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R Plamondon

Publications and source records attributed to R Plamondon.

16 recordsLinked to original sources
PubMed2001

On the stability analysis of delayed neural networks systems.

In this paper, the problems of stability of delayed neural networks are investigated, including the stability of discrete and distributed delayed neural networks. Under the generalization of dropping the Lipschitzian hypotheses for output functions, some stability criteria are obtained by using the Liapunov functional method. We do not assume the symmetry of the connection matrix and we establish that the system admits a unique equilibrium point in which the output functions do not satisfy the Lipschitz conditions and do not require them to be differential or strictly monotonously increasing. These criteria can be used to analyze the dynamics of biological neural systems or to design globally stable artificial neural networks.

Action Potentials↗
PubMed1998

A new method for the analysis of simple and complex planar rapid movements.

Recent developments in the field of simple human movement modelling provide new ways in which to view complete models for analysing and understanding complex movements. Based on a kinematic theory and a vectorial delta-lognormal model recently proposed by Plamondon (1993a); Plamondon (1995a); Plamondon (1995b); Plamondon (1995c) and Plamondon (1998), a new method for exploring and understanding the inherent mechanisms that govern planar movement generation and predict human behaviour is presented here. This paper describes an approach for analysing simple as well as complex movements such as cursive handwriting. It highlights some difficulties encountered in the analysis of complex movements. Problems such as the development of robust approaches to solve the reverse engineering problem of automatic parameter extraction of a succession of time-overlapped nonlinear functions are discussed. The analysis of natural cursive handwriting shows many interesting properties of the model and proposes new ways to study perturbed movement phenomena.

Cues↗
PubMed1998

A kinematic theory of rapid human movements: Part III. Kinetic outcomes.

This paper describes the kinematic and kinetic properties of simple rapid movements using a single and unique framework based on a delta-lognormal law (Plamondon 1993a,b, 1995a,b). Predictions concerning isotonic measurements are made using the properties of acceleration profiles, as described by the first time derivative of the delta-lognormal law. Predictions dealing with isometric measurements are directly analyzed using the delta-lognormal law, after demonstrating the experimental equivalence between isometric forces and virtual velocity profiles. The theory is also used to make statistical predictions about the variability of numerous kinematic and kinetic variables. The overall approach can be viewed as if, at some level of representation, the central nervous system were planning, executing and evaluating simple rapid movements in terms of momentum and energy instead of forces. The unifying perspective provided by the theory constitutes a powerful tool with which to study and analyze movements under numerous experimental conditions, using a single analytical law.

Algorithms↗
PubMed1998

The 2/3 power law: when and why?

This paper presents the origin of some reported observations, which links the kinematics of handwriting with a movement trajectory, best known as the 2/3 power law. Using computer simulations, it is shown that the vectorial delta-lognormal model recently proposed to describe 2D movements can successfully simulate these phenomena. Although the power law has been found to be a good predictor in many experimental conditions, a few experiments have shown that the law does not apply to all graphic movements. Using the vectorial delta-lognormal model, the conditions under which a 2/3 power relationship can be observed are presented and the reasons why it does not seem to be verified for more general handwritten patterns are highlighted.

Biomechanical Phenomena↗
PubMed1997

Speed/accuracy trade-offs in target-directed movements.

This target article presents a critical survey of the scientific literature dealing with the speed/accuracy trade-offs in rapid-aimed movements. It highlights the numerous mathematical and theoretical interpretations that have been proposed in recent decades. Although the variety of points of view reflects the richness of the field and the high degree of interest that such basic phenomena attract in the understanding of human movements, it calls into question the ability of 'many models to explain the basic observations consistently reported in the field. This target article summarizes the kinematic theory of rapid human movements, proposed recently by R. Plamondon (1993b; 1993c; 1995a; 1995b), and analyzes its predictions in the context of speed/accuracy trade-offs. Data from human movement literature are reanalyzed and reinterpreted in the context of the new theory. It is shown that the various aspects of speed/accuracy trade-offs can be taken into account by considering the asymptotic behavior of a large number of coupled linear systems, from which a delta-lognormal law can be derived to describe the velocity profile of an end-effector driven by a neuromuscular synergy. This law not only describes velocity profiles almost perfectly, it also predicts the kinematic properties of simple rapid movements and provides a consistent framework for the analysis of different types of speed/accuracy trade-offs using a quadratic (or power) law that emerges from the model.

Female↗
PubMed1996

A neural model for generating and learning a rapid movement sequence.

