Three-dimensional Kinematics Research Articles

Differences in Tridimensional Shoulder Kinematics between Asymptomatic Subjects and Subjects Suffering from Rotator Cuff Tears by Means of Inertial Sensors: A Cross-Sectional Study.

Background: The aim of this study was to analyze differences in three-dimensional shoulder kinematics between asymptomatic subjects and patients who were diagnosed with rotator cuff tears. Methods: This cross-sectional study recruited 13 symptomatic subjects and 14 asymptomatic subjects. Data were obtained from three inertial sensors placed on the humerus, scapula and sternum. Kinematic data from the glenohumeral, scapulothoracic and thoracohumeral joints were also calculated. The participants performed shoulder abductions and flexions. The principal angles of movements and resultant vectors in each axis were studied. Results: The glenohumeral joint showed differences in abduction (p = 0.001) and flexion (p = 0.000), while differences in the scapulothoracic joint were only significant during flexion (p = 0.001). The asymptomatic group showed higher velocity values in all sensors for both movements, with the differences being significant (p < 0.007). Acceleration differences were found in the scapula during abduction (p = 0.001) and flexion (p = 0.014), as well as in the sternum only during shoulder abduction (p = 0.022). Conclusion: The results showed kinematic differences between the patients and asymptomatic subjects in terms of the mobility, velocity and acceleration variables, with lower values for the patients.

Effect of the Effortful Swallow on Pharyngeal Cavity Volume: Kinematic Analysis in Three Dimensions Using 320-Row Area Detector Computed Tomography.

This study evaluated the effects of the effortful swallow (ES) on pharyngeal cavity volume using three-dimensional kinematic analyses. Nine healthy volunteers (30.7 ± 7.8years old) underwent a CT scan while swallowing 10ml of honey thick liquid using no maneuvers (control) and during an ES. Upper and lower volumes (bordered by valleculae) of the pharyngeal air column and the bolus were measured at every frame and were compared between ES and control swallows. Duration of pharyngeal obliteration and the timing of swallowing events were also measured. Maximum volume and volume at the onset of hyoid anterosuperior movement using ES were significantly smaller than those in control swallows (p = 0.012, p = 0.015) in the upper pharynx but not significantly different in lower pharynx. Minimum pharyngeal volume was sustained for a longer time when ES was used compared to control swallows in both upper and lower pharynx (upper p = 0.016, lower p = 0.027). Onset of velopharyngeal closure was earlier when comparing ES and control swallows (p = 0.04). Termination of all events was significantly delayed when the ES was used (p < 0.05). Changes in the upper pharyngeal volume and in the onset of velopharyngeal closure suggest earlier pharyngeal constriction when using the ES. Longer pharyngeal obliteration and prolonged termination of velopharyngeal closure and epiglottis inversion suggest the prolonged pharyngeal constriction during the ES. These findings suggest the ES can be useful for improving the efficiency of swallowing.

In-Vivo Quantification of Knee Deep-Flexion in Physiological Loading Condition trough Dynamic MRI

The in-vivo quantification of knee motion in physiological loading conditions is paramount for the understanding of the joint’s natural behavior and the comprehension of articular disorders. Dynamic MRI (DMRI) represents an emerging technology that makes it possible to investigate the functional interaction among all the joint tissues without risks for the patient. However, traditional MRI scanners normally offer a reduced space of motion, and complex apparatus are needed to load the articulation, due to the horizontal orientation of the scanning bed. In this study, we present an experimental and computational procedure that combines an open, weight-bearing MRI scanner with an original registration algorithm to reconstruct the three-dimensional kinematics of the knee from DMRI, thus allowing the investigation of knee deep-flexion under physiological loads in space. To improve the accuracy of the procedure, an MR-compatible rig has been developed to guide the knee flexion of the patient. We tested the procedure on three volunteers. The overall rotational and positional accuracy achieved are 1.8° ± 1.4 and 1.2 mm ± 0.8, respectively, and they are sufficient for the characterization of the joint behavior under load.

