Professor
B.S., physics (Harvey Mudd College) 1970
Ph.D., biophysics (Johns Hopkins University) 1975
Director, Neurokinesiology Laboratory

Phone: (778) 782-3141
Fax: (778) 782-3040
Email: hoffer@sfu.ca

Neural Control of Movement / Neural Prostheses

Research Program:

Starting in the 1970's, I have pioneered the use of implanted nerve cuff electrodes, initially to investigate properties of peripheral nerves relating to transmission of sensation, proprioception, reflexes, feedback control of movement, neuromuscular plasticity and nerve survival after amputation, and more recently to provide new clinical applications aimed at restoring independence in people affected by movement disorders of central origin. My current research is expanding around clinical testing and anticipated uses of implanted neuroprosthetic devices. A new collaborative project is focused on development of a non-invasive 3D imaging method to visualize the peripheral nerves inside the limbs of people, prior to a scheduled surgery. Another new collaborative project aims to extract electrical energy from natural body movements in order to, for example, automatically recharge batteries in powered implanted or wearable devices, such as neuroprostheses.

Current projects include:

  1. Development and clinical testing of fully implanted neuroprosthesis. In 1992-2000 we developed methods for extracting multiple channels of sensory information from peripheral nerves and selectively stimulating groups of muscles using implanted nerve cuff electrodes in animal models, funded by the Neural Prosthesis Program, NIH (USA). More recently, we turned our efforts to developing prototype systems for restoring the use of paralyzed limbs in people impaired by neurological injury or disease, such as spinal cord injury or stroke. We control the delivery of Functional Electrical Stimulation (FES) to paralyzed muscles using natural feedback signals that are directly obtained from appropriate sensory nerves. In 1997 we spun out of the Neurokinesiology Lab an R&D company, Neurostream Technologies Inc. for which I served as Chief Scientific Officer until 2004. We assembled a team with unique expertise in implantable electronics, mechanical and biomedical engineering, telemetry, real-time control, neurophysiology, neurokinesiology, and clinical and regulatory affairs. We developed a commercial fabrication method for Neurocuffs TM and a unique chip-based, low-noise nerve signal amplifier. In 2002 we integrated these technologies into the prototype Neurostep TM system, the first pacemaker-like, fully implanted assistive device for treating foot drop in people paralyzed by stroke. In 2003, this system was tested in a pilot feasibility study in a hemiplegic subject. In July, 2004 Neurostream Technologies was acquired by Victhom Human Bionics . Victhom is currently continuing the development and clinical testing of the Neurostep TM and is developing the technology platform for additional clinical products. I assist Victhom with these developments and participate as a Clinical Advisory Board member.
  2. Quantitative imaging of peripheral nerves. Our goal is to develop a non-invasive, non-traumatic method to precisely determine the locations and branching patterns of peripheral nerves inside a human limb and to measure the perimeters and cross-sectional areas of nerve branches. As a result of this research, we aim to provide 3-D images of peripheral nerves in patients scheduled for surgical implantation of neuroprosthetic devices that surgeons will need to attach to specific nerves, or patients scheduled to undergo repair surgery for injured peripheral nerves. Co- investigator: Dr. Faisal Beg. Funded by Rick Hansen Man in Motion Foundation.
  3. Biomechanical energy harvester. The size, weight and low specific energy of batteries can severely limit the power and duration of operation for many portable electronic devices, such as laptop computers. This problem is compounded by power requirements for electronics that are increasing much faster than improvements in battery performance. An attractive alternative energy source is human power, because of the high specific energy of food, the efficiency at which humans are able to convert food to mechanical power, and the high mechanical power outputs attainable by humans. Human power is portable, environmentally friendly, and readily available for power-consuming applications that involve direct human use, like prostheses and laptop computers. We propose to develop biomechanical energy harvesting devices that convert mechanical energy extracted from human movement into electrical energy that can be directly used to power electrical devices and to continuously recharge batteries. These harvesters will contribute to making future batteries much smaller and lighter and will allow for more sophisticated portable electronics. The technology is particularly applicable to biomedical devices that power electromechanical or neuroelectric prostheses and for powering portable electronic devices like cellular phones, personal digital assistants, global positioning system receivers, laptop computers, on any other purpose that normally requires batteries. Our long-term goal is to develop and commercialize a family of energy harvesting devices that can be either worn on the body, embedded into motorized prostheses or permanently implanted within the body. Co-principal investigator: Dr. Max Donelan . Funded by NSERC-I2I.

