PhD: Alexis Bédécarrats

Cellular study of the genesis and learning of a motivated behavior in Aplysia

Defended on December 19, 2014

Motivated behaviors such as feeding or sexual behavior are irregularly expressed by impulsive drives from the central nervous system. However, such goal-directed acts are regulated by sensory inputs and learning. In a form of associative learning, appetitive operant conditioning, an animal learns the consequences of its own actions by making the contingent association between an emitted act and delivery of a rewarding (highly appetitive) stimulus. It is now established that this learning procedure induces the transition from an initially infrequent and irregular motor activity to a frequent and regular behavior. However the cellular and central network mechanisms that mediate this behavioral plasticity remain poorly understood.

Our study on the marine sea slug Aplysia has allowed us to analyze these mechanisms in an identified neuronal network that is responsible for generating the motor patterns of the animal’s feeding behavior. Using in vitro neuronal preparations, we selectively controlled the frequency and regularity of the motor activity induced by operant learning with experimental manipulations of the functional plasticity in identified pacemaker neurons. We found for the first time a causal relationship between the learning-induced plasticity and (1) changes in pacemaker neuron membrane properties and the increased frequency of feeding motor activity, and (2), in the strength of their interconnecting electrical synapses and the regularized phenotype of this motor activity. We then addressed the role of the transmitter dopamine in the induction of this functional plasticity and specifically the expression of a frequent and stereotyped rhythmic feeding motor pattern.

Finally, we analyzed the intrinsic membrane properties of the essential pacemaker neuron for generating the irregular motor drive in naïve animals. In conclusion, the data from this thesis work have provided novel insights into the cellular and synaptic mechanisms underlying the intrinsic variability of a motivated behavior and its regulation by learning.


Bédécarrats A, Cornet C, Simmers J, Nargeot R (2013). Learn. Mem. 20, 318-327.

*Sieling F, *Bédécarrats A, Simmers J, Prinz AA, Nargeot R (2014). Differential role of nonsynaptic and synaptic plasticity in operant conditioning-induced compulsive behavior.Curr. Biol. 24, 941-950. *co-premier auteur avec Fred Sieling

PhD committee

  • Thierry BAL, 
    Directeur de Recherche, CNRS, Gif-sur-Yvette
  • Daniel CATTAERT, 
    Directeur de Recherche, CNRS, Bordeaux
    Directeur de Recherche, CNRS, Gif-sur-Yvette
  • Romuald NARGEOT, 
    Maître de Conférences, CNRS, Université de Bordeaux
  • Jean-Christophe SANDOZ, 
    Directeur de Recherche, CNRS, Gif-sur-Yvette
  • Romuald Nargeot
    Directeur de thèse MC, Univ Bordeaux, CNRS UMR 5287 – INCIA

Thesis supervisor

Romuald Nargeot
Maître de conférence – PhD
CNRS UMR 5287 –
Team : Organization and adaptability of motor systems (team leader: Muriel Thoby-Brisson)

Last update: 19 December 2014