2022-08-30, Gagliardo, Anna, Cioccarelli, Sara, Giunchi, Dimitri, Pollonara, Enrica, Colombo, Silvia, Casini, Giovanni, Bingman, Verner P.

The aim of this study was to exploit detailed analyses of GPS-recorded tracks to better characterise the impact of hippocampal (HF) lesion on spatial memory and perception in the context of homing pigeon navigation when reliant on familiar landscape features near the home loft following repeated releases from the same three locations. As reported previously, following HF lesion, a low spatio-temporal resolution analysis revealed that homing pigeons fly less direct paths home once near the loft. We now further show that 1) HF-lesioned pigeons are less likely to display fidelity to a particular flight path home when released from the same locations multiple times, 2) intact pigeons are more likely to exploit leading-line landscape features, e.g., a road or the border of a woodlot, in developing flight-path fidelity and 3) even when flying a straight path HF-lesioned homing pigeons are more likely to display relatively rapid, oscillatory heading changes as if casting about for sensory, presumably visual information. The flight behaviour differences between the intact and HF-lesioned pigeons persisted across the four releases from the three locations, although the differences became smaller with increasing experience. Taken together, the GPS-track data offer a detailed characterisation of the effects of HF lesion on landscape-based, homing pigeon navigation, offering new insight into the role of the hippocampal formation in supporting memory-related, e.g., fidelity to a familiar route home, and perhaps perceptual-related, e.g., oscillating headings, navigational processes.

2024-04-02, Cioccarelli, Sara, Giunchi, Dimitri, Pollonara, Enrica, Casini, Giovanni, Bingman, Verner P., Gagliardo, Anna

Within their familiar areas homing pigeons rely on familiar visual landscape features and landmarks for homing. However, the neural basis of visual landmark-based navigation has been so far investigated mainly in relation to the role of the hippocampal formation. The avian visual Wulst is the telencephalic projection field of the thalamofugal pathway that has been suggested to be involved in processing lateral visual inputs that originate from the far visual field. The Wulst is therefore a good candidate for a neural structure participating in the visual control of familiar visual landmark-based navigation. We repeatedly released and tracked Wulst-lesioned and control homing pigeons from three sites about 10-15 km from the loft. Wulst lesions did not impair the ability of the pigeons to orient homeward during the first release from each of the three sites nor to localise the loft within the home area. In addition, Wulst-lesioned pigeons displayed unimpaired route fidelity acquisition to a repeated homing path compared to the intact birds. However, compared to control birds, Wulst-lesioned pigeons displayed persistent oscillatory flight patterns across releases, diminished attention to linear (leading lines) landscape features, such as roads and wood edges, and less direct flight paths within the home area. Differences and similarities between the effects of Wulst and hippocampal lesions suggest that although the visual Wulst does not seem to play a direct role in the memory representation of a landscape-landmark map, it does seem to participate in influencing the perceptual construction of such a map.