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Αλέξανδρος Γ. Σφακιανάκης

Tuesday, December 1, 2020

Regulation and Ethics of Transcranial Electrical Stimulation: A General View

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Transcranial application of low-intensity electrical stimuli is a non-invasive brain stimulation procedure, which allows one to alter the excitability of cortical cells in both humans and animals. There is a broad consensus regarding the safety of this approach in humans, and different versions and protocols of this technique have been used in basic research and clinical studies for years. In this review, we aim to provide updated information on regulatory and ethical issues concerning the use of different versions of transcranial electrical stimulation (tES). This information may be critical due to its implications on the welfare and health of patients. Although tES is a safe and effective method with potential clinical and research utilities, the legal regulation criteria concerning the use different versions of tES are of critical relevance due to implications of brain stimulation for human health and well-being. Recent publications that review a nd describe all regulatory and safety aspects regarding the use of tES offer a practical vision about the most up-to-date information in this field and more relevant ethical implications.

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Brain Network Connectivity and the Choice Motor Reaction in Combatants with Mild Traumatic Brain Injuries

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We examined times (latencies) of two types of the sensorimotor (visuomotor) reactions, simple sensorimotor reaction (SSMR) and choice motor reaction (ChMR), in men (combatants) suffering from the consequences of mild traumatic brain injury (mTBI) during the Joint Forces Operation in the East of Ukraine (17 right-handed volunteers aged 27–43 years) and compared the respective values with those demonstrated by healthy control men (16 right-handed volunteers, 18–21 years). Combatants with mTBI were characterized by significantly greater values of the latency in the ChMR, mostly determined by considerably longer times necessary for decision-making processes. Results of the analysis of cerebral network connectivity based on the data of EEG recording, coherence measurements, and LORETA neurovisualization gave reasons to suppose that a large-scale synchronized frontoparietal neuronetwork functions in control subjects; this network is responsible for decision ma king according to the results of control, analysis of information, and coordination of various alternatives. Unlike this, an associative decision-making system mostly functions in combatants with mTBI; this system uses coding networks in the primary and secondary visual cortices; functioning of the above associative system is followed by the creation of imaginary phenomena and associations, which are then realized in motor acts.

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Motor Commands for Planar Movements of the Upper Limb: Modeling with Taking into Account Realistic Osteo-Muscular Relations

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Studies of motor control in humans require the formation of adequate concepts about the structure and metric characteristics of the musculoskeletal system, which provides the performance of the respective movements; such representations, in turn, are necessary prerequisites for further modeling of the phenomenology of motor control, theoretical analysis of the relevant processes, and interpretation of the obtained experimental data. We measured the length and shape of the muscles of the shoulder girdle (deltoideus pars scapilaris and pectoralis major pars clavicularis) of a healthy person performing planar (realized within the horizontal plane) movements of the upper limb, in which the hand moved via a straight line in the parafrontal plane at the level of the shoulder joint, and also calculated the corresponding arms of torques developed by these muscles. Such measurements were performed based on the results of computed tomography and 3D p rints of the bones (scapula, clavicula, and humerus). According to these data, we built regression formulas for the dependence of metric parameters of the muscles on values of the angle in the shoulder joint. The results of modeling of descending activation of these muscles during the mentioned movements are also presented; EMG signals recorded from the corresponding muscles were considered correlates of the descending commands. The results of such simulation demonstrated a satisfactory similarity between the characteristics of the modeled motor commands and those recorded in real experiments. The results obtained show that we have developed a realistic model of the musculoskeletal system of the upper extremity, which can be effectively used in studies of motor control in humans. Moreover, there are reasons to believe that our proposed method of estimating the parameters of the musculoskeletal system of the human arm is significantly more adequate than tho se previously proposed, in which the original data underwent excessive simplification.