3-D Nonlinear Guidance Law for Target Circumnavigation

In this letter, we address the problem of circumnavigating a stationary target using a single vehicle. Unlike most existing results wherein the target is encircled in a two-dimensional plane, we focus on devising a guidance strategy that enables a vehicle to encircle a target in a three-dimensional space using the relative information between the vehicle and the target. In particular, we assume that the vehicle has lateral acceleration capabilities only and that the radial acceleration is unavailable, thereby making the proposed design favorable for a class of aerial vehicles (e.g., aircraft and fixed-wing UAVs, which cannot hover and have to maneuver constantly). Therefore, the vehicle’s steering controls are its lateral acceleration components in the pitch and yaw channels. In addition, we also consider nonlinear, coupled three-dimensional engagement kinematics between the vehicle and the target to preserve the inherent coupling between various channels and to achieve satisfactory control precision even if the channels are strongly coupled. Furthermore, we minimize a relevant weighted cost function to obtain the lateral acceleration components in the pitch and the yaw channels. We finally demonstrate the efficacy of our design via simulations.

Native knee kinematics is not reproduced after sensor guided cruciates substituting total knee arthroplasty

PurposeGait analysis was used to evaluate knee kinematics in patients who underwent successful primary total knee arthroplasty (TKA) using two modern bi-cruciate substituting designs. The knee joint was balanced intraoperatively using real-time sensor technology, developed to provide dynamic feedback regarding stability and tibiofemoral load. The authors hypothesized that major differences exist in gait parameters between healthy controls and post-TKA patients.MethodsTen patients who underwent successful TKA using bi-cruciate substituting designs were evaluated at a minimum of 9 months postoperatively using three-dimensional knee kinematic analysis; a multi-camera optoelectronic system and a force platform were used. Sensor-extracted kinematic data included knee flexion angle at heel-strike (KFH), peak midstance knee flexion angle (MSKFA), maximum and minimum knee adduction angle (KAA) and knee rotational angle at heel-strike. Multiple gait analysis data from the study group were compared to a group of ten healthy controls who were matched by age, sex and BMI. Clinical outcome in the TKA group was also measured using the Knee injury and Osteoarthritis Outcome Score (KOOS).ResultsClinically, at final follow-up, a statistically significant difference in pain, general symptoms, and activities of daily living was seen between the groups. From a gait analysis standpoint, TKA patients had significantly less rotation at heel strike (p = 0.04), lower late stance peak extension moments (p = 0.02), and less Knee Adduction Angle excursion during swing phase (p = 0.04) compared to the control group. No statistically significant difference was observed for knee flexion angle at heel strike, knee adduction moment, or peak knee flexion moment between the groups.ConclusionsModern bi-cruciate substituting TKA designs failed to reproduce normal knee kinematics. The lack of full knee extension during the stance phase, absence of the “screw-home mechanism” typical of an ACL functioning knee, and the reduced fluctuation in knee adduction angle during the swing phase still represent major proprioceptive and muscular recruitment differences between normal and replaced knees.

A Framework for Analytical Validation of Inertial-Sensor-Based Knee Kinematics Using a Six-Degrees-of-Freedom Joint Simulator.

The success of kinematic analysis that relies on inertial measurement units (IMUs) heavily depends on the performance of the underlying algorithms. Quantifying the level of uncertainty associated with the models and approximations implemented within these algorithms, without the complication of soft-tissue artefact, is therefore critical. To this end, this study aimed to assess the rotational errors associated with controlled movements. Here, data of six total knee arthroplasty patients from a previously published fluoroscopy study were used to simulate realistic kinematics of daily activities using IMUs mounted to a six-degrees-of-freedom joint simulator. A model-based method involving extended Kalman filtering to derive rotational kinematics from inertial measurements was tested and compared against the ground truth simulator values. The algorithm demonstrated excellent accuracy (root-mean-square error ≤0.9°, maximum absolute error ≤3.2°) in estimating three-dimensional rotational knee kinematics during level walking. Although maximum absolute errors linked to stair descent and sit-to-stand-to-sit rose to 5.2° and 10.8°, respectively, root-mean-square errors peaked at 1.9° and 7.5°. This study hereby describes an accurate framework for evaluating the suitability of the underlying kinematic models and assumptions of an IMU-based motion analysis system, facilitating the future validation of analogous tools.

