Biomedical subjects

Pier-Giorgio Zanone

Publications and source records attributed to Pier-Giorgio Zanone.

5 recordsLinked to original sources

PubMed2005

How a new behavioral pattern is stabilized with learning determines its persistence and flexibility in memory.

Memory organization should be at times persistent and at others flexible in the face of environmental perturbations. Unlike conceptualizations that bear on the reduction of the mismatch between the memory trace and the model, it is assumed here that changes in the memory system are governed by stability principles. Results of a bimanual coordination learning task indicated that (1) persistent memories are created and stabilized, when the competition between the preexisting (0 and 180 degrees of relative phase) and the to-be-learned (90 degrees ) patterns leads to a qualitative change in the memory layout; (2) transient memories arise without stabilization, when the competition is weaker, leading to a temporary shift of an initially stable pattern (90 degrees ) toward the required value (135 degrees ). These findings call for further examination of the relationship between stability and memory persistence, which might give a new thrust to understanding its neural correlates.

Adolescent↗

PubMed2005

A dynamical analysis of tennis: concepts and data.

This research reported here draws on self-organization theories and dynamical system models to investigate the collective behaviour of tennis players. In tennis, the unceasing to-and-fro displacements of a player about a "home" reference position, located in the middle of the baseline, are akin to those of an oscillator, and the reciprocal attending of both players establishes an informational linkage. Thus, theoretically, the displacement of the two players can be analysed as a system formed by two coupled non-linear oscillators. In such a system, relative phase has been shown to be an adept measure of the temporal synchronization between the oscillators. We hypothesized that relative phase is a relevant collective variable to characterize the relative motion of tennis players. Four players were videotaped and their displacements analysed. The results revealed just two stable patterns of synchronization, in-phase and anti-phase, as the players moved in the same or opposite directions, respectively. Moreover, relative phase showed two types of evolution within trials: either it remained stable at in-phase or anti-phase, or it exhibited transitions between these two modes. In accordance with our hypothesis, the results identified relative phase as a pertinent collective variable to represent both invariance and change in the relative displacements of tennis players. Such a finding opens new avenues for investigating dual sports.

Biomechanical Phenomena↗

PubMed2004

Evaluating the coordination dynamics of handwriting.

This study aims to test the hypothesis that handwriting is governed by the dynamics of non-linear coupled oscillators. Accordingly, its first goal is to identify preferred, basic graphic shapes corresponding to spontaneously stable combinations of the two frequency-locked oscillatory x-y components of the trajectories. Six participants were required to produce 26 ellipsoids of varying eccentricities and orientations presented consecutively on a graphic tablet. These shapes corresponded to a systematic manipulation of the relative phase and the relative amplitude of the oscillators by a constant step. Results showed that among those, only eight ellipsoids were produced in a spontaneous and stable fashion. They were characterized by attraction of nearby shapes, and by a higher accuracy and velocity. Alike all periodic motion, graphic skills, hence handwriting, exhibit preferred coordination patterns, which can be ascribed to the non-linear coupling of two oscillators.

Adult↗

PubMed2004

Stability of coordination patterns in handwriting: effects of speed and hand.

Previous studies have shown the existence of preferred stroke directions and shapes in handwriting. Assuming that such a two- dimensional trajectory formation process relies on the nonlinear coordination between two abstract orthogonal oscillators, a recent study (Athenes et al., in press) investigated the relative stability and the temporal accuracy of such coordination patterns in performing various ellipsoids corresponding to different phase and amplitude relationships between the oscillators. Results showed that only a small subset of the patterns was stable and accurate. The present study tested and verified the assumption that more stable coordination patterns deteriorate less under a speed constraint. In addition, differences between the dominant and nondominant hands gave insights into various effects modulating the stability and accuracy of such preferred patterns. Evidence of preferred coordination patterns and the predictability of their deterioration corroborate the existence of dynamics underlying handwriting in terms of nonlinearly coupled oscillators.

Automatism↗

PubMed2002

The interplay of attention and bimanual coordination dynamics.

Despite their common origin, studies on motor coordination and on attentional load have developed into separate fields of investigation, bringing out findings, methods, and theories which are diverse if not mutually exclusive. Sitting at the intersection of these two fields, this article addresses the issue of behavioral flexibility by investigating how intention modifies the stability of existing patterns of coordination between moving limbs. It addresses the issue, largely ignored until now, of the attentional cost incurred by the central nervous system (CNS) in maintaining a coordination pattern at a given level of stability, in particular under different attentional priority requirements. The experimental paradigm adopted in these studies provides an original mix of a classical measure of attentional load, namely, reaction time, and of a dynamic approach to coordination, most suitable for characterizing the dynamic properties of coordinated behavior and behavioral change. Findings showed that central cost and pattern stability covary, suggesting that bimanual coordination and the attentional activity of the CNS involved in maintaining such a coordination bear on the same underlying dynamics. Such a conclusion provides a strong support to a unified approach to coordination encompassing a conceptualization in terms of information processing and another, more recent framework rooted in self-organization theories and dynamical systems models.

Attention↗