Cellular and network mechanisms of operant learning-induced compulsive behavior in Aplysia.

Romuald Nargeot, Morgane Le Bon-Jego, John Simmers
Current Biology. 2009-06-01; 19(12): 975-984
DOI: 10.1016/j.cub.2009.05.030

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1. Curr Biol. 2009 Jun 23;19(12):975-84. doi: 10.1016/j.cub.2009.05.030. Epub 2009
Jun 4.

Cellular and network mechanisms of operant learning-induced compulsive behavior
in Aplysia.

Nargeot R(1), Le Bon-Jego M, Simmers J.

Author information:
(1)Université de Bordeaux, Laboratoire Mouvement Adaptation Cognition, Centre
National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Bordeaux
F-33076, France.

Comment in
Curr Biol. 2009 Jul 14;19(13):R515-7.

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 plasticity remain poorly understood.
RESULTS: 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. Using isolated buccal ganglia, we
recorded intracellularly from an electrically coupled subset of feeding-network
neurons whose spontaneous burst discharge is responsible for instigating the
motor pattern underlying each radula bite cycle. We report that the sporadic
production of biting patterns in preparations from naive and noncontingently
trained animals derives from the inherently variable and incoherent bursting of
these pattern-initiating neurons that are each randomly capable of triggering a
given bite. However, the accelerated rhythmically recurring expression of radula
motor patterns after contingent-reward training in vivo arises from a
regularization and synchronization of burst discharge in the pattern-initiating
cells through a promotion of stereotyped burst-generating oscillations and an
increase in the strength of their electrical coupling.
CONCLUSIONS: Our results show that plasticity in the spatiotemporal organization
of pacemaker bursting, both within and between components of an action-initiating
neuronal subcircuit, provides novel cellular substrates by which operant learning
alters the recurrent expression of a simple goal-directed behavior.

DOI: 10.1016/j.cub.2009.05.030
PMID: 19500988 [Indexed for MEDLINE]

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