Biology subjects

Mushahwar, V. K.

Publications and source records attributed to Mushahwar, V. K..

4 recordsLinked to original sources

bioRxiv2026

Flexible thin-film Implant with Depth Selectivity for Intraspinal Microstimulation

Restoration of motor function after spinal cord injury remains a major challenge, as existing neuromodulation strategies such as epidural stimulation suffer from limited selectivity. Intraspinal microstimulation (ISMS) offers higher spatial precision but has been constrained by manually fabricated microwire arrays that lack reproducibility, depth control, and mechanical compatibility with neural tissue. Here, we present flex-ISMS, a thin-film, polyimide-based ISMS array integrating 42 stimulation sites distributed across 14 flexible arms. Acute in vivo implantation into the lumbosacral enlargement of domestic pigs demonstrated depth-specificity, site-selectivity and near normal recruitment of motor units resulting in graded contractions in muscles controlling the hip, knee, and ankle joints, with ranges of motion and isometric force generation approaching levels seen during natural locomotion (e.g., 40{degrees} and 30 N for knee extension). Importantly, electrodes separated by 500 {micro}m evoked distinct responses, underscoring submillimetre-scale selectivity. The high flexibility allows the device to conform to the spinal cord while displacing tissue by only 40x8 {micro}m per arm. Histological analyses showed that the 125 {micro}m diameter tungsten insertion aid of the flex-ISMS arms produced minimal acute damage, indistinguishable from that produced by conventional 50 {micro}m diameter microwires. These acute outcomes establish the surgical feasibility and functional capability of flex-ISMS, and provide the foundation for forthcoming chronic studies in spinal-cord-injured models.

bioengineering↗

bioRxiv2021

Overground Gait Kinematics and Muscle Activation Patterns in the Yucatan Mini Pig

A growing number of spinal cord injury, neuromodulation, and cell therapy studies on porcine models, especially the Yucatan minipigs (YMPs), have been recently reported. This is due to the large similarities between human and porcine neuroanatomy and biomechanics. To assess treatment modalities and locomotor recovery in this model, there is an obvious need for detailed characterization of normative overground gait in neurologically intact YMPs. The objective of this study was to assess gait biomechanics and the effect of overground walking speed on gait parameters, kinematics, and electromyographic (EMG) activity in the hindlimb muscles of YMPs. Nine neurologically-intact adult YMPs were trained to walk overground in a straight line. Whole-body kinematics and EMG activity of hindlimb muscles were recorded and analyzed at 6 different speed ranges (0.4-0.59, 0.6-0.79, 0.8-0.99, 1.0-1.19, 1.2-1.39, and 1.4-1.6 m/s). A MATLAB program was developed to detect strides and gait events automatically from motion-captured data. Significant decreases in stride duration, stance and swing times and an increase in stride length were observed with increasing speed. A transition in gait pattern occurred at the 1.0m/s walking speed. Significant increases in the range of motion of the knee and ankle joints were observed at higher speeds. Also, the points of minimum and maximum knee and ankle joint angles occurred earlier in the gait cycle at higher speeds. The onset of EMG activity in the biceps femoris muscle occurred significantly earlier in the gait cycle with increasing speed. A comprehensive characterization of overground walking in neurologically-intact YMPs is provided. These normative measures set the basis against which the effects of future interventions on locomotor capacity in YMPs can be compared.

neuroscience↗

bioRxiv2020

Comparative Neuroanatomy of the Lumbosacral Spinal Cord of the Rat, Cat, Pig, Monkey, and Human

The overall goal of this work was to create a high-resolution MRI atlas of the lumbosacral enlargement of the spinal cord of the rat (Sprague-Dawley), cat, domestic pig, rhesus monkey, and human. These species were chosen because they are commonly used in basic and translational research in spinal cord injuries and diseases. Six spinal cord specimens from each of the studied species (total of 30 specimens) were fixed, extracted, and imaged. Sizes of the spinal cord segments, cross-sectional dimensions, and locations of the spinal cord gray and white matter were quantified and compared across species. The obtained atlas establishes a reference for the neuroanatomy of the intact lumbosacral spinal cord in these species. It can also be used to guide the planning of surgical procedures of the spinal cord, technology design and development of spinal cord neuroprostheses, and the precise delivery of cells/drugs into target regions within the spinal cord parenchyma.

neuroscience↗

bioRxiv2019

Pavlovian Control of Intraspinal Microstimulation to Produce Over-Ground Walking

ObjectiveNeural interface technologies are more commonly used in people with neural injury. To achieve a symbiotic relationship between device and user, the control system of the device must augment remaining function and adapt to day-to-day changes. The goal of this study was to develop predictive control strategies to produce alternating, over-ground walking in a cat model of hemisection spinal cord injury (SCI) using intraspinal microstimulation (ISMS).\n\nApproachEight cats were anaesthetized and placed in a sling over a walkway. The residual function of a hemisection SCI was mimicked by manually moving one hind-limb through the walking cycle over the walkway. ISMS targeted motor networks in the lumbosacral enlargement to activate muscles in the other limb using low levels of current (< 130 {micro}A). Four different people took turns to move the \"intact\" limb. Two control strategies, which used ground reaction force and angular velocity information about the manually moved limb to control the timing of the transitions of the other limb, were compared. The first strategy, reaction-based control, used thresholds on the sensor values to initiate state transitions. The other strategy used a reinforcement learning strategy, Pavlovian control, to learn predictions about the sensor values. Thresholds on the predictions were used to initiate transitions.\n\nMain ResultsBoth control strategies were able to produce alternating, over-ground walking. Reaction-based control required manual tuning of the thresholds for each person to produce walking, whereas Pavlovian control did not. We demonstrate that learning occurs quickly during walking. Predictions of the sensor signals were learned quickly, initiating transitions in no more than 4 steps. Pavlovian control was resilient to transitions between people walking the limb, between cat experiments, and recovered from mistakes during walking.\n\nSignificanceThis work demonstrates that Pavlovian control can augment remaining function and allow for personalized walking with minimal tuning requirements.

bioengineering↗