Simon Giszter | Drexel University (original) (raw)

Papers by Simon Giszter

Encyclopedia of Computational Neuroscience

INTRODUCTION Recovery of function after spinal cord injury (SCI) and rehabilitation training invo... more INTRODUCTION Recovery of function after spinal cord injury (SCI) and rehabilitation training involves cooperation between novel skill development and intrinsic spinal mechanisms. Rats with complete SCI at T8-T10 at post-natal day 1-6 (NTX) as adults generate some reflex stepping motions. A subset of these rats (~ 20%) achieves autonomous weight support (WS). Motor reorganization of trunk/hindlimb sensorimotor cortex is believed to play an important role. Lesions to trunk/hindlimb cortex in WS NTX rats’ results in loss of WS function [1]. Using trunk robot rehabilitation, we previously showed that NTX rats significantly improve function and associated plasticity of trunk motor cortex. Further, NTX rats with lesions to trunk sensorimotor cortex prior to the start of robot rehabilitation did not improve function with training. Here, we test if synergies and representation in NTX rats with cortical lesion are altered by robot training as in non-lesioned NTX rats with robot rehab. We hyp...

Journal of Neurophysiology, 1998

Giszter, Simon, William Kargo, Michelle Davies, and Motohide Shibayama. Fetal transplants rescue ... more Giszter, Simon, William Kargo, Michelle Davies, and Motohide Shibayama. Fetal transplants rescue axial muscle representations in M1 cortex of neonatally transected rats that develop weight support. J. Neurophysiol. 80: 3021–3030, 1998. Intraspinal transplants of fetal spinal tissue partly alleviate motor deficits caused by spinal cord injury. How transplants modify body representation and muscle recruitment by motor cortex is currently largely unknown. We compared electromyographic responses from motor cortex stimulation in normal adult rats, adult rats that received complete spinal cord transection at the T8–T10 segmental level as neonates (TX rats), and similarly transected rats receiving transplants of embryonic spinal cord (TP rats). Rats were also compared among treatments for level of weight support and motor performance. Sixty percent of TP rats showed unassisted weight-supported locomotion as adults, whereas ∼30% of TX rats with no intervention showed unassisted weight-suppo...

Journal of Neurophysiology, 2000

The hindlimb wiping reflex of the frog is an example of a targeted trajectory that is organized a... more The hindlimb wiping reflex of the frog is an example of a targeted trajectory that is organized at the spinal level. In this paper, we examine this reflex in 45 spinal frogs to test the importance of proprioceptive afferents in trajectory formation at the spinal level. We tested hindlimb to hindlimb wiping, in which the wiping or effector limb and the target limb move together. Loss of afferent feedback from the wiping limb was produced by cutting dorsal roots 7–9. This caused altered initial trajectory direction, increased ankle path curvature, knee-joint velocity reversals, and overshooting misses of the target limb. We established that these kinematic and motor-pattern changes were due mainly to the loss of ipsilateral muscular and joint afferents. Loss of cutaneous afferents alone did not alter the initial trajectory up to target limb contact. However, there were cutaneous effects in later motor-pattern phases after the wiping and target limb had made contact: The knee extension...

Experimental neurology, Jan 28, 2016

Cervical spinal cord injury (SCI) results in permanent life-altering sensorimotor deficits, among... more Cervical spinal cord injury (SCI) results in permanent life-altering sensorimotor deficits, among which impaired breathing is one of the most devastating and life-threatening. While clinical and experimental research has revealed that some spontaneous respiratory improvement (functional plasticity) can occur post-SCI, the extent of the recovery is limited and significant deficits persist. Thus, increasing effort is being made to develop therapies that harness and enhance this neuroplastic potential to optimize long-term recovery of breathing in injured individuals. One strategy with demonstrated therapeutic potential is the use of treatments that increase neural and muscular activity (e.g. locomotor training, neural and muscular stimulation) and promote plasticity. With a focus on respiratory function post-SCI, this review will discuss advances in the use of neural interfacing strategies and activity-based treatments, and highlights some recent results from our own research.

