Epidural electrocorticography of phantom hand movement following long-term upper-limb amputation.
BACKGROUND
Prostheses for upper-limb amputees are currently controlled by either myoelectric or peripheral neural signals. Performance and dexterity of these devices is still limited, particularly when it comes to controlling hand function. Movement-related brain activity might serve as a complementary bio-signal for motor control of hand prosthesis.


METHODS
We introduced a methodology to implant a cortical interface without direct exposure of the brain surface in an upper-limb amputee. This bi-directional interface enabled us to explore the cortical physiology following long-term transhumeral amputation. In addition, we investigated neurofeedback of electrocorticographic brain activity related to the patient's motor imagery to open his missing hand, i.e., phantom hand movement, for real-time control of a virtual hand prosthesis.


RESULTS
Both event-related brain activity and cortical stimulation revealed mutually overlapping cortical representations of the phantom hand. Phantom hand movements could be robustly classified and the patient required only three training sessions to gain reliable control of the virtual hand prosthesis in an online closed-loop paradigm that discriminated between hand opening and rest.


CONCLUSIONS
Epidural implants may constitute a powerful and safe alternative communication pathway between the brain and external devices for upper-limb amputees, thereby facilitating the integrated use of different signal sources for more intuitive and specific control of multi-functional devices in clinical use.
Division of Functional and Restorative Neurosurgery and Division of Translational Neurosurgery, Department of Neurosurgery, Eberhard Karls University of Tübingen Tübingen, Germany ; Neuroprosthetics Research Group, Werner Reichardt Centre for Integrative Neuroscience, Eberhard Karls University of Tübingen Tübingen, Germany.
Alireza
A
Gharabaghi
Division of Functional and Restorative Neurosurgery and Division of Translational Neurosurgery, Department of Neurosurgery, Eberhard Karls University of Tübingen Tübingen, Germany ; Neuroprosthetics Research Group, Werner Reichardt Centre for Integrative Neuroscience, Eberhard Karls University of Tübingen Tübingen, Germany.
Georgios
G
Naros
Department of Computer Engineering, Wilhelm-Schickard Institute for Computer Science, Eberhard Karls University of Tübingen Tübingen, Germany.
Armin
A
Walter
Department of Computer Engineering, Wilhelm-Schickard Institute for Computer Science, Eberhard Karls University of Tübingen Tübingen, Germany.
Alexander
A
Roth
Department of Computer Engineering, Wilhelm-Schickard Institute for Computer Science, Eberhard Karls University of Tübingen Tübingen, Germany ; Department of Computer Engineering, University of Leipzig Leipzig, Germany.
Martin
M
Bogdan
Department of Computer Engineering, Wilhelm-Schickard Institute for Computer Science, Eberhard Karls University of Tübingen Tübingen, Germany.
Wolfgang
W
Rosenstiel
Institute for Biology III, Albert-Ludwigs-University Freiburg im Breisgau, Germany.
Carsten
C
Mehring
Institute of Medical Psychology and Behavioural Neurobiology, Eberhard Karls University of Tübingen Tübingen, Germany.
Niels
N
Birbaumer
amputee; brain–computer interface; brain–machine interface; closed-loop control; electrocorticography; epidural implant; neural prosthesis; neurofeedback