Spontaneous and centrally induced behaviors in normal and thalamic opossums

Electrical stimulation of localized areas of the opossum medulla and cerebellum induced goal-oriented eating and grooming behaviors of stereotyped gagging. Following radical telencephalic lesions, these animals showed considerable behavioral capacity and in many cases continued to demonstrate centrally induced responses. Animals with lesions, however, failed to groom or show active food-seeking behavior, and they showed poor thermoregulation in the heat, presumably because of the loss of thermoregulatory grooming. These deficits following removal of the telencephalon appear to have resulted from disruption of important sources of control over behaviors rather than from loss of basic consummatory response mechanisms, since grooming and eating, while less directed, could still be elicited by central stimulation. These results support the view that the lower brain stem may contain intrinsic neural circuits for the integration of complex behaviors.