Showing papers by "Domenico Formica published in 2012"

The passive stiffness of the wrist and forearm

Abstract: Because wrist rotation dynamics are dominated by stiffness (Charles SK, Hogan N. J Biomech 44: 614-621, 2011), understanding how humans plan and execute coordinated wrist rotations requires knowledge of the stiffness characteristics of the wrist joint. In the past, the passive stiffness of the wrist joint has been measured in 1 degree of freedom (DOF). Although these 1-DOF measurements inform us of the dynamics the neuromuscular system must overcome to rotate the wrist in pure flexion-extension (FE) or pure radial-ulnar deviation (RUD), the wrist rarely rotates in pure FE or RUD. Instead, understanding natural wrist rotations requires knowledge of wrist stiffness in combinations of FE and RUD. The purpose of this report is to present measurements of passive wrist stiffness throughout the space spanned by FE and RUD. Using a rehabilitation robot designed for the wrist and forearm, we measured the passive stiffness of the wrist joint in 10 subjects in FE, RUD, and combinations. For comparison, we measured the passive stiffness of the forearm (in pronation-supination), as well. Our measurements in pure FE and RUD agreed well with previous 1-DOF measurements. We have linearized the 2-DOF stiffness measurements and present them in the form of stiffness ellipses and as stiffness matrices useful for modeling wrist rotation dynamics. We found that passive wrist stiffness was anisotropic, with greater stiffness in RUD than in FE. We also found that passive wrist stiffness did not align with the anatomical axes of the wrist; the major and minor axes of the stiffness ellipse were rotated with respect to the FE and RUD axes by ∼20°. The direction of least stiffness was between ulnar flexion and radial extension, a direction used in many natural movements (known as the "dart-thrower's motion"), suggesting that the nervous system may take advantage of the direction of least stiffness for common wrist rotations.

Sensor-based technology in the study of motor skills in infants at risk for ASD

Abstract: Motor impairments seems to play an important role in neurodevelopmental disorders such as autism spectrum disorders (ASD). Early detection of motor abnormalities during first years of life, may give important information regarding whether a child may receive a later diagnosis of Autism: for this reason an objective assessment of motor performance is crucial. While there are several technological solutions suitable to this end, they often require highly structured environments. In this work we propose the use of a magneto-inertial platform to study early motor performance between 12-36 months of age suitable to be used in non-structured environment.

Embedding inertial-magnetic sensors in everyday objects: assessing spatial cognition in children.

Abstract: This paper describes an interdisciplinary approach to the assessment of children development of spatial cognition, with a focus on the technology. An instrumented toy (block-box) is presented which embeds magneto-inertial sensors for orientation tracking, specifically developed to assess the ability to insert objects into holes. The functional specifications are derived from experimental protocols devised by neuroscientists to assess spatial cognition skills in children. Technological choices are emphasized with respect to ecological requirements. Ad-hoc calibration procedures are presented which are suitable to unstructured environments. Preliminary results based on experimental trials carried out at a day-care on typically developing children (12–36 months old) show how the instrumented objects can be used effectively in a semi-automatic fashion (i.e., rater-independent) to derive accurate measurements such as orientation errors and insertion time which are relevant to the object insertion task. This study indicates that a technological approach to ecological assessment of spatial cognition in children is indeed feasible and maybe useful for identification and early assessment of developmental delay.

Neurophysiological bases of tremors and accelerometric parameters analysis

Abstract: Physiologic tremor is causedby three different generators with two frequency peaks that act together. A mechanical-reflex slower oscillator, that resemble the viscoelastic properties of muscle-joint complex and a faster oscillator that is the compound of loop reflex-composed by the spinal loop and supraspinal reflex loop and central neurogenic oscillator. Central neurogenic tremors seem to be generated by nerve networks in the Central Nervous System (i.e. cortico-basal ganglia-cortical loops/olivocerebellar pathways). Such disorders are mainly represented by Essential tremor and Parkinson's tremor and are characterized by a frequency independent of reflex loop time, joint inertia, and joint stiffness. Even if tremor can be easily characterized describing its frequency, amplitude and relation with muscle, rest or activity, an universal method for movement disorder diagnosis and follow-up of the symptom is still missing. Among the technological tools for tremor analysis triaxial accelerometer are able to offer low invasiveness and high reliability. This paper introduces the neurophysiological substrate of tremor and offers a proof of concept of tremor evaluation for diagnostic support and drug-efficacy in Parkinsonian and subjects affected by essential tremor. It is achieved through a self-assembled wireless, low cost and wearable device, designed for operating in patient ecological environment.

A mechatronic platform for behavioral analysis on nonhuman primates.

Abstract: In this work we present a new mechatronic platform for measuring behavior of nonhuman primates, allowing high reprogrammability and providing several possibilities of interactions. The platform is the result of a multidisciplinary design process, which has involved bio-engineers, developmental neuroscientists, primatologists, and roboticians to identify its main requirements and specifications. Although such a platform has been designed for the behavioral analysis of capuchin monkeys (Cebus apella), it can be used for behavioral studies on other nonhuman primates and children. First, a state-of-the-art principal approach used in nonhuman primate behavioral studies is reported. Second, the main advantages of the mechatronic approach are presented. In this section, the platform is described in all its parts and the possibility to use it for studies on learning mechanism based on intrinsic motivation discussed. Third, a pilot study on capuchin monkeys is provided and preliminary data are presented and discussed.

A mechatronic platform for behavioral studies on infants

Abstract: In this article the design and fabrication of a new mechatronic platform (called “Mechatronic Board”) for behavioral analysis of children are presented and discussed. The platform is the result of a multidisciplinary design approach which merges input coming from neuroscientists, psychologists, roboticians and bioengineers, with the main goal of studying learning mechanisms driven by intrinsic motivations and curiosity. A detailed analysis of the main features of the mechatronic board is provided, focusing on the key aspects which allow studying intrinsically motivated learning in children. Finally preliminary results on curiosity-driven learning, coming from a pilot study on children are reported

A basis fields approximation for modeling the passive elasticity of the wrist

Abstract: It has been suggested that joint stiffness plays a fundamental role in understanding how CNS controls wrist rotations. In a previous work, we estimated passive wrist stiffness in combinations of flexion-extension (FE) and radial-ulnar deviation (RUD) using a robot for wrist rehabilitation. In that work, we linearized the FE-RUD torque/angle field at the neutral position to obtain 2-DOF stiffness tensors. While that method provided very useful information about the characteristics of the wrist stiffness, it forces the results to be symmetrical about the origin of the reference frame, making them dependent on the choice of the neutral position. In this paper, we propose an alternative method to estimate the elastic potential energy of the wrist joint, based on the basis fields approximation approach [1]. This algorithm is capable of capturing the non-linearities of the angle-torque fields and it is not sensitive to the choice of the reference frame. Results on 4 subjects confirm previous findings that the movement of least stiffness goes from radial-extension to ulnar-flexion, known as the “dart-throwers motion” moreover, we show that the 2-D elastic field of the wrist is not linear about the neutral position. While this last result has been previously showed only in pure FE or RUD, here we present a method to characterize it in combinations of FE and RUD, thus allowing to better model general wrist rotations.