High-density Grid Research Articles

High-density Grid Catheter Localizes Eccentric Atrial Flutter to the Left Superior Pulmonary Vein Ridge Through Extreme Isochronal Compression.

High-density Grid Catheter Localizes Eccentric Atrial Flutter to the Left Superior Pulmonary Vein Ridge Through Extreme Isochronal Compression.

Elimination of Incessant Ventricular Tachycardia in Ischemic Cardiomyopathy with High-density Grid Technology.

Elimination of Incessant Ventricular Tachycardia in Ischemic Cardiomyopathy with High-density Grid Technology.

The evolving role of surface electromyography in amyotrophic lateral sclerosis: A systematic review

ObjectiveAmyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease that leads to inexorable motor decline and a median survival of three years from symptom onset. Surface EMG represents a major technological advance that has been harnessed in the development of novel neurophysiological biomarkers. We have systematically reviewed the current application of surface EMG techniques in ALS. MethodsWe searched PubMed to identify 42 studies focusing on surface EMG and its associated analytical methods in the diagnosis, prognosis and monitoring of ALS patients. ResultsA wide variety of analytical techniques were identified, involving motor unit decomposition from high-density grids, motor unit number estimation and measurements of neuronal hyperexcitability or neuromuscular architecture. Some studies have proposed specific diagnostic and prognostic criteria however clinical calibration in large ALS cohorts is currently lacking. The most validated method to monitor disease is the motor unit number index (MUNIX), which has been implemented as an outcome measure in two ALS clinical trials. ConclusionSurface EMG offers significant practical and analytical flexibility compared to invasive techniques. To capitalise on this fully, emphasis must be placed upon the multi-disciplinary collaboration of clinicians, bioengineers, mathematicians and biostatisticians. SignificanceSurface EMG techniques can enrich effective biomarker development in ALS.

Interfacing the neural output of the spinal cord: robust and reliable longitudinal identification of motor neurons in humans

Objective. Non-invasive electromyographic techniques can detect action potentials from muscle units with high spatial dimensionality. These technologies allow the decoding of large samples of motor units by using high-density grids of electrodes that are placed on the skin overlying contracting muscles and therefore provide a non-invasive representation of the human spinal cord output. Approach. From a sample of >1200 decoded motor neurons, we show that motor neuron activity can be identified in humans in the full muscle recruitment range with high accuracy. Main results. After showing the validity of decomposition with novel test parameters, we demonstrate that the same motor neurons can be tracked over a period of one-month, which allows for the longitudinal analysis of individual human neural cells. Significance. These results show the potential of an accurate and reliable assessment of large populations of motor neurons in physiological investigations. We discuss the potential of this non-invasive neural interfacing technology for the study of the neural determinants of movement and man-machine interfacing.

Functional Atrial Endocardial–Epicardial Dissociation in Patients With Structural Heart Disease Undergoing Cardiac Surgery

The goal of this study was to describe functional endocardial-epicardial dissociation (FEED), signal complexities, and three-dimensional activation dynamics of the human atrium with structural heart disease (SHD). SHD commonly predisposes to arrhythmias. Although progressive remodeling is implicated, direct demonstration of FEED in the human atrium has not been reported previously. Simultaneous intraoperative mapping of the endocardial and epicardial lateral right atrial wall was performed by using 2 high-density grid catheters during sinus rhythm, pacing drive (600ms and 400ms cycle length), and premature extrastimulation (PES). Unipolar electrograms (EGMs) were exported into custom-made software for activation and phase mapping. Difference of≥20ms between paired endocardial and epicardial electrodes defined dissociation. EGMs with≥3 deflections were classified as fractionated. Sixteen patients (mean age 60.5 ± 4.1 years; 18.7% with a history of atrial fibrillation) with SHD (43%ischemia, 57% valvular disease) were included. A total of 9,218 EGMs were analyzed. Compared with sinus rhythm, phase and activation analyses showed significant FEED during pacing at 600ms and 400ms (phase mapping 22.4% vs. 10% [p<0.0001] and 25.8% vs. 10% [p<0.0001], respectively; activation mapping 25.4% vs. 7.8% [p<0.0001] and 27.7% vs. 7.8% [p<0.0001]) and PES (phase mapping 34% vs. 10% [p<0.0001]; activation mapping 29.5% vs. 7.8% [p<0.0001]). Fractionated EGMs occurred significantly more during PES compared with sinus rhythm (50.2% vs. 39.5%; p<0.0001). Activation patterns differed significantly during pacing drive and PES, with preferential epicardial exit during the latter (15.9% vs. 13.8%; p=0.046). Simultaneous endocardial-epicardial mapping revealed significant FEED with signal fractionation and preferential epicardial breakthroughs with PES. Such complex three-dimensional interaction in electrical activation provides mechanistic insights into atrial arrhythmogenesis with SHD.

