Periodic Reporting for period 3 - NeuroMag (The Neurological Basis of the Magnetic Sense)
Reporting period: 2021-10-01 to 2023-03-31
The central goal of this proposal is to gain insight into the biophysical, cellular, and neurological underpinnings of the magnetic sense. The magnetic sense is employed by a broad range of animals to guide them as they navigate within their environment. Animals that use the sense include: bees; bats; migratory birds; rainbow trout; mole rats; sea turtles; zebrafinches and pigeons. Since the 1950's there has been persuasive behaviour evidence that the sense exists, but we still do not understand how animals detect and process magnetic information. Currently, there are three ideas that aim to explain how magnetosensation might work: (1) a light sensitive quantal based model; (2) the presence of an iron-based magnetic compass within specific cells; and (3) the utilisation of electromagnetic induction to convert magnetic information directly into an electric impulse.
This grant addresses three specific questions:
1. Where are the primary sensory cells?
2. Where is magnetic information processed in the brain?
3. How is magnetic information encoded in the brain?
We are employing pigeons as a model system, coupled with advanced techniques in molecular biology and microscopy. If we understand how animals detect magnetic fields we will be better placed to develop artificial magnetosensors. Such tools will provide scientists and clinicians with powerful new ways to activate specific neuronal populations and tackle neurological disease.
This grant addresses three specific questions:
1. Where are the primary sensory cells?
2. Where is magnetic information processed in the brain?
3. How is magnetic information encoded in the brain?
We are employing pigeons as a model system, coupled with advanced techniques in molecular biology and microscopy. If we understand how animals detect magnetic fields we will be better placed to develop artificial magnetosensors. Such tools will provide scientists and clinicians with powerful new ways to activate specific neuronal populations and tackle neurological disease.
To date our work has focused on the inner ear of pigeons, testing the hypothesis that magnetic fields are detected by electromagnetic induction. We have identified a molecule (CaV1.3) which is known to detect electric fields in sharks and skates, which is located in the sensory hair cells of the pigeon inner ear. Both theoretical and physical experiments indicate that the movement of the pigeons head through the Earth's magnetic field could induce small currents within the semi-circular canals that could be detected by this channel. This would be analogous to the generation of electricity by wind turbines, which is reliant on electromagnetic induction. We are currently characterising the electrophysiological properties of CaV1.3 in greater detail. Complementing this work we have undertaken magnetic activation assays whereby pigeons are exposed to a rotating magnetic field. Employing histological methods and light sheet microscopy we have identified brain regions that are activated by magnetic fields. This includes the vestibular nuclei, further strengthening our hypothesis that the primary receptors are located in the inner ear. In the future we aim to characterise these neuronal circuits further, with the goal of directly recording from neurons while the animal is exposed to magnetic fields. Finally, we will aim to generate pigeon induced pluripotent stem cells, so we can undertake genetic manipulations and develop cellular assays.
During the course of this project we have developed and applied novel methodologies in the pigeon. We have established magnetic activation assays, which we couple to whole brain clearing and a computational analysis of activated neurons. In addition we have established in vivo 2-photon imaging in the pigeon forebrain, which can be used to visualise neuronal activity in response to defined sensory stimuli. We continue to build and refine these methods, sharing them with the scientific community at large. We expect that this project will shed light on an age old scientific mystery - how animals detect magnetic fields.