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Neuroimage. 2014 Nov 1;101:695-703. doi: 10.1016/j.neuroimage.2014.07.049. Epub 2014 Aug 2.

Extracting kinetic information from human motor cortical signals.

Author information

1
Department of Neurology, Northwestern University, Chicago, IL 60611, USA. Electronic address: r-flint@northwestern.edu.
2
Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92617, USA.
3
Department of Neurology, Northwestern University, Chicago, IL 60611, USA.
4
Division of Neurosurgery, Duke University, Durham, NC, USA.
5
Department of Neurosurgery, Northwestern University, Chicago, IL 60611, USA.
6
Department of Neurosurgery, University of California, Irvine, Irvine, CA 92617, USA.
7
Department of Neurosurgery, Rancho Los Amigos National Rehabilitation Center, Downey, CA 90242, USA; Department of Neurosurgery, University of Southern California, Los Angeles, CA 90033, USA.
8
Department of Neurology, University of California, Irvine, Irvine, CA 92617, USA.
9
Department of Neurology, Rancho Los Amigos National Rehabilitation Center, Downey, CA 90242, USA; Department of Neurology, University of Southern California, Los Angeles, CA 90033, USA.
10
Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92617, USA; Department of Electrical Engineering and Computer Science, University of California, Irvine, Irvine, CA 92617, USA.
11
Department of Neurology, Northwestern University, Chicago, IL 60611, USA; Department of Physiology, Northwestern University, Chicago, IL 60611, USA; Department of Physical Medicine & Rehabilitation, Northwestern University, Chicago, IL 60611, USA; The Rehabilitation Institute of Chicago, Chicago, IL 60611, USA.

Abstract

Brain machine interfaces (BMIs) have the potential to provide intuitive control of neuroprostheses to restore grasp to patients with paralyzed or amputated upper limbs. For these neuroprostheses to function, the ability to accurately control grasp force is critical. Grasp force can be decoded from neuronal spikes in monkeys, and hand kinematics can be decoded using electrocorticogram (ECoG) signals recorded from the surface of the human motor cortex. We hypothesized that kinetic information about grasping could also be extracted from ECoG, and sought to decode continuously-graded grasp force. In this study, we decoded isometric pinch force with high accuracy from ECoG in 10 human subjects. The predicted signals explained from 22% to 88% (60 ± 6%, mean ± SE) of the variance in the actual force generated. We also decoded muscle activity in the finger flexors, with similar accuracy to force decoding. We found that high gamma band and time domain features of the ECoG signal were most informative about kinetics, similar to our previous findings with intracortical LFPs. In addition, we found that peak cortical representations of force applied by the index and little fingers were separated by only about 4mm. Thus, ECoG can be used to decode not only kinematics, but also kinetics of movement. This is an important step toward restoring intuitively-controlled grasp to impaired patients.

KEYWORDS:

Brain–machine interface; Decoding; EMG; Electrocorticography; Force; Motor cortex

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