Enhanced ventricular tachycardia substrate resolution with a novel omnipolar high-density mapping catheter: the omnimapping study.

Defining diastolic slow-conduction channels within the borderzone (BZ) of scar-dependent re-entrant ventricular tachycardia (VT) is key for effective mapping and ablation strategies. Understanding wavefront propagation is driving advances in high-density (HD) mapping. The newly developed Advisor™ HD Grid Mapping Catheter (HD GRID) has equidistant spacing of 16, 1mm electrodes in a 4 × 4 3mm interspaced arrangement allowing bipolar recordings along and uniquely across the splines (orthogonal vector) to facilitate substrate mapping in a WAVE configuration (WAVE). The purpose of this study was to determine the relative importance of the WAVE configuration compared to the STANDARD linear-only bipolar configuration (STANDARD) in defining VT substrate. Thirteen patients underwent VT ablation at our institution. In all cases, a substrate map was constructed with the HD GRID in the WAVE configuration (conWAVE) to guide ablation strategy. At the end of the procedure, the voltage map was remapped in the STANDARD configuration (conSTANDARD) using the turbo-map function. Detailed post-hoc analysis of the WAVE and STANDARD maps was performed blinded to the configuration. Quantification of total scar area, BZ and dense scar area with assessment of conduction channels (CC) was performed. The substrate maps conSTANDARD vs conWAVE showed statistically significant differences in the total scar area (56 ± 32cm2 vs 51 ± 30cm2; p = 0.035), dense scar area (36 ± 25cm2 vs 29 ± 22cm2; p = 0.002) and number of CC (3.3 ± 1.6 vs 4.8 ± 2.5; p = 0.026). conWAVE collected more points than the conSTANDARD settings (p = 0.001); however, it used fewer points in map construction (p = 0.023). The multipolar Advisor™ HD Grid Mapping Catheter in conWAVE provides more efficient point acquisition and greater VT substrate definition of the borderzone particularly at the low-voltage range compared to conSTANDARD. This greater resolution within the low-voltage range facilitated CC definition and quantification within the scar, which is essential in guiding the ablation strategy.

Impact of Spacing and Orientation on the Scar Threshold With a High-Density Grid Catheter.