Recent Theses Supervised:

  • 1994 Ph.D. M. Haugland. Natural sensory feedback in closed-loop control of paralyzed muscles. Univ. of Aalborg , Denmark (co-Supervisor: T.Sinkjær).
  • 1996 M.A.Sc. K. Strange. A state controller for closed-loop functional electrical stimulation regulated by natural sensory feedback. School of Engineering Science, Simon Fraser University
  • 1996 M.Sc. M. Hansen. Sensory feedback for control of reaching and grasping using FES . Univ. of Aalborg , Denmark (co-Supervisor: M. Haugland)
  • 1996 M.Sc. S. Schindler-Ivens. Prevalence of breakaway weakness in the Lower Fraser Valley of British Columbia. School of Kinesiology , Simon Fraser University
  • 1997 M.A.Sc. P. Christensen, Sensory source identification from nerve recordings with multi-channel electrode arrays. School of Engineering Science, Simon Fraser University
  • 1997 M.Sc. D. Crouch. Morphometric analysis of neural tissue following the long-term implantation of nerve cuffs in the cat forelimb. School of Kinesiology , Simon Fraser University
  • 1998 Ph.D. K. Kallesøe. Implantable Transducers for Neurokinesiological Research and Neural Prostheses, Simon Fraser University.
  • 2001 M.Sc. E. Heygood . Multichannel Nerve Electrodes for Control of Functional Electrical Stimulation Systems, Simon Fraser University.
  • 2003 M.A.Sc. M. Barú. Custom ASIC for Electroneurographic Recording using Nerve Cuff Electrodes, Simon Fraser University.
  • 2004 M.Sc. J. Kerr. A Study of the Feasibility of Using Nerve Cuff Signals as Feedback for Maintenance of Posture in Paraplegic Subjects, Simon Fraser University.

Graduate Students Currently Supervised:

  • S. Frisch, BSc (Kin), MSc candidate, School of Kinesiology , Simon Fraser University
  • M. Belot, PT, MSc candidate, School of Kinesiology , Simon Fraser University

Selected Publications:

