Neuronal ensemble control of prosthetic devices by a human with tetraplegia.

Department of Neurology, Massachusetts General Hospital, Brigham and Women's Hospital, and Spaulding Rehabilitation Hospital, Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, USA.
Nature (Impact Factor: 38.6). 08/2006; 442(7099):164-71. DOI: 10.1038/nature04970
Source: PubMed

ABSTRACT Neuromotor prostheses (NMPs) aim to replace or restore lost motor functions in paralysed humans by routeing movement-related signals from the brain, around damaged parts of the nervous system, to external effectors. To translate preclinical results from intact animals to a clinically useful NMP, movement signals must persist in cortex after spinal cord injury and be engaged by movement intent when sensory inputs and limb movement are long absent. Furthermore, NMPs would require that intention-driven neuronal activity be converted into a control signal that enables useful tasks. Here we show initial results for a tetraplegic human (MN) using a pilot NMP. Neuronal ensemble activity recorded through a 96-microelectrode array implanted in primary motor cortex demonstrated that intended hand motion modulates cortical spiking patterns three years after spinal cord injury. Decoders were created, providing a 'neural cursor' with which MN opened simulated e-mail and operated devices such as a television, even while conversing. Furthermore, MN used neural control to open and close a prosthetic hand, and perform rudimentary actions with a multi-jointed robotic arm. These early results suggest that NMPs based upon intracortical neuronal ensemble spiking activity could provide a valuable new neurotechnology to restore independence for humans with paralysis.

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    ABSTRACT: Spinal cord injury (SCI) results in a loss of function and sensation below the level of the lesion. Neuroprosthetic technology has been developed to help restore motor and autonomic functions as well as to provide sensory feedback. This paper provides an overview of neuroprosthetic technology that aims to address the priorities for functional restoration as defined by individuals with SCI. We describe neuroprostheses that are in various stages of preclinical development, clinical testing, and commercialization including functional electrical stimulators, epidural and intraspinal microstimulation, bladder neuroprosthesis, and cortical stimulation for restoring sensation. We also discuss neural recording technologies that may provide command or feedback signals for neuroprosthetic devices. Conclusion/clinical relevance: Neuroprostheses have begun to address the priorities of individuals with SCI, although there remains room for improvement. In addition to continued technological improvements, closing the loop between the technology and the user may help provide intuitive device control with high levels of performance.
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    ABSTRACT: [MSc Thesis in Greek] Functional Cortical Connectivity studies the dynamics of information flow at the brain cortex. The sensorimotor cortex is activated in a similar fashion during actual and imaginary movement. Brain – Computer Interfaces exploit brain activity for the control of external devices. In this research we studied whether the properties of cortical functional networks differ between an actual and an imaginary movement, between movements of upper and lower extremities and between alpha and beta electroencephalographic (EEG) rhythms. Seven healthy people participated (four male, three female), performing under EEG four different motor tasks consisting of 95 trials each : a) right hand motor execution, b) right hand motor imagery, c) right foot motor execution and d) right foot motor imagery. EEG was recorded with 17 electrodes on the scalp over the sensorimotor cortex. The inverse problem was computed with Current Cortical Density. Two models of Regions Of Interest (ROIs) were defined, one consisting of 16 default regions and one consisting of 20 custom regions. Cortical functional connectivity was computed using Directed Transfer Function on both ROIs models for each subject, each motor task for alpha and beta rhythms. The results were studied with Graph Analysis, computing for each case the characteristic path length, clustering coefficient, density and small-worldness. No statistically important difference was found between functional cortical networks formed by actual and imaginary movement of the upper and lower extremities (ANOVA p<0.05). Between the functional networks formed by alpha and beta rhythms the findings consisted in a decrease in characteristic path length of 28-66.17%, a decrease in clustering coefficient of 2.09-39.76% and an increase in density of 20.18-40.65%. No statistically important difference was observed for small-worldness between alpha and beta rhythm. The properties of functional networks are similar between motor execution and imagery and could be of assistance in the future towards the enhancement of Brain-Computer Interfaces technology. We also support the conclusion that alpha and beta rhythms assume different neurophysiological roles in the sensorimotor cortex, based on the functional networks that are formed and their properties. Alpha rhythm appears to be carrier of information about the detailed evolution of a neurophysiological procedure and to cover more cortical nodes. On the contrary, beta rhythm appears to carry information about the integrated neurophysiological procedure across the sensorimotor cortex and to coordinate functional clusters. The functional networks of both alpha and beta rhythms have the properties of a small-world topology.
    03/2012, Degree: MSc in Medical Informatics, Supervisor: Panagiotis D. Bamidis
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    ABSTRACT: The emerging field of neuroprosthetics is focused on the development of new therapeutic interventions that will be able to restore some lost neural function by selective electrical stimulation or by harnessing activity recorded from populations of neurons. As more and more patients benefit from these approaches, the interest in neural interfaces has grown significantly and a new generation of penetrating microelectrode arrays are providing unprecedented access to the neurons of the central nervous system (CNS). These microelectrodes have active tip dimensions that are similar in size to neurons and because they penetrate the nervous system, they provide selective access to these cells (within a few microns). However, the very long-term viability of chronically implanted microelectrodes and the capability of recording the same spiking activity over long time periods still remain to be established and confirmed in human studies. Here we review the main responses to acute implantation of microelectrode arrays, and emphasize that it will become essential to control the neural tissue damage induced by these intracortical microelectrodes in order to achieve the high clinical potentials accompanying this technology.
    Frontiers in Neuroengineering 01/2014; 7:24.

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