Dr. Andy Hoffer
Professor of Biomedical Physiology and Kinesiology
Director, Neurokinesiology Laboratory
Bachiller Engineering IAVA Montevideo
BS Physics Harvey Mudd College
PhD Biophysics Johns Hopkins University
Phone: (778) 782-3141
Email: hoffer@sfu.ca
Biography
Dr. Andy Hoffer was born in Montevideo, Uruguay where he studied engineering. Upon receiving scholarships to study in the USA, he obtained a B.S. in physics in 1970 from Harvey Mudd College and a Ph.D. in biophysics in 1975 from Johns Hopkins University. He then came to Canada for postdoctoral training at the University of Alberta, Faculty of Medicine until 1978, when he joined the Laboratory of Neural Control, U.S. National Institutes of Health, as Staff Fellow. In 1982 he returned to Canada as assistant professor and Alberta Heritage Scholar at the University of Calgary, Faculty of Medicine, where he became a full professor. In 1991 he moved to Simon Fraser University as professor and director of the School of Kinesiology (until 1997) and he is currently professor of Biomedical Physiology and Kinesiology in the Faculty of Science. Dr. Hoffer founded three biotechnology companies spun out from his SFU laboratory: Neurostream Technologies in 1998, Bionic Power in 2006 and Lungpacer Medical in 2009.
Research Summary
Beginning with the development of implantable nerve cuff recording electrodes during his doctoral thesis, Dr. Hoffer’s core research has addressed:
- How peripheral sensory and motor neurons function during voluntary movements, and
- development of assistive devices for functional rehabilitation of people affected by paralysis after brain or spinal cord injuries, limb amputations, and other neurological or neuromuscular disorders.
During the past 30 years, the SFU Neurokinesiology Laboratory and its 3 spun-out startup companies, research trainees and collaborators created uniquely specialized facilities, techniques and protocols for:
- neurophysiological and biomechanical recordings during unrestrained voluntary movements, and
- invention, design, prototyping, testing, and pre-clinical validation of neuroprosthetic and neuroassistive solutions for people with neurological, neuromuscular or sensory impairments.
Research Themes
Nerve Cuff Electrodes for Research and Clinical Uses
Doctoral Thesis at Johns Hopkins University
For his PhD thesis supervised by W.B. Marks, Andy Hoffer designed and built nerve cuffs and low-noise amplifiers that recorded μVolt-level peripheral nerve activity during locomotion. Tripolar cuffs implanted in rabbit hindlimb nerves provided the first-ever recordings of sensory firing patterns in intact animals.
Nerve fiber activity during normal movements JA Hoffer, WB Marks, WZ Rymer. Soc Neurosci Abst 4:300, 1974. |
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Postdoctoral Research at U. Alberta
Richard B. Stein’s supervision at U. of Alberta, Andy Hoffer and colleagues implanted nerve cuffs to track the survival of motor and sensory nerve fibers after peripheral nerve lesions. They subsequently pioneered new methods to assist upper limb amputees to control powered prosthetic limbs.
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LA Davis, T Gordon, JA Hoffer, J Jhamandas, RB Stein. Journal of physiology 285 (1), 543-559, 1978. |
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Differential atrophy of sensory and motor fibers following section of cat peripheral nerves JA Hoffer, RB Stein, T Gordon. Brain research 178 (2-3), 347-361, 1979 |
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Long‐term effects of axotomy on neural activity during cat locomotion. T Gordon, JA Hoffer, J Jhamandas, RB Stein. The Journal of Physiology 303 (1), 243-263 |
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New approaches to controlling powered arm prostheses, particularly by high-level amputees. RB Stein, D Charles, JA Hoffer, J Arsenault, LA Davis, S Moorman, B Moss. Bull. Prosth. Res. 17: 51-62, 1980. |
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Andy Hoffer and fellow PDF Steen Andreassen collaborated in studies to quantify stretch reflex stiffness vs. intrinsic muscle stiffness, motivated by invaluable mentorship from T. Richard Nichols while he was also a PDF training in Stein’s lab
Regulation of soleus muscle stiffness in premammillary cats: intrinsic and reflex components. JA Hoffer, S Andreassen. Journal of neurophysiology 45 (2), 267-285, 1981. |
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Staff Fellowship at the Laboratory of Neural Control, NIH
In 1978, Andy Hoffer joined the NIH Lab of Neural Control in Bethesda, MD as Staff Fellow and collaborated with Gerald Loeb to equip a unique facility where they recorded in behaving animals the activity from single neurons with floating fine-wire ”hatpin” microelectrodes as well as implanted nerve cuffs, EMG electrodes, tendon force and muscle length transducers, described in a Science paper and seven J Neurophysiol papers (spindles 1, 2, 3 and motoneurons 1, 2, 3, 4).