Assessment of Three-Dimensional Kinematics of High- and Low-Calibre Hockey Skaters on Synthetic ice Using Wearable Sensors.

Hockey skating objective assessment can help coaches detect players' performance drop early and avoid fatigue-induced injuries. This study aimed to calculate and experimentally validate the 3D angles of lower limb joints of hockey skaters obtained by inertial measurement units and explore the effectiveness of the on-ice distinctive features measured using these wearable sensors in differentiating low- and high-calibre skaters. Twelve able-bodied individuals, six high-calibre and six low-calibre skaters, were recruited to skate forward on a synthetic ice surface. Five IMUs were placed on their dominant leg and pelvis. The 3D lower-limb joint angles were obtained by IMUs and experimentally validated against those obtained by a motion capture system with a maximum root mean square error of 5 deg. Additionally, among twelve joint angle-based distinctive features identified in other on-ice studies, only three were significantly different (p-value &lt; 0.05) between high- and low-calibre skaters in this synthetic ice experiment. This study thus indicated that skating on synthetic ice alters the skating patterns such that the on-ice distinctive features can no longer differentiate between low- and high-calibre skating joint angles. This wearable technology has the potential to help skating coaches keep track of the players' progress by assessing the skaters' performance, wheresoever.

Three-dimensional deformation velocity field and kinematic characteristic of the middle and east parts of Haiyuan fault zone from InSAR and GPS observations

Three-dimensional deformation velocity field can reveal fine characteristics of surface deformation, and provide data support for the research on crustal motion mechanism and seismic hazard. In this study, the ascending and descending InSAR deformation velocity fields in the middle and east parts of Haiyuan fault zone are firstly obtained with Sentinel-1A data and SBAS InSAR technology. Then, by combining with GPS observations, the three-dimensional deformation velocity field is extracted and analyzed. Finally, the locking depths and deep slip rates at different locations are inverted by using the classical two-dimensional screw dislocation model, and the maximum shear-strain rate is investigated. The results indicate that there are significant differences in the InSAR deformation velocity field between both sides of the middle and east parts of Haiyuan fault zone. The east–west deformation velocity field clearly reveals the left-lateral strike-slip characteristic of the fault zone. The northward movement gradually changes to southward movement from northwest to southeast. The vertical deformation velocity field displays significant differences on both sides of the section between MMSF and the middle of LHSF, and the middle and eastern of HYE fault. For LHSF, the locking depth and deep slip rate are 9.7 km and 4.9 mm/a; for HYW fault, they gradually decrease from west to east, with the locking depths of 6.4 km, 3.6 km and 3.2 km, respectively, and the deep slip rates of 5.5 mm/a, 4.2 mm/a and 3.8 mm/a, respectively; for HYM fault, they are 7 km and 4.7 mm/a; for HYE fault, they are 5.8 km and 3.6 mm/a. There are two obvious extreme regions of maximum shear-strain rate along the fault strike. This study can provide a reference for investigating the mechanism of regional uplift and extension and seismic hazard.

Validity and reliability of inertial measurement units measurements for running kinematics in different foot strike pattern runners.

