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Neuroprosthetic Applications: Recent Advances

1. Cardiovascular Response to FES and Passive Stepping: Orthostatic hypotension is a common condition for individuals with stroke or spinal cord injury. The inability to regulate the central nervous system will result in pooling of blood in the lower extremities leading to orthostatic intolerance. This study compared the use of functional electrical stimulation (FES) and passive leg movements to improve orthostatic tolerance during head-up tilt. Four trial conditions were assessed during head-up tilt: (1) rest, (2) isometric FES of the hamstring, gastrocnemius and quadriceps muscle group, (3) passive mobilization using the Erigo dynamic tilt table; and (4) dynamic FES (combined 2 and 3). Ten healthy male subjects experienced 70 deg head-up tilt for 15 min under each trial condition. Heart rate, blood pressure and abdominal echograms of the inferior vena cava were recorded for each trial. Passive mobilization and dynamic FES resulted in an increase in intravascular blood volume, while isometric FES only resulted in elevating heart rate. No significant differences in blood pressure were observed under each condition. We conclude that FES combined with passive stepping movements may be an effective modality to increase circulating blood volume and thereby tolerance to postural hypotension in healthy subjects.
2. Influence of the Number and Location of Recording Contacts on the Selectivity of a Nerve Cuff Electrode: A 56-contact matrix nerve cuff electrode (7 rings with 8 contacts each) was used to obtain recordings from the rat sciatic nerve, which were then discriminated as originating from one of three fascicles (tibial, peroneal, and sural branches). The influence of the number and location of the recording contacts on the classification accuracy was studied. The performance of a classifier was shown to be superior when data was available from all 56 contacts, compared to when only the 8 contacts of the middle ring were used (as in previously proposed multi-contact tripolar cuff designs). By examining the performance variations as contacts were included one at a time (in order of decreasing positive impact on performance), it was further shown that the matrix configuration could outperform the single-ring configuration with only a small number of contacts. We can therefore conclude that the performance improvement is not due to the sheer number of contacts, but rather to the possibility of selecting the most informative locations around the nerve. The results could have important implications for the design and use of multi-contact nerve cuff electrodes.
3. Effect of Intensive FES Therapy on the Upper Limb Motor Recovery after Stroke: This case report describes a stroke patient who participated in an intensive functional electrical stimulation (FES) therapy that consisted of task-specific upper arm movements with a combination of pre-programmed electrical stimulation and manually assisted motion. The patient was a 22-year-old woman who had suffered a hemorrhagic stroke 2 years earlier. Motor function of the upper extremity was severely impaired and showed the typical flexor synergy pattern. The FES therapy was carried out for 12 weeks, two times per day, one hour in each session (108 training sessions in total). The patient showed remarkable improvement in the coordination of the shoulder and elbow joints during the kinematic test. While the motor recovery (measured using the Chedoke McMaster Stroke Assessment scale and maximal voluntary contraction level of upper arm muscles) did not show any remarkable changes, there was remarkable reduction of the arm spasticity and muscle tone; observed was a decrease in the Modified Ashworth Scale and a reduction of the H-reflex in the wrist flexor muscle. The present results suggest that intensive FES therapy has the capability of improving upper limb function in chronic stroke patients. The improvement of the upper limb motion can be attributed to the enhancement of coordinated muscle activation patterns and the reduction of spasticity and muscle tone.
Type of Seminar:
Public Seminar
Prof. Milos R. Popovic
Toronto Rehab Chair in Spinal Cord Injury Research Rehabilitation Engineering Laboratory University of Toronto & Toronto Rehab
Sep 14, 2009   11.00 /

ETH Zentrum, Building ETZ, Room E 6
Contact Person:

Prof. S. Micera
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Biographical Sketch:
Milos R. Popovic received his Ph.D. degree in mechanical engineering from the University of Toronto, Ontario, Canada in 1996, and the Dipl. Electrical Engineer degree from the University of Belgrade, Yugoslavia in 1990. Dr. Popovic is the Toronto Rehab Chair in Spinal Cord Injury Research. He is also a Professor in the Institute of Biomaterials and Biomedical Engineering at the University of Toronto, as well as Senior Scientist and the Activity Team Leader at the Toronto Rehabilitation Institute. Both institutions located in Toronto, Ontario, Canada. Dr. Popovic joined the Institute of Biomaterials and Biomedical Engineering and the Toronto Rehab in 2001. From 1997 until 2001 he led the Rehabilitation Engineering Team at the Swiss Federal Institute of Technology (ETH) and the Paraplegic Center of the University Hospital Balgrist, both in Zurich, Switzerland. From 1996 until 1997, he worked for AlliedSignal Aerospace Canada Inc. in Toronto, Canada. Dr. Popovicís fields of expertise are functional electrical stimulation, neuro-rehabilitation, brain machine interfaces, modeling and control of linear and non-linear dynamic systems, robotics, power systems, signal processing, and safety analysis. His interests are in the areas of neuro-rehabilitation, physiological control systems, assistive technology, and brain machine interfaces. In 1997, together with Dr. Thierry Keller he received the Swiss National Science Foundation Technology Transfer Award - 1st place. In 2008, Dr. Popovic was awarded the Engineering Medal for Research and Development from the Professional Engineers.