Magnetic activation in the brain of the migratory northern wheatear (Oenanthe oenanthe)

Abstract

Behavioural and neurobiological evidence suggests the involvement of the visual and trigeminal sensory systems in avian magnetoreception. The constantly growing array of new genetic approaches becoming available to scientists would bear great potential to contribute to a generally accepted understanding of the mechanisms underlying this ability, but would require to breed migratory birds in captivity. Here we show that the transcontinental night-migratory Northern Wheatear (Oenanthe oenanthe), which is currently the only migratory songbird successfully being bred in reasonable numbers in captivity, shows magnetic-field-induced neuronal activation in the trigeminal brainstem areas receiving their input through the ophthalmic branch of the trigeminal nerve. In addition, preliminary data indicate night vision-triggered activation in the anterior visual forebrain. This brain area could represent the same brain region, which has previously been named "Cluster N" and shown to be involved in processing magnetic compass information in European Robins. Thus, based on brain activation data, both visually and trigeminally mediated magnetic senses known from other birds seem to exist in Northern Wheatears. This makes this species a potentially excellent model species for future genetic research on magnetoreception in migratory birds.

Lidocaine is a nocebo treatment for trigeminally mediated magnetic orientation in birds

“…Anaesthesia with lidocaine applied to the mucous skin of the upper beak, as has been used in numerous studies in order to temporarily 'inactivate' a beak-based magnetic sensor, did not significantly affect the magnetic activation of trigemino-recipient brain structures PrV and SpV in migratory European robins, whereas sectioning of V1 led to a significant decrease in magnetic field-induced neuronal activation (figure 1g). Previous studies replicably showed that the observed activation is mediated by V1 and that it is very likely to be induced by magnetic stimuli, because downregulation of Egr-1 was achieved both by V1 sectioning and by compensation of the ambient magnetic field [51][52][53].…”

“…Finally, it was shown that V1 sectioning had no unspecific effects on the birds' ability to show migratory behaviour and to use their magnetic compass, because V1-lesioned birds oriented as well as controls in magnetic compass orientation experiments [8,24,54,55]. Based on the above considerations, we have repeatedly argued that V1 sectioning is the only sure way to prevent trigeminal magnetic information being transmitted to the brain via V1 [9,10,24,52,53,55,56].…”

“…Studies using surgical ablation of V1 reported clear behavioural effects on the birds' ability to detect and/or to react to magnetic field changes [24,50]. Moreover, a significant decrease in magnetically induced neuronal activation has been observed in the primary V1recipient hindbrain regions PrV ( principal sensory nucleus of the trigeminal nerve) and SpV (spinal trigeminal nucleus) after V1 sectioning in two migratory bird species [51,52] and homing pigeons [53]. Finally, it was shown that V1 sectioning had no unspecific effects on the birds' ability to show migratory behaviour and to use their magnetic compass, because V1-lesioned birds oriented as well as controls in magnetic compass orientation experiments [8,24,54,55].…”

“…We used the replicable observation of V1-dependent magnetic activation in PrV and SpV [17,[51][52][53] as a diagnostic tool to directly test whether lidocaine treatment affects trigeminal-based magnetic activation in the hindbrain. Therefore, the first aim of this study was to analyse magnetic field-induced neuronal activation (reflected as nuclear expression of Egr-1) in order to assess the effect of lidocaine on putative beak-based magnetoreceptors.…”

Anosmic migrating songbirds demonstrate a compensatory response following long-distance translocation: a radio-tracking study

“…In many regions of the world, total intensity and inclination (the angle between the magnetic field lines and the horizon) of the geomagnetic field varies approximately along a north-south axis, whereas declination (the angle between directions towards the magnetic and geographic poles) changes primarily along an east-west axis (Boström et al 2012; https ://ngdc.noaa.gov/ geoma g/WMM/image .shtml ). The trigeminal nerve has been shown to be involved in the avian magnetoreception (Heyers et al 2010;Lefeldt et al 2014;Elbers et al 2017), but it is not required for magnetic compass orientation (Zapka et al 2009). A further displacement experiment from the Courish Spit to Moscow demonstrated that an intact trigeminal nerve is necessary for the compensatory response shown by Reed Warblers (Kishkinev et al 2013).…”