluate exactly what has (and, more important, has not yet) been established in the empirical literature about the factors that bias the public's reception of scientific communications about climate change.

The demodulated band transform

BACKGROUND

Windowed Fourier decompositions (WFD) are widely used in measuring stationary and non-stationary spectral phenomena and in describing pairwise relationships among multiple signals. Although a variety of WFDs see frequent application in electrophysiological research, including the short-time Fourier transform, continuous wavelets, bandpass filtering and multitaper-based approaches, each carries certain drawbacks related to computational efficiency and spectral leakage. This work surveys the advantages of a WFD not previously applied in electrophysiological settings.

NEW METHODS

A computationally efficient form of complex demodulation, the demodulated band transform (DBT), is described.

RESULTS

DBT is shown to provide an efficient approach to spectral estimation with minimal susceptibility to spectral leakage. In addition, it lends itself well to adaptive filtering of non-stationary narrowband noise.

COMPARISON WITH EXISTING METHODS

A detailed comparison with alternative WFDs is offered, with an emphasis on the relationship between DBT and Thomson's multitaper. DBT is shown to perform favorably in combining computational efficiency with minimal introduction of spectral leakage.

CONCLUSION

DBT is ideally suited to efficient estimation of both stationary and non-stationary spectral and cross-spectral statistics with minimal susceptibility to spectral leakage. These qualities are broadly desirable in many settings.

Coherence across consciousness levels: Symmetric visual displays spare working memory resources

Two studies demonstrate that the need for coherence could nudge individuals to use structural similarities between binary visual displays and two concurrent cognitive tasks to unduly solve the latter in similar fashion. In an overt truth-judgement task, participants decided whether symmetric colourful displays matched conjunction or disjunction descriptions (e.g., "the black and/or the orange"). In the simultaneous covert categorisation task, they decided whether a colour name (e.g., "black") described a two-colour object or half of a single-colour object. Two response patterns emerged as follows. Participants either acknowledged or rejected matches between disjunction descriptions and two visual stimuli and, similarly, either acknowledged or rejected matches between single colour names and two-colour objects or between single colour names and half of single-colour objects. These findings confirm the coherence hypothesis, highlight the role of coherence in preserving working-memory resources, and demonstrate an interaction between high-level and low-level consciousness.

EEG alpha frequency correlates of burnout and depression: The role of gender

EEG alpha frequency band biomarkers of depression are widely explored. Due to their trait-like features, they may help distinguish between depressive and burnout symptomatology, which is often referred to as "work-related depression". The present correlational study strived to examine whether individual alpha frequency (IAF), power, and coherence in the alpha band can provide evidence for establishing burnout as a separate diagnostic entity. Resting EEG (eyes closed) was recorded in 117 individuals (42 males). In addition, the participants filled-out questionnaires of burnout and depression. Regression analyses highlighted the differential value of IAF and power in predicting burnout and depression. IAF was significantly related to depressive symptomatology, whereas power was linked mostly to burnout. Moreover, seven out of twelve interactions between EEG indicators and gender were significant. Connectivity patterns were significant for depression displaying gender-related differences. The results offer tentative support for establishing burnout as a separate clinical syndrome.

Realization of a tilted reference wave for electron holography by means of a condenser biprism

As proposed recently, a tilted reference wave in off-axis electron holography is expected to be useful for aberration measurement and correction. Furthermore, in dark-field electron holography, it is considered to replace the reference wave, which is conventionally diffracted in an unstrained object area, by a well-defined object-independent reference wave. Here, we first realize a tilted reference wave by employing a biprism placed in the condenser system above three condenser lenses producing a relative tilt magnitude up to 20/nm at the object plane (300kV). Paraxial ray-tracing predicts condenser settings for a parallel illumination at the object plane, where only one half of the round illumination disc is tilted relative to the optical axis without displacement. Holographic measurements verify the kink-like phase modulation of the incident beam and return the interference fringe contrast as a function of the relative tilt between both parts of the illumination. Contrast transfer theory including condenser aberrations and biprism instabilities was applied to explain the fringe contrast measurement. A first dark-field hologram with a tilted - object-free - reference wave was acquired and reconstructed. A new application for bright/dark-field imaging is presented.

