Anticipating the terminal position of an observed action: Effect of kinematic, structural, and identity information

International audienc

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Kisah pi

446 hlm.: 21 c

Kisah Pi/ Martel

446 hal.; 20 cm

Life Of PI :Kisah PI

20cm;446ha

Kisah Pi/ Martel

446 hal.; 20 cm

Codage positionnel des objets visuels dans l'espace de préhension

Cette thèse concerne l'intégration des indices visuels dans le codage de la distance. Estimer la distance dans notre espace proche implique de nombreux indices visuels : les indices rétiniens (projection de l'image de l'environnement sur la rétine) et les indices extrarétiniens (dérivés du système oculomoteur). Nous avons étudié le rôle respectif de ces indices visuels dans une tâche visuomotrice simple (atteinte de cibles visuelles, expérience1). Les indices rétiniens se sont avérés être impliqués de manière privilégiée dans l'estimation de la distance. Néanmoins, dès que l'environnement visuel est appauvri, les indices extrarétiniens pourraint être impliqués et notamment l'orientation du regard dans le plan vertical (expérience 2). En outre, une étape de calibration des indices rétiniens est nécessaire car l'information qu'ils fournissent est de nature relative. Nous avons testé si la taille familière des segments corporels pourrait permettre cette calibration lorsque ces derniers sont visuellement disponibles.Pour cela, nous avons évalué la perception de la distance en présence de la main avec une taille apparente normale ou modifiée (expérience 3). La taille familière semble constituer un indice participant à la calibration des indices extrarétiniens plutôt qu'à la calibration des indices rétiniens. Le codage de la distance peut également faire intervenir des propriétés dynamiques. Les capacités de prédiction de la distance d'une trajectoire motrice dépendent principalement des propriétés cinématiques du mouvement, pondéré par le répertoire moteur de l'observateur, sans impliquer les informations structurelles de nature squelettique (expérience 4)This dissertation aims at analysing integration of visual cues in distance coding. Estimate the distance in near-body space involved the contribution of two types of visual signals, namely retinal (physical aspects of the image that stem from the optical projection of the external world) and extra-retinal (from oculomoteur system) signals. The first study evaluated the role of visual cues in visuomotor task. Results showed that retinal signals turn out to be privileged in distance information. However, when the target was presented in empty workspace, extra-retinal signals should be involved and more specially the position of gaze direction in the vertical plane (experience 2). Furthermore, retinal signals that providing relative information must be calibrated. We tested whether familiar size of hand should permitted calibration of retinal signals. Therefore, we evaluated distance estimation in the presence of the hand with an apparent size that was normal or modified (experience 3). Results showed that the familiar size seemed a cue participating in the callibration of extra-retinal signals rather than retinal signals. The distance coding could also implicated dynamical properties. Prediction skill of the amplitude of the motor trajectory mainly depended on kinematics properties of movement, weighted by motor repertory of the observer without any implication of skeletal information (experience 4)LILLE3-BU (590092101) / SudocSudocFranceF

Life of PI

Pada tanggal 221 Juni 1977, kapal barang Tsimtsum berlayar dari Madras menuju Canada. Pada tanggal 2 Juli, kapal itu tenggelam di Samudera Pasifik. Hanya satu sekoci berhasil diturunkan, membawa penumpang seekor hyena, seekor zebra yang kakinya patah, seekor orang utan betina, seekor hariamu Royal Bengal seberat 225 kilogram, dan Pi anak lelaki India berusia 16 tahun.Selama lebih dari tujuh bulan sekoci itu terombang ambing di Samudra Pasifik yang biru dan ganas. Di samudra inilah sebagian Kisah Pi berlangsung. Kisah yang luar biasa, penuh keajaiban, dan seperti ucapan salah satu tokoh di dalamnya, kisah ini akan membuat orang percaya pada Tuhan.446hlm.;13,5x20c

Contribution of retinal and non-retinal sources of visual information in egocentric object localisation for action

In visuo-manual tasks, enhancing visual information by presenting a target-object on a textured background has been proved to improve distance coding. However, controversial interpretations have suggested that enriched retinal inputs either provides access to more veridical spatial information or enables extra-retinal signals (e.g. vergence) to be more accurately processed. To contrast these interpretations, the present study evaluated the spatial accuracy of upper limb movement towards visual targets presented monocularly or binocularly either in darkness or on a textured background. Action was performed whilst wearing neutral or prismatic spectacles deviating by 5.4° gaze direction but leaving spatial information on the retina virtually unchanged. We found that distance underestimation observed in darkness reduced in presence of a textured background whatever the vision condition. Surprisingly, the performance was not affected by prismatic displacement when a textured background was provided. These results indicate that distance processing for action relies mainly on retinal inputs in presence of a structured workspace, even when there is a mismatch between retinal and extra-retinal signals