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Neural Prostheses and Advanced Prosthetic Systems

For many individuals with spinal cord injury, limb loss, or Parkinson’s Disease, new technology can help to restore mobility and functionality. Researchers at ANS are designing and developing new neural prostheses and advanced mechanical prosthetic systems. Several projects are directed at translating research results from the laboratory in order to deliver practical systems that can be readily utilized on a daily basis.

R&D projects in this area include:

  • neural prostheses to restore function after spinal cord injury
  • deep brain stimulation for treatment of Parkinson’s Disease
  • advanced prosthetic systems

Active Projects


Neural Enabled Prostheses With Sensorimotor Integration

Key Personnel: R. Jung, PhD (PI); ANS/Bioengineering
J.J. Abbas, Ph.D. (ANS/Bioengineering)
B. Bakkaloglu, Ph.D. (EE)
K. Horch, Ph.D. (ANS)
S. Kiaei, PhD (EE)
M. Santello, Ph.D. (Kinesiology/Bioengineering)
S. Phillips, Ph.D. (EE/ANS)
Anthony Smith, MD (Mayo- AZ, USA)
James Patrick (Cochlear Ltd., Australia)
Harold Sears, PhD (Motion Control, Inc., Utah, USA)

Neural Enabled Prostheses With Sensorimotor Integration

Sponsor: National Institutes of Health (NIBIB) 9/30/07-6/30/12, $3,281,759

Though there have been many advances in prosthetic technologies, existing systems are significantly limited in their ability to fully restore function after limb loss. These limitations are manifest in the types of activities that can be achieved, the ease with which the tasks can be performed and the richness of the experience. Truly advanced prosthetic systems will require seamless integration of the intact sensory-motor living system with advanced highly capable artificial limbs.

Our bioengineering research partnership proposes to develop an advanced prosthetic system that uses electrodes implanted within the fascicles of peripheral nerves to provide upper extremity amputees with sensory feedback and active volitional control of the prosthesis. Two specific aims will be pursued. In the first aim of the project, which will focus on sensation, we will develop a system that can be readily evaluated in trials with human subjects. This work will utilize well-established implantable neural stimulation technology in a novel manner to elicit meaningful sensations of hand opening and grip force. This technology will be designed and implemented through clinical deployment of a prosthetic hand system in transradial amputees. In the second aim, we will focus on using the neural interface to provide the dual capabilities of sensation and control. This enhanced version of the technology will provide both the ability to stimulate afferent fibers in order for eliciting sensations and the ability to record from efferent fibers for harnessing signals to control the prosthesis. A key feature of this system will be bidirectional communication (to and from the implanted stimulator) at speeds that enable real-time sensorimotor control of the prosthesis. This technology will be designed and developed and its capabilities will be demonstrated in experiments using an animal model.

Neural Enabled Prostheses With Sensorimotor Integration

The proposed work will bring together a multidisciplinary team with expertise in rehabilitation, biomedical engineering, wireless and sensor technology development, kinesiology and neurophysiology from Arizona State University, hand surgery and occupational therapy practice at Mayo Clinic Arizona in Scottsdale, AZ, a prosthetics practice in Phoenix, AZ, a leading international medical neural implant device company, and a leading U.S. manufacturer of myoelectric and externally powered prosthetic arm systems. Key consultants with expertise in FDA processes and Technology Transfer will be part of the steering committee. Our long term goal is clinical delivery of prosthetic systems that will ultimately provide multimodal sensory perception to the user from the prosthesis and provide dynamic control of the prosthesis by capturing the intent of the user. More than 1.2 million amputees live in the US alone and of these 70% have below elbow amputations. The new technology will benefit these users in daily living tasks and provide them increased digit and thumb movement and dexterity, in addition to decreased requirement for visual attention.

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Completed Projects


Active MEMS Neural Clamps

Active MEMS Neural Clamps

Key Personnel: R. Jung, PhD (PI); ANS/Bioengineering
S. Phillips, PhD (Electrical Engineering)
J.D. Sweeney, PhD (Bioengineering)

Sponsor: National Institutes of Health
4/1/05-3/31/08, $403,756

In the past decade, significant technological and scientific advances have led to the development of neuroprosthetic devices for motor control. An important aspect in the further advancement of the control systems for such devices will be the ability to obtain stable spatiotemporally distributed recording of neural activity chronically. Similarly, neural interfaces that can provide spatiotemporally distributed stimulation of neural tissue are required. In this project, we are focusing on the development of a novel approach of recording distributed neural activity from the peripheral nervous system, in particular the mammalian spinal roots. The goal is to model, design, fabricate, test and characterize Microelectromechanical System (MEMS) based neural electrodes that actively clamp onto the spinal roots. This clamping mechanism will provide a reversible secure attachment mechanism to ensure reliable recording of the neural signals. The clamping will be driven by the body temperature at site of the implant. The clamping can be temporarily reversed for repositioning during the implant procedure by local perfusion of cooled saline solutions. The fabrication will use silicon wafer batch processing techniques that are compatible with integrated circuit manufacturing in order to enable future development of on-chip electronics for filtering, amplification and signal processing. The silicon wafer fabrication also enables future development of low-cost devices. With batch processing, we can vary the electrode and device characteristics on a single wafer to optimize performance. Several electrode configurations on the same device will be evaluated initially using amphibian nerve, then with fixed rodent nerve, and ultimately in real-time by recording autonomous respiratory activity from rat cervical spinal roots and the phrenic nerve. Ability to place the electrodes on multiple lumbosacral spinal roots will be evaluated. These results will guide the redesign of the electrodes. The novel design allows capability for repositioning of multiple spatially distributed implantable electrodes. Such electrodes will advance our capabilities of scientific investigation of neural function in awake subjects and in the development of advanced neuroprosthetic products for rehabilitation.

