A biologically inspired neural network controller for ballistic arm movements

<p>Abstract</p> <p>Background</p> <p>In humans, the implementation of multijoint tasks of the arm implies a highly complex integration of sensory information, sensorimotor transformations and motor planning. Computational models can be profitably used to better understand the mechanisms sub-serving motor control, thus providing useful perspectives and investigating different control hypotheses. To this purpose, the use of Artificial Neural Networks has been proposed to represent and interpret the movement of upper limb. In this paper, a neural network approach to the modelling of the motor control of a human arm during planar ballistic movements is presented.</p> <p>Methods</p> <p>The developed system is composed of three main computational blocks: 1) a parallel distributed learning scheme that aims at simulating the internal inverse model in the trajectory formation process; 2) a pulse generator, which is responsible for the creation of muscular synergies; and 3) a limb model based on two joints (two degrees of freedom) and six muscle-like actuators, that can accommodate for the biomechanical parameters of the arm. The learning paradigm of the neural controller is based on a pure exploration of the working space with no feedback signal. Kinematics provided by the system have been compared with those obtained in literature from experimental data of humans.</p> <p>Results</p> <p>The model reproduces kinematics of arm movements, with bell-shaped wrist velocity profiles and approximately straight trajectories, and gives rise to the generation of synergies for the execution of movements. The model allows achieving amplitude and direction errors of respectively 0.52 cm and 0.2 radians.</p> <p>Curvature values are similar to those encountered in experimental measures with humans.</p> <p>The neural controller also manages environmental modifications such as the insertion of different force fields acting on the end-effector.</p> <p>Conclusion</p> <p>The proposed system has been shown to properly simulate the development of internal models and to control the generation and execution of ballistic planar arm movements. Since the neural controller learns to manage movements on the basis of kinematic information and arm characteristics, it could in perspective command a neuroprosthesis instead of a biomechanical model of a human upper limb, and it could thus give rise to novel rehabilitation techniques.</p

Recurrent neck pain as a variant of migraine: Description of four cases

Four patients who had recurrent attacks of idiopathic unilateral neck pain and tenderness of the ipsilateral carotid artery are described. Two patients had never had headache. The other two had migraine without aura. All patients had dilatation of extracranial arteries during the attacks (telethermographic examination), oculosympathetic hypofunction (pupillary tests), and positive responses to vasoactive drugs which are commonly used for migraine treatment. Recurrent neck pain involving the carotid artery seems to be a variant form of migraine that may occur alone or in association with headache in patients with involvement of extracranial arteries

Quantitation of stretch reflexes by perturbing arm movements

A torque motor controlled by a microcomputer provide mechanical or magnetical stimuli to neurologic patients while the move their upper arms along a circular trajectory. In this way it is possible to standardize both the arm movements, the perturbation and the kind of stretch reflexes elicited

Changes in color vision after a single dose of Vigabatrin or Carbamazepine in healthy volunteers

Impact Factor 1.94

B/W and Color Tangent screen automatic campimetry

B/W test is used in daily clinical routine for the reliable informations it gives concerning vascular and oncologic brain diseases. A new automatic technique is also described which examines the patient skill to discriminate one colour against the others along twelve meridians

Topografia del campo visivo gestita da personal computer

E' stata realizzata una apparecchiatura per l'analisi automatica del campo visivo utilizzando un personal computer Apple II. La stimolazione luminosa è ottenuta mediante diodi LED montati su di una cupola emisferica in materiale plastico opaco. Le modalità di presentazione degli stimoli e l'acquisizione delle risposte date dal paziente sono gestite dal microcomputer tramite una opportuna interfaccia. Il software sviluppato effettua una analisi in tempo reale dei dati acquisiti, eseguendo un algoritmo di ricerca dei confini degli scotomi. Il risultato dell'esame consiste in una mappa topografica del campo visivo del paziente

A processing system for acquisition and analysis of visual field defects

A microcomputer with standard peripherals is used to examine the Central Visual Field up to 20°

Computer aided visual field diagnosis

An automatic method for VF acquisition is presented. The diagnosis of VF defects is obtained by clever computer implementatio

Chromatic perception test: a computer based approach

The analysis of luminance visual defects (i.e., obtained with white stimuli on a black background) in the central area of 20°-30° around the fovea provides a valuable tool in neuro-ophthalmological diagnosis. Concerning chromaticity tests, it is well known that they improve the diagnosis of many neurological diseases, such as Multiple Sclerosis, Optic Neuritis, diseases due to vitamin deficiency.. A new automatic technique for testing both B/W and colour campimetry on a computerized apparatus has been set-up and tested on the population of patients of the V Clinica Neurologica of the Umberto I° Hospital of Rome