Multipolar catheters are increasingly used for high-density mapping. However, the threshold to define scar areas has not been well described for each configuration. We sought to elucidate the impact of bipolar spacing and orientation on the optimal threshold to match magnetic resonance imaging-defined scar. The HD-Grid catheter uniquely allows for different spatially stable bipolar configurations to be tested. We analyzed the electrograms with settings of HD-16 (3 mm spacing in both along and across bipoles) and HD-32 (1 mm spacing in along bipoles and 3 mm spacing in across bipoles) and determined the optimal cutoff for scar detection in 6 infarcted sheep. From 456 total acquisition sites (mean 76±12 per case), 14 750 points with the HD-16 and 32286 points with the HD-32 configuration for bipolar electrograms were analyzed. For bipolar voltages, the optimal cutoff value to detect the magnetic resonance imaging-defined scar based on the Youden's Index, and the area under the receiver operating characteristic curve (AUROC) differed depending on the spacing and orientation of bipoles; across 0.84 mV (AUROC, 0.920; 95% CI, 0.911-0.928), along 0.76 mV (AUROC, 0.903; 95% CI, 0.893-0.912), north-east direction 0.95 mV (AUROC, 0.923; 95% CI, 0.913-0.932), and south-east direction, 0.87 mV (AUROC, 0.906; 95% CI, 0.895-0.917) in HD-16; and across 0.83 mV (AUROC, 0.917; 95% CI, 0.911-0.924), along 0.46 mV (AUROC, 0.890; 95% CI, 0.883-0.897), north-east direction 0.89 mV (AUROC, 0.923; 95% CI, 0.917-0.929), and south-east direction 0.83 mV (AUROC, 0.913; 95% CI, 0.906-0.920) in HD-32. Significant differences in AUROC were seen between HD-16 along versus across (P=0.002), HD-16 north-east direction versus south-east direction (P=0.01), HD-32 north-east direction versus south-east direction (P<0.0001), and HD-16 along versus HD-32 along (P=0.006). The AUROC was significantly larger (P<0.01) when only the best points on each given site were selected for analysis, compared with when all points were used. Spacing and orientation of bipoles impacts the accuracy of scar detection. Optimal threshold specific to each bipolar configuration should be determined. Selecting one best voltage point among multiple points projected on the same surface is also critical on the Ensite-system to increase the accuracy of scar-mapping.

Using Ground Penetrating Radar Methods to Investigate Reinforced Concrete Structures

This paper provides an overview of the existing literature on the subject of ground penetrating radar (GPR) methods for the investigation of reinforced concrete structures. An overview of the use of concrete and reinforced concrete in civil engineering infrastructures is given. A review of the main destructive and non-destructive testing methods in the field is presented, and an increase in the use of GPR to reinforced concrete structures is highlighted. It was also observed that research in some application areas has been predominantly or exclusively carried out at a laboratory scale, and that similarly, other more application-oriented research has been developed only on real-life structures. The effectiveness of GPR in these areas is demonstrated. Furthermore, a case study is presented on a new methodological and data processing approach for the assessment of reinforced concrete structures using a high-frequency dual-polarised antenna system. Results have proven the advantages of using the proposed methodology and GPR system in order to improve the detectability of rebars, including secondary bottom lines of reinforcement. The horizontal polarisation was proven to be more stable compared to the vertical. Finally, it has been demonstrated that a more accurate location of the rebars in a high-density grid mesh arrangement can be obtained by means of data migration processing with a scan spacing of 5 cm and wave velocity information through the use of the hyperbola fitting method from at least 30% of the targets.

High-density ECoG improves the detection of high frequency oscillations that predict seizure outcome

ObjectivesResidual fast ripples (FR) in the intraoperative ECoG are highly specific predictors of postsurgical seizure recurrence. However, a FR is generated by a small patch of cortical tissue. Spatial sampling with standard electrodes may thus miss clinically relevant information. MethodsWe analyzed FR rates in the intraoperative ECoG of 22 patients that underwent resective epilepsy surgery. We used standard electrodes with 10 mm inter-contact spacing (standard ECoG) in 14 surgeries and high-density grid electrodes with 5 mm spacing (hd-ECoG) in 8 surgeries. We detected FR using a previously validated automatic detector. ResultsPostoperative seizure freedom was achieved in 14/22 (64%) cases. Across all 42 ECoG recordings, FR rates were higher for hd-ECoG than for standard ECoG. In the 14 seizure free patients (ILAE 1), no residual FR were detected (specificity = 100%). In the 8 patients with seizure recurrence (ILAE > 1), residual FR were detected in 1/7 standard ECoG and 1/1 hd-ECoG (Accuracy ACCstandard ECoG = 57%, CI [29% 82%], ACChd-ECoG = 100%, CI [63% 100%]). ConclusionDenser spatial sampling by hd-ECoG improved FR detection compared to standard ECoG. SignificanceHd-ECoG may advance seizure freedom after epilepsy surgery.