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A Rodent Model for Locomotor Training with FNS

A Rodent Model for Locomotor Training with FNS

Key Personnel: R. Jung, PhD (PI)
J.J. Abbas, PhD (ANS/Bioengineering)

Sponsor: National Institutes of Health (NCMRR_NICHD; R01HD40335),
1/17/02- 6/30/06, $775,418

The long-term goal of this work is to develop strategies for using functional neuromuscular stimulation (FNS) of paralyzed muscles to enhance the recovery of individuals with incomplete spinal cord injury. The proposed work is motivated by three important developments. First, recent basic science and clinical studies have demonstrated that the degree of functional recovery of the injured spinal cord depends on the activity patterns of neural inputs to the spinal cord.

Second, recent advances have produced adaptive controllers for FNS systems that provide a means of automatically adjusting stimulation parameters to reliably achieve specified rhythmic movements.

Third, rodent models of spinal cord injury (complete and incomplete lesions) are extensively being used at the molecular, cellular, and systems level to investigate the effects of traumatic injury and to assess the results of therapeutic intervention. A combination therapy that utilizes locomotor training with FNS and pharmacological intervention is likely to be the most effective in enhancing the reorganization (plasticity) of the spinal circuitry that is spared after spinal trauma. A rodent model for FNS-assisted locomotion would facilitate quantitative evaluation of therapeutic regimens that include FNS and would provide the ability to characterize effects of FNS-assisted locomotion on the neuroanatomy and neurophysiology of the injured spinal cord.

A Rodent Model for Locomotor Training with FNS

This biomedical engineering research grant proposal will develop a rodent model of locomotor training that utilizes treadmill walking and functional neuromuscular stimulation (FNS) with fixed-pattern and adaptive controllers. Kinematic and electromyogram (EMG) patterns of intact animals will be examined and then used to develop stimulation patterns for FNS-assisted movement. A series of tasks will be performed using FNS stimulation of hindlimb muscles in spinalized rats. These tasks will progress in difficulty from controlling suspended hindlimb movements to controlling hindlimb movements during treadmill locomotion in spinalized rats with partial weight support. Two different FNS control strategies will be used for each movement: a fixed-pattern, or open-loop, stimulation pattern and an adaptive stimulation control system. The adaptive stimulation control system will build upon our previous work and is expected to provide movement patterns that are more accurate and more repeatable.

Successful completion of the proposed project will result in a novel animal model for FNS-assisted locomotor training and provide quantitative methods for evaluating locomotor behavior. In future studies, we plan to use a rodent model of incomplete spinal cord injury with FNS-assisted locomotion to test the hypothesis that FNS-assisted locomotor training enhances motor recovery after incomplete spinal cord injury. We anticipate that the improved performance provided by the adaptive control system may enhance the therapeutic effects of the technique. This locomotor training could also be combined with pharmacological intervention, tissue transplant, and neural repair therapies to determine if locomotor training can enhance the effectiveness of these therapies.

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Effect of Deep Brain Stimulation on Locomotion Control in Parkinson’s Disease

Key Personnel: J.J. Abbas, PhD (ANS/Bioengineering)
K. Narayanan, PhD (ANS)
J. Samantha, MD (ANS/Banner Good Samaritan Medical Center)
P. Mahant, MD (ANS/Banner Good Samaritan Medical Center)

Deep brain stimulation (DBS) has been used to reduce tremor and improve or restore motor function and locomotion in individuals with Parkinson’s Disease (PD). Although some studies have investigated the effects of various treatments on locomotion control in PD patients, the effects of the DBS system on locomotion control are poorly understood. The purpose of this research study is to assess the ability of DBS systems to assist PD patients in controlling locomotion. Information derived from this study will help researchers and clinicians develop strategies to use the DBS system more effectively. By examining movement of the center of gravity (COG) and forces under the foot, the study proposed here would attempt to assess the effect of the DBS systems on locomotion control when PDpatients are asked to walk at a comfortable pace.

The specific aims of this study are: (1) to compare the locomotion control abilities of 3 subject groups: patients with advanced PD who use and implanted DBS system (PD-DBS); patients with advanced PD who are being treated with Levadopa (PD-LD); and healthy age-matched individuals (non-PD), (2) to test the effect on locomotion control of varying levels of stimulation in patients in the PD-DBS group, and (3) to compare results from the locomotion control tests to results from more commonly used clinical tests (UPDRS, ‘get up and go’).

