EARLY AUDITORY FILIAL LEARNING IN DEGUS (OCTODON-DEGUS) - BEHAVIORAL AND AUTORADIOGRAPHIC STUDIES

Degu mothers (Octodon degus) utter specific maternal calls during nurs ing which presumably stimulate and reinforce suckling. Pups from surgi cally muted mothers show a reduced gain of body weight during postnata l development compared to pups from normally vocalizing mothers. Our b ehavioral studies suggest that the pups have to learn the meaning of t he maternal calls during the first two weeks of life. Two-week-old pup s from normally vocalizing mothers expressed a preference for the mate rnal call in a behavioral discrimination test, in contrast to pups fro m surgically muted mothers. Investigation of brain activities using th e 2-[C-14]fluoro -deoxyglucose (2-FDG) method revealed that pups from normal mothers display a significantly higher 2-FDG uptake in precentr al medial, anterior cingulate cortex and a slight, non-significant inc rease in the prelimbic cortex and orbital PFC upon presentation of the maternal call, compared to pups from muted mothers, for which the mat ernal call was unfamiliar and meaningless. These prefrontal cortical a reas are known to be involved in associative learning processes and ou r data suggest that they are involved in the association between the m aternal call and the positive emotional situation during nursing.