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Partial Inhibition of Na + /K + -ATPase and Plasma Membrane Ca 2+ -ATPase from the Rat Cerebral Cortex by S-Nitrosoglutathione

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S-nitrosoglutathione (GSNO) is an endogenous S-nitrosylated glutathione derivative (GSH) involved in NO signaling. GSNO acts as a carrier of nitrosyl groups to cysteine (both free amino acid and its residues in proteins), a glutathionylation agent, and an NO donor. We investigated the effects of GSNO, GSH, and oxidized glutathione (GSSG) on the activity of two main ion pumps of the plasma membrane, Na+/K+-ATPase (NKA) and plasma membrane Ca2+-ATPase (PMCA). Plasma membranes were obtained from the rat cerebral cortex by differential centrifugation. Preincubation of the saponinpermeabilized plasma membranes at 37°C (but not at 0°C) with various concentrations of GSNO led to partial inhibition of ATPase activities of NKA and PMCA (on average, by 19.4 ± 2.2 and 42.1 ± 3% at 10 mM GSNO, respectively). The addition of GSH instead of GSNO did not affect the enzyme activities, while GSSG inhibited these enzymes much weaker than G SNO. The inhibited enzyme activities after the action of GSNO were partially restored after incubation of the membranes with a thiol-reducing agent, 2-mercaptoethanol. GSNO-dependent inhibition of NKA was not observed in the presence of ouabain (>1.0 μM), when only isozymes having an α1-subunit were active. GSNO inhibited both high- and lowsensitive to Ca2+ (calmodulin-dependent and calmodulin-independent) PMCA activities by 51 and 33%, respectively, with no changes in Km for Ca2+. It is assumed that GSNO or its degradation product(s), by modifying the thiol groups in NKA and PMCA molecules, partly inhibit their activity. Only NKA isozymes with α2 and α3 subunits, which are highly sensitive to ouabain, are likely to manifest such sensitivity. Inhibition of PMCA is not associated with a change in its sensitivity to Ca2+.

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Geospatial Virtual/Augmented Environment: Applications for Children with Pervasive Developmental Disorders

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The aim of this research is to describe applications of virtual/augmented reality (VR/AR) to the problems of children with pervasive developmental disorders (PDDs). We will try to verify whether the use of these techniques makes interventions in the case of children with PDDs (concerning their learning and communicative abilities and the state of their emotional sphere) expedient or not. This paper focuses on the use of new information and communication technologies (NICTs) in the treatment of these children and current researches. We will also observe the involvement of NICTs (such as VR/AR) in changing activities made with these tools on the didactic and methodological level. These analyzes will allow us to answer the following research problematic: How does the application of VR/AR in the case of children with PDDs contribute to the development of learning, communicative skills, and recognition and expression of the emotions?

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A Wireless Sensorized Insole Design for Spatio-Temporal Gait Analysis

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Gait disorders significantly affect the quality of life and limit individual freedom of the subjects affected. Our knowledge of the spatio-temporal gait parameters provides great insight into the musculoskeletal biology, especially into the foot pathology during gait. The aim of our study was to develop a wireless insole system for both feet and to quantify the gait parameters along with the center of pressure (CP) trajectory. Force-sensitive resistors (FSRs) were used as the pressure sensing elements for experimental study on a total of 10 healthy subjects (28 ± 2.7 years). The subjects were asked to walk with the instrumented insoles on three different terrain lengths of 12, 16, or 20 m. The gait parameters (number of strides, stride length, % swing, % stance, etc.), and the CP trajectory for each step of both feet was calculated. It was statistically established that the stance percentage of each foot is generally greater, on average, than the swing perc entage. Continuous evaluation of the foot trajectory revealed new insights into the intratrial characteristics of the subjects. The reproducibility of the device has been tested by repeating the experiment for three trials for each path length, and the results demonstrated that the gait parameters, including CP positions, are consistent with each other. An indigenous device has been developed to quantify various gait parameters. The CP trajectories were compared for each trial of a subject, and the results led to the conclusion that the gait of a subject remains constant, irrespectively of the number of trials and path distance. The parameters and CP characteristics provide beneficial knowledge of the appropriate gait performance evaluation and foot functions for clinical rehabilitation.

