Effects of telencephalic ablation on shoaling behavior in goldfish.

The role of the telencephalon in the shoaling behavior of the goldfish, Carassius auratus, was investigated. Experiments were carried out in a tank divided into three compartments. Subjects were introduced into the center compartment of the tank. In the activity phase, subjects swam alone, and swimming distance was used as an index of activity. In the shoaling behavior phase, a stimulus fish was introduced into one of the side compartments, and the time spent near the side compartment by the subject was used as index of shoaling behavior. After these measurements were made, visual and motor abilities were examined using the optomotor response. Subjects then received surgery and the same procedure was repeated. In Experiment 1, the effects of total ablation of the telencephalon and a section of the olfactory tract (OlT) were examined. The ablation group exhibited reduced activity and shoaling behavior compared with the sham and OlT group. In Experiment 2, the role of the dorsal part of the telencephalon was examined after damaging the dorsomedial and dorsolateral telencephalon. Lesions in either portion had no effect and no simple visual or motor deficits were seen. These results suggest that the ventral part of the telencephalon mediates shoaling behavior.