Art et cognition (2000)

Ce texte est un bilan de l'appel à proposition dissu de l'ACI cognitique.Bilan de l'appel à proposition "Art et Cognition

Quand le comportement découvrit les neurones…

Dans les années 1960, Pierre Drach, alors directeur adjoint du CNRS pour les sciences exactes, préconise, dans le cadre du 3e plan, la création d’un institut de psychophysiologie. François Clarac et Jean Massion reviennent sur la genèse d’un institut qui profitait de la décentralisation et de la présence d’un pôle fort en neurologie à Marseille.François Clarac and Jean Massion recount the creation of an institute dedicated to psychophysiology and neurophysiology in the 1960s in Marseille

Perinatal Development of the Motor Systems Involved in Postural Control

Motor behaviors of some species, such as the rat and the human baby, are quite immature at birth. Here we review recent data on some of the mechanisms underlying the postnatal maturation of posture in the rat, in particular the development of pathways descending from the brain stem and projecting onto the lumbar enlargement of the spinal cord. A short-lasting depletion in serotonin affects both posture and the excitability of motoneurons. Here we try to extrapolate to human development and suggest that the abnormalities in motor control observed in childhood—e.g, deficits in motor coordination—might have their roots in the prenatal period, in particular serotonin depletion due to exposure to several environmental and toxicological factors during pregnancy

Les modèles animaux et leur limites

L’humanité, pour se mieux connaître, a étudié le monde animal en mettant en place des modèles d’animaux choisis pour permettre l’analyse et la compréhension de nombre de fonctions particulières. Les résultats obtenus ont permis de comprendre, non seulement leurs anatomies, physiologies ou comportements mais aussi, par un simple transfert, d’aborder les fonctions de l’espèce humaine.Cette approche a donné lieu à des modèles fructueux malgré l’écart existant entre l’animalité et l’humanité.To have a better knowledge of themselves, humans have carried through a detailed survey of animal kingdom. They have thus developed animal models to explore particular functions. Results proved to be very useful to understand all together animal anatomy, physiology and behaviour. Despite differences, these functions were considered as close enough to help understanding human ones. Such an approach can appear as quite useful even though these models often remain quite far from human ones

Rami motor neurons and motor control of the swimmeret system of Homarus gammarus

International audienc

Synaptic connections of the common inhibitory motoneurone within the fifth thoracic ganglion of crayfish

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Synaptic connections between sensory afferents and the inhibitory motoneuron in the crayfish

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The in vitro neonatal spinal cord preparation : A new insight into mammalian locomotor mechanisms.

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Synaptic connections between sensory afferents and the inhibitory motoneuron in the crayfish

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Functional analysis of the sensory motor pathway of resistance reflex in crayfish. II. Integration Of sensory inputs in motor neurons

International audienceThe in vitro preparation of the fifth thoracic ganglion of the crayfish was used to analyze the connections supporting the monosynaptic reflex responses recorded from the depressor motor neurons (Dep MNs). Dep MNs are directly connected by the release-sensitive afferents from a proprioceptor, the coxo-basipodite chordotonal organ (CBCO), which is released by upward movements of the leg. Sine-wave movements, applied to the CBCO strand from the most released position, allowed us to stimulate the greatest part of release-sensitive CBCO fibers. Systematic intracellular recordings from all Dep MNs performed in high divalent cation saline allowed us to determine the connections between CBCO afferents and their postsynaptic Dep MNs: it highlighted the sequential activation of the different Dep MNs involved in the monosynaptic reflex. The convergence of different sensory afferents onto a given Dep MN, and the divergence of a given sensory afferent onto several Dep MNs illustrates the complexity of the sensory-motor reflex loops involved in the control of locomotion and posture. Electrophysiological experiments and simulations were performed to analyze the mechanisms by which Dep MNs integrate the large amount of sensory input that they receive. Paired intracellular recording experiments demonstrated that postsynaptic response shapes characteristic of both phasic and phaso-tonic afferents could be induced by varying the presynaptic firing frequency, whatever the postsynaptic Dep MN. Compartment model simulations were used to analyze the role of the sensory-motor synapse characteristics in the summation properties of postsynaptic MN. They demonstrated the importance of the postsynaptic compartment geometry, because large postsynaptic compartments allowed to generate greater excitatory postsynaptic potential (EPSP) summations than small ones. The results presented show that velocity information is the most effective to elicit large compound EPSPs in MNs. We therefore suggest that the negative feedback reflex is mainly based on the detection of leg movements