This study aimed to assess the validity and reliability of the three-dimensional joint kinematic outcomes obtained by the inertial measurement units (IMUs) for runners with rearfoot strike pattern (RFS) and non-rearfoot strike pattern (NRFS). The IMUs system and optical motion capture system were used to simultaneous collect 3D kinematic of lower extremity joint data from participants running at 12km/h. The joint angle waveforms showed a high correlation between the two systems after the offset correction in the sagittal plane (NRFS: coefficient of multiple correlation (CMC) = 0.924-0.968, root mean square error (RMSE) = 4.6°-13.7°; RFS: CMC = 0.930-0.965, RMSE = 3.1°-7.7°), but revealed high variability in the frontal and transverse planes (NRFS: CMC = 0.924-0.968, RMSE = 4.6°-13.7°; RFS: CMC = 0.930-0.965, RMSE = 3.1°-7.7°). The between-rater and between-day reliability were shown to be very good to excellent in the sagittal plane (between-rater: NRFS: CMC = 0.967-0.975, RMSE = 1.9°-2.9°, RFS: CMC = 0.922-0.989, RMSE = 1.0°-2.5°; between-day: NRFS: CMC = 0.950-0.978, RMSE = 1.6°-2.7°, RFS: CMC = 0.920-0.989, RMSE = 1.7°-2.2°), whereas the reliability was weak to very good (between-rater: NRFS: CMC = 0.480-0.947, RMSE = 1.1°-2.7°, RFS: CMC = 0.646-0.873, RMSE = 0.7°-2.4°; between-day: NRFS: CMC = 0.666-0.867, RMSE = 0.7°-2.8°, RFS: CMC = 0.321-0.805, RMSE = 0.9°-5.0°) in the frontal and transverse planes across all joints in both types of runners. The IMUs system was a feasible tool for measuring lower extremity joint kinematics in the sagittal plane during running, especially for RFS runners. However, the joint kinematics data in frontal and transverse planes derived by the IMUs system need to be used with caution.

Using statistical parametric mapping to assess the association of duty factor and step frequency on running kinetic.

Duty factor (DF) and step frequency (SF) were previously defined as the key running pattern determinants. Hence, this study aimed to investigate the association of DF and SF on 1) the vertical and fore-aft ground reaction force signals using statistical parametric mapping; 2) the force related variables (peaks, loading rates, impulses); and 3) the spring-mass characteristics of the lower limb, assessed by computing the force-length relationship and leg stiffness, for treadmill runs at several endurance running speeds. One hundred and fifteen runners ran at 9, 11, and 13km/h. Force data (1000Hz) and whole-body three-dimensional kinematics (200Hz) were acquired by an instrumented treadmill and optoelectronic system, respectively. Both lower DF and SF led to larger vertical and fore-aft ground reaction force fluctuations, but to a lower extent for SF than for DF. Besides, the linearity of the force-length relationship during the leg compression decreased with increasing DF or with decreasing SF but did not change during the leg decompression. These findings showed that the lower the DF and the higher the SF, the more the runner relies on the optimization of the spring-mass model, whereas the higher the DF and the lower the SF, the more the runner promotes forward propulsion.

The effects of fatigability on shooting skill performance in goalball penalty shots

This study evaluated the influence of acute fatigue on shooting skill performance in goalball penalty shots. Eleven sub-elite male players were evaluated in an official court using a two-dimensional procedure (60 Hz) to compute the mean radial error, bivariate variable error and accuracy, and three-dimensional kinematics (240 Hz) to measure ball velocity. Rating of perceived exertion, blood lactate concentration and knee extension isometric maximal voluntary contractions were assessed at rest and immediately after the completion of an incremental test specific to goalball. Although significant differences were observed for rating of perceived exertion (pre: M = .36 AU, SD = .67; post: M = 9.27 AU, SD = .79), blood lactate concentration (M = 1.33 mM, SD = .51; M = 9.04 mM, SD = 2.25) and peak force (M = 597.85 N, SD = 132.35; M = 513.37 N, SD =107.00) at the end of the incremental test, no differences were identified in the pre and post moments for mean radial error (M = .10 m, SD = 1.01; M =.37 m, SD = 2.19), bivariate variable error (M = 3.56 m, SD = .70; M = 3.25 m, SD = .70), accuracy (M = 3.68 m, SD = .74; M = 3.78 m, SD = 1.13) and ball velocity (M = 18.53 m.s-1, SD = 1.53; M =18.46 m.s-1, SD = 1.65). We concluded that even though significant levels of fatigability can be attributed to the incremental test specific to goalball, shooting skill performance in goalball penalty shots does not appear to be affected. However, further investigations are needed so that goalball coaches can develop strategies that contribute to improve performance in this technical action. Such improvements are decisive for the outcome of a match.