Spatial-temporal Evolution and Completeness Analysis of OpenStreetMap Building Data in China from 2012 to 2017

Abstract. OpenStreetMap (OSM), as a typical volunteered geographic information project, is an online map with free content and everyone can edit and use it (Goodchild 2007). A range of applications has been proposed using OSM data, including routing and navigation, crisis mapping, 3D modelling, land use/cover mapping. This is because the OSM data is not only free of use, but also has a global coverage and high currentness. In despite of the above advantages, however, most of the OSM data were contributed by ‘non-professional’ or ‘amateur geographers’ (Goodchild 2008; Haklay 2010). Therefore, a lot of concerns have been paid attention to the quality issue of the OSM data. Assessing the quality of OSM data has become a hot topic in the field of geographic information science.Extensive studies have been carried out on assessing various quality measures (e.g. positional accuracy, completeness and attribute accuracy) of OSM datasets in different countries or districts such as Germany, England, France, Italy, Canada and the United States. In the meanwhile, the road feature of an OSM dataset has been paid much attention to. To our knowledge, however, not any study has been focused on assessing the data quality of OSM building data in China, although it may be an essential data source for urban planning and management, 3D modelling and indoor navigation. Therefore, the aim of this study is to investigate the OSM building data in China. More precisely, an analysis of the spatial-temporal evolution and completeness of OSM building data in China from 2012 to 2017 was carried out. The tenet of our study was to employ two quality indicators, i.e. building count (Gröchenig et al. 2013, Barron et al. 2014, Fan 2016) and building density (Zhou 2018), for the analyses. First, the numbers of OSM building data from 2012 to 2017 were calculated in terms of both provincial- and prefecture-level divisions in China; The OSM building count were then compared among different divisions and also different years (2012–2017) for analyzing the evolution of OSM building data in China in both temporal dimension and spatial scale. Moreover, the correlations between OSM building counts and four potential factors (i.e. gross domestic product (GDP), population, urban land area, OSM road length), which may influence the development of OSM building data in China, were respectively investigated. Second, a 1 × 1 km2 regular grid was overlapped onto the OSM building datasets in urban areas for calculating the OSM building density of each grid cell; Moreover, high-density grid cells (whose OSM building data were almost complete) were extracted and analyzed through a simple clustering method, in order to investigate the spatial pattern of OSM building data in urban areas. Results showed that,1) The OSM building data in China increased almost 20 times from the years 2012 to 2017, especially for those located in the eastern coastal regions of China (e.g. the provincial-level divisions: Jinagsu, Zhejiang, Guangzhou and Shandong and the prefecture-level divisions: Beijing, Nantong, Shanghai, Tianjin, Suzhou, Yangzhou and Dalian). In most cases, both the GDP and OSM road length factors had a moderate correlation with the OSM building count. 2) Most of the grid cells in urban areas still had no building or their building densities were equal to 0%, which indicated that the OSM building dataset in China was far from being complete. From analyzing the high density grid cells, two typical spatial distribution modes, i.e. dispersion and aggregation, were found in different prefecture-level divisions. As an example, the high-density grid cells for some prefecture-level divisions (e.g. Luoyang, Yueyang and Dalian) were mostly aggregated in the city cores; while those for some (e.g. Beijing Tianjin and Shanghai) were located in the hot spots such as business districts, attractions and transportation hubs.The above results may benefit for users (especially those researchers and educators) to choose appropriate study area(s) from the OSM building dataset in China. In the meanwhile, the volunteers around the world may be motivated to contribute more OSM building data in this region. Further research work may include: developing quality indicators for quantitative completeness estimation of OSM building data, especially in rural areas; and investigating other quality measures (e.g. positional accuracy and semantic accuracy) or geographical features (e.g. railways, land uses, and points of interest) in China’s OSM dataset.

