Variação circadiana na habituação da resposta exploratoria a estimulos sonoros em pombos (Columba livia), submetidos a condições de claro-escuro e de claro constante

AUTOR(ES)
DATA DE PUBLICAÇÃO

1993

RESUMO

The present work investigated habituation learning to acoustic stimulation in the context of temporal organization of behavior. The process of habituation of the exploratory responses to sound was analvsed in three experiments. The main purpose of these experiments was the analysis of these responses as function of the time of habituation sessions, i.e., mornins or nisht tests. The experiments differed in relation to the light cycles to which adult pigeons were exposed : 12:12h light-dark cycle in Experiment 1; continuous ilumination in Experiment 2 and twodays of continuous ilumination interposedto a 12:12 light-dark cycle, in Experiment3. Time for testins was matched for the three experimentswith morning tests at 7:30 a.m., one hour after light onset. and night tests at 7:30 p.m., one hour after turn out of light. Piseons were exposed to 1000-Hz.83-dB. ls sound (stimulus A) at 30 seconds intervals until habituation of the exploratory and startle response or until a maximum of 100 stimulus when the learning criterion was not observed. The learnins criterionwas 10 trials without the occurrence of these responses. Twenty-fourhours after habituation to stimulus A the birds were tested with a SOO-Hz, 8S-dB, 1s sound (stimulus B). Retesting. with the same sequence of proceduresbut reversal of the time of test was carried out 18 days after stimulus B habituation. Results from Experiment 1 showed an increased number of habituation trials in nocturnal (p(0,05) as compared to the morning tests for both stimulus A and B. The number of trials until habituation in the Experiment 2 showed differences between morning-night test onlv for stimulus A session. Pigeons exposed to two-davs Df continuous ilumination in Experiment 3 also showed a morning-night difference. although it was not significant. Taken together the data from these experiments suggest one temporal organization of the habituation learning processes and raises issues concerning the biological meaning of sound stimulation in light and dark environmental conditions. The differences observed between the three experiments also sugsest a role for the melatonin hormone in these processes. Pigeons maintained under continuous lisht or exposed to two-days of continuous il1umination prior to tests. which were probably characterized by decreased levels of melatonin, showed facilitation of habituationwhen compared to pigeons maintained under light-darkcycle. The lower levels of melatonin may act toward a facilitation of habituation. lt was also arsued a possible stress variable due to exposition to two-days ofcontinuous lisht. In this condition the animaIs probablv did not have enough time for adaptation to the new situation of constant light. Further studies are necessary for a precise characterization of those morning-night differences in habituation to sound as expression of a circadian rhvthmiticy

ASSUNTO(S)

pombo - comportamento estimulos sensoriais

ACESSO AO ARTIGO

Documentos Relacionados