VARIABILITY IN GENERAL ACTIVITY AND THE EXPRESSION OF COMPLEX BEHAVIOR IN THE FETAL-RAT (RATTUS-NORVEGICUS)

Rat fetuses exhibit intrinsic fluctuations in general motor activity a nd respond to an artificial nipple (AN) with mouthing and oral graspin g behavior. The present study examined the relation between the organi zation of general activity and the expression of these specific respon ses to an AN on Embryonic Day 21. In Experiment 1, continuous exposure to the AN resulted in nonspecific behavioral activation characterized by an increase in amplitude and high-frequency variability. In Experi ment 2, increased amplitude and variability in general activity preced ing discrete presentations of the AN resulted in more mouthing and ora l grasping responses to the AM. These results suggest that presentatio n of the AN triggers behavioral reorganization in which the level and variability of overall activity may facilitate expression of well-defi ned action patterns.