Neural Dynamics of Context-Sensitive Adjustments in Cognitive Flexibility

To adaptively interact with the uncertainties of daily life, we must match our level of cognitive flexibility to contextual demands—being more flexible when frequent shifting between different tasks is required and more stable when the current task requires a strong focus of attention. Such cognitive flexibility adjustments in response to changing contextual demands have been observed in cued task-switching paradigms, where the performance cost incurred by switching versus repeating tasks (switch cost) scales inversely with the proportion of switches (PS) within a block of trials. However, the neural underpinnings of these adjustments in cognitive flexibility are not well understood. Here, we recorded 64-channel EEG measures of electrical brain activity as participants switched between letter and digit categorization tasks in varying PS contexts, from which we extracted ERPs elicited by the task cue and alpha power differences during the cue-to-target interval and the resting precue period. The temporal resolution of the EEG allowed us to test whether contextual adjustments in cognitive flexibility are mediated by tonic changes in processing mode or by changes in phasic, task cue-triggered processes. We observed reliable modulation of behavioral switch cost by PS context that was mirrored in both cue-evoked ERP and time–frequency effects but not by blockwide precue EEG changes. These results indicate that different levels of cognitive flexibility are instantiated after the presentation of task cues, rather than by being maintained as a tonic state throughout low- or high-switch contexts.

RATIO OF TOTAL SLOW AND SUPER SLOW CEREBRAL BIOELECTRICAL ACTIVITY IN CHILDREN WITH HYPOXIA

The aim of the study is to identify changes in the total slow and super slow bioelectric activity of the cerebral hemispheres in 8–11-year-old children under reduced oxygen partial pressure in the inhaled air and in norm. Materials and Methods. The authors examined 82 8–11-year-old children. EEG registration was carried out on a complex Russian device "Telepat-103" with computer processing of the results. Slow potentials were recorded using a special computer complex for studying constant potential level (CPL) and cerebral energy consumption "Neuroenergon". Hypoxia was created by a special medical device "Hypoxicator" (Trade Medical). The choice of the oxygen content in the test hypoxic mixture (14 % O2) was based on the results of a three-stage hypoxic test carried out before the complex examination. Results. Hypoxia increases the index and amplitude of delta oscillations and decreases the number of alpha waves in 8–11-year-old children. The results obtained indicate that it is more important to provide the brain with a sufficient amount of oxygen corresponding to its needs than simply to increase the brain blood supply during hypoxia. The study also indicates the contribution of the body's sensitivity to hypoxic response. Under hypoxia, an increase in the constant potential level in the studied brain areas is observed in 8–11-year-old children. An increase in electrical activity during normobaric hypoxia is noted at low baseline values of constant potential level. An increase in the slow electrical brain activity occurs due to the change of brain energy supply according to the biochemical indicators of energy metabolism. Short-term hypoxia is accompanied by a simultaneous increase in slow-wave activity due to delta activity and CPL in 8–11-year-old children. Conclusion. Thus, we can say that a picture of functional brain activity with simultaneous inhibitory phenomena in the cortex is formed. It may reflect the development of a special state of the central nervous system. Key words: constant potential level, electroencephalography, hypoxia, adaptation to hypoxia. Цель работы – выявление изменений суммарной медленной и сверхмедленной биоэлектрической активности полушарий головного мозга у детей в возрасте от 8 до 11 лет в условиях нормального и сниженного парциального давления кислорода во вдыхаемом воздухе. Материалы и методы. Обследовано 82 ребенка 8–11-летнего возраста. Регистрация ЭЭГ осуществлялась на комплексной отечественной установке «Телепат-103» с компьютерной обработкой результатов. Медленные потенциалы фиксировались с помощью специального компьютерного комплекса для исследования уровня постоянных потенциалов (УПП) и энергозатрат головного мозга «Нейроэнергон». Гипоксические условия создавались аппаратом «Гипоксикатор» фирмы Trade Medical. Выбор содержания кислорода в тестирующей гипоксической смеси (14 % О2) основывался на результатах проведенного до комплексного обследования трехступенчатого гипоксического теста. Результаты. У детей от 8 до 11 лет действие гипоксии на головной мозг приводит к возрастанию индекса и амплитуды дельта-колебаний и убыванию числа альфа-волн. Полученные результаты говорят о том, что большое значение имеет не столько усиление кровоснабжения головного мозга при гипоксии, сколько обеспечение мозга достаточным, соответствующим его потребностям, количеством кислорода, а также о роли чувствительности организма к гипоксии. При воздействии гипоксии у детей этого возраста наблюдается возрастание уровня постоянных потенциалов в исследуемых областях головного мозга. При низких фоновых значениях уровня постоянных потенциалов отмечается возрастание электрической активности при нормобарической гипоксии. Возрастание медленной электрической активности головного мозга происходит из-за того, что изменяется энергообеспечение головного мозга по биохимическим показателям энергетического обмена. Действие кратковременной гипоксии сопровождается одновременным возрастанием медленноволновой активности за счет дельта-активности и УПП у детей от 8 до 11 лет. Выводы. Таким образом, можно говорить о том, что формируется своеобразная картина функциональной активности с одновременными тормозными явлениями в коре, что может являться отражением развития особого состояния центральной нервной системы. Ключевые слова: уровень постоянных потенциалов, электроэнцефалография, гипоксия, адаптация к гипоксии.

