Dendritic processing: using microstructures to solve a hitherto intractable neurobiological problem.

In vivo, intracellular recordings of mammalian brain stem motoneurones, followed by peroxidase staining and tridimensional reconstruction, suggest that the shape of the dendritic tree plays an important role in the processing of neural information. To test this hypothesis attempts were made to guide, in culture, the growth of neuritic branches of neurones dissociated from the hypoglossal nucleus of rat brain stem. This was performed using topographical and adhesive microstructures which were designed to control the shape of the neuritic tree. Guidance of the neuritic processes can be observed with small grooves engraved on quartz and plastic substrates, and simple shapes with few processes and bifurcations on each neurite could be obtained using adhesive microstructures. These procedures, which allow the shape of a neurone to be controlled, are very promising in the study, by means of classical electrophysiological methods as well as optical recordings, of the involvement of dendritic architecture in the processing of neural information.