Friedrich Bonhoeffer - Biophysics

Using the main visual processing area in chicken embryos as a model, the department explored how the nervous system forms connections, often over large distances.

The department explored the development of the nervous system. One central questions was how axons originating in one place search out their often distant target nerve cells to connect with them specifically, as a first step in circuit formation.

The department chose the retino-tectal projection in the visual system as their model system. Axons originating in the eye project to the optic tectum, the main visual processor in the brain of vertebrates. Neighboring cells in the retina are connected to neighboring cells in the tectum, so that the tectum ‘maps’ the outside world.

Working with chicken embryos, Bonhoeffer and his team developed the ‘stripe assay”, planting tissue from the retina on surface that allows the (re-)growing axons to chose between two alternating substrates consisting of cell membranes from different parts of the tectum. This allowed them to show that retinal axons ‘choose’ to grow on the ‘correct’ membranes – because they were repelled from growing on membranes from inappropriate regions.