Novelty response in the weakly electric fish Gymnotus carapo: seasonal differences and the participation of the telencephalon in its modulation.
The arousal or novelty response (increased frequency of electric organ discharge in the presence of an electric stimulus delivered by a pair of electrodes placed in the water of the experimental chamber) and its habituation were studied in Gymnotus carapo, a weak field electric fish, in different seasons (September and March) and in animals with extensive or restricted telencephalic lesions. The novelty response was reduced but not abolished by repeated stimuli at fixed intervals in normal animals both in September (pre-mating season) and in March (beginning of the dry season). The magnitude of the novelty response did not differ between sham-operated animals and animals with extensive (detelencephalization) or restricted telencephalic lesions (dorsocentral area) within their respective groups (September or March). The novelty response to the first applied stimulus was significantly greater in normal, sham-operated, and derelencephalated animals in September compared to March, although baseline firing rate did not differ. The maximum extent of response reduction occurred after the 18th stimulus in September for all three experimental groups, whereas in the 4 groups tested in March the maximum reduction occurred between the 16th and 72nd stimulus, indicating that in March there is a greater fluctuation in the arousal level.
Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil. slcorrea@rfi.fmrp.usp.br
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Lopes Corrêa
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Hoffmann
D000818:Animals; D004555:Electric Fish / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D005106:Exploratory Behavior / Q000502:physiology*; D006185:Habituation, Psychophysiologic / Q000502:physiology; D012621:Seasons; D013687:Telencephalon / Q000502:physiology*