Interpolation of daily rainfall data using censored Bayesian spatially varying model

This paper illustrates a Bayesian spatially varying space-time model to analyse daily precipitation in the Murray Darling Basin (MDB) of Australia. The model is capable of addressing data censoring at zero rainfall days using a latent Gaussian spatial field. The model is also useful for analysing data obtained from sparse locations, where spatially varying parameters are used to interpolate the rainfall estimates in high-density grids across the MDB region. We find that the proposed censored method provides a better out-of-sample predictive performance for the daily rainfall measurements compared to a non-truncated method. Additionally, it identifies location specific trends over the study region. The model is constructed under the Bayesian paradigm and the Markov chain Monte Carlo algorithm is used to obtain inferences of the model parameters. The R software spTDyn is hence extended to version 2.0 to implement the model.

Model updating of uncertain parameters of carbon/epoxy composite plates from experimental modal data

This work presents a methodology to obtain physically-sound models of composite structure laminates using a combination of modal analysis, numerical modelling and parameter updating, avoiding the common uncertainties on the constructions of similar numerical models. Moreover this model establishes the baseline (pristine situation) of the dynamic behaviour of the set of composite plates. Therefore it could be applied for condition assessment or quality manufacturing control of existing structures through a non-destructive Structural Health Monitoring (SHM), and hence it could help to detect degradation or defects of the composite components. The driven data of the methodology were the modal frequencies and shapes of composite plates. To obtain these values an extensive experimental campaign of modal analysis has been performed on a set of carbon/epoxy laminates. A multiple input single output technique has been applied, using a roving hammer exciting the plates at evenly distributed Degrees of Freedom (DoF), and a mono-axial accelerometer attached to a single DoF reference point. The use of a high dense grid of points has allowed to identify a number of natural frequencies greater than usual in similar works, as well as improving the smoothness of the mode shape. Modal characteristics numerically obtained from a Finite Element Method (FEM) model based on manufacturer reference data were compared with experimental results. This baseline model was updated through a gradient based optimization algorithm. Before the process of model updating, a sensitivity analysis has been performed to identify the driven uncertain parameters using a Montecarlo approach. This technique reduces the number of parameters to be optimized to a small set increasing the efficiency of the methodology. As a result of the whole process, a physically more accurate model is obtained on which discrepancies with the corresponding experimentally measured modal parameters are drastically reduced. Analysis of the consistency of the adjusted numerical parameters has been done with alternative experimental tests (Quasi Static Loading (QSL) and Ultrasonic inspection).

High-density 360-degree Circle Grid for Detection of After Discharges During Functional Brain Mapping in Patients with Glioma (S3.006)

High-density 360-degree Circle Grid for Detection of After Discharges During Functional Brain Mapping in Patients with Glioma (S3.006)

Reliability Physics Approach for High-Density Ball Grid Arrays in Autonomous Vehicle Applications

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Integration of advanced sensing systems in autonomous vehicles is possible due to high performance processors that utilize high-density ball grid array (HD-BGA) packaging. The configuration of advanced sensors within autonomous vehicles requires the placement of processing modules within non-conventional vehicles compartments that can drastically influence the reliability of HD-BGAs. Durability of HD-BGAs to different loads depend on their location within the vehicle as well as the form factor of the package itself. Reliability Physics Approach (RPA) combines simulation tools and empirical models to predict the reliability of advanced electronic packages under complex environmental and operational loads by identifying the susceptibility of electronic components to the dominant failure mechanism. In this paper, the reliability of an electronic module will be investigated under various vibration loads at different vehicle compartments and the influence of mounting configuration of electronic module to housing under thermal loads. In addition, the BGA form factor will be investigated to demonstrate the implementation of RPA early in the design process to develop such mitigation techniques as underfill selection to improve the reliability of HD-BGAs in autonomous vehicle applications.&lt;/div&gt;&lt;/div&gt;

The increase in muscle force after 4weeks of strength training is mediated by adaptations in motor unit recruitment and rate coding.