The Astrometric Animation of Water Masers toward the Mira Variable BX Cam

We report very long baseline interferometry (VLBI) monitoring observations of the 22 GHz water (H2O) masers around the Mira variable BX Cam, which were carried out as a part of the EAVN Synthesis of Stellar Maser Animations project. Data of 37 epochs in total were obtained from 2018 May to 2021 June with a time interval of 3–4 weeks, spanning approximately three stellar pulsation periods (P = ∼440 days). In particular, the dual-beam system equipped on the VERA stations was used to measure the kinematics and parallaxes of the H2O maser features. The measured parallax, π = 1.79 ± 0.08 mas, is consistent with Gaia EDR3 and previously measured VLBI parallaxes within a 1σ error level. The position of the central star was estimated, based on both the Gaia EDR3 data and the center position of the ring-like 43 GHz silicon-monoxide (SiO) maser distribution imaged with the Korean VLBI Network. The three-dimensional H2O maser kinematics indicates that the circumstellar envelope is expanding at a velocity of 13 ± 4 km s−1, while there are asymmetries in both the spatial and velocity distributions of the maser features. Furthermore, the H2O maser animation achieved by our dense monitoring program manifests the propagation of shock waves in the circumstellar envelope of BX Cam.

Angular Velocities and Linear Accelerations Derived from Inertial Measurement Units Can Be Used as Proxy Measures of Knee Variables Associated with ACL Injury

Given the high rates of both primary and secondary anterior cruciate ligament (ACL) injuries in multidirectional field sports, there is a need to develop easily accessible methods for practitioners to monitor ACL injury risk. Field-based methods to assess knee variables associated with ACL injury are of particular interest to practitioners for monitoring injury risk in applied sports settings. Knee variables or proxy measures derived from wearable inertial measurement units (IMUs) may thus provide a powerful tool for efficient injury risk management. Therefore, the aim of this study was to identify whether there were correlations between laboratory-derived knee variables (knee range of motion (RoM), change in knee moment, and knee stiffness) and metrics derived from IMUs (angular velocities and accelerations) placed on the tibia and thigh, across a range of movements performed in practitioner assessments used to monitor ACL injury risk. Ground reaction forces, three-dimensional kinematics, and triaxial IMU data were recorded from nineteen healthy male participants performing bilateral and unilateral drop jumps, and a 90° cutting task. Spearman's correlations were used to examine the correlations between knee variables and IMU-derived metrics. A significant strong positive correlation was observed between knee RoM and the area under the tibia angular velocity curve in all movements. Significant strong correlations were also observed in the unilateral drop jump between knee RoM, change in knee moment, and knee stiffness, and the area under the tibia acceleration curve (rs = 0.776, rs = -0.712, and rs = -0.765, respectively). A significant moderate correlation was observed between both knee RoM and knee stiffness, and the area under the thigh angular velocity curve (rs = 0.682 and rs = -0.641, respectively). The findings from this study suggest that it may be feasible to use IMU-derived angular velocities and acceleration measurements as proxy measures of knee variables in movements included in practitioner assessments used to monitor ACL injury risk.

Data-driven strength and conditioning, and technical training programs for goalkeeper’s diving save in football

ABSTRACT The goal of this study was to evaluate the technical and physical adaptations to a data-driven 12-weeks training programs that incorporated recent findings from biomechanical studies on the diving save. Three-dimensional kinematics and kinetics were collected and analysed from 11 goalkeepers diving to save high (190 cm) and low (30 cm) balls at three occasions: twice pre-training and once post-training. Intraclass correlation coefficients were found to be excellent (>.7) between the pre-training tests, and there were no learning effects between them. Three-way repeated measures ANOVAs were used to evaluate the effect of dive side, dive height and training programme (pre- vs post-training) on normalised dive time [s·m−1], average centre of mass (CoM) horizontal velocity [m·s−1] and total power [W] generated at contralateral and ipsilateral push-offs. Compared to pre-training, the post-training results revealed greater average CoM horizontal velocity (+.82 m·s−1, 95% CI = [.62, 1.02]) and power (+523 W, 95% CI = [313, 732]) at contralateral push-off. These adaptations caused a reduction in normalised dive time (- .008 s·m−1, 95% CI = [- .014, - .002]) at post-training compared to pre-training. This translates to 42 cm more goal area coverage in a penalty situation.

