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Sci Rep. 2018 Nov 5;8(1):16357. doi: 10.1038/s41598-018-34711-1.

Brain-machine interface cursor position only weakly affects monkey and human motor cortical activity in the absence of arm movements.

Stavisky SD1,2, Kao JC3,4, Nuyujukian P5,3,6,7,8, Pandarinath C5,3, Blabe C5, Ryu SI3,9, Hochberg LR10,11,12,13, Henderson JM5,7,8, Shenoy KV3,6,7,8,14,15.

Author information

1
Neurosurgery Department, Stanford University, Stanford, CA, USA. sergey.stavisky@stanford.edu.
2
Electrical Engineering Department, Stanford University, Stanford, CA, USA. sergey.stavisky@stanford.edu.
3
Electrical Engineering Department, Stanford University, Stanford, CA, USA.
4
Electrical and Computer Engineering Department, University of California at Los Angeles, Los Angeles, CA, USA.
5
Neurosurgery Department, Stanford University, Stanford, CA, USA.
6
Bioengineering Department, Stanford University, Stanford, CA, USA.
7
Stanford Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, USA.
8
Bio-X Program, Stanford University, Stanford, CA, USA.
9
Neurosurgery Department, Palo Alto Medical Foundation, Palo Alto, CA, USA.
10
Center for Neurorestoration and Neurotechnology, Rehabilitation R&D Service, VA Medical Center, Providence, RI, USA.
11
School of Engineering and Carney Institute for Brain Science Brown University, Providence, RI, USA.
12
Department of Neurology, Harvard Medical School, Boston, MA, USA.
13
Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital, Boston, MA, USA.
14
Neurobiology Department, Stanford University, Stanford, CA, USA.
15
Howard Hughes Medical Institute at Stanford University, Stanford, CA, USA.

Abstract

Brain-machine interfaces (BMIs) that decode movement intentions should ignore neural modulation sources distinct from the intended command. However, neurophysiology and control theory suggest that motor cortex reflects the motor effector's position, which could be a nuisance variable. We investigated motor cortical correlates of BMI cursor position with or without concurrent arm movement. We show in two monkeys that subtracting away estimated neural correlates of position improves online BMI performance only if the animals were allowed to move their arm. To understand why, we compared the neural variance attributable to cursor position when the same task was performed using arm reaching, versus arms-restrained BMI use. Firing rates correlated with both BMI cursor and hand positions, but hand positional effects were greater. To examine whether BMI position influences decoding in people with paralysis, we analyzed data from two intracortical BMI clinical trial participants and performed an online decoder comparison in one participant. We found only small motor cortical correlates, which did not affect performance. These results suggest that arm movement and proprioception are the major contributors to position-related motor cortical correlates. Cursor position visual feedback is therefore unlikely to affect the performance of BMI-driven prosthetic systems being developed for people with paralysis.

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