Center for Neuroprosthetics and Institute of Bioengineering

Lausanne, Switzerland

Center for Neuroprosthetics and Institute of Bioengineering

Lausanne, Switzerland
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Marianelli P.,BioRobotics Institute | Capogrosso M.,Center for Neuroprosthetics and Institute of Bioengineering | Luciani L.B.,BioRobotics Institute | Panarese A.,BioRobotics Institute | Micera S.,Center for Neuroprosthetics and Institute of Bioengineering
IEEE Transactions on Neural Systems and Rehabilitation Engineering | Year: 2015

The vestibular organs are very important to generate reflexes critical for stabilizing gaze and body posture. Vestibular diseases significantly reduce the quality of life of people who are affected by them. Some research groups have recently started developing vestibular neuroprostheses to mitigate these symptoms. However, many scientific and technological issues need to be addressed to optimise their use in clinical trials. We developed a computational model able to mimic the response of human vestibular nerves and which can be exploited for "in-silico" testing of new strategies to design implantable vestibular prostheses. First, a digital model of the vestibular system was reconstructed from anatomical data. Monopolar stimulation was delivered at different positions and distances from ampullary nerves. The electrical potential induced by the injected current was computed through finite-element methods and drove extra-cellular stimulation of fibers in the vestibular, facial, and cochlear nerves. The electrical activity of vestibular nerves and the resulting eye movements elicited by different stimulation protocols were investigated. A set of electrode configurations was analyzed in terms of selectivity at increasing injected current. Electrode position along the nerve plays a major role in producing undesired activity in other nontargeted nerves, whereas distance from the fiber does not significantly affect selectivity. Indications are provided to minimize misalignment in nonoptimal electrode locations. Eye movements elicited by the different stimulation protocols are calculated and compared to experimental values, for the purpose of model validation.

Coscia M.,Center for Neuroprosthetics and Institute of Bioengineering | Coscia M.,CNR Institute of Neuroscience | Coscia M.,Sant'Anna School of Advanced Studies | Cheung V.C.,Massachusetts Institute of Technology | And 7 more authors.
Journal of NeuroEngineering and Rehabilitation | Year: 2014

Background: Compensating for the effect of gravity by providing arm-weight support (WS) is a technique often utilized in the rehabilitation of patients with neurological conditions such as stroke to facilitate the performance of arm movements during therapy. Although it has been shown that, in healthy subjects as well as in stroke survivors, the use of arm WS during the performance of reaching movements leads to a general reduction, as expected, in the level of activation of upper limb muscles, the effects of different levels of WS on the characteristics of the kinematics of motion and of the activity of upper limb muscles have not been thoroughly investigated before. Methods. In this study, we systematically assessed the characteristics of the kinematics of motion and of the activity of 14 upper limb muscles in a group of 9 healthy subjects who performed 3-D arm reaching movements while provided with different levels of arm WS. We studied the hand trajectory and the trunk, shoulder, and elbow joint angular displacement trajectories for different levels of arm WS. Besides, we analyzed the amplitude of the surface electromyographic (EMG) data collected from upper limb muscles and investigated patterns of coordination via the analysis of muscle synergies. Results: The characteristics of the kinematics of motion varied across WS conditions but did not show distinct trends with the level of arm WS. The level of activation of upper limb muscles generally decreased, as expected, with the increase in arm WS. The same eight muscle synergies were identified in all WS conditions. Their level of activation depended on the provided level of arm WS. Conclusions: The analysis of muscle synergies allowed us to identify a modular organization underlying the generation of arm reaching movements that appears to be invariant to the level of arm WS. The results of this study provide a normative dataset for the assessment of the effects of the level of arm WS on muscle synergies in stroke survivors and other patients who could benefit from upper limb rehabilitation with arm WS. © 2014 Coscia et al.; licensee BioMed Central Ltd.

Aprigliano F.,Sant'Anna School of Advanced Studies | Martelli D.,Sant'Anna School of Advanced Studies | Tropea P.,Sant'Anna School of Advanced Studies | Micera S.,Sant'Anna School of Advanced Studies | And 2 more authors.
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2015

Falls are a major cause of morbidity and death in elderly people. Understanding how subjects maintain stability while walking or while being exposed to perturbations is important in order to prevent falls. Here, five healthy subjects were asked to manage unexpected slipping-like perturbations of increasing intensities (i.e., soft, medium and strong) in order to investigate the effects of the perturbation intensity on the biomechanical behavior and on the dynamical stability, described by the Margin of Stability. The lower limb kinematic (i.e., hip, knee and ankle joints angles) was computed before and after the onset of the perturbation. The compensatory time and the Margin of Stability were calculated after the onset of the perturbation. As expected, results showed that the perturbation altered the subjects' kinematic and the modulation of the perturbation intensity was reflected in the dynamical stability: the stronger was the perturbation, the lower was the Margin of Stability describing a lower balance recovery. © 2015 IEEE.

Wenger N.,Ecole Polytechnique Federale de Lausanne | Wenger N.,Charité - Medical University of Berlin | Moraud E.M.,Center for Neuroprosthetics and Institute of Bioengineering | Gandar J.,Ecole Polytechnique Federale de Lausanne | And 32 more authors.
Nature Medicine | Year: 2016

Electrical neuromodulation of lumbar segments improves motor control after spinal cord injury in animal models and humans. However, the physiological principles underlying the effect of this intervention remain poorly understood, which has limited the therapeutic approach to continuous stimulation applied to restricted spinal cord locations. Here we developed stimulation protocols that reproduce the natural dynamics of motoneuron activation during locomotion. For this, we computed the spatiotemporal activation pattern of muscle synergies during locomotion in healthy rats. Computer simulations identified optimal electrode locations to target each synergy through the recruitment of proprioceptive feedback circuits. This framework steered the design of spatially selective spinal implants and real-time control software that modulate extensor and flexor synergies with precise temporal resolution. Spatiotemporal neuromodulation therapies improved gait quality, weight-bearing capacity, endurance and skilled locomotion in several rodent models of spinal cord injury. These new concepts are directly translatable to strategies to improve motor control in humans. © 2016 Nature America, Inc. All rights reserved.

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