Encoding compass information in the brain

​To unravel how compass information is encoded in the brain, we study the monarch butterfly brain electrophysiologically. Thereby, we use intracellular and extracellular (tetrode) recordings. During intracellular recordings, we use sharp electrodes that allows us to observe the neural activity of a single neuron. Subsequently, we inject a tracer into the neuron for an anatomical characterization. The neurons are tested for their sensitivity to sky compass signals such as polarized light, or the sun, and to local landmarks. As these intracellular recordings allow only for a time-limited analysis, we are also recording the cells’ activity extracellularly (tetrode recordings). This does not only allow us to study the activity of a group of neurons for several hours, but it allows the recording from neurons in the brain, while the animal is behaving (e.g. while the animal is tethered to a rod at the center of a flight simulator).

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SPECIFIC QUESTIONS

• The coding of the relevance of different celestial cues.
• The coding of landmark information in the brain.
• The processing of time information in the sky compass network.
• The modulation of the compass network during flight.

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Participating SCIENTISTS

• M. Jerome Beetz (Postdoc) - Tetrode recordings
• Tu Anh Thi Nguyen (PhD student) - Intracellular recordings
• Christian Kraus (PhD student) - Tetrode recordings
• Basil el Jundi (PI)

Intracellular recording setup (photo: T.A. Nguyen Thi)

Response of a compass neuron to a 360° rotation of a polarizer (intracellular recording).

Tetrode recording from a compass neuron that responds to polarized light (recording from M.J. Beetz)