Antonio Augusto Fasolo Quevedo

Comparison of grasping movements made by healthy subjects in a 3-dimensional immersive virtual versus physical environment☆☆☆

Virtual reality (VR) technology is being used with increasing frequency as a training medium for motor rehabilitation. However, before addressing training effectiveness in virtual environments (VEs), it is necessary to identify if movements made in such environments are kinematically similar to those made in physical environments (PEs) and the effect of provision of haptic feedback on these movement patterns. These questions are important since reach-to-grasp movements may be inaccurate when visual or haptic feedback is altered or absent. Our goal was to compare kinematics of reaching and grasping movements to three objects performed in an immersive three-dimensional (3D) VE with haptic feedback (cyberglove/grasp system) viewed through a head-mounted display to those made in an equivalent physical environment (PE). We also compared movements in PE made with and without wearing the cyberglove/grasp haptic feedback system. Ten healthy subjects (8 women, 62.1±8.8years) reached and grasped objects requiring 3 different grasp types (can, diameter 65.6mm, cylindrical grasp; screwdriver, diameter 31.6mm, power grasp; pen, diameter 7.5mm, precision grasp) in PE and visually similar virtual objects in VE. Temporal and spatial arm and trunk kinematics were analyzed. Movements were slower and grip apertures were wider when wearing the glove in both the PE and the VE compared to movements made in the PE without the glove. When wearing the glove, subjects used similar reaching trajectories in both environments, preserved the coordination between reaching and grasping and scaled grip aperture to object size for the larger object (cylindrical grasp). However, in VE compared to PE, movements were slower and had longer deceleration times, elbow extension was greater when reaching to the smallest object and apertures were wider for the power and precision grip tasks. Overall, the differences in spatial and temporal kinematics of movements between environments were greater than those due only to wearing the cyberglove/grasp system. Differences in movement kinematics due to the viewing environment were likely due to a lack of prior experience with the virtual environment, an uncertainty of object location and the restricted field-of-view when wearing the head-mounted display. The results can be used to inform the design and disposition of objects within 3D VEs for the study of the control of prehension and for upper limb rehabilitation.

Quality of Grasping and the Role of Haptics in a 3-D Immersive Virtual Reality Environment in Individuals With Stroke

Reaching and grasping parameters with and without haptic feedback were characterized in people with chronic post-stroke behaviors. Twelve (67 ±10 years) individuals with chronic stroke and arm/hand paresis (Fugl-Meyer Assessment-Arm: ≥46/66 pts) participated. Three dimensional (3-D) temporal and spatial kinematics of reaching and grasping movements to three objects (can: cylindrical grasp; screwdriver: power grasp; pen: precision grasp) in a physical environment (PE) with and without additional haptic feedback and a 3-D virtual environment (VE) with haptic feedback were recorded. Participants reached, grasped and transported physical and virtual objects using similar movement strategies in all conditions. Reaches made in VE were less smooth and slower compared to the PE. Arm and trunk kinematics were similar in both environments and glove conditions. For grasping, stroke subjects preserved aperture scaling to object size but used wider hand apertures with longer delays between times to maximal reaching velocity and maximal grasping aperture. Wearing the glove decreased reaching velocity. Our results in a small group of subjects suggest that providing haptic information in the VE did not affect the validity of reaching and grasping movement. Small disparities in movement parameters between environments may be due to differences in perception of object distance in VE. Reach-to-grasp kinematics to smaller objects may be improved by better 3-D rendering. Comparable kinematics between environments and conditions is encouraging for the incorporation of high quality VEs in rehabilitation programs aimed at improving upper limb recovery.

Comparison of reaching and grasping kinematics in patients with hemiparesis and in healthy controls in virtual and physical environments

Kinematics of reaching and grasping movements to physical and virtual objects placed on a table in front of the body midline were compared in 10 healthy and 12 hemiparetic subjects post-stroke. Despite minor differences in performance variables (movement time, arm trajectory) and joint ranges, arm and hand movement patterns were similar in the two environments. Differences may be due to attributes of the VR environment. Relevance to rehabilitation will be discussed.

High-reliability microcontroller nerve stimulator for assistance in regional anaesthesia procedures

Abstract In the last decades, the use of nerve stimulators to aid in regional anaesthesia has been shown to benefit the patient since it allows a better location of the nerve plexus, leading to correct positioning of the needle through which the anaesthetic is applied. However, most of the nerve stimulators available in the market for this purpose do not have the minimum recommended features for a good stimulator, and this can lead to risks to the patient. Thus, this study aims to develop an equipment, using embedded electronics, which meets all the characteristics, for a successful blockade. The system is made of modules for generation and overall control of the current pulse and the patient and user interfaces. The results show that the designed system fits into required specifications for a good and reliable nerve stimulator. Linearity proved satisfactory, ensuring accuracy in electrical current amplitude for a wide range of body impedances. Field tests have proven very successful. The anaesthesiologist that used the system reported that, in all cases, plexus blocking was achieved with higher quality, faster anaesthetic diffusion and without needed of an additional dose when compared with same procedure without the use of the device.

Biopotential Amplification System Developed for Surface Electromyography Using Dry Electrodes

Herein we show the results of dry electrodes based on two types of electrodes chromium-gold and gold and the integration to a real-time sEMG collection system. The system uses a PXI chassis with a National Instruments FPGA module that performs a manual selection of amplification gains. A real-time PXI module was utilized with LabVIEW to allow the use of EMG signal decomposition techniques in the study of motion intention identification, prosthesis movements, and neuromuscular integrity analysis.