Lateral and medial telencephalic pallium lesions impair spatial memory in goldfish

Fish, like many other animals, navigate to ensure survival. While the telencephalon region of the teleost fish brain is believed to play a critical role in navigation, lesion and electrophysiology studies differ as to whether navigation is situated in the lateral pallium or the medial pallium. To address this inconsistency, we replicated combined behavioral and lesion studies in the goldfish. Goldfish were trained in two navigation tasks testing allocentric navigation on a horizontal plus-maze and a horizontal breadboard to get a reward. The fish were divided randomly into lateral pallium lesion, medial pallium lesion, and sham groups and retested for their success rates. The lateral lesion group had a significant decrease of success on the breadboard task but not on the plus-maze task, whereas the medial lesion affected both tasks significantly. These results suggest that both the medial and lateral pallium are essential for the coding of spatial memory and challenge the assumption that one distinct region of the pallium is involved in spatial memory in teleost.