SPATIAL COGNITION AND NEURAL BASIS OF FAMILIAR LANDMARK-BASED NAVIGATION IN BIRDS

This thesis aims at studying spatial cognition in homing pigeons by investigating the role of two forebrain regions, the hippocampal formation (HF) and the visual Wulst, in familiar landmark-based navigation, and the functional lateralisation of the visual system in spatial behaviours. Chapter II reports a study on the role of homing pigeon HF in navigation within the home area performed by analysing GPS tracks of pigeons subjected to repeated releases. This study offered a new insight into the role of the HF in supporting memory-related navigational processes, e.g. route fidelity based on landscape linear features. Chapter III reports two novel GPS tracking studies on the role of the visual Wulst in familiar landmark-based navigation. It emerged that Wulst-lesioned pigeons displayed persistent oscillatory flight patterns and were not attracted by linear landscape features. The general meaning of the oscillation likely reflects the need for detailed visual processing of heterogeneous/novel environments, as this behaviour is landscape-depended. Pigeons oscillate more while flying over the land compared to the sea. In addition, while intact pigeons were likely to decrease their oscillations at increasing familiarity with the landscape, the Wulst-lesioned pigeons displayed a persistent oscillation, regardless of landscape familiarity. This suggests that the Wulst might play a role in attending to landscape features, contributing together with the HF to the construction of visual map. Chapter IV describes two experiments conducted on monocularly occluded pigeons that aimed at testing functional lateralisation of the avian visual system in spatial tasks. The performances of monocularly occluded pigeons challenged to localise a food reward in an outdoor octagonal arena in presence or absence of coloured beacons, and before and after clock-shift, showed that there is no functional lateralisation of the visual system in the use of the sun compass. However, an advantage of the left eye/right hemisphere system emerged in the reliance on visual featural information. The analysis of the flight pattern of monocularly occluded pigeons released from familiar locations showed an advantage of the left eye/right hemisphere system in processing visual landmarks. The findings of this thesis hopefully contributed to a better understanding of the neural mechanisms underlying familiar landmark-based navigation and sun compass orientation in birds.