Journal of Neuroscience, 2016

Robot therapy promotes functional recovery after spinal cord injury (SCI) in animal and clinical ... more Robot therapy promotes functional recovery after spinal cord injury (SCI) in animal and clinical studies. Trunk actions are important in adult rats spinalized as neonates (NTX rats) that walk autonomously. Quadrupedal robot rehabilitation was tested using an implanted orthosis at the pelvis. Trunk cortical reorganization follows such rehabilitation. Here, we test the functional outcomes of such training. Robot impedance control at the pelvis allowed hindlimb, trunk, and forelimb mechanical interactions. Rats gradually increased weight support. Rats showed significant improvement in hindlimb stepping ability, quadrupedal weight support, and all measures examined. Function in NTX rats both before and after training showed bimodal distributions, with "poor" and "high weight support" groupings. A total of 35% of rats initially classified as "poor" were able to increase their weight-supported step measures to a level considered "high weight support" after robot training, thus moving between weight support groups. Recovered function in these rats persisted on treadmill with the robot both actuated and nonactuated, but returned to pretraining levels if they were completely disconnected from the robot. Locomotor recovery in robot rehabilitation of NTX rats thus likely included context dependence and/or incorporation of models of robot mechanics that became essential parts of their learned strategy. Such learned dependence is likely a hurdle to autonomy to be overcome for many robot locomotor therapies. Notwithstanding these limitations, trunk-based quadrupedal robot rehabilitation helped the rats to visit mechanical states they would never have achieved alone, to learn novel coordinations, and to achieve major improvements in locomotor function.

Motor control, 2015

Trunk muscle timing impairment has been associated with non-specific low back pain (NSLBP), but t... more Trunk muscle timing impairment has been associated with non-specific low back pain (NSLBP), but this finding has not been consistent. This study investigated trunk muscle timing in a subgroup of patients with NSLBP attributed to movement coordination impairment (MCI) and matched asymptomatic controls in response to a rapid arm-raising task. Twenty-one NSLBP subjects and 21 matched controls had arm motion and surface EMG data collected from 7 bilateral trunk muscles. Muscle onset and offset relative to deltoid muscle activation and arm motion, duration of muscle burst and abdominal-extensor co-contraction time were derived. Trunk muscle onset and offset latencies, and burst and co-contraction durations were not different (p>0.05) between groups. Patterns of trunk muscle activation and deactivation relative to arm motion were not different. Task performance was similar between groups. Trunk muscle timing does not appear to be an underlying impairment in the subgroup of NSLBP with MCI.

The Journal of Neuroscience : The Official Journal of the Society for Neuroscience

We analyzed whether acute treatment with serotonergic agonists would improve motor function in ra... more We analyzed whether acute treatment with serotonergic agonists would improve motor function in rats with transected spinal cords (spinal rats) and in rats that received transplants of fetal spinal cord into the transection site (transplant rats). Neonates received midthoracic spinal transections within 48 hr of birth; transplant rats received fetal (embryonic day 14) spinal cord grafts at the time of transection. At 3 weeks, rats began 1-2 months of training in treadmill locomotion. Rats in the transplant group developed better weight-supported stepping than spinal rats. Systemic administration of two directly acting agonists for serotonergic 5-HT(2) receptor subtypes, quipazine and (+/-)-1-[2, 5]-dimethoxy-4-iodophenyl-2-aminopropane), further increased weight-supported stepping in transplant rats. The improvement was dose-dependent and greatest in rats with poor to moderate baseline weight support. In contrast, indirectly acting serotonergic agonists, which block reuptake of 5-HT ...

Conference Proceedings. 2nd International IEEE EMBS Conference on Neural Engineering, 2005.

Abstract-We present a real-time system for small animal neurorobotics and neuroprosthetics at spi... more Abstract-We present a real-time system for small animal neurorobotics and neuroprosthetics at spinal or cortical levels. The system combines biomechanics, neural recording and a 3D robotics system including Sensable Devices Phantoms, ATI 6 axis force transducers, ...