Thirty people will take part in this study. All sessions will be conducted at the Clinical Neurobiology and Bioengineering Research Lab at the Banner Good Samaritan Medical Center in Phoenix, AZ. Each session will consist of 1-2 hours of experimental trials interspersed with rest periods. During the experimental trials, the subject will walk with shoes fitted with force sensitive insoles and accelerometer device fastened by an elastic waist belt to the subject’s back in the lumbosacral region of the vertebral column, close to the subject’s center of gravity while standing. Prior to beginning data collection in each condition, the subject will be evaluated using the Unified Parkinson’s Disease Rating Scale (UPDRS) by a trained clinician. There will be two types of experimental trials performed on PD-DBS subjects: (1) “optimal-stimulation” - stimulation settings that are clinically determined as optimal settings for each subject, and (2) “reduced-stimulation” - stimulation settings that are 60-80% of the clinically determined optimal settings. The subject’s ability to walk independently at these stimulation settings will be assessed using the UPDRS clinical rating scale. Using the shoes with force sensitive insoles, forces applied to the ground during ambulation will be measured and using the accelerometer fastened to the back, changes of body motion will be measured. The body motion signals can be further processed to get information about walking speed, stride length, accelerations at heel contact, mid-stance and initial push-off. These variables will be analyzed to quantify the differences in locomotion control in the above three different groups and also to quantify the effects of DBS on locomotion control.

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DBS Electrode Location and Clinical Outcomes in Parkinson’s Disease

Key Personnel: J.J. Abbas, PhD (ANS/Bioengineering)
D. Lieberman, MD (Arizona Center for Neurosurgery)
K. Narayanan, PhD (ANS)

Deep brain stimulation (DBS) has been used to reduce tremor and improve or restore motor function in individuals suffering from Parkinson’s disease. Although some studies have investigated the effects of electrode locations on the clinical outcomes of Parkinsonian subjects, location effects are still poorly understood. The purpose of this research study is to determine if there are any correlations between DBS electrode location and the motor outcomes of patients with Parkinson’s disease. Coordinates describing electrode locations will be calculated from pre- and post-operative magnetic resonance images (MRIs). Information derived from this study will help researchers and clinicians develop strategies to use the DBS system more effectively. The specific aims of this study are as follows:

DBS Electrode Location and Clinical Outcomes in Parkinson’s Disease
  • To quantify the difference between intended and actual electrode placement.
  • measure electrode coordinates in the entire sample
  • calculate the difference between actual and target coordinates

To characterize the relationship between specific electrode location and clinical DBS effects. This work will use retrospective analysis of existing brain images and clinical records from DBS system users to:

  • determine the location of the active contacts relative to key neural structures
  • catalog the nature and degree of PD symptoms prior to DBS system implantation
  • catalog the nature and degree of clinical impact of the DBS system, including adverse effects

Fifty to seventy people will take part in this study. Subjects will need to attend one meeting to read and sign the informed consent letter. This meeting will be held at Banner Good Samaritan Medical Center in Phoenix, Arizona. Initial analysis of the MRIs will take approximately two months and will be performed in the Image-Guided Neurosurgery office, also located at Banner Good Samaritan Medical Center in Phoenix, Arizona. A Medtronic StealthStation® (Minneapolis, MN) will be used to reconstruct the pre-op and post-op MRIs in three-dimensional space and to manually fuse them based on common anatomical landmarks--anterior and posterior commissures (AC and PC). Target and actual electrode coordinates will be determined relative to the AC-PC line and the mid-commissural point. Differences between target and actual coordinates will be calculated in each plane. Coordinates for the active contact(s) chosen for each electrode will be calculated relative to the AC-PC line, the mid-commissural point, the ventral FF border, the ventral-posterior STN border, the dorsal STN border, the substantia nigra and other brain structures. These data will be analyzed using cluster analysis to establish subject groupings. The clinical records for each of the subjects will be reviewed to catalog PD symptoms prior to implantation and effects of DBS on those symptoms as evidenced by the individual components of the UPDRS scores. Comparisons (ANOVA) will be made on all performance parameters between the established subject groupings.

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Analysis of Prosthetic Feet in Above Knee Amputees

Analysis of Prosthetic Feet in Above Knee Amputees

Key Personnel: J.J. Abbas, PhD (ANS/Bioengineering)

The goal of this research is threefold: 1) To quantify the benefits associated with the prescription of prosthetic feet intended for active above knee amputees, 2) To identify which aspects of a prosthetic foot design are most important to active above knee amputees, and 3) To isolate specific design characteristics of prosthetic feet as they relate to patient preference, gait and metabolism and make recommendations for future designs. The functionality of the SACH, Jaipur and Variflex prosthetic feet is being assessed in above knee amputees walking at different speeds. Biomechanical analysis of gait patterns and analysis of metabolic costs will be used to characterize the effect of prosthetic foot characteristics on walking patterns and energy costs.

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