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Does Perceived Quality of Care Moderate Postpartum Depression? A Secondary Analysis of a Two-Stage Survey

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Abstract

Objective

The purpose of this study was to examine if women's perceptions of the quality of hospital care during childbirth moderate their risks for symptoms of postpartum depression (PPD).

Methods

This cross-sectional secondary analysis analyzed data from the Listening to Mothers III (2013) series surveys with a weighted sample size of 1057 of women surveyed from across the United States. PPD symptoms were defined according the Patient Health Questionnaire-2. Associations between risk factors and PPD symptoms were tested using logistic regressions with the moderating variable of perceived quality of care then added to models with significant risk factors.

Results

Of the 22 potential risk factors for PPD symptoms, 10 were found to be significantly associated with PPD symptoms in this sample of women. Very good perceived quality of care moderated the following risk factors for PPD symptoms in a protective direction: relationship status (p = 0.01), pre-pregnancy BMI (p = 0.02), and pain that interfered with routine activities 2 months postpartum (p = 0.003).

Conclusions

These findings suggest risk factors for PPD symptoms are moderated by perceived quality of care and therefore, maternity providers can influence women's psychological wellbeing postpartum by providing very good perceived quality of care during the hospital stay for birth. However, these findings should be interpreted cautiously due to a lack of a direct, proven relationship between provider action and women's perceived quality of care.

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Is effector visibility critical for performance asymmetries in the Simon task? Evidence from hand- and foot-press responses

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Abstract

The Simon effect is a stimulus-response compatibility effect in which the spatial dimension of the stimulus is task-irrelevant. This effect is often larger in reaction time (RT) for the stimulus located on the dominant-hand side of participants, for most of which it is the right hand, due to dominant-hand keypress responses being faster than non-dominant-hand responses. Experiment 1 demonstrated that pedal-press responses with the left and right feet show a similar asymmetry, favoring the right response for right-footed persons. The asymmetric pattern for keypress responses was absent in results of Wallace (Journal of Experimental Psychology, 93, 163–168, 1972) when participants were not permitted to see the response keys or their hands placed on the keys at any time during the experiment, whereas we found the asymmetric pattern in a recent study when participants placed their hands on the keys prior to their being covere d up. Experiments 2 and 3 showed that the Simon effect asymmetry for RT was evident even when participants were prevented from seeing the response device and their responding hands or feet. Although both hands and feet showed a Simon effect asymmetry in RT, consideration of incorrect responses suggested that whereas the asymmetry for hands is not due to a response bias, that for the feet may be due at least in part to such bias. Regardless, our results suggest that the Simon effect asymmetry is mainly an artifact of comparing conditions for which one response is made by the faster dominant right effector and the other with the slower non-dominant left effector.

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Statistical regularities cause attentional suppression with target-matching distractors

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Abstract

Visual search may be disrupted by the presentation of salient, but irrelevant stimuli. To reduce the impact of salient distractors, attention may suppress their processing below baseline level. While there are many studies on the attentional suppression of distractors with features distinct from the target (e.g., a color distractor with a shape target), there is little and inconsistent evidence for attentional suppression with distractors sharing the target feature. In this study, distractor and target were temporally separated in a cue–target paradigm, where the cue was shown briefly before the target display. With target-matching cues, RTs were shorter when the cue appeared at the target location (valid cues) compared with when it appeared at a nontarget location (invalid cues). To induce attentional suppression, we presented the cue more frequently at one out of four possible target positions. We found that invalid cues appearing at the high-frequency cue po sition produced less interference than invalid cues appearing at a low-frequency cue position. Crucially, target processing was also impaired at the high-frequency cue position, providing strong evidence for attentional suppression of the cued location. Overall, attentional suppression of the frequent distractor location could be established through feature-based attention, suggesting that feature-based attention may guide attentional suppression just as it guides attentional enhancement.

