Browsing by Keyword "proprioception"
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Item Integrated and flexible multichannel interface for electrotactile stimulation(2016-06-14) Štrbac, Matija; Belić, Minja; Isaković, Milica; Kojić, Vladimir; Bijelić, Goran; Popović, Igor; Radotić, Milutin; Došen, Strahinja; Marković, Marko; Farina, Dario; Keller, Thierry; SG; Mercado; Tecnalia Research & InnovationObjective. The aim of the present work was to develop and test a flexible electrotactile stimulation system to provide real-time feedback to the prosthesis user. The system requirements were to accommodate the capabilities of advanced multi-DOF myoelectric hand prostheses and transmit the feedback variables (proprioception and force) using intuitive coding, with high resolution and after minimal training. Approach. We developed a fully-programmable and integrated electrotactile interface supporting time and space distributed stimulation over custom designed flexible array electrodes. The system implements low-level access to individual stimulation channels as well as a set of high-level mapping functions translating the state of a multi-DoF prosthesis (aperture, grasping force, wrist rotation) into a set of predefined dynamic stimulation profiles. The system was evaluated using discrimination tests employing spatial and frequency coding (10 able-bodied subjects) and dynamic patterns (10 able-bodied and 6 amputee subjects). The outcome measure was the success rate (SR) in discrimination. Main results. The more practical electrode with the common anode configuration performed similarly to the more usual concentric arrangement. The subjects could discriminate six spatial and four frequency levels with SR >90% after a few minutes of training, whereas the performance significantly deteriorated for more levels. The dynamic patterns were intuitive for the subjects, although amputees showed lower SR than able-bodied individuals (86% 10% versus 99% 3%). Significance. The tests demonstrated that the system was easy to setup and apply. The design and resolution of the multipad electrode was evaluated. Importantly, the novel dynamic patterns, which were successfully tested, can be superimposed to transmit multiple feedback variables intuitively and simultaneously. This is especially relevant for closing the loop in modern multifunction prostheses. Therefore, the proposed system is convenient for practical applications and can be used to implement sensory perception training and/or closed-loop control of myoelectric prostheses, providing grasping force and proprioceptive feedback.Item A strategy of faster movements used by elderly humans to lift objects of increasing weight in ecological context(2017-08-15) Hoellinger, Thomas; McIntyre, Joseph; Jami, Lena; Hanneton, Sylvain; Cheron, Guy; Roby-Brami, Agnes; Robótica MédicaIt is not known whether, during the course of aging, changes occur in the motor strategies used by the CNS for lifting objects of different weights. Here, we analyzed the kinematics of object-lifting in two different healthy groups (young and elderly people) plus one well-known deafferented patient (GL). The task was to reach and lift onto a shelf an opaque cylindrical object with changing weight. The movements of the hand and object were recorded with electromagnetic sensors. In an ecological context (i.e. no instruction was given about movement speed), we found that younger participants, elderly people and GL did not all move at the same speed and that, surprisingly, elder people are faster. We also observed that the lifting trajectories were constant for both the elderly and the deafferented patient while younger participants raised their hand higher when the object weighed more. It appears that, depending on age and on available proprioceptive information, the CNS uses different strategies of lifting. We suggest that elder people tend to optimize their feedforward control in order to compensate for less functional afferent feedback, perhaps to optimize movement time and energy expenditure at the expense of high precision. In the case of complete loss of proprioceptive input, however, compensation follows a different strategy as suggested by GL's behavior who moved more slowly compared to both our younger and older participants.