Sex-Specific Brain Responses to Imaginary Dance but Not Physical Dance: An Electroencephalography Study of Functional Connectivity and Electrical Brain Activity

To date, most neurophysiological dance research has been conducted exclusively with female participants in observational studies (i.e., participants observe or imagine a dance choreography). In this regard, the sex-specific acute neurophysiological effect of physically executed dance can be considered a widely unexplored field of research. This study examines the acute impact of a modern jazz dance choreography on brain activity and functional connectivity using electroencephalography (EEG). In a within-subject design, 11 female and 11 male participants were examined under four test conditions: physically dancing the choreography with and without music and imagining the choreography with and without music. Prior to the EEG measurements, the participants acquired the choreography over 3 weeks with one session per week. Subsequently, the participants conducted all four test conditions in a randomized order on a single day, with the EEG measurements taken before and after each condition. Differences between the male and female participants were established in brain activity and functional connectivity analyses under the condition of imagined dance without music. No statistical differences between sexes were found in the other three conditions (physically executed dance with and without music as well as imagined dance with music). Physically dancing and music seem to have sex-independent effects on the human brain. However, thinking of dance without music seems to be rather sex-specific. The results point to a promising approach to decipher sex-specific differences in the use of dance or music. This approach could further be used to achieve a more group-specific or even more individualized and situationally adapted use of dance interventions, e.g., in the context of sports, physical education, or therapy. The extent to which the identified differences are due to culturally specific attitudes in the sex-specific contact with dance and music needs to be clarified in future research.

Bidirectional Association Between Sleep and Brain Atrophy in Aging

Human brain aging is characterized by the gradual deterioration of its function and structure, affected by the interplay of a multitude of causal factors. The sleep, a periodically repeating state of reversible unconsciousness characterized by distinct electrical brain activity, is crucial for maintaining brain homeostasis. Indeed, insufficient sleep was associated with accelerated brain atrophy and impaired brain functional connectivity. Concurrently, alteration of sleep-related transient electrical events in senescence was correlated with structural and functional deterioration of brain regions responsible for their generation, implying the interconnectedness of sleep and brain structure. This review discusses currently available data on the link between human brain aging and sleep derived from various neuroimaging and neurophysiological methods. We advocate the notion of a mutual relationship between the sleep structure and age-related alterations of functional and structural brain integrity, pointing out the position of high-quality sleep as a potent preventive factor of early brain aging and neurodegeneration. However, further studies are needed to reveal the causality of the relationship between sleep and brain aging.

Is Artistic Composition in Abstract Art Detected Automatically?

Most artists who create abstract paintings place the pictorial elements not at random, but arrange them intentionally in a specific artistic composition. This arrangement results in a pattern of image properties that differs from image versions in which the same pictorial elements are randomly shuffled. In the article under discussion, the original abstract paintings of the author’s image set were rated as more ordered and harmonious but less interesting than their shuffled counterparts. The authors tested whether the human brain distinguishes between these original and shuffled images by recording electrical brain activity in a particular paradigm that evokes a so-called visual mismatch negativity. The results revealed that the brain detects the differences between the two types of images fast and automatically. These findings are in line with models that postulate a significant role of early (low-level) perceptual processing of formal image properties in aesthetic evaluations.

Looking for consistency in an uncertain world: test-retest reliability of neurophysiological and behavioral readouts in autism

Background Autism spectrum disorders (ASD) are associated with altered sensory processing and perception. Scalp recordings of electrical brain activity time-locked to sensory events (event-related potentials; ERPs) provide precise information on the time-course of related altered neural activity, and can be used to model the cortical loci of the underlying neural networks. Establishing the test-retest reliability of these sensory brain responses in ASD is critical to their use as biomarkers of neural dysfunction in this population. Methods EEG and behavioral data were acquired from 33 children diagnosed with ASD aged 6–9.4 years old, while they performed a child-friendly task at two different time-points, separated by an average of 5.2 months. In two blocked conditions, participants responded to the occurrence of an auditory target that was either preceded or not by repeating visual stimuli. Intraclass correlation coefficients (ICCs) were used to assess test-retest reliability of measures of sensory (auditory and visual) ERPs and performance, for the two experimental conditions. To assess the degree of reliability of the variability of responses within individuals, this analysis was performed on the variance of the measurements, in addition to their means. This yielded a total of 24 measures for which ICCs were calculated. Results The data yielded significant good ICC values for 10 of the 24 measurements. These spanned across behavioral and ERPs data, experimental conditions, and mean as well as variance measures. Measures of the visual evoked responses accounted for a disproportionately large number of the significant ICCs; follow-up analyses suggested that the contribution of a greater number of trials to the visual compared to the auditory ERP partially accounted for this. Conclusions This analysis reveals that sensory ERPs and related behavior can be highly reliable across multiple measurement time-points in ASD. The data further suggest that the inter-trial and inter-participant variability reported in the ASD literature likely represents replicable individual participant neural processing differences. The stability of these neuronal readouts supports their use as biomarkers in clinical and translational studies on ASD. Given the minimum interval between test/retest sessions across our cohort, we also conclude that for the tested age-range of ~ 6 to 9.4 years, these reliability measures are valid for at least a 3-month interval. Limitations related to EEG task demands and study length in the context of a clinical trial are considered.