Previous studies have indicated that several weeks of strength training is sufficient to elicit significant adaptations in the neural drive sent to the muscles. There are few data, however, on the changes elicited by strength training in the recruitment and rate coding of motor units during voluntary contractions. We show for the first time that the discharge characteristics of motor units in the tibialis anterior muscle tracked across the intervention are changed by 4weeks of strength training with isometric voluntary contractions. The specific adaptations included significant increases in motor unit discharge rate, decreases in the recruitment-threshold force of motor units and a similar input-output gain of the motor neurons. The findings suggest that the adaptations in motor unit function may be attributable to changes in synaptic input to the motor neuron pool or to adaptations in intrinsic motor neuron properties. The strength of a muscle typically begins to increase after only a few sessions of strength training. This increase is usually attributed to changes in the neural drive to muscle as a result of adaptations at the cortical or spinal level. We investigated the change in the discharge characteristics of large populations of longitudinally tracked motor units in tibialis anterior before and after 4weeks of strength training the ankle-dorsiflexor muscles with isometric contractions. The adaptations exhibited by 14 individuals were compared with 14 control subjects. High-density electromyogram grids with 128 electrodes recorded the myoelectric activity during isometric ramp contractions to the target forces of 35%, 50% and 70% of maximal voluntary force. The motor unit recruitment and derecruitment thresholds, discharge rate, interspike intervals and estimates of synaptic inputs to motor neurons were assessed. The normalized recruitment-threshold forces of the motor units were decreased after strength training (P<0.05). Moreover, discharge rate increased by 3.3±2.5pps (average across subjects and motor units) during the plateau phase of the submaximal isometric contractions (P<0.001). Discharge rates at recruitment and derecruitment were not modified by training (P<0.05). The association between force and motor unit discharge rate during the ramp-phase of the contractions was also not altered by training (P<0.05). These results demonstrate for the first time that the increase in muscle force after 4weeks of strength training is the result of an increase in motor neuron output from the spinal cord to the muscle.

An Analysis of the Evolution, Completeness and Spatial Patterns of OpenStreetMap Building Data in China

OpenStreetMap (OSM) is a free map that can be created, edited, and updated by volunteers globally. The quality of OSM datasets is therefore of great concern. Extensive studies have focused on assessing the completeness (a quality measure) of OSM datasets in various countries, but very few have been paid attention to investigating the OSM building dataset in China. This study aims to present an analysis of the evolution, completeness and spatial patterns of OSM building data in China across the years 2012 to 2017. This is done using two quality indicators, OSM building count and OSM building density, although a corresponding reference dataset for the whole country is not freely available. Development of OSM building counts from 2012 to 2017 is analyzed in terms of provincial- and prefecture-level divisions. Factors that may affect the development of OSM building data in China are also analyzed. A 1 × 1 km2 regular grid is overlapped onto urban areas of each prefecture-level division, and the OSM building density of each grid cell is calculated. Spatial distributions of high-density grid cells for prefecture-level divisions are analyzed. Results show that: (1) the OSM building count increases by almost 20 times from 2012 to 2017, and in most cases, economic (gross domestic product) and OSM road length are two factors that may influence the development of OSM building data in China; (2) most grid cells in urban areas do not have any building data, but two typical patterns (dispersion and aggregation) of high-density grid cells are found among prefecture-level divisions.