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Long term comparative evaluation of two types of absorbable meshes in partial abdominal wall defects: an experimental study in rabbits

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Abstract

Purpose

Synthetic prosthetic materials that are fully absorbable seek to reduce the host foreign body reaction and promote host tissue regeneration. This preclinical trial was designed to analyse, in the long term, the behaviour of two prosthetic meshes, one synthetic and one composed of porcine collagen, in abdominal wall reconstruction.

Methods

Partial defects were created in the abdominal walls of New Zealand rabbits and repaired using a synthetic absorbable mesh (Phasix™) or a non-crosslinked collagen bioprosthesis (Protexa™). After 3, 6, 12 and 18 months, specimens were recovered for light microscopy and collagen expression analysis to examine new host tissue incorporation, macrophage response and biomechanical strength.

Results

Both materials showed good host tissue incorporation in line with their spatial structure. At 18 months postimplant, Protexa™ was highly reabsorbed while the biodegradation of Phasix™ was still incomplete. Collagenization of both materials was good. Macrophage counts steadily decreased over time in response to Phasix™, yet persisted in the collagen meshes. At 18 months, zones of loose tissue were observed at the implant site in the absence of herniation in both implant types. The stress–stretch behaviour of Phasix™ implants decreased over time, being more pronounced during the period of 12–18 months. Nevertheless, the abdominal wall repaired with Protexa™ became stiffer over time.

Conclusion

Eighteen months after the implant both materials showed good compatibility but the biodegradation of Phasix™ and Protexa™ was incomplete. No signs of hernia were observed at 18 months with the stress–stretch relations being similar for both implants, regardless of the more compliant abdominal wall repaired with Protexa™ at short term.

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Could we reduce adhesions to the intra-abdominal mesh in the first week? Experimental study with different methods of fixation

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Abstract

Background

Adhesion formation is a major problem when a mesh is exposed to intraabodminal viscera, with potential severe complications (bowel occlusion, fistulas or abscesses). New methods for preventing adhesions from a polypropylene mesh placed intra-abdominally or to solve difficult situations, such as when the peritoneum cannot be closed during a TAPP repair for an inguinal hernia, are still being seeked. This study mimics in an animal model a situation that can be found in clinical practice during laparoscopic inguinal hernioplasty. A polypropylene mesh could be exposed to the intra-abdominal cavity even when the peritoneum is closed due to different circumstances, with no options to guarantee the prosthetic material of being exposed to the intrabdominal viscera. Different options have been suggested to solve these situations, being proposed in this study to cover the visceral surface of the mesh with an absorbable sponge containing thrombin, fibrinogen, and clotti ng factors (Tachosil®, Nycomed, Takeda, Osaka, Japan), to assess its use as a barrier to prevent postoperative adhesion formation.

Material and methods

Thirty Wistar white rats (300–450 mg) were included in this study as experimental animals, being randomized into three groups (A, B, and C). We performed a bilateral prosthetic repair with conventional polypropylene mesh (2 × 2 cm, 82 kD). Prosthesis fixation was performed as follows. Group A: absorbable suture; group B: metal staples; group C: metal tackers. A piece of insulating absorbable sponge (Tachosil® 5 × 5 cm) was placed to cover the visceral surface of mesh placed at the right side of each animal. After 10 days, we performed a gross examination (by laparoscopy and laparotomy), measuring the quantity and the quality of the adhesions. Samples were taken for histopathological analysis.

Results

Tachosil®-treated prostheses showed a statistically significant decrease in the quality of the adhesion found (p < 0.05). In addition, a smaller quantity of adhesions was identified in barrier-treated animals, although this lacked statistical significance. The histologic analysis showed no significant differences: more edema with the untreated mesh and increased angiogenesis and a lower degree of necrosis in mesh covered with Tachosil®.

Conclusions

The use of Tachosil® as a barrier material led to the absence of strong adhesions as it prevented direct contact between the mesh and the internal organs, preventing major problems associated with strong adhesions.

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