Clinical Case of the Occurrence of Stroke Followed by Death After Vaccine Against SARS-CoV-2

Introduction: The current COVID-19 pandemic has involved developing vaccines to control the virulence of SARS-CoV-2. More than 4.1 million people have died from COVID-19.1 In response to this public health emergency, several vaccines against COVID-19 have been developed, with more than 3.7 billion doses administered worldwide. After the introduction of the adenovirus vector vaccine ChAdOx1, several cases of severe venous thrombosis with thrombocytopenia were reported worldwide. Objective: It was to present a case report of a 25-year-old female patient who presented extensive left intraparenchymal hematoma and rapid progression to brain death followed by death. Case report: A 25-year-old woman, CSS, was vaccinated against COVID-19 with the adenovirus ChAdOx1, 14 days after admission, evolved with a fever that started about 13 days ago, associated with holocranial, tight, moderate-intensity headache. On the day of admission, she was found by the torporous, unresponsive, and vomiting family, referred to the hospital emergency room. The patient was admitted to Glasgow 4 with evidence of anisocoria, with the left pupils larger than the right, rapidly progressing to mydriasis. Cranial computed tomography (CT) showed extensive left intraparenchymal hematoma, performing urgent decompressive craniectomy and placement of an intracranial pressure monitoring catheter. The cerebrospinal fluid exam did not show bacteria or fungi. CT angiography showed extensive thrombosis of the anterior portions of the superior sagittal sinus and probable thrombosis of the superficial drainage veins of the frontal regions. Skull CT revealed diffuse and bilateral ischemia. Laboratory tests showed mild thrombocytopenia and no change in the coagulogram. After one day, the patient evolved with worsening neurological status. Sedation was turned off to start the brain death protocol, which was confirmed twice. Finally, an electroencephalogram was performed with evidence of a straight-line tracing, without evidence of electrical brain activity. Final considerations: Several studies have been published regarding cerebral thrombosis, stroke, and thrombotic thrombocytopenic events. Thus, safe and effective vaccines against COVID-19 are an urgent need, as they can leave pathophysiological responses of hypercoagulability and thrombo inflammation associated with acute infection.

An in-vivo validation of ESI methods with focal sources

Electrical source imaging (ESI) aims at reconstructing the electrical brain activity from measurements of the electric field on the scalp. Even though the localization of single focal sources should be relatively straightforward, different methods provide diverse solutions due to the different underlying assumptions. Furthermore, their input parameter(s) further affects the solution provided by each method, making localization even more challenging. In addition, validations and comparisons are typically performed either on synthetic data or through post-operative outcomes, in both cases with considerable limitations.We use an in-vivo high-density EEG dataset recorded during intracranial single pulse electrical stimulation, in which the true sources are substantially dipolar and their locations are known. We compare ten different ESI methods under multiple choices of input parameters, to assess the accuracy of the best reconstruction, as well as the impact of the parameters on the localization performance.Best reconstructions often fall within 1 cm from the true source, with more accurate methods outperforming less accurate ones by 1 cm, on average. Expectedly, dipolar methods tend to outperform distributed methods. Sensitivity to input parameters varies widely between methods. Depth weighting played no role for three out of six methods implementing it. In terms of regularization parameters, for several distributed methods SNR=1 unexpectedly turned out to be the best choice among the tested ones.Our data show similar levels of accuracy of ESI techniques when applied to “conventional” (32 channels) and dense (64, 128, 256 channels) EEG recordings.Overall findings reinforce the importance that ESI may have in the clinical context, especially when applied to identify the surgical target in potential candidates for epilepsy surgery.

Separable neural signatures of confidence during perceptual decisions

Perceptual confidence is an evaluation of the validity of perceptual decisions. While there is behavioural evidence that confidence evaluation differs from perceptual decision-making, disentangling these two processes remains a challenge at the neural level. Here, we examined the electrical brain activity of human participants in a protracted perceptual decision-making task where observers tend to commit to perceptual decisions early whilst continuing to monitor sensory evidence for evaluating confidence. Premature decision commitments were revealed by patterns of spectral power overlying motor cortex, followed by an attenuation of the neural representation of perceptual decision evidence. A distinct neural representation was associated with the computation of confidence, with sources localised in the superior parietal and orbitofrontal cortices. In agreement with a dissociation between perception and confidence, these neural resources were recruited even after observers committed to their perceptual decisions, and thus delineate an integral neural circuit for evaluating perceptual decision confidence.