Phylogenetic, ontogenetic and adult adaptive plasticity of rhythmic neural networks: A common neuromodulatory mechanism?
J Comp Physiol A. 2004-06-25; 190(9): 691-705
DOI: 10.1007/s00359-004-0533-4
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Fénelon VS(1), Le Feuvre Y, Meyrand P.
Author information:
(1)CNRS UMR 5816, University of Bordeaux I, Avenue des Facultés, 33405, Talence,
France.
Neuromodulatory inputs are known to play a major role in the adaptive plasticity
of rhythmic neural networks in adult animals. Using the crustacean stomatogastric
nervous system, we have investigated the role of modulatory inputs in the
development of rhythmic neural networks. We found that the same neuronal
population is organised into a single network in the embryo, as opposed to the
two networks present in the adult. However, these adult networks pre-exist in the
embryo and can be unmasked by specific alterations of the neuromodulatory
environment. Similarly, adult networks may switch back to the embryonic phenotype
by manipulating neuromodulatory inputs. During development, we found that the
early established neuromodulatory population display alteration in expressed
neurotransmitter phenotypes, and that although the population of modulatory
neurones is established early, with morphology and projection pattern similar to
adult ones, their neurotransmitter phenotype may appear gradually. Therefore the
abrupt switch from embryonic to adult network expression occurring at
metamorphosis may be due to network reconfiguration in response to changes in
modulatory input, as found in adult adaptive plasticity. Strikingly, related
crustacean species express different motor outputs using the same basic network
circuitry, due to species-specific alteration in neuromodulatory substances
within homologous projecting neurones. Therefore we propose that alterations
within neuromodulatory systems to a given rhythmic neural network displaying the
same basic circuitry may account for the generation of different motor outputs
throughout development (ontogenetic plasticity), adulthood (adaptive plasticity)
and evolution (phylogenetic plasticity).