Spectrally resolved fast transient brain states in electrophysiological data

The brain is capable of producing coordinated fast changing neural dynamics across multiple brain regions in order to adapt to rapidly changing environments. However, it is non-trivial to identify multiregion dynamics at fast sub-second time-scales in electrophysiological data. We propose a method that, with no knowledge of any task timings, can simultaneously identify and describe fast transient multiregion dynamics in terms of their temporal, spectral and spatial properties. The approach models brain activity using a discrete set of sequential states, with each state distinguished by its own multiregion spectral properties. This can identify potentially very short-lived visits to a brain state, at the same time as inferring the state's properties, by pooling over many repeated visits to that state. We show how this can be used to compute state-specific measures such as power spectra and coherence. We demonstrate that this can be used to identify short-lived transient brain states with distinct power and functional connectivity (e.g., coherence) properties in an MEG data set collected during a volitional motor task.

State-Dependent Differences in Functional Connectivity in Young Children With Autism Spectrum Disorder

Background

While there is increasing evidence of altered brain connectivity in autism, the degree and direction of these alterations in connectivity and their uniqueness to autism has not been established. The aim of the present study was to compare connectivity in children with autism to that of typically developing controls and children with developmental delay without autism.

Methods

We assessed EEG spectral power, coherence, phase lag, Pearson and partial correlations, and epileptiform activity during the awake, slow wave sleep, and REM sleep states in 137 children aged 2 to 6 years with autism (n = 87), developmental delay without autism (n = 21), or typical development (n = 29).

Findings

We found that brain connectivity, as measured by coherence, phase lag, and Pearson and partial correlations distinguished children with autism from both neurotypical and developmentally delayed children. In general, children with autism had increased coherence which was most prominent during slow wave sleep.

Interpretation

Functional connectivity is distinctly different in children with autism compared to samples with typical development and developmental delay without autism. Differences in connectivity in autism are state and region related. In this study, children with autism were characterized by a dynamically evolving pattern of altered connectivity.

•

We used EEG to examine the connectivity in young children in awake, rapid eye movement, and slow wave sleep (SWS) states.

•

Differences in coherence between the autism group and the other groups were maximal during SWS.

•

Sleep may be the most sensitive time to measure differences in neuro-development before they are observable in behavior.

Shared mechanisms underlie normal healthy sleep and normal brain development. Therefore, we suspect that differences in the way that the brain is behaving during sleep have the potential to tell us about what might be developing incorrectly in people with neurodevelopmental disorders. In addition, sleep evaluations of children allow us to filter out waking distractions, so that we are truly measuring the brain working offline. For instance, the differences in the way the brain was connected that we observed between our three study groups were by far the most notable during slow wave sleep. This finding highlights the importance of taking the state of the brain into account when commenting on the ‘connectedness’ of the brain as a potential biomarker for neurodevelopmental disorders. Future attempts to classify developmental disorders by using differences in connectivity must take into account brain state, whether awake or asleep as well as developmental stage.

Descending neural drives to ankle muscles during gait and their relationships with clinical functions in patients after stroke

OBJECTIVE

The objective of this study was to investigate the descending neural drive to ankle muscles during gait in stroke patients using a coherence analysis of surface electromyographic (EMG) recordings and the relationships of the drive with clinical functions.

METHODS

EMG recordings of the paired tibialis anterior (TA), medial and lateral gastrocnemius (MG and LG), and TA-LG muscles were used to calculate intramuscular, synergistic, and agonist-antagonist muscle coherence, respectively, in 11 stroke patients and 9 healthy controls. Paretic motor function, sensory function, spasticity, ankle muscle strength, and gait performance were evaluated.

RESULTS

Paretic TA-TA and MG-LG beta band (15-30 Hz) coherences were significantly lower compared with the non-paretic side and controls. TA-LG beta band coherence was significantly higher on both sides compared with controls. Paretic TA-TA beta band coherence positively correlated with gait speed, and paretic TA-LG beta band coherence negatively correlated with paretic ankle plantar flexor muscle strength.