  • Hoffer, J.A., Barú, M., Bedard, S., Calderon, E., Desmoulin, G., Dhawan, P., Jenne, G., Kerr, J., Whittaker, M. and Zwimpfer, T. Initial results with fully implanted NeurostepTM FES system for foot drop. International Functional Electrical Stimulation Soc., 10th Ann. Conf., Montreal, Canada, pp. 53-55, July 2005.
  • Murphy, B., Krieger, C. and Hoffer, J.A. Chronically implanted epineural electrodes for repeated assessment of nerve conduction velocity and compound action potential amplitude in rodents, J. Neurosci. Methods 132:25-33, 2004.
  • Hoffer, J.A. and K. Kallesøe, How to use nerve cuffs to stimulate, record or modulate neural activity. Chapter 5 in Neural Prostheses for Restoration of Sensory and Motor Function, K.A. Moxon and J.K. Chapin, Eds., CRC Press, pp. 139-175, 2001.
  • Hoffer, J.A. and K. Kallesøe, Nerve cuffs for nerve repair and regeneration, Progr. Brain Res. 128:121-134, 2000.
  • Strange, K. and Hoffer, J.A. Gait phase information provided by sensory nerve activity during walking: applicability as state controller feedback for FES . IEEE Trans. Biomed. Engineering 46:797-809, 1999.
  • Strange, K. and Hoffer, J.A. Restoration of use of paralyzed limb muscles using sensory nerve signals for state control of FES-assisted walking. IEEE Trans. Rehab. Engineering 7:289-300, 1999.
  • Eng, J.J. and Hoffer, J.A. Regional variability of stretch reflex amplitude in the cat medial gastrocnemius muscle during a postural task. J. Neurophysiol. 78:1150-1154, 1997.
  • Hoffer, J.A., Stein, R.B., Haugland, M., Sinkjær, T., Durfee, W.K., Schwartz, A.B., Loeb, G.E. and Kantor, C. Neural signals for command control and feedback in functional neuromuscular stimulation: a review. J. Rehab. Res. & Dev. 33:145-157, 1996.
  • Boorman, G.I., Hoffer, J.A., Kallesøe, K., Mah, C. and Viberg, D. A measure of peripheral nerve stimulation efficacy applicable to H-reflex studies. Can. J. Neurol. Sci. 23:264-270, 1996.
  • Haugland, M., J.A. Hoffer and T. Sinkjaer. Skin contact force information in sensory nerve signals recorded by implanted cuff electrodes. IEEE Trans. Rehab. Engng. 2:18-28, 1994.
  • Haugland, M. and J.A. Hoffer. Slip information provided by nerve cuff signals: application in closed-loop control of functional electrical stimulation. IEEE Trans. Rehab. Engng. 2:29-36, 1994.
  • Hoffer, J.A., Caputi, A.A. and Pose, I.E. Activity of muscle proprioceptors in cat posture and locomotion: relation to EMG, tendon force, and the movement of fibres and aponeurotic segments. In: Muscle Afferents and Spinal Control of Movement, L. Jami, E. Pierrot-Deseilligny, D. Zytnicki, editors, IBRO Symposium Series, Pergamon Press, pp. 113-121, 1992.
  • Hoffer, J.A. Techniques to record spinal cord, peripheral nerve and muscle activity in freely moving animals. In Neurophysiological Techniques: Applications to Neural Systems, Neuromethods 15, Eds. A.A. Boulton, G.B. Baker and C.H. Vanderwolf. Humana Press, pp. 65-145, 1990.

Selected Publications:

  • Hoffer, J.A. Closed-loop, Implanted-sensor, Functional Electrical Stimulation System for Partial Restoration of Motor Functions: United States Patent No. 4,750,499.
  • K. Kallesøe, J.A. Hoffer, K. Strange and I. Valenzuela Implantable Cuff having Improved Closure. United States Patent No. 5,487,756 awarded on January 30, 1996.
  • J.A. Hoffer, Y. Chen, K. Strange and P. Christensen, Nerve Cuff having One or More Isolated Chambers. United States Patent 5,824,027, awarded on October 20, 1998.
  • K. Kallesøe, J.A. Hoffer, K. Strange and I. Valenzuela, Implantable Cuff having Improved Closure, Canada Patent 2,139,097 awarded on Aug. 19, 2003.
  • J.A. Hoffer, Y. Chen, K. Strange and P. Christensen, Nerve Cuff having One or More Isolated Chambers. European Patent No. 1,001,827 awarded on 14 January 2004.
  • J.A. Hoffer, Electrical stimulation method for treating phantom limb pain and/ or for providing sensory feedback arising from a prosthetic limb. International P.C.T. Patent filed July 5, 2000.
  • M. Barú, J.A. Hoffer, E. Calderon, G. Jenne and A. Calderon, Implantable nerve signal sensing and stimulation device and method for treating foot drop and other neurological disorders. International Patent application (PCT number PCT/IB2004/001023) filed April 2, 2004 ; published 14 October 2004.
  • M. Barú, J.A. Hoffer, E. Calderon, G. Jenne and A. Calderon, Implantable nerve signal sensing and stimulation device and method for treating foot drop and other neurological disorders. U.S. Patent application number 20050010265 filed April 2, 2004 ; published 13 January 2005.
  • J.A. Hoffer and G. Jenne, Implantable modular, multi channel connector system for nerve signal sensing and electrical stimulation applications. U.S. Patent application number 20050118887, filed June 3, 2004 , published June 2, 2005.

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