Alloy-assisted Auger recombination in InGaN

It has been numerically investigated the effect of alloying on the Auger recombination rate in wurtzite type n-InGaN. In order to explicitly take into account the effect of alloy disorder, the calculations have been performed with a 256-atom supercell that includes In and Ga atoms randomly distributed over the supercell sites to obtain a given composition. A full band structure (no band scissors-shifting) and high-dense inhomogeneous k-point grid were used to improve the accuracy of the calculations. We show that the large number of allowed interband Auger transitions originated by the breaking of the translational periodicity plays a crucial role in the wide band gap InGaN alloys. The alloy-assisted Auger coefficients for these alloys are in the 1.0 × 10−32–4.7 × 10−31 cm6/s range

Efficient Memristor-Based Architecture for Intrusion Detection and High-Speed Packet Classification

Deep packet inspection (DPI) is a critical component to prevent intrusion detection. This requires a detailed analysis of each network packet header and body. Although this is often done on dedicated high-power servers in most networked systems, mobile systems could potentially be vulnerable to attack if utilized on an unprotected network. In this case, having DPI hardware on the mobile system would be highly beneficial. Unfortunately, DPI hardware is generally area and power consuming, making its implementation difficult in mobile systems. We developed a memristor crossbar-based approach, inspired by memristor crossbar neuromorphic circuits, for a low-power, low-area, and high-throughput DPI system that examines both the header and body of a packet. Two key types of circuits are presented: static pattern matching and regular expression circuits. This system is able to reduce execution time and power consumption due to its high-density grid and massive parallelism. Independent searches are performed using low-power memristor crossbar arrays giving rise to a throughput of 160Gbps with no loss in the classification accuracy.

A Fatigue Involved Modification Framework for Force Estimation in Fatiguing Contraction.

To alleviate the negative impacts of muscle fatigue on a force estimation model, a modification framework taking use of fatigue index was put forward in this paper. Muscle force and surface electromyography were first collected using high-density electrode grid and dynamometer. Then, multi-step signal pre-processing and a nonnegative matrix factorization-based signal optimization were conducted, with fatigue indices being extracted in the same time. Next, a degree 4 polynomial fitting model was employed to undertake the training process, and the relationship between the generated model parameters and fatigue indices was built up. In the end, the parameter-index relationship was applied on different testing sets to complete fatigue-modified force estimation. Significant improvement was found in most testing cases across different sexes and ages. Relative decreases of 36.5%, 20.7%, and 20.4% in the percentage root mean square error were achieved by young males, young females, and elderly males. The proposed method can boost the performances of force estimation models, thereby contributing to the development of a variety of fields including biomechanical study, rehabilitation treatment, and prosthesis research.

GridLoc: An automatic and unsupervised localization method for high-density ECoG grids

Precise localization of electrodes is essential in the field of high-density (HD) electrocorticography (ECoG) brain signal analysis in order to accurately interpret the recorded activity in relation to functional anatomy. Current localization methods for subchronically implanted HD electrode grids involve post-operative imaging. However, for situations where post-operative imaging is not available, such as during acute measurements in awake surgery, electrode localization is complicated. Intra-operative photographs may be informative, but not for electrode grids positioned partially or fully under the skull. Here we present an automatic and unsupervised method to localize HD electrode grids that does not require post-operative imaging. The localization method, named GridLoc, is based on the hypothesis that the anatomical and vascular brain structures under the ECoG electrodes have an effect on the amplitude of the recorded ECoG signal. More specifically, we hypothesize that the spatial match between resting-state high-frequency band power (45–120 Hz) patterns over the grid and the anatomical features of the brain under the electrodes, such as the presence of sulci and larger blood vessels, can be used for adequate HD grid localization. We validate this hypothesis and compare the GridLoc results with electrode locations determined with post-operative imaging and/or photographs in 8 patients implanted with HD-ECoG grids. Locations agreed with an average difference of 1.94 ± 0.11 mm, which is comparable to differences reported earlier between post-operative imaging and photograph methods. The results suggest that resting-state high-frequency band activity can be used for accurate localization of HD grid electrodes on a pre-operative MRI scan and that GridLoc provides a convenient alternative to methods that rely on post-operative imaging or intra-operative photographs.