Paris West University Nanterre La Défense

About: Paris West University Nanterre La Défense is a education organization based out in Paris, France. It is known for research contribution in the topics: Computer science & Politics. The organization has 895 authors who have published 1430 publications receiving 21712 citations.

Kinematic synergy adaptation to an unstable support surface and equilibrium maintenance during forward trunk movement

Abstract: The aim of this investigation was to study the adaptation to an unstable support surface of kinematic synergy responsible for equilibrium control during upper trunk movements. Eight adult subjects were asked to bend their upper trunk forward to an angle of 35� and then to hold the final position for 3 s, first in a standard condition, with two feet on the ground and the second, on a rocking platform swinging in the sagittal plane. The movement characteristics (duration, amplitude, and mean angular velocity of the trunk), the time course of the antero-posterior center of mass (CM) shift during the movement, and the EMG pattern of the main muscles involved in the movement were studied under the two experimental conditions. Kinematic synergy was quan- tified by performing a principal component analysis on the hip, knee, and ankle angle changes occurring during the movement. The results indicate that (1) the CM shift from the very onset of the movement remains controlled during performance of the forward trunk movement when the equilibrium constraints were increased; (2) the principal component analysis of the hip, knee, and ankle angle changes occurring during the movement showed a transition from one principal component (PC1) in the standard condition to two components in the rocking platform condition; (3) the greatest contribution of PC1 (weight coefficients) was located at the hip level in both the standard and rocking platform conditions, while the greatest contribution of PC2 in the rocking platform condition was located at the ankle level; and (4) the EMG pattern underlying kinematic synergy is modified. It is concluded that a simple adaptation of kinematic synergy by changing the weight coefficients of each pair of joints participating in the movement is no longer sufficient when the equilibrium constraints increase and, rather, disturbs equilibrium. The CNS has to provide two par- allel controls, one to perform the trunk movement and the other to preserve equilibrium.

Individual vocal recognition in zebra finches relies on song syllable structure rather than song syllable order

Abstract: Many species are able to vocally recognize individual conspecifics and this capacity seems widespread in oscine songbirds. The exact acoustic features used for such recognition are often not clear. In the zebra finch (Taeniopygia guttata), the song motif is composed of a few syllables repeated in a fixed sequential order and song bouts include several repetitions of the motif. Here, we used an operant discrimination task, the GO/NOGO procedure, to show that zebra finches are capable of individual vocal recognition even if the bird has to distinguish males that all produce an imitation of the same song model. Furthermore, we studied whether such individual vocal recognition was based on spectro-temporal details of song syllables, i.e. the local fine structure of the song, or on the sequential order in which song syllables are arranged in the song bout. To this end, we trained male and female zebra finches to discriminate songs of one male conspecific from those of four others. After learning this baseline discrimination, subjects were exposed to a novel set of stimuli originating from the same individuals, in order to test for their capability to generalise. Subjects correctly classified those novel stimuli, illustrating their ability for individual vocal recognition. Then they were exposed to hybrid stimuli combining the syllable sequences of one individual with the spectro-temporal features of another. Behavioural responses of subjects to hybrid stimuli suggest that they rely on spectro-temporal details of syllables and might pay less attention to syllable sequences for individual vocal recognition.

L'investissement socialement responsable en France : opportunité « de niche », ou placement « mainstream » ?

Abstract: Cet article porte sur les activites actuelles et futures des equipes d’analyse Investissement Socialement Responsable (ISR) de la gestion d’actifs en France. L’objectif de cet article est d’etudier une eventuelle convergence entre la gestion d’actifs classique et la gestion ISR, notamment au travers d’une etude detaillee des tâches realisees par ces equipes et de leur positionnement dans l’industrie de la gestion d’actifs. Les resultats d’une enquete realisee en France en 2009 aupres des principaux acteurs du domaine y sont presentes. Ces resultats semblent indiquer une convergence en cours entre l’ISR et la gestion classique (mainstream), meme s’il semble encore y avoir une grande heterogeneite de pratiques qui traduit une phase de transition, dans un domaine encore tres fragmente.