Deconstructing the flight paths of hippocampal-lesioned homing pigeons as they navigate near home offers insight into spatial perception and memory without a hippocampus

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 landscapebased, 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.