Regaining motor function is of high priority to patients with spinal cord injury (SCI). A variety of electronic devices that interface with the brain or spinal cord, which have applications in neural prosthetics and neurorehabilitation, are in development. Owing to our advancing understanding of activity-dependent synaptic plasticity, new technologies to monitor, decode and manipulate neural activity are being translated to patient populations, and have demonstrated clinical efficacy. Brain–machine interfaces that decode motor intentions from cortical signals are enabling patient-driven control of assistive devices such as computers and robotic prostheses, whereas electrical stimulation of the spinal cord and muscles can aid in retraining of motor circuits and improve residual capabilities in patients with SCI. Next-generation interfaces that combine recording and stimulating capabilities in so-called closed-loop devices will further extend the potential for neuroelectronic augmentation of injured motor circuits. Emerging evidence suggests that integration of closed-loop interfaces into intentional motor behaviours has therapeutic benefits that outlast the use of these devices as prostheses. In this Review, we summarize this evidence and propose that several known plasticity mechanisms, operating in a complementary manner, might underlie the therapeutic effects that are achieved by closing the loop between electronic devices and the nervous system.
Brain–machine interfaces (BMIs) that record and decode signals from the brain enable volitional control of assistive devices, and modify patterns of cortical activity through the process of neurofeedback
The translation of invasive BMIs from animal studies to patients suggests that these technologies could control functional electrical stimulation for the restoration of movement to paralysed limbs
Epidural and intraspinal stimulation generates functional limb movements involving the coordinated activity of multiple muscles, and the activation of spinal circuitry in combination with volitional intent could have therapeutic benefits
Correlated patterns of spiking activity drive synaptic and structural plasticity, and experimental protocols that involve stimulation of the CNS and PNS have been used to artificially induce specific changes in neural connectivity
Neural prostheses that combine recording and stimulation capabilities within wearable or implantable closed-loop devices could replace or augment injured pathways from the cortex to the spinal cord
Long-term operation of closed-loop devices may have further therapeutic benefits through several complementary mechanisms of activity-dependent plasticity
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A. Jackson is supported by a Wellcome Trust Research Career Development Fellowship (086561). J. B. Zimmermann is supported by a Wellcome Trust Ph.D. Studentship (087223).
The authors declare no competing financial interests.
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Jackson, A., Zimmermann, J. Neural interfaces for the brain and spinal cord—restoring motor function. Nat Rev Neurol 8, 690–699 (2012). https://doi.org/10.1038/nrneurol.2012.219
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