Abstract
In European Robins, Erithacus rubecula, the magnetic compass is lateralized in favor of the right eye/left hemisphere of the brain. This lateralization develops during the first winter and initially shows a great plasticity. During the first spring migration, it can be temporarily removed by covering the right eye. In the present paper, we used the migratory orientation of robins to analyze the circumstances under which the lateralization can be undone. Already a period of 1½ h being monocularly left-eyed before tests began proved sufficient to restore the ability to use the left eye for orientation, but this effect was rather short-lived, as lateralization recurred again within the next 1½ h. Interpretable magnetic information mediated by the left eye was necessary for removing the lateralization. In addition, monocularly, the left eye seeing robins could adjust to magnetic intensities outside the normal functional window, but this ability was not transferred to the “right-eye system”. Our results make it clear that asymmetry of magnetic compass perception is amenable to short-term changes, depending on lateralized stimulation. This could mean that the left hemispheric dominance for the analysis of magnetic compass information depends on lateralized interhemispheric interactions that in young birds can swiftly be altered by environmental effects.
Highlights
In most vertebrates studied up to now, several perceptual, cognitive, and motor systems display a left–right difference of neural processing [1,2]
Our previous study [29] had shown that, during the first spring migration, covering the right eye for 6 h had temporarily restored the ability for magnetic compass orientation to the left eye
The respective data are given in Figure 1: after having the right eye covered for 6 h, the robins could orient with their right eye (6hpeL-R) as well as with their left eye (6peL-L)
Summary
In most vertebrates studied up to now, several perceptual, cognitive, and motor systems display a left–right difference of neural processing [1,2] This ubiquity of functional brain asymmetries is probably the result of some fundamental benefits. Various studies could demonstrate in several species, ranging from fish to humans, that those individuals that are more strongly lateralized in a certain function display higher performances when this function is tested [3,4,5]. This is possibly due to three mechanisms. For example, lateralized and non-lateralized chicks are tested in a foraging task that requires them to find grains scattered
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