A masked least-squares smoothing procedure for artifact reduction in scanning-EMG recordings

Scanning-EMG is an electrophysiological technique in which the electrical activity of the motor unit is recorded at multiple points along a corridor crossing the motor unit territory. Correct analysis of the scanning-EMG signal requires prior elimination of interference from nearby motor units. Although the traditional processing based on the median filtering is effective in removing such interference, it distorts the physiological waveform of the scanning-EMG signal. In this study, we describe a new scanning-EMG signal processing algorithm that preserves the physiological signal waveform while effectively removing interference from other motor units. To obtain a cleaned-up version of the scanning signal, the masked least-squares smoothing (MLSS) algorithm recalculates and replaces each sample value of the signal using a least-squares smoothing in the spatial dimension, taking into account the information of only those samples that are not contaminated with activity of other motor units. The performance of the new algorithm with simulated scanning-EMG signals is studied and compared with the performance of the median algorithm and tested with real scanning signals. Results show that the MLSS algorithm distorts the waveform of the scanning-EMG signal much less than the median algorithm (approximately 3.5 dB gain), being at the same time very effective at removing interference components.

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Graphical Abstract The raw scanning-EMG signal (left figure) is processed by the MLSS algorithm in order to remove the artifact interference. Firstly, artifacts are detected from the raw signal, obtaining a validity mask (central figure) that determines the samples that have been contaminated by artifacts. Secondly, a least-squares smoothing procedure in the spatial dimension is applied to the raw signal using the not contaminated samples according to the validity mask. The resulting MLSS-processed scanning-EMG signal (right figure) is clean of artifact interference.

     

Does 3-dimensional imaging of the third molar reduce the risk of experiencing inferior alveolar nerve injury owing to extraction?: A meta-analysis

Background

Clinicians generally use panoramic radiographic (PR) images to assess the proximity of the mandibular third molar to the inferior alveolar nerve (IAN). However, in cases in which a patient needs to undergo a third-molar extraction, many clinicians also assess computed tomographic (CT) images to prevent nerve damage.

Functional and structural characterization of four mouse monoclonal antibodies to complement C3 with potential therapeutic and diagnostic applications

C3 is the central component of the complement system. Upon activation, C3 sequentially generates various proteolytic fragments, C3a, C3b, iC3b, C3dg, each of them exposing novel surfaces, which are sites of interaction with other proteins. C3 and its fragments are therapeutic targets and markers of complement activation. We report the structural and functional characterization of four monoclonal antibodies (mAbs) generated by immunizing C3‐deficient mice with a mixture of human C3b, iC3b and C3dg fragments, and discuss their potential applications. This collection includes three mAbs interacting with native C3 and inhibiting AP complement activation; two of them by blocking the cleavage of C3 by the AP C3‐converase and one by impeding formation of the AP C3‐convertase. The interaction sites of these mAbs in the target molecules were determined by resolving the structures of Fab fragments bound to C3b and/or iC3b using electron microscopy. A fourth mAb specifically recognizes the iC3b, C3dg, and C3d fragments. It binds to an evolutionary‐conserved neoepitope generated after C3b cleavage by FI, detecting iC3b/C3dg deposition over opsonized surfaces by flow cytometry and immunohistochemistry in human and other species. Because well‐characterized anti‐complement mAbs are uncommon, the mAbs reported here may offer interesting therapeutic and diagnostic opportunities.     