Discharge patterns of hindlimb motoneurons during normal cat locomotion JA Hoffer, MJ O'Donovan, CA Pratt, GE Loeb. Science 213 (4506), 466-467. 1981. |
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Targeted Reinnervation of Nerve Stumps in Amputees
In an Ann Biomed Eng 1980 paper, Hoffer and Loeb analyzed the potential for long-term clinical uses of the five implanted technologies. Of these, neurograms recorded from intact nerves by cuff electrodes were the most likely to remain stable over many months and years.
In amputees, however, cut motor axons atrophy, and their signals become too small to record reliably. Hoffer and Loeb introduced the concept of “targeted reinnervation”: graft the nerve stumps onto donor muscles. This idea was later put into practice by Todd Kuiken and now provides amputees with enhanced motor signals to control prostheses.
Implantable electrical and mechanical interfaces with nerve and muscle JA Hoffer, GE Loeb. Annals of biomedical engineering 8 (4), 351-360, 1980. |
Professor and Alberta Heritage Fellow at U. Calgary
In 1982 Andy Hoffer took a faculty position at the University of Calgary where, with an Alberta Heritage Medical Research Establishment grant, he built a chronic recording lab and continued using and refining implantable sensing technologies jointly developed at NIH. With grants from MRC, NCE, Rick Hansen and U.S. Spinal Cord Research Foundation he attracted excellent trainees, including Angel Caputi with whom the Calgary team pioneered the capability to record muscle fiber length changes in intact animals using ultrasound transit-time; Thomas Sinkjær, with whom they compared muscle stiffness and reflex properties in intact and decerebrated animals, and Morten Haugland, whose thesis described properties of sensory afferent signals recorded from peripheral nerves in response to skin contact forces. Hoffer was also granted his first US patent while in Calgary, for a nerve-cuff based invention.
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JA Hoffer. US Patent 4,750,499, 1988. |
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JA Hoffer, AA Caputi, IE Pose, RI Griffiths. Progress in brain research 80, 75-85, 1989. |
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Factors determining segmental reflex action in normal and decerebrate cats T Sinkjær, JA Hoffer. Journal of neurophysiology 64 (5), 1625-1635, 1990. |
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Techniques to study spinal-cord, peripheral nerve, and muscle activity in freely moving animals JA Hoffer. Neurophysiological Techniques, 65-145, 1990. |
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Skin contact force information in sensory nerve signals recorded by implanted cuff electrodes MK Haugland, JA Hoffer, T Sinkjær. IEEE Transactions on Rehabilitation Engineering 2 (1), 18-28, 1994. |
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MK Haugland, JA Hoffer. IEEE Transactions on Rehabilitation Engineering 2 (1), 29-36, 1994. |
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MK Haugland, JA Hoffer. IEEE Transactions on Rehabilitation Engineering 2 (1), 37-40., 1994. |
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Professor and Director of the Neurokinesiology Laboratory at Simon Fraser University
In 1991 Hoffer took a continuing faculty position at SFU, where he also served as the Director of the School of Kinesiology until 1997. He moved most of his Calgary lab equipment, several team members and MRC and NCE funds to SFU, and in 1992 was awarded a large research contract by the NIH/NINDS Neural Prosthesis Program to develop laser-based methods to fabricate advanced nerve cuff electrodes and to demonstrate their long-term stability, safety and efficacy in pre-clinical trials in animals. This research resulted in several publications and patents, including:
Implantable cuff having improved closure K Kallesoe, JA Hoffer, K Strange, I Valenzuela. US Patent 5,487,756, 1996. |
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Nerve cuff having one or more isolated chambers JA Hoffer, Y Chen, KD Strange, PR Christensen. US Patent 5,824,027, 1998. |
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KD Strange, JA Hoffer. IEEE Transactions on Rehabilitation Engineering 7 (3), 289-300, 1999. |
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M Baru, JA Hoffer, E Calderon, GB Jenne, A Calderon. US Patent 7,636,602, 2009. |
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Neural signals for command control and feedback in functional neuromuscular stimulation: a review JA Hoffer, RB Stein, MK Haugland, T Sinkjaer, WK Durfee, AB Schwartz. J Rehabil Res Dev 33 (2), 145-157, 1996. |
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Nerve cuff, method and apparatus for manufacturing same JA Hoffer, MO Imbeau, JM Vallieres. US Patent 8,214,056, 2012. |
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