Journal of Neuroscience, 2015

Trunk motor control is crucial for postural stability and propulsion after low thoracic spinal co... more Trunk motor control is crucial for postural stability and propulsion after low thoracic spinal cord injury (SCI) in animals and humans. Robotic rehabilitation aimed at trunk shows promise in SCI animal models and patients. However, little is known about the effect of SCI and robot rehabilitation of trunk on cortical motor representations. We previously showed reorganization of trunk motor cortex after adult SCI. Non-stepping training also exacerbated some SCI-driven plastic changes. Here we examine effects of robot rehabilitation that promotes recovery of hindlimb weight support functions on trunk motor cortex representations. Adult rats spinal transected as neonates (NTX rats) at the T9/10 level significantly improve function with our robot rehabilitation paradigm, whereas treadmill-only trained do not. We used intracortical microstimulation to map motor cortex in two NTX groups: (1) treadmill trained (control group); and (2) robot-assisted treadmill trained (improved function group). We found significant robot rehabilitation-driven changes in motor cortex: (1) caudal trunk motor areas expanded; (2) trunk coactivation at cortex sites increased; (3) richness of trunk cortex motor representations, as examined by cumulative entropy and mutual information for different trunk representations, increased; (4) trunk motor representations in the cortex moved toward more normal topography; and (5) trunk and forelimb motor representations that SCI-driven plasticity and compensations had caused to overlap were segregated. We conclude that effective robot rehabilitation training induces significant reorganization of trunk motor cortex and partially reverses some plastic changes that may be adaptive in non-stepping paraplegia after SCI.

2014 40th Annual Northeast Bioengineering Conference (NEBEC), 2014

ABSTRACT Sensorimotor integration during spinal reflexes is discontinuous and context based unlik... more ABSTRACT Sensorimotor integration during spinal reflexes is discontinuous and context based unlike previously proposed continuous feedback models. Cutaneous and proprioceptive modalities play a key role in planning and execution of the hindlimb wipe reflex in adult spinal bullfrogs (Rana catesbeiana). However the temporal dynamics of this integration is still unclear. Studies have suggested that intrinsic musculoskeletal properties can correct for path deviations caused by pulsed force perturbations, without the need for active corrections. In this study, we test the efficacy of these intrinsic properties throughout the physiological workspace of the frog by employing a computational biomechanical simulation paradigm built in Opensim. Our results suggest that although viscoelastic effects lead to better convergence in trajectories, they are not as effective throughout the workspace. However targeting performance is significantly improved by contextually gating the proprioceptive feedback. These results are in agreement with observed activity in the frogs and suggest that reflex gating may be an important component of spinal sensorimotor reflex control.

Frontiers in neuroscience, 2015

The current literature on Intra-Spinal Micro-Stimulation (ISMS) for motor prostheses is reviewed ... more The current literature on Intra-Spinal Micro-Stimulation (ISMS) for motor prostheses is reviewed in light of neurobiological data on spinal organization, and a neurobiological perspective on output motor modularity, ISMS maps, stimulation combination effects, and stability. By comparing published data in these areas, the review identifies several gaps in current knowledge that are crucial to the development of effective intraspinal neuroprostheses. Gaps can be categorized into a lack of systematic and reproducible details of: (a) Topography and threshold for ISMS across the segmental motor system, the topography of autonomic recruitment by ISMS, and the coupling relations between these two types of outputs in practice. (b) Compositional rules for ISMS motor responses tested across the full range of the target spinal topographies. (c) Rules for ISMS effects' dependence on spinal cord state and neural dynamics during naturally elicited or ISMS triggered behaviors. (d) Plasticity o...

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011

Epidural stimulation to trigger locomotion is a promising treatment after spinal cord injury (SCI... more Epidural stimulation to trigger locomotion is a promising treatment after spinal cord injury (SCI). Continuous stimulation during locomotion is the conventional method. To improve recovery, we tested an innovative robot-driven epidural stimulation method, combined with a trunk-based neurorobotic system. The system was tested in rat, and the results were compared with the results of the neurorobotic therapy combined with the conventional epidural stimulation method. The rats had better recovery after treatment with the robot-driven epidural stimulation than conventional stimulation in our neurorobotic rehabilitation system.

Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics, 2008

A range of passive and active devices are under development or are already in clinical use to par... more A range of passive and active devices are under development or are already in clinical use to partially restore function after spinal cord injury (SCI). Prosthetic devices to promote host tissue regeneration and plasticity and reconnection are under development, comprising bioengineered bridging materials free of cells. Alternatively, artificial electrical stimulation and robotic bridges may be used, which is our focus here. A range of neuroprostheses interfacing either with CNS or peripheral nervous system both above and below the lesion are under investigation and are at different stages of development or translation to the clinic. In addition, there are orthotic and robotic devices which are being developed and tested in the laboratory and clinic that can provide mechanical assistance, training or substitution after SCI. The range of different approaches used draw on many different aspects of our current but limited understanding of neural regeneration and plasticity, and spinal ...