Task-driven intra- and interarea communications in primate cerebral cortex

Neural correlations during a cognitive task are central to study brain information processing and computation. However, they have been poorly analyzed due to the difficulty of recording simultaneous single neurons during task performance. In the present work, we quantified neural directional correlations using spike trains that were simultaneously recorded in sensory, premotor, and motor cortical areas of two monkeys during a somatosensory discrimination task. Upon modeling spike trains as binary time series, we used a nonparametric Bayesian method to estimate pairwise directional correlations between many pairs of neurons throughout different stages of the task, namely, perception, working memory, decision making, and motor report. We find that solving the task involves feedforward and feedback correlation paths linking sensory and motor areas during certain task intervals. Specifically, information is communicated by task-driven neural correlations that are significantly delayed across secondary somatosensory cortex, premotor, and motor areas when decision making takes place. Crucially, when sensory comparison is no longer requested for task performance, a major proportion of directional correlations consistently vanish across all cortical areas.The problem of neural communication in the brain has been little explored traditionally due to the need for simultaneous recordings (1). The arrival of new techniques to record both neural population activity and single-neuron action potentials offers new prospects to study this problem (2, 3). Recently, population recordings have motivated a large number of works on multiunit interactions, including the study of interactions between local field potentials (LFPs) (4–6), LFPs and multiunit activity (5), and LFPs and neuronal spikes (7), but less attention has been paid to interactions between single-unit recordings (8). However, the analysis of simultaneous spike trains becomes critical because it is generally assumed that neurons are key units in distributing information across brain areas (9).An ideal paradigm to study neural communication is the somatosensory discrimination task designed by Romo and coworkers (10). In this task, a trained monkey discriminates the difference in frequency between two mechanical vibrations delivered sequentially to one fingertip (Fig. 1A). Essentially, the monkey must hold the first stimulus frequency (f1) in working memory, must compare the second stimulus frequency (f2) with the memory trace of f1 to form a decision of whether f2 > f1 or f2 < f1, and must postpone the decision until a sensory cue triggers the motor report (11). At the end of every trial, the monkey is rewarded with a drop of liquid for correct discriminations. Previous work on this task has analyzed how single-neuron responses across sensory and motor areas linearly correlate with stimuli and the decision report during the key stages of the task (12). The results show that stimuli are mostly encoded in somatosensory areas, the processes of working memory; that comparison takes place in the secondary somatosensory cortex (S2) and premotor areas; and that behavioral information is primarily found in premotor and motor areas. Thus, the somatosensory discrimination task activates complex processes that are required to communicate information from the areas that encode the stimuli to the areas that integrate them and report the decision.Open in a separate windowFig. 1.Somatosensory discrimination task and cortical recording sites. (A) Sequence of events during the discrimination and passive stimulation tasks (f1, first stimulus; f2, second stimulus; kd, key down; ku, key up; pb, pushbutton; pd, probe down; pu, probe up) (Materials and Methods). (B) Top view of the monkey brain and the recorded cortical areas (green spots).In the present work, we study this communication paradigm through the analysis of simultaneous recordings of neurons engaged in the task (6, 13) from two monkeys. Indeed, by applying nonlinear statistical methods, we estimate modulated cortical correlations that help describe how task-related information flows from sensory to motor areas when a correct decision is made.     

Screening outcome and surgical treatment during and after the transition from screen‐film to digital screening mammography in the south of The Netherlands

We determined screening outcome of subsequent screens during and after the transition from screen‐film mammography (SFM) to full‐field digital mammography (FFDM). A consecutive series of 102,863 subsequent (SFM screens with a prior SFM screen (SFM‐SFM cohort), 91,941 FFDM screens with a prior SFM screen (FFDM‐SFM cohort) and 90,407 FFDM screens with a prior FFDM screen (FFDM‐FFDM cohort) were obtained between January 2006 and July 2013. The referral rate and cancer detection rate (CDR) per 1,000 screens were higher at FFDM‐SFM than at SFM–SFM (2.7% vs. 1.2% (p < 0.001) and 7.0 vs. 4.9, p < 0.001), at the expense of a lower positive predictive value (PPV) of referral (25.8% vs. 39.6%, p < 0.001). These parameters were comparable for FFDM‐SFM and FFDM–FFDM. Ductal carcinoma in situ (DCIS) and invasive cancer rates increased during transition and remained stable after transition. The rate of DCIS of intermediate grade increased during the transition from 0.2 per 1,000 screened women at SFM‐SFM to 0.6 at FFDM‐SFM (p < 0.001) and 0.5 at FFDM‐FFDM (p = 0.001). Compared to SFM‐SFM, a significantly higher rate of invasive cancers were stage T1a‐b at FFDM‐SFM (p < 0.001) and FFDM‐FFDM (p < 0.001). Breast conserving surgery rates increased during transition (p < 0.001) and remained stable afterwards. The CDR and referral rate remained significantly higher at FFDM than at SFM, at the expense of a decreased PPV of referral. During transition, DCIS was more often of intermediate grade and invasive cancers were of smaller size.     

