Browsing by Author "Pinto, Belmiro V."
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- Asymmetrical processing of olfactory input in the piriform cortex mediates "activation" of the avian navigation circuitryPublication . Jorge, Paulo; Marques, Paulo A. M.; Pinto, Belmiro V.; Phillips, John B.The role of odors in the long-distance navigation of birds has elicited intense debate for more than half a century. Failure to resolve many of the issues fueling this debate is due at least in part to the absence of controls for a variety of non-specific effects that odors have on the navigational process. The present experiments were carried out to investigate whether the olfactory inputs are involved only in “activation” of neuronal circuitry involved in navigation or are also playing a role in providing directional information. Experienced adult pigeons were exposed to controlled olfactory stimuli during different segments of the journey (release site vs. displacement + release site). Protein levels of IEGs (immediate early genes used to mark synaptic activity) were analyzed in areas within the olfactory/navigation avian circuitry. The results indicate that 1) exposure to natural odors at the release site (and not before) elicit greater activation across brain regions than exposure to filtered air, artificial odors, and natural odors along the entire outward journey (from home to the release site, inclusive); 2) activation of the piriform cortex in terms of odor discrimination is lateralized; 3) activation of the navigation circuitry is achieved by means of lateralized activation of piriform cortex neurons. Altogether, the findings provide the first direct evidence that activation of the avian navigation circuitry is mediated by asymmetrical processing of olfactory input occurring in the right piriform cortex.
- Involvement of the avian dorsal thalamic nuclei in homing pigeon navigationPublication . Jorge, Paulo E.; Pinto, Belmiro V.; Bingman, Verner P.; Phillips, John B.The navigational ability of birds has been a focus of popular and scientific interest for centuries, but relatively little is known about the neuronal networks that support avian navigation. In the brain, regions like the piriform cortex, olfactory bulbs, hippocampal formation, vestibular nuclei, and the wulst, are among the brain regions often discussed as involved in avian navigation. However, despite large literature showing a prominent role of some anterior and dorsal thalamic nuclei in mammalian spatial navigation, little is known about the role of the thalamus in avian navigation. Here, we analyzed a possible role of the dorsal anterior thalamic nuclei in avian navigation by combining olfactory manipulations during the transport of young homing pigeons to a release site and c-Fos immunohistochemistry for the mapping brain activity. The results reveal that odor modulated neurons in the avian dorsolateral lateral (DLL) subdivision of the anterior thalamic nuclei are actively involved in processing outward journey, navigational information. Outward journey information is used by pigeons to correctly determine the homeward direction. DLL participation in acquiring path-based information, and its modulation by olfactory exposure, broadens our understanding of the neural pathways underlying avian navigation.
- Olfactory information from the path is relevant to the homing process of adult pigeonsPublication . Jorge, Paulo E.; Pinto, Belmiro V.The contribution of path information to the homing process of adult experienced pigeons is by no means consensual. Adult pigeons are expected to determine the homeward direction solely based on information gathered at the release site (i.e., map information). However, several are the evidences suggesting that path information is somehow important to the homing process. Using adult homing pigeons andmanipulation of the pigeons’ access to olfactory information from the displacement to the release site bymeans of nasal plugs that were applied unilaterally, we accessed the contribution of olfactory path information to the homing process. Pigeons transported to the release site with only the right nostril plugged were impaired on the determination of the initial homeward direction, while pigeons transported to the release site with only the left nostril plugged were impaired on the homing speed. The present findings highlight the importance of information from the path to the navigational process wherein olfactory path information contributes to the accurate determination of the homeward direction and in keeping the pigeon’s motivation to fly home.