CONCLUSIONS

The intramuscular and synergistic muscle neural drives were reduced during gait on the paretic side in stroke patients. The agonist-antagonist muscle neural drive was increased to compensate for paretic ankle muscle weakness.

SIGNIFICANCE

Descending neural drive reorganization to agonist-antagonist muscles is important for patients with paretic ankle muscle weakness.

Surface Laplacians (SL) and phase properties of EEG rhythms: Simulated generators in a volume-conduction model

Surface Laplacian (SL) methods offer advantages in spectral analysis owing to the well-known implications of volume conduction. Although recognition of the superiority of SL over reference-dependent measures is widespread, well-reasoned cautions have precluded their universal adoption. Notably, the expected selectivity of SL for superficial rather than deep generators has relegated SL to the role of an add-on to conventional analyses, rather than as an independent area of inquiry, despite empirical findings supporting the consistency and replicability of physiological effects of interest. It has also been reasoned that the contrast-enhancing effects of SL necessarily make it insensitive to broadly distributed generators, including those suspected for oscillatory rhythms such as EEG alpha. These concerns are further exacerbated for phase-sensitive measures (e.g., phase-locking, coherence), where key features of physiological generators have yet to be evaluated. While the neuronal generators of empirically-derived EEG measures cannot be precisely known due to the inverse problem, simple dipole generator configurations can be simulated using a 4-sphere head model and linearly combined. We simulated subdural and deep generators and distributed dipole layers using sine and cosine waveforms, quantified at 67-scalp sites corresponding to those used in previous research. Reference-dependent (nose, average, mastoids reference) EEG and corresponding SL topographies were used to probe signal fidelity in the topography of the measured amplitude spectra, phase and coherence of sinusoidal stimuli at and between "active" recording sites. SL consistently outperformed the conventional EEG measures, indicating that continued reluctance by the research community is unfounded.

Memory load effect in auditory-verbal short-term memory task: EEG fractal and spectral analysis

The objective of this preliminary study was to quantify changes in complexity of EEG using fractal dimension (FD) alongside linear methods of spectral power, event-related spectral perturbations, coherence, and source localization of EEG generators for theta (4-7 Hz), alpha (8-12 Hz), and beta (13-23 Hz) frequency bands due to a memory load effect in an auditory-verbal short-term memory (AVSTM) task for words. We examined 20 healthy individuals using the Sternberg's paradigm with increasing memory load (three, five, and seven words). The stimuli were four-letter words. Artifact-free 5-s EEG segments during retention period were analyzed. The most significant finding was the increase in FD with the increase in memory load in temporal regions T3 and T4, and in parietal region Pz, while decrease in FD with increase in memory load was registered in frontal midline region Fz. Results point to increase in frontal midline (Fz) theta spectral power, decrease in alpha spectral power in parietal region-Pz, and increase in beta spectral power in T3 and T4 region with increase in memory load. Decrease in theta coherence within right hemisphere due to memory load was obtained. Alpha coherence increased in posterior regions with anterior decrease. Beta coherence increased in fronto-temporal regions. Source localization delineated theta activity increase in frontal midline region, alpha decrease in superior parietal region, and beta increase in superior temporal gyrus with increase in memory load. In conclusion, FD as a nonlinear measure may serve as a sensitive index for quantifying dynamical changes in EEG signals during AVSTM tasks.

Aberrant Thalamocortical Synchrony Associated with Behavioral Manifestations in Git1 (-/-) Mice

Cross-talk between the thalamus and cortex has been implicated in attention but its pathogenic role in attention-deficit/hyperactivity disorder (ADHD) remains unknown. Here, I demonstrate that Git1^-/- mice, previously proposed as an animal model for ADHD, show abnormal theta oscillation in the thalamus. Multi-electrode recordings revealed that Git1^-/- mice have hyper-synchrony of neural activities between the thalamus and cortex. The abnormal thalamic oscillation and thalamocortical synchrony in Git1^-/- mice were markedly reduced by amphetamine. In addition, ethosuximide ameliorates abnormal thalamic oscillation and ADHD-like hyperactivity shown in Git1^-/- mice. My study suggests critical roles of GIT1 and thalamocortical neural circuitry in ADHD.