Romuald Nargeot

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BACKGROUND Learning in exploratory and goal-directed behaviors can modify decision-making processes in the initiation of appropriate action and thereby transform the irregular and infrequent expression of such behaviors into inflexible, compulsive-like repetitive actions. However, the neuronal mechanisms underlying such learning-derived behavioral(More)
Exploring the pathways of manganese (Mn(2+)) transport in the nervous system becomes of interest as many recent studies use Mn(2+) as a neural tract tracer in mammals. In this study, we performed manganese enhanced MRI (MEMRI) at 17.2 T on the buccal ganglia of Aplysia californica. The main advantage of this model over mammalian systems is that it contains(More)
Whereas major insights into the neuronal basis of adaptive behavior have been gained from the study of automatic behaviors, including reflexive and rhythmic motor acts, the neural substrates for goal-directed behaviors in which decision-making about action selection and initiation are crucial, remain poorly understood. However, the mollusk Aplysia is(More)
Associative learning in goal-directed behaviors, in contrast to reflexive behaviors, can alter processes of decision-making in the selection of appropriate action and its initiation, thereby enabling animals, including humans, to gain a predictive understanding of their external environment. In the mollusc Aplysia, recent studies on appetitive operant(More)
Motivated behaviors comprise appetitive actions whose occurrence results partly from an internally driven incentive to act. Such impulsive behavior can also be regulated by external rewarding stimuli that, through learning processes, can lead to accelerated and seemingly automatic, compulsive-like recurrences of the rewarded act. Here, we explored such(More)
Feeding in Aplysia provides an amenable model system for analyzing the neuronal substrates of motivated behavior and its adaptability by associative reward learning and neuromodulation. Among such learning processes, appetitive operant conditioning that leads to a compulsive-like expression of feeding actions is known to be associated with changes in the(More)
In this work, we show the feasibility of performing functional MRI studies with single-cell resolution. At ultrahigh magnetic field, manganese-enhanced magnetic resonance microscopy allows the identification of most motor neurons in the buccal network of Aplysia at low, nontoxic Mn(2+) concentrations. We establish that Mn(2+) accumulates intracellularly on(More)
BACKGROUND Rewarding stimuli in associative learning can transform the irregularly and infrequently generated motor patterns underlying motivated behaviors into output for accelerated and stereotyped repetitive action. This transition to compulsive behavioral expression is associated with modified synaptic and membrane properties of central neurons, but(More)
Appetitive operant conditioning, a form of associative learning, produces a long-lasting switch in the mollusk Aplysia's food-seeking behavior from irregular, impulsive like radula biting movements into stereotyped, compulsive like recurrences of this cyclic act [1]. Three bilateral pairs of neurons (B63, B65, and B30) in the feeding central pattern(More)
The present study examined the correlation between the level of activity neuron B52 and the transition from protraction to retraction phases of buccal motor patterns (BMPs) and the termination of the BMPs. The level of activity in B52 during the protraction phase was positively correlated with the duration of that phase. A second burst of activity in B52(More)