Abstract 12248: Decreased Left Ventricular Hemodynamic Forces As A Novel Biomarker Of Myocardial Dysfunction In Duchenne Muscular Dystrophy

Introduction: Patients with Duchenne muscular dystrophy (DMD) develop progressive cardiomyopathy. Cardiac magnetic resonance (CMR) imaging is used to identify global and regional function, as well as myocardial fibrosis in DMD. Unique left ventricular (LV) biomechanics cannot be assessed through conventional CMR techniques. Thus, we investigated hemodynamic force (HDF) through cine derived wall motion in the LV as a novel biomarker of myocardial dysfunction in DMD patients. Methods: This retrospective study consisted of CMR studies from DMD patients and age-matched controls. Feature-tracking (Qstrain, Medis) was performed on short-axis and long-axis cine imaging to capture LV wall motion. A novel technique based on diffeomorphic mapping was used to calculate three-dimensional LV kinematic models and HDF vectors throughout the cardiac cycle (Figure 1A). The apical-basal, lateral-septal, and anterior-posterior HDF vectors were correlated with global and regional functional parameters. Results: Eleven DMD and 11 controls were enrolled with LV EF 51 ± 6 vs 56 ± 6 (p = 0.09). DMD patients had decreased apical-basal and lateral-septal HDF across multiple points in the cardiac cycle compared to controls (Figure 1B). Six DMD patients with LV EF &lt; 55% were compared to 5 DMD patients with normal EF, demonstrating significant decrease in apical-basal systolic root mean square (RMS) HDF (p = 0.015), lateral-septal systolic RMS HDF (p = 0.009), anterior-posterior diastolic RMS HDF (p = 0.011), and magnitude systolic RMS HDF (p = 0.011) in patients with dysfunction. Absolute magnitude RMS HDF in all axes correlated with LV global longitudinal strain, LV global circumferential strain, and LV EF (r = 0.59 to 0.81, p &lt; 0.05). Conclusions: Cine derived HDF may be a more sensitive measure of LV dysfunction in DMD patients. Apical-basal HDF has potential as a novel biomarker for progression of disease.

Modeling the musculoskeletal system of an insect thorax for flapping flight

Indirect actuation of the wings via thoracic deformation is a unique mechanism widely observed in flying insect species. The physical properties of the thorax have been intensively studied in terms of their ability to efficiently generate wingbeats. The basic mechanism of indirect wing actuation is generally explained as a lever model on a cross-sectional plane, where the dorsoventral movement of the mesonotum (dorsal exoskeleton of the mesothorax) generated by contractions of indirect muscles actuates the wing. However, the model considers the mesonotum as an ideal flat plane, whereas the mesonotum is hemispherical and becomes locally deformed during flight. Furthermore, the conventional model is two-dimensional; therefore, three-dimensional wing kinematics by indirect muscles have not been studied to date. In this study, we develop structural models of the mesonotum and mesothorax of the hawkmoth Agrius convolvuli, reconstructed from serial cross-sectional images. External forces are applied to the models to mimic muscle contraction, and mesonotum deformation and wing trajectories are analyzed using finite element analysis. We find that applying longitudinal strain to the mesonotum to mimic strain by depressor muscle contraction reproduces local deformation comparable to that of the thorax during flight. Furthermore, the phase difference of the forces applied to the depressor and elevator muscles changes the wing trajectory from a figure eight to a circle, which is qualitatively consistent with the tethered flight experiment. These results indicate that the local deformation of the mesonotum due to its morphology and the thoracic deformation via indirect power muscles can modulate three-dimensional wing trajectories.

New insight into the swimming kinematics of wild Green sea turtles (Chelonia mydas)

Biomechanically, sea turtles could be perceived as birds of the ocean as they glide and flap their forelimbs to produce the necessary forces required for locomotion, making sea turtles an interesting animal to study. However, being an endangered species makes studying the sea turtle's biomechanics a complex problem to solve, both technically and ethically, without causing disturbance. This work develops a novel, non-invasive procedure to develop full three-dimensional kinematics for wild sea turtles by filming the animals in Australia's Great Barrier Reef using underwater drones without disturbing them. We found that the wild animals had very different swimming patterns than previous studies on juveniles in captivity. Our findings show that the flipper goes through a closed-loop trajectory with extended sweeping of the flipper tip towards the centre of the carapace to create a clapping motion. We have named this the “sweep stroke” and in contrast to previously described four-stage models, it creates a five-stage cycle swimming locomotion model. The model presented here could lead to a better comprehension of the sea turtle propulsion methods and their fluid–structure interaction.