In this article, a neural model for generating and learning a rapid ballistic movement sequence in two-dimensional (2D) space is presented and evaluated in the light of some considerations about handwriting generation. The model is based on a central nucleus (called a planning space) consisting of a fully connected grid of leaky integrators simulating neurons, and reading an input vector [symbol: see text] (t) which represents the external movement of the end effector. The movement sequencing results in a succession of motor strokes whose instantiation is controlled by the global activation of the planning space as defined by a competitive interaction between the neurons of the grid. Constraints such as spatial accuracy and movement time are exploited for the correct synchronization of the impulse commands. These commands are then fed into a neuromuscular synergy whose output is governed by a delta lognormal equation. Each movement sequence is memorized originally as a symbolic engram representing the sequence of the principal reference points of the 2D movement. These points, called virtual targets, correspond to the targets of each single rapid motor stroke composing the movement sequence. The task during the learning phase is to detect the engram corresponding to a new observed movement; the process is controlled by the dynamics of the neural grid.

Computer Simulation↗
PubMed1995

A kinematic theory of rapid human movements. Part I. Movement representation and generation.

This paper proposes a kinematic theory that can be used to study and analyze rapid human movements. It describes a synergy in terms of the agonist and antagonist neuromuscular systems involved in the production of these movements. It is shown that these systems have a log-normal impulse response that results from the limiting behavior of a large number of interdependent neuromuscular networks, as predicted by the central limit theorem. The delta log-normal law that follows from this model is very general and can reproduce almost perfectly the complete velocity patterns of an end-effector. The theory accounts for the invariance and rescalability of these patterns, as well as for the various observations that have been reported concerning the change in maximum and mean velocities, time to maximum velocity, etc., under different experimental conditions. Movement time, load effects, and control strategies are discussed in a companion paper.

Algorithms↗
PubMed1995

A kinematic theory of rapid human movements. Part II. Movement time and control.

This paper describes how a synergy made up of a pair of agonist and antagonist systems involved in the production of a rapid movement can control movement time. A quadratic law is derived to predict the movement time as a function of the various parameters describing the neuromuscular synergy. Conditions for a simplified description of the process, using a power law, are also presented. It is predicted that movement time can be controlled at the input level by the ratio of the agonist to antagonist commands or at the system level by modifying the total log-time delay or the log-response time of the agonist or antagonist neuromuscular networks. Adapting this approach to the specific case of movements executed under different spatial accuracy demands, it is found that movement time is linked to the inverse of the relative spatial error by similar laws. The whole approach is used to explain within a single framework all the observations that have been reported concerning speed/accuracy trade-offs. Strategies for controlling movement amplitude and duration are analyzed, and other predictions dealing with EMG, acceleration patterns, load effects and changes in the asymmetry of the velocity profile are also discussed.

Algorithms↗
PubMed1993

Modelling velocity profiles of rapid movements: a comparative study.

In this paper we compare 23 different models that can be used to describe the asymmetric bell-shaped velocity profiles of rapid-aimed movements. The comparison is performed with the help of an analysis-by-synthesis experiment over a database of 1052 straight lines produced by nine human subjects. For each line and for each model, a set of parameters is extracted that minimizes the error between the original and the reconstructed data. Performance analysis on the basis of the mean-square-error clearly reflects the superiority of the support-bounded lognormal model to globally describe the velocity profile characterizing rapid movements.

Biomechanical Phenomena↗
PubMed1993

Looking at handwriting generation from a velocity control perspective.

This paper presents a model that explains the origin of the asymmetric bell-shaped velocity profiles generally observed in handwriting and other rapid movements. Applying the central limit theorem to describe the converging behavior of a sequence of dependent neural and muscular networks, it is shown that velocity profiles can be described by log-normal curves. An analysis-by-synthesis experiment is reported to support the model and to specify its mathematical implementation. Practical implications of this approach are discussed at the end of the paper to provide an analytical definition of a stroke, to clarify the concept of fluency and to suggest a powerful method for segmenting complex movements, particularly cursive script.

Acceleration↗
PubMed1983

Tip potential of open-tip glass microelectrodes: theoretical and experimental studies.

A mathematical analysis of the tip potential based on the main physicochemical phenomena occurring at the tip of a glass microelectrode is presented. The factors considered in the theoretical analysis are the diffusion of ions through the open tip, the conduction in the bulk solutions, the longitudinal conduction in the double layers at the glass-electrolyte interfaces, and to some extent, in a hydrated glass layer. A graphical analysis of the mathematical expressions as a function of the resistivity of test solutions is done and the distribution of the source potentials giving rise to the tip potential is studied. The experimental results presented in the paper confirm the validity of the proposed theoretical model. Comments for an improved use of glass microelectrodes in electrophysiological experiments are given throughout the paper.

Diffusion↗