Y-STR variation in the Basque diaspora in the Western USA: evolutionary and forensic perspectives

Individuals of Basque origin migrated in large numbers to the Western USA in the second half of the nineteenth century, and the flow continued with less intensity during the last century. The European source population, that of the Basque Country, has long been a cultural and geographical isolate. Previous studies have demonstrated that Y-STR frequencies of Basques are different from those of other Spanish and European populations [1]. The Basque diaspora in the Western USA is a recent migration, but the founder effect and the incorporation of new American Y chromosomes into the paternal genetic pool of the Basque diaspora could have influenced its genetic structure and could thus have practical implications for forensic genetics. To check for genetic substructure among the European source and Basque diaspora populations and determine the most suitable population database for the Basque diaspora in the Western USA, we have analysed the haplotype distribution of 17 Y-STRs in both populations. We have found that the Basque diaspora in the Western USA largely conserve the Y chromosome lineage characteristic of the autochthonous European Basque population with no statistically significant differences. This implies that a common 17 Y-STR Basque population database could be used to calculate identification or kinship parameters regardless of whether the Basque individuals are from the European Basque Country or from the Basque diaspora in the Western USA.     

Epstein–Barr virus‐positive post‐transplant lymphoproliferative disorder of the central nervous system,after renal transplantation with a discrepancy in viral load between peripheral blood and cerebrospinal fluid

A 43‐year‐old female developed an Epstein–Barr virus (EBV)‐positive post‐transplant lymphoproliferative disorder (PTLD) in the central nervous system (CNS), 14 years after renal transplantation. One year prior to presentation, the patients’ treatment regimen was altered from cyclosporine, azathioprine, and prednisone to mycophenolate mofetil and prednisone. Magnetic resonance imaging of the brain revealed lesions suspect for malignant lymphoma. The EBV real‐time polymerase chain reaction (PCR) on peripheral blood was negative, but highly positive on cerebrospinal fluid. EBV‐positive PTLD was confirmed using histological analysis of cerebral biopsies. Despite tapering of immune suppressive medication and treatment with rituximab and chemotherapy, the patient deceased 50 days after presentation. This case illustrates that vigilance is required when presented with a negative EBV PCR result on peripheral blood when PTLD of the CNS is suspected. This late presentation suggests a relation to the switch in immunosuppressive regimen 1 year earlier.     

Does aerobic exercise intensity affect health‐related parameters in overweight women?

The aim of this study was to compare the effect of a cycling training programme performed at intensity corresponding to the lowest value of the respiratory quotient (RQ) versus at intensity corresponding to the ventilatory threshold (VT), on body composition and health‐related parameters in overweight women. Thirty‐two sedentary obese women (27–42 years old) were studied in a randomized trial of either RQ (n = 17) or VT (n = 15). RQ and VT training sessions were equalized by time (60 min) and performed in a cycloergometer. Anthropometry, body composition, lipid profile, glucose, basal metabolic rate (BMR) and fitness (maximal oxygen uptake) were evaluated before and after 12 weeks of intervention. Body weight, body mass index, fatness and fitness were improved in both groups (P<0·001). Triglycerides (TG) levels decreased only in response to RQ (P<0·001) and fat‐free mass (FFM) to VT (P = 0·002). No differences were observed between groups. Both exercise intensities seem to be effective for improving health in overweight women. However, low‐intensity compared with the high‐intensity exercise training appears to have additional benefits on TG levels and to maintenance of FFM.     

Pediatric Transesophageal Echocardiography by Means of a Miniature 5-MHz Multiplane Transducer

The development of a miniature multiplane transesophageal echocardiographic (TEE) transducer for pediatric use is the latest development in TEE. Horizontal, longitudinal, and all possible intermediate oblique planes can be obtained with minimal transducer manipulation. We studied 48 patients with an experimental 5-MHz transducer, which contains 48 transmitting elements. The dimensions of the tip are 27 × 10.6 × 7.9 mm. Patients ages ranged from 2 days to 16 years, their weights from 3.6–67 kg. Multiplane TEE proved to be complementary to the single horizontal plane in assessing the right ventricular outflow tract, the left ventricular outflow tract, ascending aorta, the atrial septum, the atrioventricular (AV) valves, especially in AV septal defects, and double inlet left ventricle (DILV). Moreover, multiplane TEE was extremely helpful in judging the outflow tracts and ventricular septal defects in more complex heart defects such as DILV, double outlet right ventricle, and hearts with discordant connections. Multiplane TEE offered superb monitoring of cardiac interventions. We conclude that multiplane TEE provides new imaging planes and enables visualization of every major structure of the heart by unlimited scan planes. Multiplane TEE is indispensable in congenital heart defects. Thus, multiplane TEE adds to diagnostic assurance and enhances decision making for surgery.