La réalité virtuelle, un outil pertinent pour la sensibilisation au métier de masseur-kinésithérapeute

The motor cortex plays a critical role in accurate visually guided movements such as reaching and target stepping. However, the manner in which vision influences the movement-related activity of neurons in the motor cortex is not well understood. In this study we have investigated how the locomotion-related activity of neurons in the motor cortex is modified when subjects switch between walking in the darkness and in light.Three adult cats were trained to walk through corridors of an experimental chamber for a food reward. On randomly selected trials, lights were extinguished for approximately 4 s when the cat was in a straight portion of the chamber's corridor. Discharges of 146 neurons from layer V of the motor cortex, including 51 pyramidal tract cells (PTNs), were recorded and compared between light and dark conditions. It was found that while cats’ movements during locomotion in light and darkness were similar (as judged from the analysis of three-dimensional limb kinematics and the activity of limb muscles), the firing behavior of 49% (71/146) of neurons was different between the two walking conditions. This included differences in the mean discharge rate (19%, 28/146 of neurons), depth of stride-related frequency modulation (24%, 32/131), duration of the period of elevated firing ([PEF], 19%, 25/131), and number of PEFs among stride-related neurons (26%, 34/131). 20% of responding neurons exhibited more than one type of change.We conclude that visual input plays a very significant role in determining neuronal activity in the motor cortex during locomotion by altering one, or occasionally multiple, parameters of locomotion-related discharges of its neurons.

Estimation of skeletal kinematics in freely moving rodents

Forming a complete picture of the relationship between neural activity and skeletal kinematics requires quantification of skeletal joint biomechanics during free behavior; however, without detailed knowledge of the underlying skeletal motion, inferring limb kinematics using surface-tracking approaches is difficult, especially for animals where the relationship between the surface and underlying skeleton changes during motion. Here we developed a videography-based method enabling detailed three-dimensional kinematic quantification of an anatomically defined skeleton in untethered freely behaving rats and mice. This skeleton-based model was constrained using anatomical principles and joint motion limits and provided skeletal pose estimates for a range of body sizes, even when limbs were occluded. Model-inferred limb positions and joint kinematics during gait and gap-crossing behaviors were verified by direct measurement of either limb placement or limb kinematics using inertial measurement units. Together we show that complex decision-making behaviors can be accurately reconstructed at the level of skeletal kinematics using our anatomically constrained model.

Triple-differential cross sections in three-dimensional kinematics for electron-impact-ionization dynamics of tetrahydrofuran at 250-eV projectile energy

We report a combined experimental and theoretical study of the ionization dynamics of tetrahydrofuran induced by 250 eV electron impact in which the highest occupied molecular orbital is ionized leading to the stable parent ion. Experimentally a reaction microscope was used, covering nearly the entire $4\ensuremath{\pi}$ solid angle for the ejected slow electron. We present the triple-differential cross sections for the projectile scattering angles of ${\ensuremath{\theta}}_{1}$ = $\ensuremath{-}{10}^{\ensuremath{\circ}}$ as a function of the emission angle of the ejected electrons with energies of ${E}_{2}=10$, 15, and 20 eV, i.e., for asymmetric energy sharing between the scattered and ejected electrons. The measured triple-differential cross sections are internormalized across the three ejected energies. The experimental data are compared with predictions from the molecular three-body distorted-wave (M3DW), the multicenter distorted-wave (MCDW) approaches, and a modified MCDW-WM method which includes the postcollision interaction using the Ward-Macek approximation. Generally, the M3DW cross sections show better agreement with experiment than the MCDW calculations except for the emission angles near the projectile forward direction. The MCDW and MCDW-WM calculations do not reproduce the recoil lobes and show very small intensity for the cross sections outside the scattering plane.