Behavioral and in vitro correlates of compulsive-like food seeking induced by operant conditioning in Aplysia.
Journal of Neuroscience. 2007-07-25; 27(30): 8059-8070
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1. J Neurosci. 2007 Jul 25;27(30):8059-70.
Behavioral and in vitro correlates of compulsive-like food seeking induced by
operant conditioning in Aplysia.
Nargeot R(1), Petrissans C, Simmers J.
(1)Universités Bordeaux 2, 1, Centre National de la Recherche Scientifique, Unité
Mixte de Recherche 5227, Bordeaux, 33076 France.
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 behavioral plasticity in Aplysia by
analyzing how appetitive reward stimulation in a form of operant conditioning can
modify a goal-directed component of the animal’s food-seeking behavior. In naive
animals, protraction/retraction cycles of the tongue-like radula are expressed
sporadically with highly variable interbite intervals. In contrast, animals that
were previously given a food-reward stimulus in association with each spontaneous
radula bite now expressed movement cycles with an elevated frequency and a
stereotyped rhythmic organization. This rate increase and regularization, which
was retained for several hours after training, depended on both the reward
quality and its contingency because accelerated, stereotyped biting was not
induced in animals that had previously received a less-palatable food stimulus or
had been subjected to nonassociative reward stimulation. Neuronal correlates of
these learning-induced changes were also expressed in the radula motor
pattern-generating circuitry of isolated buccal ganglia. In such in vitro
preparations, moreover, manipulation of the burst frequency of the bilateral
motor pattern-initiating B63 interneurons indicated that the regularization of
radula motor pattern generation in contingently trained animals occurred
separately from an increase in cycle rate, thereby suggesting independent
processes of network plasticity. These data therefore suggest that operant
conditioning can induce compulsive-like actions in Aplysia feeding behavior and
provide a substrate for a cellular analysis of the underlying mechanisms.
PMID: 17652597 [Indexed for MEDLINE]