Advances in neurology, 1997

The results of the present experiments demonstrate that fetal spinal cord transplants placed into... more The results of the present experiments demonstrate that fetal spinal cord transplants placed into the site of a complete transection in newborn rats permit the development of complex patterns of locomotion. These patterns differ in some respects from normal, but include weight support, appropriate postural adjustment, and coordination between forelimbs and hindlimbs. 5-HT agonists administered to transplanted rats can further modify these motor patterns in ways that may prove able to enhance locomotion. When placed into lesion cavities in adult spinal cord, cells genetically modified to express neurotrophins can survive, differentiate, and mimic at least one consequence of fetal transplants, rescue of axotomized neurons from retrograde cell death.

2006 International Conference of the IEEE Engineering in Medicine and Biology Society

We examine robotic rehabilitation and assessment of spinalized rats, using robot applied forces a... more We examine robotic rehabilitation and assessment of spinalized rats, using robot applied forces at the pelvis, as a prelude to a neurorobotic BMI. Using a surgically implanted frame, a cantilevered phantom robot is attached to the rat pelvis. An isotropic elastic field of constant stiffness is applied and the equilibrium is adjusted to provide a 'natural' trunk posture. Rats are trained daily for 20 minutes, 5 days per week in the field. Significant within trial, and long term adaptation occurs. The interaction force assessments from the robot reveal significant differences between spinalized control rats, and rats receiving implants of E14 dorsal raphe tissue to provide a serotonin source. Our system provides an animal model of rehabilitation through robot interaction at the pelvis.

Encyclopedia of Computational Neuroscience, 2013

Journal of Neuroscience, 2011

Brain-machine interfaces (BMIs) should ideally show robust adaptation of the BMI across different... more Brain-machine interfaces (BMIs) should ideally show robust adaptation of the BMI across different tasks and daily activities. Most BMIs have used overpracticed tasks. Little is known about BMIs in dynamic environments. How are mechanically body-coupled BMIs integrated into ongoing rhythmic dynamics, for example, in locomotion? To examine this, we designed a novel BMI using neural discharge in the hindlimb/trunk motor cortex in rats during locomotion to control a robot attached at the pelvis. We tested neural adaptation when rats experienced (1) control locomotion, (2) "simple elastic load" (a robot load on locomotion without any BMI neural control), and (3) "BMI with elastic load" (in which the robot loaded locomotion and a BMI neural control could counter this load). Rats significantly offset applied loads with the BMI while preserving more normal pelvic height compared with load alone. Adaptation occurred over ϳ100-200 step cycles in a trial. Firing rates increased in both the loaded conditions compared with baseline. Mean phases of the discharge of cells in the step cycle shifted significantly between BMI and the simple load condition. Over time, more BMI cells became positively correlated with the external force and modulated more deeply, and the network correlations of neurons on a 100 ms timescale increased. Loading alone showed none of these effects. The BMI neural changes of rate and force correlations persisted or increased over repeated trials. Our results show that rats have the capacity to use motor adaptation and motor learning to fairly rapidly engage hindlimb/trunk-coupled BMIs in their locomotion.

Journal of Neuroscience Methods, 2014

Background-Rodents are important model systems used to explore Spinal Cord Injury (SCI) and rehab... more Background-Rodents are important model systems used to explore Spinal Cord Injury (SCI) and rehabilitation, and Brain Machine Interfaces. We present a new method to provide mechanical interaction for BMI and rehabilitation in rat models of SCI. New Method-We present the design and implantation procedures for a pelvic orthosis that allows direct force application to the skeleton in brain machine interface and robot rehabilitation applications in rodents. We detail the materials, construction, machining, surgery and validation of the device. Results-We describe the statistical validation of the implant procedures by comparing stepping parameters of 8 rats prior to and after implantation and surgical recovery. An ANOVA showed no effects of the implantation on stepping. Paired tests in the individual rats also showed no effect in 7/8 rats and minor effects in the last rat, within the group's variance. Comparison with Existing Methods-Our method allows interaction with rats at the pelvis without any perturbation of normal stepping in the intact rat. The method bypasses slings, and cuffs, avoiding cuff or slings squeezing the abdomen, or other altered sensory feedback. Our implant osseointegrates, and thus allows an efficient high bandwidth mechanical coupling to a robot. The implants support quadrupedal training and are readily integrated into either treadmill or overground contexts. Conclusions-Our novel device and procedures support a range of novel experimental designs and motor tests for rehabilitative and augmentation devices in intact and SCI model rats, with the advantage of allowing direct force application at the pelvic bones.