Evaluating Muscle Synergies With EMG Data and Physics Simulation in the Neurorobotics Platform.

Although we can measure muscle activity and analyze their activation patterns, we understand little about how individual muscles affect the joint torque generated. It is known that they are controlled by circuits in the spinal cord, a system much less well-understood than the cortex. Knowing the contribution of the muscles toward a joint torque would improve our understanding of human limb control. We present a novel framework to examine the control of biomechanics using physics simulations informed by electromyography (EMG) data. These signals drive a virtual musculoskeletal model in the Neurorobotics Platform (NRP), which we then use to evaluate resulting joint torques. We use our framework to analyze raw EMG data collected during an isometric knee extension study to identify synergies that drive a musculoskeletal lower limb model. The resulting knee torques are used as a reference for genetic algorithms (GA) to generate new simulated activation patterns. On the platform the GA finds solutions that generate torques matching those observed. Possible solutions include synergies that are similar to those extracted from the human study. In addition, the GA finds activation patterns that are different from the biological ones while still producing the same knee torque. The NRP forms a highly modular integrated simulation platform allowing these in silico experiments. We argue that our framework allows for research of the neurobiomechanical control of muscles during tasks, which would otherwise not be possible.

The effect of limb position on a static knee extension task can be explained with a simple spinal cord circuit model.

The influence of proprioceptive feedback on muscle activity during isometric tasks is the subject of conflicting studies. We performed an isometric knee extension task experiment based on two common clinical tests for mobility and flexibility. The task was carried out at four preset angles of the knee, and we recorded from five muscles for two different hip positions. We applied muscle synergy analysis using nonnegative matrix factorization on surface electromyograph recordings to identify patterns in the data that changed with internal knee angle, suggesting a link between proprioception and muscle activity. We hypothesized that such patterns arise from the way proprioceptive and cortical signals are integrated in neural circuits of the spinal cord. Using the MIIND neural simulation platform, we developed a computational model based on current understanding of spinal circuits with an adjustable afferent input. The model produces the same synergy trends as observed in the data, driven by changes in the afferent input. To match the activation patterns from each knee angle and position of the experiment, the model predicts the need for three distinct inputs: two to control a nonlinear bias toward the extensors and against the flexors, and a further input to control additional inhibition of rectus femoris. The results show that proprioception may be involved in modulating muscle synergies encoded in cortical or spinal neural circuits.NEW & NOTEWORTHY The role of sensory feedback in motor control when limbs are held in a fixed position is disputed. We performed a novel experiment involving fixed position tasks based on two common clinical tests. We identified patterns of muscle activity during the tasks that changed with different leg positions and then inferred how sensory feedback might influence the observations. We developed a computational model that required three distinct inputs to reproduce the activity patterns observed experimentally. The model provides a neural explanation for how the activity patterns can be changed by sensory feedback.

Neural Anatomy of the Anterolateral Thigh Flap.

The anterolateral thigh (ALT) flap is one of the commonly used sensate flaps for intra-oral, hand, and foot reconstruction. The objective of this study was to describe the anatomic location of the sensory nerves supplying the ALT flap in relation to the surface landmarks and with the vascular pedicles. The dissections were carried out in 28 embalmed specimens. An axial line from the anterior superior iliac spine to the superolateral border of the patella and two circles with radii of 5 and 10 cm centered on the midpoint of the former line were used for the surface landmarks. At the intersection point of the axial line and the 10-cm circle, the main lateral femoral cutaneous nerve (LFCN) and its anterior branch were located within 1 and 2.4 cm, respectively. At the intersection point of the axial line and the 5-cm circle, the anterior branch of the LFCN was located within 2.8 cm. The anterior branch of the LFCN can be detected within 3 cm from the central perforator pedicle in all specimens. The posterior branch of the LFCN, superior perforator nerve, and median perforator nerve were found in more variable locations. The findings from our study provide additional information for clinical use in the planning of sensate ALT flap harvest.

Effects of curcumin on restoration and improvement of microvasculature characteristic in diabetic rat's choroid of eye.

OBJECTIVE: To investigate the effect ofcurcumin on microvasculature changes in STZ-induced diabetic rat' choroid ofeye. MATERIAL AND METHOD: Male rats were divided into three groups: control (C) Diabetic rats were induced by streptozotocin (STZ) (60 mg/kg BW) (DM) diabetic rats treated with curcumin (DMC) (200 mg/kg BW). After 8 weeks of experiments, microvasculature changes of rat's choroid were studied under vascular corrosion cast technique with scanning electron microscope (SEM). RESULTS: There were pathology and destruction of choroid microvasculature of DM group that revealed reduced and shrunken sizes of large and small blood vessels, compared with control group; long posterior ciliary arteries (LPCAs) (C = 113.70 +/- 1.38, DM = 83.53 +/- 2.70, DMC = 109.64 +/- 3.41 microm), choroid arteries (C = 94.97 +/- 2.79, DM = 59.36 +/- 2.61, DMC = 80.31 +/- 3.73 microm), vortex veins (C = 74.11 +/- 3.24, DM = 46.71 +/- 2.56, DMC = 64.66 +/- 3.60 microm), and Choriocapillaris (choroidal capillaries) (C = 13.61 +/- 0.62, DM = 4.46 +/- 0.24, DMC = 9.96 +/- 0.70 microm), respectively. In DM group, LPCAs and Choroid arteries were tortuous and showed shrinkage. Vortex veins became narrow. Choriocapillaris showed the pathological characteristics of vascular lesions including of shrinkage, constriction, microaneurysm and blind ending. Fascinatingly, Choroid microvasculature of the eye in curcumin treated group developed into regenerate and repaired conditions with healthy and normal characteristics. CONCLUSION: Efficiency of curcumin treatment beneficially repaired and regenerated the redevelopment of choroid's microvascular complications of eye in 8-week experiments. Potential treatment with curcumin in diabetes has demonstrated in a meaningful way the therapeutic consequences in the improvement and recovery of choroidal blood vessels in eye pathology ofdiabetic rats.