The ability of homing pigeons to return to their loft from unknown places has fascinated scientists for centuries. It is well established that homing pigeons, like migratory birds, posses an innate magnetic inclination compass to determine direction by measuring the angle between the magnetic field vector and the Earth's surface. Recent work has indicated that the avian magnetic compass is light mediated and appears to mediate magnetic information to the brain. This occurs via a visual pathway with processing in the visual Wulst area of the forebrain. There is, however, also evidence from other avian species that magnetic direction may be detected with iron-based mechanoreceptors in the olfactory epithelium. The goal of this study was to develop a novel conditioning paradigm requiring pigeons to solve a spatial task based on magnetic inclination cues and to gain a greater understanding of the neural mechanisms involved in the pigeon magnetic compass. We conducted impairment lesions in the visual Wulst area and found that the birds were no longer able to complete the task. This allowed us to test whether there is an equivalent area to the Cluster N in this species' forebrain. Our results indicate that this area of the brain is needed. Lastly, we surgically cut the trigeminal nerve to test whether this nerve transmits magnetic inclination cues by way of an iron-based magnetoreceptor. This demonstrates a transmission pathway for magnetic inclination information in pigeons.
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Acerbi, Merissa, "The Effect of Visual Wulst Lesions and Trigeminal Nerve Sectioning on the Discrimination of Magnetic Inclination in the Homing Pigeon (Columba livia)" (2013). Honors Projects. 94.
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