I have been simulating single axon and whole nerve resonses to applied electrical fields for 10 years. My simulations incorporate bio-inspired 3D finite element models in Ansoft Maxwell, double-cable axon models in NEURON, and analyses in MATLAB. I use the simulations to optimize the design of nerve cuff electrodes that are used to restore function in paralyzed individuals.
Currently, I am simulating the response of the human sciatic, tibial, and fibular (peroneal) nerve to electrical stimulation. I have also simulated the response of the femoral nerve and retinal ganglion cells to electrical stimulation.
My computer simulation work has been refered to as "the current state of the art" by Dr. Cameron McIntyre, which is a true honor coming from him. It has also been featured on the cover of a past edition of IEEE's TNSRE Journal.
I evaluate the efficacy of the manufactured electrodes through intraoperative experiments. The electrode is placed around the nerve of an able-bodied volunteer in acute (very short duration) experiments or implanted in those with paralysis. Using a custom software suite and a mobile data acquisition cart, I deliver controlled stimuli to the nerve and record the muscles' responses (EMGs) to those stimuli. These data help me determine if the electrode can selectively recruit specific muscles or restore specific functions.
Sensory
I am interested in expanding my research to include stimulating sensory fibers. A project I may soon be involved with will attempt to restore sensation in amputees through controlled stimulation of residual nerves. This would allow a prosthesis user to "feel" with the prosthesis and attempts to provide sensory feedback to user.
Autonomic
Also, I am interested in expanding my research to include interfacing with and control of the autonomic nervous system. One project am interested in is selective stimulation of the vagus nerve in humans to control food motility through the gut in order to reduce obesity.
In addition to computer simulations and electrode evaluation, I am also interested in developing new methods for peripheral nerve imaging. Such technology could be used for neurodiagnostics as well as for developing better neural interfaces and surgical implantation approaches. If you are an expert in MRI, fMRI, DTI, US, CT, or any other imaging modality, I would be intersted in talking to you about the possibility of imaging nerves at a high resolution. Please contact me.
In addition to neural modeling, electrode evaluation, and neural imaging, I am also intersted in a variety of other, unrelated areas of research.
Lately, I've become interested in predicting the success of start-up companies based on a number of parameters, including a quantified value of key members' professional and social network.
"Probabilistic Modeling of Selective Stimulation of the Human Sciatic Nerve with a Flat Interface Nerve Electrode"
MA Schiefer, DJ Tyler, RJ Triolo
IEEE-EMBC, Boston, Aug 2011
Proper ankle control is critical to both standing balance and efficient walking. This study hypothesized that a Flat Interface Nerve Electrode (FINE) placed around the sciatic nerve with a fixed number of contacts at predetermined locations and without a priori knowledge of the nerve's underlying neuroanatomy can selectively control each ankle motion. Models of the human sciatic nerve surrounded by a FINE of varying size were created and used to calculate the probability of selective activation of axons within any arbitrarily designated group of fascicles. Simulations suggest that currently available implantable technology cannot selectively recruit each target plantar flexor individually but can restore plantar flexion or dorsiflexion from a site on the sciatic nerve without spillover to antagonists. Successful activation of individual ankle muscles in 90% of the population can be achieved by utilizing bipolar stimulation and/or by increasing the number of contacts within the cuff.Proper ankle control is critical to both standing balance and efficient walking. This study hypothesized that a FINE placed around the sciatic nerve with a fixed number of contacts at predetermined locations and without a priori knowledge of the nerve's underlying neuroanatomy can selectively control each ankle motion. Models of the human sciatic nerve surrounded by a FINE of varying size were created and used to calculate the probability of selective activation of axons within any arbitrarily designated group of fascicles. Simulations suggest that currently available implantable technology cannot selectively recruit each target plantar flexor individually but can restore plantar flexion or dorsiflexion from a site on the sciatic nerve without spillover to antagonists. Successful activation of individual ankle muscles in 90% of the population can be achieved by utilizing bipolar stimulation and/or by increasing the number of contacts within the cuff.
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"Probabilistic modeling of selective stimulation of the human sciatic nerve with a flat interface nerve electrode"
MA Schiefer, DJ Tyler, RJ Triolo
J Comp Neurosci 2012, 10.1007/s10827-011-0381-5.
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PubMed
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IOP Science
"Selective stimulation of the human femoral nerve with a flat interface nerve electrode"
MA Schiefer, KH Polasek, RJ Triolo, GCJ Pinault, DJ Tyler
J Neural Eng. 2010 Apr;7(2):26006. Epub 2010 Mar 8.
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PubMed
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IOP Science
"Intraoperative evaluation of the spiral nerve cuff electrode on the femoral nerve trunk"
KH Polasek, MA Schiefer, GCJ Pinault, RJ Triolo, DJ Tyler
J Neural Eng. 2009 Dec;6(6):066005. Epub 2009 Nov 9.
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PubMed
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Article
"Fascicular perineurium thickness, size, and position affect model predictions of neural excitation"
Y Grinberg, MA Schiefer, DJ Tyler, KJ Gustafson
IEEE Trans Neural Syst Rehabil Eng. 2008 Dec;16(6):572-81.
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PubMed
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Article
"A model of selective activation of the femoral nerve with a flat interface nerve electrode for a lower extremity neuroprosthesis"
MA Schiefer, RJ Triolo, DJ Tyler
IEEE Trans Neural Syst Rehabil Eng. 2008 Apr;16(2):195-204.
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PubMed
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Article
"Sites of neuronal excitation by epiretinal electrical stimulation"
MA Schiefer& WM Grill
IEEE Trans Neural Syst Rehabil Eng. 2006 Mar;14(1):5-13.
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PubMed
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Article
"Structural mechanisms to produce differential dendritic gains"
DC Lee, AL Jensen, MA Schiefer, CW Morgan, WM Grill
Brain Res. 2005 Feb 8;1033(2):117-27.
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If you are intersted in starting a collaboration,
working together on a funded grant or grant application,
or have general questions about my research or the field,
please feel free to contact me.
Dr. Matthew A. Schiefer
Dept. of Biomedical Engineering
Wickenden Bldg
Case Western Reserve University
10900 Euclid Ave
Cleveland, OH 44106
If you are intersted in starting a collaboration,
working together on a funded grant or grant application,
or have general questions about my research or the field,
please feel free to contact me.
Dr. Matthew A. Schiefer
Dept. of Biomedical Engineering
Wickenden Bldg
Case Western Reserve University
10900 Euclid Ave
Cleveland, OH 44106
Neural Simulations
Neural Imaging
