Neural responses to magnetic orientation information in songbirds
Abstract
Effective navigation and orientation is essential for animals to survive. The study of migratory birds provides insights into these processes, particularly through mechanisms like the geomagnetic compass, which uses Earth's magnetic field for directional information. A brain region in songbirds relevant to this is cluster N, known for its potential role in processing geomagnetic information. Notably, cluster N appears exclusive to nocturnally migratory birds, being active solely at night, and lesion studies reveal that an intact cluster N is necessary for geomagnetic compass orientation. However, given the scarcity of empirical data concerning cluster N, substantial questions persist regarding its function. This thesis aimed to expand our understanding of cluster N. I addressed three key research questions in three experiments: 1. Is cluster N's activation flexible or circadian-controlled? (Chapter 2), 2. Is cluster N's activity linked to migratory flight? (Chapter 3), and 3. Do non-migratory birds possess cluster N, despite prior assumptions? (Chapter 4). Results in Chapter 2 demonstrated that cluster N is flexibly activated, with cluster N activity correlating with nocturnal migratory restlessness rather than circadian control. In Chapter 3, investigations on yellow-rumped warblers did not reveal associations between migratory flight in a wind tunnel and cluster N activity, nor associations between flight and activity in the hippocampus—a region crucial for spatial memory. In chapter 4, I found no differences in cluster N or hippocampus activity between zebra finches that were either trained to use magnetic cues to find food or those assigned to a control condition (i.e., no training). However, patterns of neural activation hinted at potential cluster N activity in these non-migratory birds. Collectively, this research enriches our grasp of cluster N's role in orientation behaviour and migration in birds, and expands the study of cluster N to a wider range of bird species than previously studied.